Need your Carb Knowledge

Zero333 · Posted: March 8, 2009, 11:09 am Post subject: Need your Carb Knowledge

Because I more or less have none. I just picked up an 81' xs 650 with VMs on it. The bike wasn't running. I charged the battery and the thing kicked right on. It idles just fine around 750 rpms but as soon as I try to twist the throttle the bike either bogs down and turns off or it revs up and will not come back down. I will twist to lets say 1500 rpms and the thing will just run way up to 3000 and stay there. Some times it will come down extremely slow. I checked the cables and when the bike is off the throttle works perfectly, no sticking or anything. From what I have read this could mean that the bike is running VERY lean. How could this be adjusted. I read the VM manual cover to cover and realize this is most likely an issue with my needle jet and jet needle but I am looking for a confirmation from the experts here. Any other idea of what I should try before I take the carbs apart? I have never tackled carbs at this lever so I am trying to avoid the entire break down/clean/back on the bike cycle. Then again if that is what is required I am more then willing to do so.

Thanks

yamaman · Posted: March 8, 2009, 11:24 am Post subject: Re: Need your Carb Knowledge

Yeah, sounds like a lean issue. Check the easiest bits first, are the manifolds sealed? Sometimes it can be hard to get the VM's to sit right in the manifolds, so check all that out.

How do your plugs look?

Airfilter?

Then maybe time to pull the carbs down & give them a clean, take note of the sizes of everything while it's down. Some VM set ups wont run at all on these. Theres a thread nearby with a few baseine settings, make sure your somewhere near those.

Could be as simple as some old crap fuel in the bowls, seeing as it hasn't been running for a while!

You've got the manual, nothing to be scared of, just one step at a time & be patient. Have a nice clean area to work in. Do one at a time so you don't confuse yourself, enjoy!
Cheers

weekendrider · Posted: March 8, 2009, 11:28 am Post subject: Re: Need your Carb Knowledge

Start and let it idle. Spray short bursts of carb cleaner at specific areas. If it is a vacuum leak it will pick the cleaner and it will act as a fuel increasing the rpm. Intakes might be the place to start. If that doesn't produce results it may be time to take them apart.

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