GS650 missing at 5k rpm

[rakos]

Hi all,
I am new to GSResources. Working on restoring '82 GS650L. Runs pretty good up to 5K, then major sputter, miss, lurch. I am about 1/2 trottle (and will not run better for any faster throttle opening).
Cleaned the heck out of the carbs. Boots seem to be ok, although the filter box was reduced by an inch or so otherwise would not fit into crevice.
Only other clue is that the spark plugs seem to indicate rich mixture.
Would appreciate any help.
John, Ottawa, Canada
john@rakos.com

[tom203]

Another 650 owner?? Welcome. What do you mean by "filter box was reduced by an inch ..etc" ??? When you cleaned carbs did you check main jet size- sometimes PO's get creative?
Trying running in "pr" spot on petcock to ensure enough fuel is being delivered to carbs at this throttle setting (yeah, I know you said it looked rich) also loosen gas tank cap just in case a vacuum is restricting fuel flow.
Ignition timing is fully advanced by about 3k, but never hurts to check that mechanical advancer is not stuck.

[BassCliff]

Greetings and Salutations!!

Hi Mr. rakos,


30+ year old bike need maintenance, a lot of maintenance. If you are here you probably have a 30 year old motorcycle that needs about 20 years worth of maintenance. You'll find all kinds of helpful tips, procedures, manuals, diagrams, "how-to" guides, etc, in the links below. Let's get started.

Let me dump a TON of information on you and share some GS lovin'.

I just stopped by to welcome you to the forum in my own, special way.

If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....

Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...



Please Click Here For Your Mega-Welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike!

More links to helpful threads in the forum:
Help! Your Bike Won't Start
DON'T DO THESE THINGS
Help! Your Bike Won't Run Well
Oh God! Pods!


Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff

[Freebeer]

Hi rakos,

I'm also having a similar issue (82 650GL, same as yours). Just got done re-building and cleaning the carbs fully.

I have tried running the bike on prime, and that didn't help, so it shouldn't be a vacuum issue. The main fuel line down to the carb is very large and not kinked, so that shouldn't be a problem with fuel delivery.

This weekend, I will be getting a cover for my airbox to get that all sealed up, but I doubt that is a huge issue since it ran OK last summer (didn't run great, but better than it is now).

Keep us posted on what you find out, and I will do the same.

[tom203]

Hi rakos,

I'm also having a similar issue (82 650GL, same as yours). Just got done re-building and cleaning the carbs fully.

I have tried running the bike on prime, and that didn't help, so it shouldn't be a vacuum issue. The main fuel line down to the carb is very large and not kinked, so that shouldn't be a problem with fuel delivery

OK, but did you check to make sure gas tank cap was not causing vacuum buildup- restricting fuel delivery (even in prime) ?
By 5k rpm, it's all up to main jet area- you need fuel and those CV diaphragms to lift and allow air to flow generously or the motor will start wheezing.

[Freebeer]

Hmm...Great question.

I will next test to see if the motor bogs with the gas cap off the bike. I will have to wait until Monday morning to test, as I am going to Las Vegas for the weekend

The last thing that I did to the bike was to take apart the gas cap and run compressed air through the little hole at the top of the cap to make sure it wasn't blocked. Maybe I didn't reassemble it correctly.

[Dave8338]

Either something isn't clean somewhere OR you have intake o-rings to replace.

ALSO... these 650s WILL NOT run correctly on stock jetting, with an open air box, drilled air box, dried and shrunken anything. They NEED to be sealed up tight, tighter than my 850 for sure. Also, something as simple as an under-oiled or over-oiled foam filter, will change how they run.

Welcome to the forum.