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Fill it with wires!
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Discussion Starter #81
Went back out and tried again. This time I got all of the carbs pretty well synced together. But when I blip the throttle the RPMs just hang for a while before returning to idle, which definitely feels wrong.

https://youtu.be/mCz820pEgRU

(Psst, is there a way to embed videos?)
 

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Fill it with wires!
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64 Posts
Discussion Starter #82
Based on a suggestion from Reddit I went out and ran a compression test.

All of these are with the carbs installed and the air filter box off. Numbering 1 to 4, left to right from the riders perspective. Used a MAC brand gauge that I haven't used before.

Engine cold:
1 - 120psi
2 - 130psi
3 - 130psi
4 - 120psi

Engine warmed up (~190F)
1 - 105
2 - 135
3 - 135
4 - 105

Ran again with a Pitsburgh guage:
1 - 55
2 - 65
3 - 65
4 - 50

Ran again with MAC gauge and some oil in the cylinder:
1 - 180
2 - 195
3 - 210
4 - 160
 

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Fill it with wires!
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Discussion Starter #83
So the manual shows ~210psi as typical... These cylinders are almost half that. And having the compression go up so much after adding oil points to the rings being totally shot.

It looks like even if I get the bike all buttoned up and running, I'm in for an engine rebuild shortly.

I'm not sure what the next step is going to be. I can toss the thing back together, and if I'm lucky sell it for half of what I paid. I can work on making it look nice and then sell it, but that feels scummy to do and is a lot of effort. Or I can go through with the engine rebuild, sink another $400 of piston rings into it and just hope that I have a working bike on the other side...
 

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Fill it with wires!
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Discussion Starter #84
More thinking on the compression test...

If the compression was really that bad, surely I would have noticed oil in the exhaust, even at idle? I say that because someone mentioned that maybe the hose leading up to my compression tester was long enough to distort the values. Even if the engine is just "tired" I would rather get the bike together and spend some time on the road before deciding to keep it and rebuild or get rid of it.

Here is a picture of the compression test setup, the tube to the gauge is about two feet long and the release valve is at the gauge.
 

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I haven't read the whole thread, and don't know what was suggested, but did you remember to open the throttle while cranking the motor over during the compression test?
 

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I'm glad you figured out something even if it isn't great news. I admire your determination to figure this out. You may not have noticed any oil in your exhaust I did notice something when I watched your carb sync videos, you're getting exhaust in your crankcase. I've never seen smoke come out of my crankcase breather hose like yours does, if that is exhaust. Would seem like that would point to bad rings, right? Also I commented on your vacuum numbers being really low, does compression directly effect that as well? Questions for Google or a more knowledgeable forum member.

Good luck and keep us posted.
 

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But when I blip the throttle the RPMs just hang for a while before returning to idle, which definitely feels wrong.
Idle mixture screw wrong setting, make it richer.
I have 3 turns out when I'm not wring, factory is 2.5 turns.

Or some dirt in the carb... happens sometimes...

For your compression issue - check if the valves a not leaking.
 

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Fill it with wires!
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Discussion Starter #88
I guess I missed getting an email notification?... Oh well. The updated site looks nice.

It's been about two months, I've switched jobs and am slowly working my way back to having time for this bike again.

I haven't read the whole thread, and don't know what was suggested, but did you remember to open the throttle while cranking the motor over during the compression test?
I didn't the first time. And now it's been long enough that I'm not sure if I went back and had the throttle open. I do know to do that now though, so thanks!

I'm glad you figured out something even if it isn't great news. I admire your determination to figure this out. You may not have noticed any oil in your exhaust I did notice something when I watched your carb sync videos, you're getting exhaust in your crankcase. I've never seen smoke come out of my crankcase breather hose like yours does, if that is exhaust. Would seem like that would point to bad rings, right? Also I commented on your vacuum numbers being really low, does compression directly effect that as well? Questions for Google or a more knowledgeable forum member.

Good luck and keep us posted.
Thanks for the encouraging words, and I'm very appreciative for your notes on the crankcase breather. I suspected that it was blowby before, but knowing that it doesn't happen for you pretty much confirms it. I'm sure now that the rings are shot.

Idle mixture screw wrong setting, make it richer.
I have 3 turns out when I'm not wring, factory is 2.5 turns.

Or some dirt in the carb... happens sometimes...

For your compression issue - check if the valves a not leaking.
Thanks. I tried with 3 turns out too it didn't seem to help (it actually didn't seem to change at all?!)
I'm not sure how to check the valves.. But that leads to my next point:

I'm looking over the manual now to begin stripping the bike down and pulling the engine. If I can change out the rings (and that's about all that it needs) and get it back together, then maybe I'll have a better shot at getting this thing on the road?
 
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