Carb Problems With A GS650

[Don Lobacz]

You have CV carbs and they need a vacuum differential behind the carbs to lift the slides. The pods have reduced that vacuum. The best thing to do is put the stock airbox back on and rejet slightly for the header. I sold a GS650 last year and it ran like a dream: fast, smooth, responsive. I'm surprised that others who have had problems rejetting CVs haven't jumped in on this thread. I may still have a 650 airbox sitting around somewhere, too.

[Dano]

It accelerates somewhat decent. The idle is fine. There is no miss or hesitation. It tops out at 60 no matter if it is full throttle or little throttle. Top gear, 60mph is as fast as it will go. Also, the needle jets have not been shimmed.

Dano

[Dano]

If you do have a stock airbox, let me know what you want for it. I really do need the stock airbox. I am having alot of problems finding any kind of parts for this bike in the area (southeast virginia). Thanks for the info.

Dano

[Don Lobacz]

You can check the diaphrams and slide action by blowing compressed air into that curved, oblong orifice on the top back of the carb throats. The slides should rise easily and consistently.

[KEITH KRAUSE]

You have CV carbs and they need a vacuum differential behind the carbs to lift the slides. The pods have reduced that vacuum. The best thing to do is put the stock airbox back on and rejet slightly for the header. I sold a GS650 last year and it ran like a dream: fast, smooth, responsive. I'm surprised that others who have had problems rejetting CVs haven't jumped in on this thread. I may still have a 650 airbox sitting around somewhere, too.

Thanks for jogging my memory Don.
Dano, when you install pod filters on a bike with CV carbs, you have to drill out the vacuum orifice leading to the diaphragm chamber. A jet kit gives you the drill along with the adjustable needles.
A CV carb will idle and accept MAYBE a little throttle if its vacuum is compromised or the diaphragm is failing. It will not accept any more throttle than just above "idle". That's why your bike tops out at 60 mph in top gear regardless of how much throttle you give it.
I knew it was probably a diaphragm/vacuum problem but forgot about needing to drill the vacuum hole. That's what makes forums good. You get everyone involved and one thing leads to another. Again, Don gets the atta-boy here.
You sound like you would be happy with a stock air box and just increase the main one full size to allow for the pipe and maybe a 1/4 turn or so out on your mixtures screws. Needle adjustments are probably not needed.

[Dano]

I do not know exactly where on my carbs I need to drill.If you know could you please let me know.Also are the jet sizes i have right now (47.5& 125) going to be alright after I drill?Can i drill without buying a jet kit?I think I can just shim the needles and drill out the orifices.What do you think?I also wanted to thank you for all the useful info you've been a great help. So THANKS.

Dano

[KEITH KRAUSE]

I do not know exactly where on my carbs I need to drill.If you know could you please let me know.Also are the jet sizes i have right now (47.5& 125) going to be alright after I drill?Can i drill without buying a jet kit?I think I can just shim the needles and drill out the orifices.What do you think?I also wanted to thank you for all the useful info you've been a great help. So THANKS.

Dano

There is a hole that allows vacuum into the diaphragm chamber. This hole has to be enlarged. The hole has to be a certain size and drilled correctly.
This info is in the jet kit and because there could be specifics, I don't want to guess and lead you to doing something that would ruin parts in your carbs. Enlarging the vacuum orifice is necessary for throttle response, so your jet size choices are a seperate issue. My previous post is the jet sizes I would try for starters if you don't buy a jet kit.
Someone here who has done the job correctly may help you with the drilling, or you might post a topic for this info? Just be sure of who's helping you or the parts will be ruined.
You can drill without a jet kit, but you'll still have to make your stock jet needle work. Simply finding the correct thickness spacers and raising the needles may or may not be enough. Some jet kits include an adjustable needle that is also TAPERED differently. They change the shape of the needle because it performs better. I have no hands on experience with your model so I can't say if you'll be OK just by shimming up the needles. Personally, I would buy the jet kit.

[Dano]

OK, I've syncronized, set the floats to 21mm. Drilled out the vacuum orifice, cleaned all the jets, raised the needles, checked all 4 plugs and still just 60mph top gear. What else could it possibly be.???? I even taped the pod fileters half closed. It seems that no matter what adjustments I make, all I can get out of her is 60mph. I'm totally lost. It starts fine, idles fine. Acceleration could be better, but it's not too bad. Is there anyway the voltage regulator could cause any problems? Anything else that could? I would like to just give up, but I'm obsessed now. I want to be able to get it to run like it should. I know it's going to be fun once it's right. So any other suggestions would be great. Thanks

Dano

[KEITH KRAUSE]

Where did you get the info to drill out the vacuum holes? What did you do in raising the jet needles? By your posts, I have to believe there's something wrong with your carbs. Vacuum related. Your choice of mains and pilot jets would not result in a 60 mph top speed.

[Dark Jedi]

It may be time to read your plugs again, too. The plugs tell all...

Check your spark on all plugs, you should have a fat blue spark from every plug.

Check your advance timing, if applicable. (83, that has the electronic timing, dosen't it?)

Run screaming from the garage and have a beer.