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Carb Jetting

  • Thread starter Thread starter Wingnut
  • Start date Start date
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Wingnut

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:D
I had an unusualy good experience with carb mixtures today that I thought I would share. I bought this GS850G a few months ago, never rode it, disassembled and detailed it and now it's on the road. No prior GS experience. Runs great, so I thought, but found the throttle to be kind of "on or off" when you come off of idle. By this I mean, while riding, if you let off the gas and then roll the throttle back on the bike would lurch a little. It was hard to be smooth with the throttle. I just figured that's the way the bike was. So I rode to work this week a few times, getting out at midnight, with temps In the 40"s and noticed a hesitation for the first two miles, then it would be better. This made me think the bike was too lean. So I pulled the plugs to find them snow white. Air cooled engines and overly lean conditions are not good! I pulled the top off of the carbs to raise the needle clips to the next groove only to find there aren't any more grooves, just the one. But there was a washer under the clip and a plastic spacer on top. So I reversed their positions which effectively raised the needles 1/8 (?) inch. Took the bike for a ride and the engine is unbelievable. Low RPM response is greatly improved. The throttle rolls off and back on smooth as silk. You can drive the RPM's down to 2000 in 5th gear and roll the throttle back on and it will accelerate positively and smoothly! Excelent! Took another plug reading when I got home and found them a little tan. Perfect. I was impressed with this bike before but now I am really thrilled. I think the reason for the need to change settings from the factory is the bike has a K-N filter in the stock air box. It doesn't take much to screw up the factory settings.
Was that the proper way to raise those needles?

Thanks,
bob
 
If the bike runs as good as you say, you can't argue with that.
To raise the needle about 1/8" is about the same as 2 positions on an adjustable needle? A stock bike except for a K&N replacement filter would not require that much of an adjustment. It must have been running very lean. Is the air box lid still on? I hope you don't actually have an intake leak and raising the needles just compensated for this lean condition.
It could also be said the plastic spacer above the clip eliminates metal to metal contact (on some designs). Hopefully this won't create a problem later.
I'm not trying to sound negative, but you did ask for opinions about this method of raising the needle. Like I said, if you know the other parts are working well and the bike runs good, that's all that matters! :)
 
Thanks for the input.
After I posted I was also thinking about the fact that here in Connecticut our gasoline is 10% methanol, (corn squeezings) and this also creates a lean condition. (Lawn mower shops here claim they are seeing alot of melted down little 2 stokes due to this.) I did check for intake leaks with some starter fliud while the bike was idling and was unable to find any. As far as the metal to metal contact, the top of the needle is captured by a plastic tower held in with a circlip so that should be O.K. If I develope any problems I'll be sure to repost.
Thanks again,

bob
 
Carb jetting

Carb jetting

Excellent! I was wondering what the plastic spacer/c-clip relationship was on my bike, and this may have shed some light on it.

I started tuning my 83 GS1100E for the addition of pods to the carbs. There was already a header installed when I bought it. The main jets were up one half size to 112.5, and looking at the needles, the plastic spacer was UNDER the clip.
There was no other positions on the needle for the clip to go on, so no tuning possible there. But I found an exploded view of my carbs in a manual that indicated the spacer on TOP of the clip. So maybe the previous owner had done that to tune for the pipe.

Anyway, I resulted working up to 140 mains with the plastic spacers on the needles under the clips. With the K&N pods, the beast runs great. Plugs look great, I'm gonna quit while I'm ahead.
 
muscle

Hey thanks for that info. I was wondering if my carbs had been improperly assembled and that the plastic spacer was supposed to be under the clip. Apparently not. Glad to hear you are running well. I spent all last summer driving and tuning my Mustang 5.0 4 barrel, and when it was almost perfect I stepped way out of the box and now it runs terrible. Need to start all over. But it is kinda fun experimenting. These carb things sometimes go well..and sometimes not.
 
Just rebuilt my gsx750es with K&N Filters having problems with back fire and not getting more than 5000rpm, I know they have to be rejetted so moved clip to top of jet needle a little better but not right. So I will try this method any other ideas would be great. Many thanks Mickey
 
worked a treat once I figured to move clip down the needle and not to the top. saved a fortune on rejetting many thanks :D
 
81' GS1100EX with 4 into 1 Wolf Header and K&N filters (4) . Does anyone have suggestions regarding the best jetting for this arrangement? I live in Calgary Ab. Canada which has a altitude of approx 1049m (3442ft) above sea level.

If you have the K&N style filters as well you may have noticed that when the bike is left sitting on the side-stand in the rain your right side filter gets soaked! I built brackets to attach the factory chrome trim off the front half (collector) of the air box. This keeps the filter more or less dry and looks better too. The back half factory airbox has now been closed at the front with a spray can top and a hose clamp, makes a good toolbox!

ride safe,

Dave S.
 
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