82 Suzuki GS650 Bogging on Acceleration

[Jefferson]

Hey all;

New to this site, and just getting back into motorcycles (after a hiatus while our kids grew up ).

We recently purchased a 1982 Suzuki GS650L. It was very cheap, but has a few glitches. Here's the main one:

The thing bogs down on moderate to hard acceleration - and I do mean badly.

I've had the carbs off, done all the cleaning, replaced the HUGE main jets with the right sized one. But we're talking bad bogging here.

Everything seems to be clean and adjusted, including the slides & needles.


The thing is driving me nuts! What do I have wrong?

Thanks!

[CORSCO]

Sounds like possible carbon build-up on the intake valves (if you are positive the carbs are right).

Try a fuel cleaner/additive to clean-up the carbon. I like Amsoil Fuel Additive or Yamaha's Ring Free. Yamaha Combustion Chamber is a more intense cleaning. It is an aerosol sprayed in the intake tract while running.

Try these items. If carbon is the problem, you will know quicker than you can run out a tank of gas.

Good luck.

[Technik]

This is a trick I've used on cars and it's worked, not sure how it'd transfer to bikes but I'll share it anyway.

We always used water to remove carbon from an engine. Don't panic, not a lot... just fill a small cup (we usually used a cap from a can of spray paint/cleaner/etc. and use a vacuum line to sip it into the engine while running. The basics of this are the fact that carbon is water soluble, and also the fact that at operating temp, you don't have to worry about the water getting in and hydrolocking the engine because it evaporates far too quickly.

I've used this on many a filthy engine before pulling them apart, and all came out with nice, clean, shiny valves and combustion chambers.

[TechTMW]

You can do that w/ motorcycles as well.

[CORSCO]

That's what the Combustion Chamber Cleaner does.

[Jefferson]

Well... I've got it running quite a bit better - due to more cleaning, etc.

I have run SeaFoam and Chemtron carb & injection cleaners through the tank (at different times). Everything SHOULD be pretty clean.


Now... today I was driving down the highway with it. The cycle has a very hard time doing 60mph - which I find hard to believe would be the case with a 650.

But every once in awhile the cycle would just bog down, lose power and cut me down to about 30 mph. Then, as mysteriously as it lost power, it would pick up again and take off.


I'm stumped.

[TechTMW]

I got nothing specific for you at this moment, but it sounds more like an electrical problem if it's intermittent like that.

[Jefferson]

I found that the #2 spark plug was not firing. And what's really weird about it is that normally you could tell, just by the sound, that one of your cylinders isn't firing. But this one - even lame - left it running smoothly, although without much power.

The cycle is running much better now, but still not perfect. I'm still scratching my head & grunting, though not as hard now.


Thanks for the advice!