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Old 06-12-2013, 09:38 AM   #16
More_Miles
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Quote:
Originally Posted by akpasta View Post
Thanks again for the replies folks, you've got a pretty helpful community here.

I'm not able to find any marks on the "flywheel." Is the flywheel the giant rotor in the center of the points area? Is the flywheel the thing that spins inside the timing hole with the non-visible S and visible F marks?

Flywheel = AKA clutch carrier on "newer" airheads. I think yours is considered "newer" as is my '83.

It's the big honking rotating thingie behind the timing hole.
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Old 06-12-2013, 10:05 AM   #17
trabbart
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when a car looses power alway change the rotor and cap from the distributor,
loosing power is ignition,,,,weak spark. weak explosion,,weak power......

my bike had the 27 year old coils, when i changed them for new it was way faster,,i also replaced the coil wires,the points looked like new and i lett them in there ,,,, remove the old ignition stuff before you get stranded. its junk after 25 years,,,maby some will ride with it,,but they dont know how weak there spark is,,,if it was not the problem you have won a few horses and can exclude the coils and wires and win some horses somewhere else.

start the bike cold, feel at both exhaustpipes ,,you might feel differances in heat.
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Old 06-12-2013, 10:15 AM   #18
chasbmw
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Quote:
Originally Posted by akpasta View Post
Thanks again for the replies folks, you've got a pretty helpful community here.

I'm not able to find any marks on the "flywheel." Is the flywheel the giant rotor in the center of the points area? Is the flywheel the thing that spins inside the timing hole with the non-visible S and visible F marks?

Timing at advance feels really good, but after I ran for about 5 miles the left cylinder seemed to drop a bit at low rpms, I'll recheck my points and set the float on the left side- I set it on the right. Maybe some of the grease I put on the advance cam slipped onto the points, who knows.

I also need to do a general re-setting of carbs, per manual.

The fact that I can't see the S-Marks in the window is weird though. But I suppose with only one set of points, if your gap is right, they ought to open at the right time anyways, right? Maybe not, I dunno. If I want to static time for idle, what marking would I look at with my little points timing bulb?

Adjusting the points is kind of a bitch with that advance mechanism in the way. Anyone know where I can get one of these nifty tools that fits over the points cam so you can get full gap without the advancer in place? I suppose you could make one out of a worn-out advancer but I don't have one of those yet
Static timing on the points will be at the S mark, but your problems will most likely to be due to the float level being set too low. Very easy to do? And you do need to do a full tune up including all fluids and greases.
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Old 06-12-2013, 10:39 AM   #19
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Originally Posted by chasbmw View Post
Static timing on the points will be at the S mark, but your problems will most likely to be due to the float level being set too low. Very easy to do? And you do need to do a full tune up including all fluids and greases.
I did a little research and found where to look for the marks at static. I'll start there with a static light, then confirm advance with strobe.

Took apart right side carb to examine things, not the left side yet cuz the right looked so good. Setting float level is incredibly easy i'll do it on the left. Replaced engine oil already of course, but haven't done front disc brake drain or the rear drive shaft fluid, will get to those next.

I also really wanna check valve clearance and rocker arm clearance but I don't have a torque wrench, is it absolutely necessary to re-torque the valve cover bolt with a torque wrench?

Also going to check compression on each side as the left side seems to burn some oil and smoke a bit. How much compression is decent on these guys?

Is there a standard setting for the mixture screws on each carb?

Thanks everyone for all the advice, huge help.
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Old 06-12-2013, 11:34 AM   #20
Plaka
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Originally Posted by trabbart View Post
when a car looses power alway change the rotor and cap from the distributor,
loosing power is ignition,,,,weak spark. weak explosion,,weak power......

my bike had the 27 year old coils, when i changed them for new it was way faster,,i also replaced the coil wires,the points looked like new and i lett them in there ,,,, remove the old ignition stuff before you get stranded. its junk after 25 years,,,maby some will ride with it,,but they dont know how weak there spark is,,,if it was not the problem you have won a few horses and can exclude the coils and wires and win some horses somewhere else.

start the bike cold, feel at both exhaustpipes ,,you might feel differances in heat.
I agree---partially. Spark plug wires take a beating in the wind. OEM BMW wires are very good, but still wear in time and are worth checking. If the resistances are good, they're good. Coils last a very long time except for the crack-o-matics. That was a defect issue. The points mechanism lasts forever. The point faces and rubbing block are the wear items. Theoretically the advance springs will weaken but it's undetectable.

The bottom line is: just test the sparks. If they are good all is well there.

On a long distance move w/my Toyota truck I was getting power loss on the hills, heavy load and pulling a trailer. I hit an auto parts store in a small town and replaced the coil, cap&rotor, plugs and I think the wires. World of difference. But it had 250,000 on it. More recently I smoked the ignition module hooking up a battery backwards. Not wanting to spend $300 on a new module I put a $40 chevy unit in. Turns out the modules are only good for 300,000 anyway. I opened up the old one. Talk about a brick shit house! The electronics were potted in a clear gel that was still gooey. BMW should build something like that. I carry a spare for the Chevy unit in the glove compartment. I give it a couple of years maybe. I carry a spare for the BMW unit on longer trips. When I ran Boyers and Dynas, I carried my points plate setup on longer trips.

Better running truck:


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Old 06-12-2013, 12:07 PM   #21
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Originally Posted by akpasta View Post
I did a little research and found where to look for the marks at static. I'll start there with a static light, then confirm advance with strobe.

Took apart right side carb to examine things, not the left side yet cuz the right looked so good. Setting float level is incredibly easy i'll do it on the left. Replaced engine oil already of course, but haven't done front disc brake drain or the rear drive shaft fluid, will get to those next.

I also really wanna check valve clearance and rocker arm clearance but I don't have a torque wrench, is it absolutely necessary to re-torque the valve cover bolt with a torque wrench?

Also going to check compression on each side as the left side seems to burn some oil and smoke a bit. How much compression is decent on these guys?

Is there a standard setting for the mixture screws on each carb?

Thanks everyone for all the advice, huge help.
I would put priority on changing the fork oil. it's simple, cheap and if not done yearly can result in a PITA fork rebuild. That is one to baseline quickly. The shaft and rear drive oils are also easy. Be careful with the fill amounts. If the seal between the shaft and rear drive is bad you will get oil transfer from shaft to drive, over filling drive. So you want to baseline this too. Just something to be aware of as an owner.

The brake fluid would be next priority. You don't want corrosion in the cylinders. Another yearly deal. Just change it. If you have a helper have them gently squeeze the lever while you open and close the bleed valve. Get a small container of brake fluid and run it all through. (it stores poorly, may as well use it all). Or you can fit speed bleeders to make it a one person job. They are little check valves that replace the bleeder nipples. Ensure the rubber caps for the nipples are in good condition. Put some silicone grease in them. I also flush the nipples with a little spray brake cleaner after I am done w/ the fluid. The fluid is hydroscopic and peels paint, causes rust like crazy. So cleaning the fluid out of the nipples and then capping them well is an anti-corrosion move. Keeps them easy to work on.

Left side commonly smokes on start up if parked on the side stand. Guess where the oil in the cylinder is going when you shut it off? Try center standing it more and see if it helps.

Compression values are in your manual. What you want is high and even both sides.

You don't torque valve cover nuts. The center one is sensitive to stripping, but it also does little if anything. Hand tighten very gently. When you have the rocker cover off, put some teflon tape on that center stud. Yellow gas pipe tape is thicker and easier to handle. Then when you put the chrome nut on later and gently hand tighten it, it won't fall off on the road. (yeah, that gently). Or use the blue small screw locktite on it. (not the ordinary blue).

You do need a torque wrench to torque the heads prior to setting the valves. So buy one. The beam and pointer type works fine for this. Cheap too. Put a mark on it with tape/marker so you don't have to read numbers. Accuracy is ample. These are awkward for some things (torquing pan screws) but fine for heads.

Get some go/no-go feeler gauges for setting the valve. Another minimal expense ($6?). Simpler to use and get excellent accuracy. Set valves stone cold.

Nominal value for air screw is in the manual. You only use it to set up for tuning the carbs.

See:

http://www.eskimo.com/~newowl/settin..._CV_carbs.html

Why do I keep referring you to your manual? I think it's Disston that has the sig line " Don't memorize what you can look up". So I don't. I could look it up in my manual or you could look it up in yours...


The relationship between static timing and full advance is fixed. If the static is correct, the full advance will fall into place, as long as the advance weights are not sticking. If you want to change where the full advance point falls, then you just change the static point. Timing light confirms it. (and is handy for other things). The spec for static will have things running right EXCEPT for the piss they sell for gas these days and your compression values. If your comression is running high and the gas octane is low, you can get knocking problems. You would retard the timing from stock to help out.


If the compression is low it indicates a worn engine. But if it'sd high, it doesn not mean it ain't worn. Carbon build up can raise the compression qhite a bit.

A Streamlight Reach works great for inspecting the piston crown and valves through the spark plug hole. You can see how much carbon you cot and if the valve lips and seats look good. The thing is not too expensive, very high quality, durable and handy as hell. There is a pic of me using mine to inspect tranny splines in my build thread. You can also look up your nose with it, which I've had to do on occasion (I walk into things). Only downside is the AAAA batteries. But they last long and can be found.


If you don't have a maintenance log, I would start one.
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Old 06-12-2013, 05:02 PM   #22
Kai Ju
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Gas cap vent

I haven't seen anybody mention the gas cap. My /7 had similar symptoms and it was because the cap didn't vent.
I was fine as long as I stayed below 70 mph, once above that it lost power. I just reached for the cap and unscrewed it a bit and power was restored. I repaired it by drilling a small hole in the cap from the bottom.
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Old 06-12-2013, 11:01 PM   #23
trabbart
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great truck,,, i have a buick riviera boattail,,,if i loose the power to burn rubber its always ignition, even the sligthest move of the distributor can make a huge difference. once i lost power due of a bad torque converter,,took me a while till i found out wat was wrong.

my airhead was iddeling nice had great power with the good looking coils, but it made a huge difference to swap them. i just dont thrust old stuff anymore. they heat up and heat gives more ohm's,,and then the heat more,,and more,,especially at high rpm when they get the full blast ,,that is when they fail or when the spark gets weak,,and when are they heated up? after a few hours,,,yes when your far from home.....

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Old 06-12-2013, 11:06 PM   #24
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As per everyone's advice, seems like I needed to go through all the basic maintenance procedures like timing, valves, carb syncing, etc.

Today I tried to sync the carbs, and failed. I could NOT get the carbs to sync. It was frustrating as hell. Something is up. I started- as Clymer says- with the butterfly screws just barely touching the levers, then one full turn in; and, the mixture screws one full turn out from all the way in.

The cylinders behave entirely different! When cylinders are firing alone (spark cable disconnected) Right side idles way higher, to get it to mellow out, I have to completely back the butterfly screw out to the point that it is not engaged at all, and back out the mixture screw 1-2 turns, at which point the idle slows but it starts smoking cuz it's running so damn rich.

At left side when running on its own, to get it to the same rpm (about 600) I have to screw the butterfly way in and the mixture screw out! It's the opposite!

Before I started fucking with carb sync both mixture screws were 1/2 out from all the way in, butterflys i dunno but it idled at around 1000-1250rpms but the left side was farting at idle and the left cylinder wouldn't idle by itself, I knew they weren't synced.

This bike got me along a 200 trip with some kinda problem, that could be spark or fuel related. Given the problems I'm experiencing I think it could be carb related? Should I just buy a rebuild kit for the carbs and replace o-rings, diaphragms, etc?

These bikes seem very serviceable and they are very fun to ride. This one is truly flummoxing me. But I just realized I forgot about float level on the left side, haven't set that yet, damn. Long days at work can mess up the memory. Could that have an effect on carb syncing?

Timing is super easy to set though!

One more thing. Does it matter to set the valve clearance before everything else? Someone told me to do that, but I don't really see why. If valve clearance were that bad, how would I have got through a 200mile trip?

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Old 06-12-2013, 11:10 PM   #25
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Originally Posted by Kai Ju View Post
I haven't seen anybody mention the gas cap. My /7 had similar symptoms and it was because the cap didn't vent.
I was fine as long as I stayed below 70 mph, once above that it lost power. I just reached for the cap and unscrewed it a bit and power was restored. I repaired it by drilling a small hole in the cap from the bottom.
Don't think it's gas cap vent. Like I said, I could ride at 70+mph for some time, the cutting out happened 50+ miles into my trip, which started out with some consistent fast freeway riding.
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Old 06-12-2013, 11:30 PM   #26
Plaka
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Originally Posted by akpasta View Post
As per everyone's advice, seems like I needed to go through all the basic maintenance procedures like timing, valves, carb syncing, etc.

Today I tried to sync the carbs, and failed. I could NOT get the carbs to sync. It was frustrating as hell. Something is up. I started- as Clymer says- with the butterfly screws just barely touching the levers, then one full turn in; and, the mixture screws one full turn out from all the way in.

The cylinders behave entirely different! When cylinders are firing alone (spark cable disconnected) Right side idles way higher, to get it to mellow out, I have to completely back the butterfly screw out to the point that it is not engaged at all, and back out the mixture screw 1-2 turns, at which point the idle slows but it starts smoking cuz it's running so damn rich.

At left side when running on its own, to get it to the same rpm (about 600) I have to screw the butterfly way in and the mixture screw out! It's the opposite!

Before I started fucking with carb sync both mixture screws were 1/2 out from all the way in, butterflys i dunno but it idled at around 1000-1250rpms but the left side was farting at idle and the left cylinder wouldn't idle by itself, I knew they weren't synced.

This bike got me along a 200 trip with some kinda problem, that could be spark or fuel related. Given the problems I'm experiencing I think it could be carb related? Should I just buy a rebuild kit for the carbs and replace o-rings, diaphragms, etc?

These bikes seem very serviceable and they are very fun to ride. This one is truly flummoxing me. But I just realized I forgot about float level on the left side, haven't set that yet, damn. Long days at work can mess up the memory. Could that have an effect on carb syncing?

Timing is super easy to set though!

One more thing. Does it matter to set the valve clearance before everything else? Someone told me to do that, but I don't really see why. If valve clearance were that bad, how would I have got through a 200mile trip?
see:

http://www.eskimo.com/~newowl/settin..._CV_carbs.html


Take me a month of sundays to explain the WHY of all that stuff. Just try it, like it says. Let the WHY come later.

If you run with a coil disconnected (like pulling the plug wire off the plug instead of shorting it out), you will do damage---to the coils if nothing else. Will fry an electronic ignition in a heartbeat.

yeah, float height matters. That determines the pressure delivered to the jets and in turn what the jets will deliver for a given air velocity. That's why you got floats. It isn't a simple float valve setup to fill the bowl, it's for pressure normalizing. Fuel pressure varies with the height of the fuel in the tank. The float bowl setup eliminates that variation.


Slow down.
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Old 06-12-2013, 11:35 PM   #27
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Thank you for bearing with me. Float level was supposed to be the first thing I did but I flat out forgot. Will be the first thing tomorrow.

I've always just disconnected the spark plug coil on my 64 Honda. You said electronic ignition, ya? My R100 is points still, is that okay or still damaging?

Thanks for the link, I'll try your method next.
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Old 06-12-2013, 11:43 PM   #28
Plaka
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Thank you for bearing with me. Float level was supposed to be the first thing I did but I flat out forgot. Will be the first thing tomorrow.

I've always just disconnected the spark plug coil on my 64 Honda. You said electronic ignition, ya? My R100 is points still, is that okay or still damaging?

Thanks for the link, I'll try your method next.
Is it a '64 honda and where is that thing anyway?

Only short the plugs, OK? coil generates thousands of volts from a resonance with the condenser. Give that no where to go and it goes somewhere anyway, punching through whatever insulation is in it's way and creating back EMPs if it feels like it. Just don't.

Valves is first thing tomorrow. Stone cold. Then timing, then play with the carbs.

Do it in order.

Slow down.
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Old 06-12-2013, 11:49 PM   #29
Plaka
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Don't think it's gas cap vent. Like I said, I could ride at 70+mph for some time, the cutting out happened 50+ miles into my trip, which started out with some consistent fast freeway riding.
could still be a vent issue. When fuel is high in the tank, there is more pressure at the carb needle jet but less air in the tank to buffer vacuum situation. As fuel gets lower less pressure to the carb but more air volume to buffer. So it's a complex relationship between fuel level, fuel consumption and venting. Just make sure the vent is clear, end of that one. If you ever see the tank bulging in the sun or hissing when you open the cap, you gotta problem.
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Old 06-12-2013, 11:51 PM   #30
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Thanks. I'll start with the valves tomorrow.
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