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Old 09-25-2012, 08:39 AM   #541
blaine.hale OP
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What's funny is that I've gotten so used to the r90 stock setup and how to use them in pair with some engine braking that when I hop on my brothers r1200gs or that k100 I used to have, I get myself in more trouble with their modern setups.
Tight brakes scare the crap out of me. I've actually locked up the r90 front brake no problem in an emergency....maybe it's just my weight or maybe it's the rebuild and braided lines but I really haven't complained much about the braking power.
The only time I've felt myself wanting more braking is when I'm fully loaded down on a 2 week trip and behind 2 r1200gs bikes. They love to engine brake and stop on a whim, not having to panic and grab the brake as hard as possible would be nice. I stop just fine, but I wouldn't mind more space between us after said stop :) Makes your butt hole pucker up a bit.

I was actually wondering about that 17mm kit...I've heard in the past that the lower sized ones will give harder braking and the larger will give a smoother feel.
Also, I'll just be using the old stock iron drilled disks.

*Just to keep the thread moving. I recently put points back in the bike because one cylinder was running way cooler than the other and carbon fouling plugs left and right. The running cool portion of that was a problem since day one of the boyer being in there.
Slapped points in, set gap and without even properly timing it, she fired up quicker than the boyer and ran fantastic. I know it's set a little advanced so I'll time it tonight.
I haven't ridden enough to see if that solved the issue but the already blackened plug I had in that cylinder started to lose some of that carbon and that side no longer craps out a black cloud when starting...crossing my fingers. Once that's resolved, THE HOSKES GO ON!!
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Old 09-25-2012, 09:29 AM   #542
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Just to set the record straight, with twin discs a 17mm MC will result in wooden brakes with little feel , a smaller MC will give you a progressive brake with feel and which you can safely use without the risk of locking. The BMW handle bar MC looks stock and takes out the crappy stock cable set up. BMW engineers did not get everything right first time and if you want to use your bike, the stock 35 year old braking system does not really cut it in modern traffic.
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Old 09-25-2012, 07:54 PM   #543
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Trying to to bisect this carbon fouling issue further. I'm back on points but that seems to have not resolved it. It seems the cylinder in question has noticeably less compression.
Electrical seems to be ruled out. Anything else to look for before pulling the top end?
Air leaks and clogged filters may sometimes cause this as well, right?
Anything with the valves that can cause lost compression and carbon fouling? I've check torque on the cylinder and its all as tight as should be. Any small things to look over before getting to the large things?
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Old 09-25-2012, 08:31 PM   #544
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Quote:
Originally Posted by blaine.hale View Post

It seems the cylinder in question has noticeably less compression... Any small things to look over before getting to the large things?
First try checking compression. That's easy. If one side's different do a leak down test before disassembling things to see what the problem really is. If nothing's obviously wrong there try switching spark plug leads. Leave the HT wires connected to the coil, but switch which cylinder they're connected to. See if the problem moves. No? Try switching carbs one side to the other. Did the problem move? No? Is your breather blowing a lot of oil?
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Old 09-28-2012, 07:06 AM   #545
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Right side (the side in question) actually has more compression than the left.


Left side read a little higher on the second test so the cylinders only were 3-4 off from each other at most.


The right side plug now looks like it's wet and black instead of bone dry carbon. I pulled it while the engine had run 5 min prior but that's definitely oil (gas would have dried up by the time I took the picture.)


So here's what happened. I pulled off both carbs. I didn't check before adjusting but I'm pretty sure both or 1 carb was on position 2 on the needle when r90 is supposed to be on position 1. The right side carb and boot had a fair amount of oil from the breath (this was updated to reed when the engine was rebuilt) and there was an air leak with oil/gas covering the inside front of the down tube.
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Old 09-28-2012, 07:25 AM   #546
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Sounds like breather fumes fouling the plug. Try routing the breather line somewhere else and see if that fixes.
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Old 09-28-2012, 07:32 AM   #547
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Originally Posted by Wirespokes View Post
Sounds like breather fumes fouling the plug. Try routing the breather line somewhere else and see if that fixes.
Exactly what Fred was suggesting as well. I shall give that a go :)
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Old 09-28-2012, 07:37 AM   #548
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As a side note Blaine .. How do you find the the Acron Compression Tester ... I was about to order the exact model you have.
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Old 09-28-2012, 07:53 AM   #549
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As a side note Blaine .. How do you find the the Acron Compression Tester ... I was about to order the exact model you have.
I picked it up at advanced auto. Eh, it's alright. It's pretty difficult to use on my Bultaco and a bit awkward on the BMW. I wish it had a quick disconnect on the spark plug end of it, that would make it great. I really want a solid tube attachment for the airhead too, the hose is awkward.
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Old 09-28-2012, 08:10 AM   #550
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Good to see that your mechanicals are in good order. 3-4psi difference between cylinders ain't no thang. Did you try measuring them with carbs off? A lot of people on here say it makes no difference leaving the carbs on if you crack the throttle open, but I've tried with and without and there WAS a difference, at least on the bike I tried it on. If you're so inclined, try both sides with the carbs removed and see if there's a difference. Back to your problem, it now comes down to spark, mixture, and/or breather oil. Attack.
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Old 09-28-2012, 08:18 AM   #551
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Originally Posted by Airhead Wrangler View Post
Good to see that your mechanicals are in good order. 3-4psi difference between cylinders ain't no thang. Did you try measuring them with carbs off? A lot of people on here say it makes no difference leaving the carbs on if you crack the throttle open, but I've tried with and without and there WAS a difference, at least on the bike I tried it on. If you're so inclined, try both sides with the carbs removed and see if there's a difference. Back to your problem, it now comes down to spark, mixture, and/or breather oil. Attack.
I definitely pulled the carbs off for the test.
I've gone from electronic ignition, back to points for the spark test and that seems to have moved it from carbon fouling and crapping black smoke to NO black smoke and an oil/rich plug...not necessarily fouled.
My best estimate at this point is that it was a nice combo of things. Bad boyer ignition causing weak spark, too much oil in the carb cause it to cool even further with that weak spark and a possible air leak.
All of the above, with the exception of the excessive oil has been remedied so I'm going to ride for a 100 or so miles with the breather redirected and fiddle with the mixture screw to see if I can't bring the white back out of that plug!

Just to add to all this brain storming, she starts ridiculously easy and just runs fantastic now that I'm back on points. When I say starts easy, I mean I can put it on chock and actually KICK it over in 1 kick if I get it in the right position...and everyone thought the kickstart was useless.
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Old 09-28-2012, 10:34 AM   #552
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OOoo. After adjusting that needle height, she starts with no choke! It hasn't done that since before the rebuild. That, alone, makes me happy.
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Old 09-28-2012, 10:40 AM   #553
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Originally Posted by blaine.hale View Post
OOoo. After adjusting that needle height, she starts with no choke! It hasn't done that since before the rebuild. That, alone, makes me happy.
Now take that drain tube and just lay it into the center of the airfilter. You might have to affix it with a twit tie to the metal support of the filter ... but it can be done. I'll bet it clears up then ... and to be honest, having an 'oil soaked' airfilter really isn't that bad (but it will shorten the useful life of the filter). Changeing one of those breather valves is a PITA. I can drop by on the way home if you need it ...
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Old 09-28-2012, 10:46 AM   #554
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Quote:
Originally Posted by blaine.hale View Post
OOoo. After adjusting that needle height, she starts with no choke! It hasn't done that since before the rebuild. That, alone, makes me happy.
If it starts cold with no choke then it be rich. Big time. This is one thing I agree with the shaft on. Starting cold without choke is not a good sign. That means that once it's hot (where you spend the majority of your riding time), it's running WAY rich.
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Old 09-28-2012, 11:01 AM   #555
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Well that brings up something new then, because the mixture is at the recommended 1/2-1 turn out (I usually land around 3/4 turn) on both carbs. Crap. More fiddling tonight.

*edit: The mixture hasn't been touched since the needles were corrected...that's probably why.
*double edit: Fred, I won't be there till later tonight...having a cookout for my work team.
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blaine.hale screwed with this post 09-28-2012 at 11:13 AM
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