Please Help Jet my GS for Open Exhaust

[Canadian Eh]

I've searched but haven't found info I'm looking for here.
So i have rebuilt the carbs with spec jets (cant recall size) on my '82 GS650 GLZ BUT have now chosen to go a different direction with this build and Bobbify. I have [basically open] Reinhart exhaust and the original airbox with foam filter. Please help me calculate the jets and give me all the recommended settings to tune properly for this setup at sea level (Canadaian west coast eh). It starts and warms up with choke fine and revs fine sitting but after about 20-30 seconds riding it starts to die then dies. It will start again (barely) with choke but hates running again. I then hit the highway to give 'er heck but it pops, farts and feels like its running on 1 cylinder Then dies again. DUH, I says to myself - jetting.

Thanks guys n Gals,
Trev

 

[Big T]

Post this in the Carb subforum

 

[zed1015]

Doesn't sound like an actual jetting issue although with the open pipe you should increase the main jet a size or two but running slightly lean won't cause the problem you are having.
It sounds like you are having fuel supply issues which may be fuel tap , kinked fuel hose or float height related etc.
If this only arose after having the carbs apart then something done there or incorrectly assembled is most likely the cause.

 

[Canadian Eh]

Doesn't sound like an actual jetting issue although with the open pipe you should increase the main jet a size or two but running slightly lean won't cause the problem you are having.
It sounds like you are having fuel supply issues which may be fuel tap , kinked fuel hose or float height related etc.
If this only arose after having the carbs apart then something done there or incorrectly assembled is most likely the cause.

Thanks, I agree its something fuel related for sure. By fuel tap I suspect you mean the petcock? Ijust put a new OEM one on so I doubt thats it. Float height and jets is what I'll have to work on next. I really appreciate the reply!

 

[zuluwiz]

When was the last time you checked the valves?

 

[Canadian Eh]

When was the last time you checked the valves?

I recently had a bike mechanic shim the valves so they've been checked.
cheers

 

[Canadian Eh]

Doesn't sound like an actual jetting issue although with the open pipe you should increase the main jet a size or two but running slightly lean won't cause the problem you are having.
It sounds like you are having fuel supply issues which may be fuel tap , kinked fuel hose or float height related etc.
If this only arose after having the carbs apart then something done there or incorrectly assembled is most likely the cause.

All fuel issues have been checked and remedied. New Petcock, no kinked lines, float heights adjusted and a dynojet kit installed. Issue persists.
Is there any possibility there is an electrical issue that only shows an issue when you get riding? - ie you idle and rev fine but get out on the road and it starts bagging. Mechanic isnstumped and wants to try a different cdi ignitor. I have no idea

 

[Guest]

Mechanic isnstumped and wants to try a different cdi ignitor. I have no idea

If your "mechanic" wants to try a different "CDI", you need a new mechanic. That bike never had a CDI.

Also, be warned that there are some on the forum that will not give any support after you mention "open exhaust". They might mention how socially irresponsible it is, and then not give any further support, or they will just ignore any other requests you might have. I sort of agree with them about loud exhaust, but I will mention that with a stock airbox, you might not need to re-jet. Maybe one size up, maybe none at all.

 

[bull958]

Make sure your tank is venting.

 

[Rich82GS750TZ]

Make sure your tank is venting.

I was thinking the same. Easy enough to check. Run the bike w/ the gas cap off. Of course you don't want a lot of fuel in the tank for this exercise. If the dying-in-20-30-seconds-of-riding goes away, rebuild or replace your gas cap, as it isn't venting.

 

[rphillips]

Vent is sure something to check out, but really wouldn't think the tank not venting could cause a problem within 20 or 30 sec. Easy to check to know for sure.

 

[salty_monk]

I would suspect air leaks around your airbox or at the boots where it joins the cards or the intake boot O rings. If you still have the original airbox then the jetting changes for an exhaust are not that big (not enough to cause what you are talking about).

Did you oil the foam filter? Running it dry might lean it out enough to cause those issues I guess.....

For the pipe just go up a step (5) on the main jet and raise the needle one notch (I believe it's still adjustable needles in Canada) then tune the air corrector screw 2.5-3 turns out from lightly seated most likely.

 

[Canadian Eh]

Hi all. THANK YOU for your replies. I will let you know what has been happening since you replied - I haven't checked back in a long time.
Since 2 mechanics have suggested that dynojetting would fix the problem i bought a kit and installed to no avail. Since THAT waste of time, I have found the Suzuki GS Guru locally who said I could pick his brain all I want. Just as a couple of you have mentioned, he mentioned gas cap venting but also said the stock beige coils are garbage and have been an issue since the bikes were young. I just ordered new (green) 3ohm Dynatek coils so will install them soon and let you know how those 2 things help.

 

[rphillips]

Well, I guess I've been lucky, never a problem from a stock Suzuki coil. Have a set of Accell on my GS1100E that was there when I bought it, and wish it still had the OEM.,

 

[Canadian Eh]

I would suspect air leaks around your airbox or at the boots where it joins the cards or the intake boot O rings. If you still have the original airbox then the jetting changes for an exhaust are not that big (not enough to cause what you are talking about).

Did you oil the foam filter? Running it dry might lean it out enough to cause those issues I guess.....

For the pipe just go up a step (5) on the main jet and raise the needle one notch (I believe it's still adjustable needles in Canada) then tune the air corrector screw 2.5-3 turns out from lightly seated most likely.

It is a new air filter that was pre-oiled and I have brand new boots that connect to the carbs. Thanks for the set-up tips

 

[Canadian Eh]

Well, I guess I've been lucky, never a problem from a stock Suzuki coil. Have a set of Accell on my GS1100E that was there when I bought it, and wish it still had the OEM.,

Maybe you have been lucky - I sure haven't. Perhaps certain years were a problem then the issue was remedied? He worked for Suzuki when the bikes were new and said they replaced them often only a few years after new - they would overheat and get dark goo on them or something?

 

[Canadian Eh]

Vent is sure something to check out, but really wouldn't think the tank not venting could cause a problem within 20 or 30 sec. Easy to check to know for sure.

Definitely my first test!

 

[Canadian Eh]

If your "mechanic" wants to try a different "CDI", you need a new mechanic. That bike never had a CDI.

Also, be warned that there are some on the forum that will not give any support after you mention "open exhaust". They might mention how socially irresponsible it is, and then not give any further support, or they will just ignore any other requests you might have. I sort of agree with them about loud exhaust, but I will mention that with a stock airbox, you might not need to re-jet. Maybe one size up, maybe none at all.

Hi, yes, I have been told by others that the exhaust won't affect the jetting much at all - also been told that the stock jetting was a little on the large side for richness

 

[Rich82GS750TZ]

- also been told that the stock jetting was a little on the large side for richness

Never heard of that. I’ve always read that, if anything, the stock jetting is undersized, causing a slightly lean condition. :-k

 

[rphillips]

Yep, I'm with him ^^^^, that's what I've always heard, did it for EPA regs., everything was always jetted lean.