Mixture Setting

[JTGS850GL]

Dude... Is that chewing tobacco?

Seriously, if that's what built up in a short time after a complete strip and dip, then you've got some serious fuel contamination problems. Time to clean the carbs again. What did you use for float bowl gaskets?

[AJ]

Dude... Is that chewing tobacco?

Seriously, if that's what built up in a short time after a complete strip and dip, then you've got some serious fuel contamination problems. Time to clean the carbs again. What did you use for float bowl gaskets?

You might consider adding an in-line fuel filter as well.

I didn't respond to the gunk getting into the float bowls because crap in the bowls will only clog jets, making the mixture lean (or no fuel at all for clogged jets), and that won't foul the spark plugs.

Remove your petcock, fill your fuel tank with some nails and screws and shake the heck out of it, then rings well. Next, seal the holes in the tank, pour some Naval Jelly from the hardware store in the tank, fill it with hot water and let it sit for a few hours.

[ned-999]

Very clean looking scoot, Ned. Always nice to see people's bikes.

Fouled plugs occur from:
1) too much gas (rich mixture)
2) too little air (rich mixture)
3) poor ignition system (weak spark)
4) poor oil sealing (oil fouling)

3 & 4) Verify that the ignition is good and that you're not burning oil.

1) Too much gas: If you're running stock jets and haven't raised the needles, that's probably not the problem. Plus, open pipes and/or higher flowing air filter usually help you flow more air, requiring you to increase the main jets and possible change or raise the needles to enrichen the mixture back to correct levels.

2) Too little air: Real K&N filters are a bit of a pain. If you over oil them, they won't flow enough air, thus acting like a choke and making the mixture overly rich. You may need to wrap those filters in paper towels to remove excess oil. Or, if those are Chinese copies of K&N filters, then they are regular paper filters and probably should not be oiled at all! If they are indeed paper filters and you did not oil them, did you ever get them wet? Paper fibers swell after getting wet and the filters will be ruined even after they dry out.

Given your descriptions above, I'd recommend replacing (or cleaning) the spark plugs, verify the ignition (strong spark), then remove the air filters and see if the condition improves. Running without filters is not a great idea, but running around for an hour won't hurt too much.

Well I have noticed that the inlet rubbers actually flex when the engine is running which did surprise me because i didn't think there was that much vacuum ! You can see them pulsating quite a lot in rhythm with the engine. Is that normal ??

[ned-999]

Dude... Is that chewing tobacco?

Seriously, if that's what built up in a short time after a complete strip and dip, then you've got some serious fuel contamination problems. Time to clean the carbs again. What did you use for float bowl gaskets?

The gaskets are black rubber, I can see why you asking there does seem some strange stuff around the gasket seating area. I think the advice re cleaning out the tank properly is a priority !! and re cleaning the carbs..... again

[ned-999]

You might consider adding an in-line fuel filter as well.

I didn't respond to the gunk getting into the float bowls because crap in the bowls will only clog jets, making the mixture lean (or no fuel at all for clogged jets), and that won't foul the spark plugs.

Remove your petcock, fill your fuel tank with some nails and screws and shake the heck out of it, then rings well. Next, seal the holes in the tank, pour some Naval Jelly from the hardware store in the tank, fill it with hot water and let it sit for a few hours.

There is a in-line filter. So im assuming what ever it is in the gas somehow solidifies in the float bowl !! The nails and screws sound a drastic but il give it a go. Thanks

[ned-999]

There are a few pictures and a video of it running here :-

http://s1287.photobucket.com/user/ned-999/library/GS750E%20Chopper

[mvalenti]

Ned,

You definitely need to dip those carbs again, 24 hrs each min. Then blow them all out. While they are soaking inspect your valve clearances and reshim if necessary. Empty out your gas tank, buy some BB's and pour them in the tank, fill 1/4 with hot soapy water, cap on and shake the heck out of it. if your seeing some rust come out, then you may need to seal the tank. Jetting the carbs is a must for any modifications to the stock exhaust and intake.

[AJ]

Well I have noticed that the inlet rubbers actually flex when the engine is running which did surprise me because i didn't think there was that much vacuum ! You can see them pulsating quite a lot in rhythm with the engine. Is that normal ??

Definitely try removing the air filters and see if that keeps the plugs from fouling. Those rubber intake manifolds should be pretty stiff when the carbs are inserted, although the rubber is not super thick.

Agree with mvalenti and others who recommend another cleaning of the carbs (but dirty carbs with plugged jets lead to LEAN condition, and plugs don't foul when the mixture is lean).

Also, recommend you install some type of strap to support the weight of your carbs since the airbox has been removed. I used a heavy weight zip tie to hold the carbs up. It's barely noticeable.

[ned-999]

Definitely try removing the air filters and see if that keeps the plugs from fouling. Those rubber intake manifolds should be pretty stiff when the carbs are inserted, although the rubber is not super thick.

Agree with mvalenti and others who recommend another cleaning of the carbs (but dirty carbs with plugged jets lead to LEAN condition, and plugs don't foul when the mixture is lean).

Also, recommend you install some type of strap to support the weight of your carbs since the airbox has been removed. I used a heavy weight zip tie to hold the carbs up. It's barely noticeable.

Will do the cleaning. Ive got a bespoke threaded rod that screws to the frame from the carb rail so its pretty rigid. The air filters do look like they are restricting the air intake if they are noticeably deforming on every intake stroke. Il take them off and see if they still do !!

[gustovh]

You should see/feel an intake pulse on the carb mounts when running, normal for a 16 valve motor.
V

[ned-999]

Hi ive taken them all apart and cleaned them out ..... Just on thing puzzling me. Ive been searching the forum for info on jet sizes which I have found. So the stock jet is 112.5 and the jet I have in is 147.5 which I think is way too big as follows.

Exhaust: +4 main jet sizes for no muffler (open headers)

Intake: K&N Pod Filters = +4 sizes Main Fuel Jet

Equals: +8 main fuel jet sizes above baseline Subtract: -2 main fuel jet size per formula

Equals: +6 main fuel jet sizes due to modifications. Well what is 6 sizes up on jet sizes ???? I recon its 130 can anyone confirm that for me please.

Thanks

[ned-999]

Well they are all back together with 130 jets. I've yet to take it our but it's now backfiring on one cylinder. All I've done is clean out the carbs and put in smaller jets. Are the jets too small now.

[Steve]

So the stock jet is 112.5 ... Well what is 6 sizes up on jet sizes ???? I recon its 130 can anyone confirm that for me please.

Thanks

Six sizes up from 112.5 would be 127.5.

Well they are all back together with 130 jets. I've yet to take it our but it's now backfiring on one cylinder. All I've done is clean out the carbs and put in smaller jets. Are the jets too small now.

What are your spark plugs telling you?

I can't see your plugs from here, and you are thankfully out of earshot, so you will have to rely on the appearance of your sparkplugs.

.

[ned-999]

Think I've found the problem that is contributing. Very weak spark and when you turn the ignition on all four plugs spark, and I got a shock from the key. The coils must be earthing somewhere. At least I have something concrete to work on.