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GS1100E pilot screw setting

  • Thread starter Thread starter RJ
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RJ

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For all you guys who have the Dynojet kits in your GS1100E's: I'm running a Stage III kit with 4 K&N's and a Kerker header. How far do you have your pilot screws turned out? Although I gained a noticeable power increase, the bike runs a bit rough on part throttle at 3-4000 rpms. The carbs appeared to be pretty well synched prior to installing the jet kit with the pilot screws turned out 1-1/2 turns out. Thanks, RJ.
 
Re: GS1100E pilot screw setting

It may not be the pilot screw settings. Having changed exhaust system, jets and air filters, you have changed the mass flow/volume. This means you have changed velocity/vacuum levels. Although you carbs may still be balanced relative to them all flowing at the same velocity, it is a sure bet they are not flowing at the same velocity as they were before the changes.
vacuum between the carbs must be the same, but it must also be at a specific level/value. Check you plug center ceramics for color, this will tell you whether you need to richen or lean mixture. Increasing vacuum will richen mixture and decreasing vacuum levels will lean it.

Earl


RJ said:
For all you guys who have the Dynojet kits in your GS1100E's: I'm running a Stage III kit with 4 K&N's and a Kerker header. How far do you have your pilot screws turned out? Although I gained a noticeable power increase, the bike runs a bit rough on part throttle at 3-4000 rpms. The carbs appeared to be pretty well synched prior to installing the jet kit with the pilot screws turned out 1-1/2 turns out. Thanks, RJ.
Click to expand...
 
Re: GS1100E pilot screw setting

RJ said:
For all you guys who have the Dynojet kits in your GS1100E's: I'm running a Stage III kit with 4 K&N's and a Kerker header. How far do you have your pilot screws turned out? Although I gained a noticeable power increase, the bike runs a bit rough on part throttle at 3-4000 rpms. The carbs appeared to be pretty well synched prior to installing the jet kit with the pilot screws turned out 1-1/2 turns out. Thanks, RJ.
Click to expand...
What do you mean by running rough? Hesitation/surging (lean) or sputtering/bogging (rich)? What do the plugs say?
At your described throttle setting and rpm, you are on the jet needle with some overlap effect from the pilot circuit/mixture screw. If lean, you may be able to adjust the mixture screws out another 1/2 to 1 full turn. Try it, but I bet you'll have to raise the needles another notch.
If rich, 1 1/2 turns out sounds very common, so I would leave the screws alone and lower the needle a notch.
I assume the carbs are positively clean inside and your ignition timing is correct. Also, did your Dynojet kit instructions require the two floatbowl vent tubes be removed? This helps the jets draw fuel easier, so remove them if you havn't yet.
 
By running rough I mean pretty much the sputterrng kind of running. When I gas it the bike smooths out, it's just at cruising speed that it sputters some, although it doesn't really bog. It's kind of hard to tell if the bike is running rich or lean since I don't have many miles on the plugs since I installed the jet kit.

One of the main reasons I installed the jet kit is that I've also been having a problem with popping on trailing throttle. I've read some sources that say it's normal for a megaphone type exhaust to do this, but I don't buy it. By the way, there are no instructions to modify the float functioning of the carbs with the jet kit.

Hey Earl, how would I go about checking and adjusting the vacuum between the carbs? RJ
 
OK. Ride the bike enough to give some plug reads. Take a read after cruising several miles at about 40/50 mph.
With intake mod's and jet kits, they do tell us that you may have some "driveability" issues. One of the most common issues is popping when letting off the throttle, especially at higher rpm's. A minimal amount of popping is OK. To try and get rid of all the popping usually results in worse problems. You CAN find a good compromise. The mixture screws should be able to be adjusted to make you happy regarding the popping.
Even if the kit instructions said nothing about removing the two floatbowl vent tubes, you still should. With the increased intake, a vortex is created in the vent tubes and this makes it hard for the jets to draw fuel. It is most noticable at slower cruising speeds, feels very much like fuel starvation. Since we cannot increase the venting ability, the best we can do is minimize the resistance. The vortex and the tube itself are the resistance.
When synching, I have always had good luck with doing a VERY good manual synch' first. Then when I start the motor the mercury levels are almost always in the proper range and within 3 cm of each other. I get them to within 1 cm of each other very quickly. If a poor manual synch' is done, it can be a lot of adjusting up and down to get the levels right. You can adjust the levels only to see the rpm's too high. Then you lower the idle screw and the levels are still not right. You can end up with the adjustments so far off that the idle screwknob does'nt even come into contact anymore but you are "idling" way too high.
If you manually sinc' the way the factory manual says to, fully closed and fully opened throttle positions, you will find the levels are within range upon start up. A little adjusting gets them reasonably level with each other. If they are not, then you most likely have mechanical problem(s).
 
Hmmm... my instructions in my jet kit never mentioned taking off the vent tubes, but I bought mine 18 years ago so they might have revised them. I'll have to give that a try myself and see if anything happens. Concerning the off throttle popping, I went up one size on my pilot jets and it helped some and didn't seem to affect anything else that I could tell. I also tried adjusting the needles and just created problems at other throttle settings. One thing I haven't had done to mine in years is synching the carbs. I might try that this spring.
 
Jeff Tate said:
Hmmm... my instructions in my jet kit never mentioned taking off the vent tubes, but I bought mine 18 years ago so they might have revised them. I'll have to give that a try myself and see if anything happens. Concerning the off throttle popping, I went up one size on my pilot jets and it helped some and didn't seem to affect anything else that I could tell. I also tried adjusting the needles and just created problems at other throttle settings. One thing I haven't had done to mine in years is synching the carbs. I might try that this spring.
Click to expand...
If you don't notice any fuel starvation or hesitating, you may be OK with the tubes on. I know for a fact the VM carbs do not vent well unless the tubes are removed. Many people with CV carbs have said the same thing, while other CV carb owners don't notice anything. I can't explain why some people notice it and some don't. The idea makes perfect sense to me though, so I would remove them even if I did'nt notice fuel starvation.
You can call Dynojet too. They have an 800 number. They are very helpful with questions.
 
OK, I'll ask a stupid question at this point; Where exactly is the vent tube? I have a factory shop manual that makes no mention of such a thing. The only tube that I see going into the float bowl looks to be the starter jet (which also isn't specifically mentioned in the exploded view of the carbs, but is referred to later on in the chapter).
 
RJ said:
OK, I'll ask a stupid question at this point; Where exactly is the vent tube? I have a factory shop manual that makes no mention of such a thing. The only tube that I see going into the float bowl looks to be the starter jet (which also isn't specifically mentioned in the exploded view of the carbs, but is referred to later on in the chapter).
Click to expand...
There are two vent tubes. One on the inner side of carb #1 and one on the inner side of carb #4. Just above the float chamber. Some carbs may have the tube coming off a "T" that's in between carbs 1 and 2, and 3 and 4. Each tube vents 2 carbs. The tubes/lines are usually 3/16". They are attached to a 3/16" nipple on the inner side of the carb or a "T" and are then routed under the seat or that general area.
 
RJ

I have the same set up...see my response to CNDBandits post. I had sputtering off idle raised the needles one notch and then had a flat spot 3000-4000 RPM raised another notch and now have smooth throttle response throughout the RPM range.
 
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