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Old 03-26-2013, 04:29 PM   #16
disston
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Originally Posted by supershaft View Post
Man. My BS meter has been red lining lately. Float bowl height is not about hydraulic pressure. It's about the height of the fuel in the jet tube and how far the low pressure above the fuel has to pick it up. Closer (higher) is easier (richer).
That seems a better explanation Physics wise but the actual function is not really important. Both explanations want an even sufficient float level. Doesn't mater how you understand it if you end up with the same result.

But I think your right.
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Old 03-26-2013, 04:46 PM   #17
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Originally Posted by disston View Post
That seems a better explanation Physics wise but the actual function is not really important. Both explanations want an even sufficient float level. Doesn't mater how you understand it if you end up with the same result.

But I think your right.
In the long run it does matter if you understand what you are doing. It helps you start thinking for yourself. In my experience, height effects the idle circuit quit a bit.
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Old 03-26-2013, 05:56 PM   #18
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I wonder if there's any evidence, even just anecdotal, that one might favour a slightly lower float vs a slightly higher float, or vice-versa. (Although maybe there are too many variables.) I just rebuilt my carbs, and felt I was pretty meticulous, but I'm still a bit rich, and a bit more on the left side. I keep tweaking float height and I think it's helping, but it's so incremental at this point.

My 100/7 has the 150 mains and 50 Idle jets. I changed everything but the nozzle needles, which I now regret. I've ordered new ones and will open the carbs back up to install. I do know for sure that my float height was too high and was causing much of my richness, but I still want to get it closer. I might also try 142 mains.
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Old 03-26-2013, 06:07 PM   #19
Plaka
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Originally Posted by CanadaBiker View Post
I wonder if there's any evidence, even just anecdotal, that one might favour a slightly lower float vs a slightly higher float, or vice-versa. (Although maybe there are too many variables.) I just rebuilt my carbs, and felt I was pretty meticulous, but I'm still a bit rich, and a bit more on the left side. I keep tweaking float height and I think it's helping, but it's so incremental at this point.

My 100/7 has the 150 mains and 50 Idle jets. I changed everything but the nozzle needles, which I now regret. I've ordered new ones and will open the carbs back up to install. I do know for sure that my float height was too high and was causing much of my richness, but I still want to get it closer. I might also try 142 mains.
When you are evaluating rich or lean you also have to consider throttle opening so you know what circuit you are running on.

Nice diagram on this in the bing manual.
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Old 03-26-2013, 06:51 PM   #20
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Is this what you are calling a nozzle needle? #9



I call that one the jet needle. It may go by some other names but I think this is the most common name. What ever you call it it is a wear part. By that I mean of course that it suffers wear from use and should be replaced. Bing recommends replacing these after 25,000 miles. I think you may get more than that out of them but should maybe replace them by 30 or 35K.

As the jet needle is raised by the slide it opens the flow of the needle jet, also #9 in the next drawing;



This too is a wear part and should be replaced with the jet needle.

Not all of the parts in these carbs are usually replaced. I don't know what you mean when you say you replaced "everything". That's almost impossible. I think you mean the O-rings and gaskets. Maybe floats and float needles and maybe diaphragms? All of that is commonly replaced. What we have been hearing from other riders is that they didn't realize the jet needle and the needle jet were wear parts. They rub against each other when the needle moves up and down.

All the jets in the carbs are brass and a good cleaning is all most of them need, other than these two. One exception is the idle mixture screw. It has the small spring on it and it is the screw you turn when adjusting the mixture. This part is made of steel and it can be rusty. If so replace it.

In operation the Bing carbs need a certain minimum amount of fuel in the bowl and too much will cause problems too. The effect of raising and lowering the fuel level will be very slight with in these confines. The action of the mixture screw will be more noticeable.
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Old 03-26-2013, 08:02 PM   #21
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Originally Posted by Plaka View Post
When you are evaluating rich or lean you also have to consider throttle opening so you know what circuit you are running on.

Nice diagram on this in the bing manual.
Yeah, you're absolutely right. I haven't done a proper plug chop. The plugs look pretty decent but do get some soot. The kind that wipes off very easily, and the porcelain on the centre electrode looks nice and tan under the soot, so it could very well be an issue in the first 1/4 throttle, or what not.

Quote:
Originally Posted by disston View Post
Is this what you are calling a nozzle needle? #9



I call that one the jet needle. It may go by some other names but I think this is the most common name. What ever you call it it is a wear part. By that I mean of course that it suffers wear from use and should be replaced. Bing recommends replacing these after 25,000 miles. I think you may get more than that out of them but should maybe replace them by 30 or 35K.

As the jet needle is raised by the slide it opens the flow of the needle jet, also #9 in the next drawing;



This too is a wear part and should be replaced with the jet needle.

Not all of the parts in these carbs are usually replaced. I don't know what you mean when you say you replaced "everything". That's almost impossible. I think you mean the O-rings and gaskets. Maybe floats and float needles and maybe diaphragms? All of that is commonly replaced. What we have been hearing from other riders is that they didn't realize the jet needle and the needle jet were wear parts. They rub against each other when the needle moves up and down.

All the jets in the carbs are brass and a good cleaning is all most of them need, other than these two. One exception is the idle mixture screw. It has the small spring on it and it is the screw you turn when adjusting the mixture. This part is made of steel and it can be rusty. If so replace it.

In operation the Bing carbs need a certain minimum amount of fuel in the bowl and too much will cause problems too. The effect of raising and lowering the fuel level will be very slight with in these confines. The action of the mixture screw will be more noticeable.
I replaced all o-rings, gaskets, floats, float pins, float needle, and diaphragms. So no, I guess not everything. :) It was after a bit more research that I realized the jet needle and needle jet are wear items. I've ordered new of those, as well as new mixture screws and springs.

(I also replaced the rubber grommets on both sides of the carbs, as well as the suction funnels.)

My plugs still show a bit rich, so maybe the jet needles were worn. The bike has 70k miles, and I don't know if the PO ever did them. I now also have a bit of a hanging idle when I rev it in neutral. The idle hangs high, about 2k, then slowly drops back to 1k after a minute or so. Sometimes longer. I checked for air leaks and didn't find any. I did notice that my mixture screws make huge changes with small moves, which is a good sign, no? The hanging idle is lessened if I go a bit to the rich side of the screw at 1.5 turns out. At 1 turn out, the hanging idle is the worst. At half a turn out, it pops a bit on decel.

I double checked my choke circuits and my butterflies to make sure I had installed correctly, so I don't think that's the issue. I checked the float height with the carbs on the bike, and letting the gas flow. But I didn't measure fuel in the float. A few small changes helped my sooty left plug, but I'd like to get it perfect. I wonder if my hanging idle is any clue.

I did have my vac gauges on the bike, but I felt like I was chasing my tail. (I had an easier time on my old CB Four) The left side needed to be lifted, but it seemed like I couldn't get it to respond with a few changes on the main idle screw. I was worried that my gauges or hoses were leaking so I gave up for now, and will get fresh hoses and double check my gauges. Oddly the vac seemed almost even at off idle--2k rpms or so.

Not sure if this is related, but I noticed that my new diaphragms were stiff compared to the old ones. The slides didn't seem to want to drop right down when I had the carbs on the bench. The kit was from MotoBins, and I've heard about problems with stiffer diaphragms, but not sure if these are those problem ones. Maybe they were just stiff compared to old ones.

Anyway, blah blah blah, chasing carb setups. I thought I was good at it after my old Honda Four. I do know that I'm not gonna give up until it runs perfect. :)
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Old 03-26-2013, 08:47 PM   #22
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Originally Posted by CanadaBiker View Post
Yeah, you're absolutely right. I haven't done a proper plug chop. The plugs look pretty decent but do get some soot. The kind that wipes off very easily, and the porcelain on the centre electrode looks nice and tan under the soot, so it could very well be an issue in the first 1/4 throttle, or what not.



I replaced all o-rings, gaskets, floats, float pins, float needle, and diaphragms. So no, I guess not everything. :) It was after a bit more research that I realized the jet needle and needle jet are wear items. I've ordered new of those, as well as new mixture screws and springs.

(I also replaced the rubber grommets on both sides of the carbs, as well as the suction funnels.)

My plugs still show a bit rich, so maybe the jet needles were worn. The bike has 70k miles, and I don't know if the PO ever did them. I now also have a bit of a hanging idle when I rev it in neutral. The idle hangs high, about 2k, then slowly drops back to 1k after a minute or so. Sometimes longer. I checked for air leaks and didn't find any. I did notice that my mixture screws make huge changes with small moves, which is a good sign, no? The hanging idle is lessened if I go a bit to the rich side of the screw at 1.5 turns out. At 1 turn out, the hanging idle is the worst. At half a turn out, it pops a bit on decel.

I double checked my choke circuits and my butterflies to make sure I had installed correctly, so I don't think that's the issue. I checked the float height with the carbs on the bike, and letting the gas flow. But I didn't measure fuel in the float. A few small changes helped my sooty left plug, but I'd like to get it perfect. I wonder if my hanging idle is any clue.

I did have my vac gauges on the bike, but I felt like I was chasing my tail. (I had an easier time on my old CB Four) The left side needed to be lifted, but it seemed like I couldn't get it to respond with a few changes on the main idle screw. I was worried that my gauges or hoses were leaking so I gave up for now, and will get fresh hoses and double check my gauges. Oddly the vac seemed almost even at off idle--2k rpms or so.

Not sure if this is related, but I noticed that my new diaphragms were stiff compared to the old ones. The slides didn't seem to want to drop right down when I had the carbs on the bench. The kit was from MotoBins, and I've heard about problems with stiffer diaphragms, but not sure if these are those problem ones. Maybe they were just stiff compared to old ones.

Anyway, blah blah blah, chasing carb setups. I thought I was good at it after my old Honda Four. I do know that I'm not gonna give up until it runs perfect. :)
Perfection is for the Gods. We are but mortals. If you seek perfection you seek to become one of Them, and They will not appreciate it, and exact a considerable price. I am neither particularly religious, nor kidding. But if there is one thing I try to get pious about, it is avoiding perfection. BMW owners are well known for certain neuroticisms, obsessive compulsiveness leading the pack. The more you can get over it, the more you can truly live and the more fun you will have. This isn't intuitive because the neurotic process serves a function. Abandoning that function is scary and one imagines missing the satisfaction it brings. Think again. Get help if you need to.

You replaced a whole bunch of stuff that rarely needs replacing and definitely should be evaluated for wear before spending a dime. That was gas, oil and tire money you spent. It was a day off from work you could have been riding. I know, some people have tons of cash and could care less. But then why not just buy new carbs and not have to screw with them?

Diaphragms last a long time. I've gotten over 100k on them. They don't get replaced unless they have a hole. I carry a spare set on really long trips. I have fitted stainless carb top screws and I keep them in good shape so it's a snap to replace a diaphragm on the road. There is a little flat wedge shaped piece of metal in with the diaphragms that captures the cable settings exactly so I can put them back where they were.

Butterflies never come out unless they are leaking at the shafts. They get new screws properly staked if the screws come out. Some re-use the screws if they are in good enough shape..

I've owned several vacuum carb balancers: mercury sticks, a Walus differential gauge. Gah. The old power balancing routine works better than all of them for getting a balanced and very smooth engine. I use some fancy clip on 4 plug balancers in the shop and have a very small set of the original style (spoke) balancers in the tool kit I can use anywhere.

The principle of vacuum balancing is wrong. If you balance the vacuum drawn by each carb you have to assume this translates into the power put out by each side. Turns out it isn't a great correlation. If you just balance the power put out by each side you are working directly on the thing that matters. Let the vacuum do what it wants. Many others prefer looking at vacuum gauges rather than their tachs (and listening). I've gotten enough comments about how smoothly my engines run to know I'm doing something right.

Light soot on the plug is normal. Happens every time you start it up, especially on the chokes. Do a chop after a run at speed and see what you get.

Drop some of the money you spent on carb parts on a Streamlight Reach.

http://www.walmart.com/ip/17011842?w...l5=pla&veh=sem

Then pull the plugs and with the piston at TDC look in through the spark plug hole with the Reach and check out the piston crown. Turn the motor over so you can see the lips of the valves as well.

There is an arrow and some letters on the piston crown. If you can see them, good. If the buildup is so thick they don't show, run some Seafoam, Techron or similar for a half dozen tanks and look again. More buildup on one side vs. the other throws off your compression and in turn the balance. In general, get wary when one side takes a lot of adjustment to match it to the other side. The left side generally has more carbon. A very careful compression check will reveal this also.

Good luck and sorry (somewhat) for getting on your case so much. BMW owners really are notorious though and it's sort of a sad affliction.
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Old 03-26-2013, 09:13 PM   #23
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Perfection is for the Gods. We are but mortals. If you seek perfection you seek to become one of Them, and They will not appreciate it, and exact a considerable price. I am neither particularly religious, nor kidding. But if there is one thing I try to get pious about, it is avoiding perfection. BMW owners are well known for certain neuroticisms, obsessive compulsiveness leading the pack. The more you can get over it, the more you can truly live and the more fun you will have. This isn't intuitive because the neurotic process serves a function. Abandoning that function is scary and one imagines missing the satisfaction it brings. Think again. Get help if you need to.

You replaced a whole bunch of stuff that rarely needs replacing and definitely should be evaluated for wear before spending a dime. That was gas, oil and tire money you spent. It was a day off from work you could have been riding. I know, some people have tons of cash and could care less. But then why not just buy new carbs and not have to screw with them?

Diaphragms last a long time. I've gotten over 100k on them. They don't get replaced unless they have a hole. I carry a spare set on really long trips. I have fitted stainless carb top screws and I keep them in good shape so it's a snap to replace a diaphragm on the road. There is a little flat wedge shaped piece of metal in with the diaphragms that captures the cable settings exactly so I can put them back where they were.

Butterflies never come out unless they are leaking at the shafts. They get new screws properly staked if the screws come out. Some re-use the screws if they are in good enough shape..

I've owned several vacuum carb balancers: mercury sticks, a Walus differential gauge. Gah. The old power balancing routine works better than all of them for getting a balanced and very smooth engine. I use some fancy clip on 4 plug balancers in the shop and have a very small set of the original style (spoke) balancers in the tool kit I can use anywhere.

The principle of vacuum balancing is wrong. If you balance the vacuum drawn by each carb you have to assume this translates into the power put out by each side. Turns out it isn't a great correlation. If you just balance the power put out by each side you are working directly on the thing that matters. Let the vacuum do what it wants. Many others prefer looking at vacuum gauges rather than their tachs (and listening). I've gotten enough comments about how smoothly my engines run to know I'm doing something right.

Light soot on the plug is normal. Happens every time you start it up, especially on the chokes. Do a chop after a run at speed and see what you get.

Drop some of the money you spent on carb parts on a Streamlight Reach.

http://www.walmart.com/ip/17011842?w...l5=pla&veh=sem

Then pull the plugs and with the piston at TDC look in through the spark plug hole with the Reach and check out the piston crown. Turn the motor over so you can see the lips of the valves as well.

There is an arrow and some letters on the piston crown. If you can see them, good. If the buildup is so thick they don't show, run some Seafoam, Techron or similar for a half dozen tanks and look again. More buildup on one side vs. the other throws off your compression and in turn the balance. In general, get wary when one side takes a lot of adjustment to match it to the other side. The left side generally has more carbon. A very careful compression check will reveal this also.

Good luck and sorry (somewhat) for getting on your case so much. BMW owners really are notorious though and it's sort of a sad affliction.
Ah yes, perfect is the enemy of good, that's for sure. Funny, I try to remember that, but then my mind wanders to the mechanics of it all, and I figure if it ain't broken, it should run right. I blame my father. He's the kind of guy that would take his various new Ford 150s back to the dealer once a week for years 'cause it had a 'rattle it shouldn't'. The mechanic would grumble, but then often find out he was right. He's lightened up with age, so maybe I'll get there. Or run out of money.

I'll do a proper plug chop and have a peek inside the top end. I'll also check out the local Walmart.

Could you expand on the power balancing routine. I sort of know a little about it. Listening to the exhaust and watching the tach on separate sides? I have a new Boyer, (which I'm not yet completely sold on), so I assume I'll need to fab some proper shorting sticks for fear of damaging the module?

Of all the bikes I've had, I always said I'd never end up on a BMW, but subconsciously, I also knew that that wasn't true, and of course I'd end up on a BMW, who was I kidding.
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Old 03-26-2013, 10:39 PM   #24
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Well, the O-rings and gaskets probably actually did need replacing. That and the needle jets and jet needles that you are now getting. Thick diaphragms? Sounds like trouble. Motobins sells some off stuff from what I have seen but so are the BMW dealerships lately. I would get my diaphragms from a dealer. Your chances of getting the right ones are much higher. Thick diaphragms would change jetting. Probably richer. The ones you took out are probably perfect. Same with the floats.

It sounds like one of your throttle cables does not have enough free play? Once you get that sorted your off idle sync will be off and you will have to adjust the other side's cable adjuster.

PROPERLY damped manometers are the best way to sync carbs. They are in fact THE scientific standard because they simply are Mother Nature showing you what is going on as far as each cylinder pulling air is concerned while it is running and as it actually runs all in real time.

Versus pulling one dead cylinder along and at the same time clearing itself up from just getting completely flooded while it was shorted checking the other cylinder? All that tells you is what rpm that cylinder drags the other dead cylinder along at while it is trying to clear itself from just having been flooded but guess what? They don't normally run like that. What matters is what is going on while it is running as it runs while it runs in its normal running condition. Ports are flowed and balanced with manometers for good reasons. Don't treat it any worse since it is together and running.

Jetting? Get it running right first. They very often are jetted rich from the factory. Your idle mixture screw is critical. Learn how to adjust EACH carb independently. In till it stumbles. Out till it stumbles. Half way in between or a tad richer. One carb might stumble twelve hours apart. The other six. An hour richer past 6 hours on the first and a half hour richer past three hours on the second. Does that make sense?

Plug chops? Most everyone thinks rich is too lean from looking at plugs. Leave that for the experts. Besides, jetting takes buying a lot of jets.

supershaft screwed with this post 03-26-2013 at 11:18 PM
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Old 03-26-2013, 10:39 PM   #25
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Stop picking on the guy Plaka. (he does that to everyone). Nothing wrong with rebuilding the carbs. And the rubber bits do get old. And they need a good cleaning.

In the first parts fisch I show there is a large spring on top of the piston, #7. If you don't have those in your carbs they can be added. Sometimes they help.

I too have had issues with hanging idle. It may be the Gasohol? Or I may need valve work?
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Old 03-26-2013, 10:42 PM   #26
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Ah yes, perfect is the enemy of good, that's for sure. Funny, I try to remember that, but then my mind wanders to the mechanics of it all, and I figure if it ain't broken, it should run right. I blame my father. He's the kind of guy that would take his various new Ford 150s back to the dealer once a week for years 'cause it had a 'rattle it shouldn't'. The mechanic would grumble, but then often find out he was right. He's lightened up with age, so maybe I'll get there. Or run out of money.

I'll do a proper plug chop and have a peek inside the top end. I'll also check out the local Walmart.

Could you expand on the power balancing routine. I sort of know a little about it. Listening to the exhaust and watching the tach on separate sides? I have a new Boyer, (which I'm not yet completely sold on), so I assume I'll need to fab some proper shorting sticks for fear of damaging the module?

Of all the bikes I've had, I always said I'd never end up on a BMW, but subconsciously, I also knew that that wasn't true, and of course I'd end up on a BMW, who was I kidding.
I had two Boyers. The first one lasted a good long time and then failed the nice way---it died as in daid. Some Dyna III's I had died by going intermittent, which was a PITA. Anyway I got another Boyer and it was still going when I parted the bike. It was a newer and improved one. I believe they continue to improve them. My first one was 20 something years ago.

The power balancing routine is simple. You short out the plug on one side and see how strong the engine is running on the other side, then switch sides, quickly. When it's right, the rpm (on the tach and by ear) doesn't change. I mean not at all. You can get a little perfectionistic here (), just don't overheat the engine because you're being so slow.

Under no circumstances do you want a coil to fire without the plug wire grounded. So make your shorting wires with care. if you are using plug caps that go directly on threaded spark plug tops, then a spoke nipple is the same thread as that spark plug tops. Get two spokes and nipples, chop the spokes to about 3" (+-.005"). Take the piece with the threads and solder the nipple to the unthreaded end. Now you have a rod that threads onto the plug and the plug cap clips firmly to the other.

If you are using plug caps that go on the bushing type spark plug (often that bushing screws on and off, but not always) then get some stiff wire (music wire, hobby shop) of the correct size. Solder a brass bushing off an old spark plug to one end and the clip that engages the bushing (Auto parts store that has raw plug wire components). Again you have a rig that is solid on the plug and in the cap.

Then you need two long insulated screwdrivers. ie, long cheap screwdrivers with plastic handles.

Warm bike up.

if you have fans (nice) set them up blowing on the jugs.

Slacken throttle cables at the carb completely. Chokes fully off. (loosen the adjusters and make sure they are off-off down at the carb lever)

Set idle mixture and throttle stop screws at nominal values per manual.

Start bike and adjust idle mixture screw one side at a time so bike runs best (by ear). 1/4 turn at a time and allow 15 seconds for engine speed to stabilize.

Now short one side by placing the screwdriver on the shorting wire and sliding it forward to contact the fins. The other side (making power) should hit 2-3 times then die. Adjust throttle stop screw to get this. Do the other side the same way.

Idle it and check idle speed on tach. If too high back off idle stop screws a bit and the same amount both sides. (maybe 1/8 to 1/4 turn) and check the balance again with the shorting wires and screwdrivers. When you got it, each side will hit the same before dying and the idle speed will be what you want.

Adjust the throttle cables at the carb to just leave a little slack.

Now start it and wind it up a bit then short the left side while you wind it up to standard cruising RPM running on the right side only. Stand on the left and lean over. This is important, you are going for an ideal balance at that RPM. It will be slightly off everywhere else. So set it up for where you ride the most. +-100rpm or so won't matter. When it's there lock the throttle at the handgrip with the throttle lock screw, grap the other screwdriver out of your back pocket and lay it on the shorting wire on the right side. Slide the right screwdriver forward to short that side while you pull the left screwdriver back to allow that side to fire. RPM shouldn't change. I have recommended which side you start with because of where your hands are and when.

Kill it with the kill switch. You now know which side is strong and which weak. Take up some throttle cable on the weak side. Do it again. When you are very close you can switch back and forth a couple times by sliding the screwdriver (always keep them in contact with the shorting wires, just easier) to watch what happens. When you are dead on the RPM won't change.

Check the idle speed again. If high your high speed adjustment is pulling the throttle off the stop screw. Redo the high speed but start with more slack in the cables. You want just enough slack at idle so the stop screw is doing something. Too much and it doesn't come off idle well and you waste travel at the bar, too little and the stop screw ain't doing the stopping. Lots of leeway. Do it once and you'll know what to leave.

First time through you're slow. Stop and let it cool. Doesn't hurt to practice your moves cold before you start. What do you hold where, where is the other screwdriver so you can grab it, how to you wind it up and lock it with one hand, etc.

Do it a few times and it gets very quick and it's always very accurate. Shorting wires go in the toolkit. You can find something to substitute for the screwdrivers most places. You carry tape, just need some coathanger or whatever.

I did the above from memory. Don't think I missed anything. Watch out for the shorting wires when you're done, they're hot.

This method not only considers the mixture on each side but also the compression as working against the compression on the other side. Not only carbon build up but slight variances in valve settings (always do valves before carbs and use Go-No Go feeler gauges) alter compression. In addition intake and exhaust tract variances affect power (although this shows up in vacuum if the setup is sensitive enough). Another advantage, besides portability, is you do not introduce other equipment and it's variability.

Plaka screwed with this post 03-27-2013 at 12:22 AM
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Old 03-26-2013, 10:59 PM   #27
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Originally Posted by Plaka View Post
I had two Boyers. The first one lasted a good long time and then failed the nice way---it died as in daid. Some Dyna III's I had died by going intermittent, which was a PITA. Anyway I got another Boyer and it was still going when I parted the bike. It was a newer and improved one. I believe they continue to improve them. My first one was 20 something years ago.

The power balancing routine is simple. You short out the plug on one side and see how strong the engine is running on the other side, then switch sides, quickly. When it's right, the rpm (on the tach and by ear) doesn't change. I mean not at all. You can get a little perfectionistic here (), just don't overheat the engine because you're being so slow.

Under no circumstances do you want a coil to fire without the plug wire grounded. So make your shorting wires with care. if you are using plug caps that go directly on threaded spark plug tops, then a spoke nipple is the same thread as that spark plug tops. Get two spokes and nipples, chop the spokes to about 3" (+-.005"). Take the piece with the threads and solder the nipple to the unthreaded end. Now you have a rod that threads onto the plug and the plug cap clips firmly to the other.

If you are using plug caps that go on the bushing type spark plug (often that bushing screws on and off, but not always) then get some stiff wire (music wire, hobby shop) of the correct size. Solder a brass bushing off an old spark plug to one end and the clip that engages the bushing (Auto parts store that has raw plug wire components). Again you have a rig that is solid on the plug and in the cap.

Then you need two long insulated screwdrivers. ie, long cheap screwdrivers with plastic handles.

Warm bike up.

if you have fans (nice) set them up blowing on the jugs.

Slacken throttle cables at the carb completely. Chokes fully off. (loosen the adjusters and make sure they are off-off down at the carb lever)

Set idle mixture and throttle stop screws at nominal values per manual.

Start bike and adjust idle mixture screw one side at a time so bike runs best (by ear). 1/4 turn at a time and allow 15 seconds for engine speed to stabilize.

Now short one side by placing the screwdriver on the shorting wire and sliding it forward to contact the fins. The other side (making power) should hit 2-3 times then die. Adjust throttle stop screw to get this. Do the other side the same way.

Idle it and check idle speed on tach. If too high back off idle stop screws a bit and the same amount both sides. (maybe 1/8 to 1/4 turn) and check the balance again with the shorting wires and screwdrivers. When you got it, each side will hit the same before dying and the idle speed will be what you want.

Adjust the throttle cables at the carb to just leave a little slack.

Now start it and wind it up a bit then short the left side while you wind it up to standard cruising RPM running on the right side only. Stand on the left and lean over. This is important, you are going for an ideal balance at that RPM. It will be slightly off everywhere else. So set it up for where you ride the most. +-100rpm or so won't matter. When it's there lock the throttle at the handgrip with the throttle lock screw, grap the other screwdriver out of your back pocket and lay it on the shorting wire on the right side. Slide the right screwdriver forward to short that side while you pull the left screwdriver back to allow that side to fire. RPM shouldn't change. I have recommended which side you start with because of where your hands are and when.

Kill it with the kill switch. You now know which side is strong and which weak. Take up some throttle cable on the weak side. Do it again. When you are very close you can switch back and forth a couple times by sliding the screwdriver (always keep them in contact with the shorting wires, just easier) to watch what happens. When you are dead on the RPM won't change.

Check the idle speed again. If high your high speed adjustment is pulling the throttle off the stop screw. Redo the high speed but start with more slack in the cables. You want just enough slack at idle so the stop screw is doing something. Too much and it doesn't come off idle well and you waste travel at the bar, too little and the stop screw ain't doing the stopping. Lots of leeway. Do it once and you'll know what to leave.

First time through you're slow. Stop and let it cool. Doesn't hurt to practice your moves cold before you start. What do you hold where, where is the other screwdriver so you can grab it, how to you wind it up and lock it with one hand, etc.

Do it a few times and it gets very quick and it's always very accurate. Shorting wires go in the toolkit. You can find something to substitute for the screwdrivers most places. You carry tape, just need some coathanger or whatever.

I did the above from memory. Don't think I missed anything. Watch out for the shorting wires when you're done, they're hot.

This method not only considers the mixture on each side but also the compression as working against the compression on the other side. Not only carbon build up but slight variances in valve settings (always do valves before carbs and use Go-No Go feeler gauges) alter comprehension. In addition intake and exhaust tract variences affect power (although this shows up in vacuum if the setup is sensitive enough). Another advantage, besides portability, is you do not introduce other equipment and it's variability.


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Old 03-26-2013, 11:08 PM   #28
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Old 03-26-2013, 11:09 PM   #29
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Yeah, I couldn't read it all the way though either.
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Old 03-26-2013, 11:11 PM   #30
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