vwcorvette
vwcorvette SuperDork
8/4/18 4:39 p.m.

Finally got the bike together enough to start it. Only runs on left cylinder. I can get right cylinder to run but I have to cover the carb opening with my hand to choke it. Checked valve clearances: in spec. Good spark. Left cylinder, the firing one, low compression. Right cylinder, non running, high compression. 

Carbs have been rebuilt.  Currently no exhaust at all. Needs rubbers between carbs and airbox. 

Thoughts?? 

Ransom
Ransom PowerDork
8/5/18 12:10 p.m.

I have to guess either a rebuilding issue with the carbs, or just a lack of balance. Are they really, really matched for idle position and cable pull? Any chance that some passage(s) in the RH carb didn't get cleaned? (or got aggressively cleaned with a wire or something that opened a hole too far?)

I don't know the carb type, but do you know the tricks of things like putting the same size wire under both butterflies (or slides) with the bike not running, and making sure they both get pulled free simultaneously as you open the throttle? That is, if the wires are held by the butterflies or slides and you pull gently on the wires, they should both come free at the same instant as you twist the grip.

The fact you can make it run by "choking" it makes it pretty clear that there's just something different about the two sides. Matching settings is the easy check. After that I think I'd be sticking bits of the RH carb back in the ultrasonic cleaner (and if it hasn't been there, here's your excuse to grab an HF ultrasonic cleaner!)

Bummer about the lower compression on the left.

Appleseed
Appleseed MegaDork
8/5/18 12:11 p.m.

The air leak due to no airbox gaskets might be screwing with them. I'd probably crack open the carbs again for cleaning. It's easy to miss something. 

Rusnak_322
Rusnak_322 Dork
8/6/18 8:44 a.m.

how is the diaphragm on the carb on the side that is not running? Will it stay running with starting fluid? 

vwcorvette
vwcorvette SuperDork
8/6/18 6:12 p.m.

I think many of you are on the right path. Gonna pull the carbs and go thru them again. 

8valve
8valve Reader
8/6/18 7:09 p.m.

Swap the pilots R to L and see what happens.

44Dwarf
44Dwarf UberDork
8/7/18 6:12 a.m.

FYI:  Do not use modern carb cleaner anywhere near the rubber diaphragms it will swell them up yes they return after it flashes but it messes with them. if you need to clean the slide spray it on a rag then wipe.  It does sound like a balance issue. if you pulled the rack apart the common mistake is the small but stiff spring between the two carbs getting lost or put on the wrong side of the balance adjuster.  If even seen bike shop mess that up.  On-line micro-fishe helps out a lot with how things go.  bike bandit, cheap cycle parts etc.

 

vwcorvette
vwcorvette SuperDork
8/7/18 10:19 p.m.

Found a video showing operation of the carbs. Missing linkage between the throttle bodies or my buddy assembled them incorrectly. Will know more in a day or two. He's rechecking the carbs for blockages and such. 

44Dwarf
44Dwarf UberDork
8/8/18 11:56 a.m.

Just in case you do find you need diaphragms JBM industries makes them.   http://jbmindustries.com/

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