carbs won't rev up unless choke is on.

[toymechanic.]

Cleaned and rebuilt carbs and the engine won't rev up after it is warm unless the choke is on. I have screwed the air mixture screws out and it is getting better, but they are out now about 5 or 6 rounds. Any ideas what the problem may be? Are my idle jets too small maybe. I soaked the carbs in Berrymans over night! Then spray them with carb cleaner in a spray can. So i am pretty confident that they are clean. Oh yeah let me mension I added a K&N air cleaner but it has stock exhaust! I have ridden for 57 miles and in order to take off from a stop the choke has to be on! Once it is under way it is fine with the choke off. It has 7785 original miles on it.

Thanks in advance!

Gary

 

[tconroy]

do you stil have the stock airbox? You might try putting it back on and see what happens

 

[SqDancerLynn1]

If you put K&N filters on you are running way too lean Their is not enough adjustment in the mixture screws to make up the difference YOU need to put bigger main jets in the carb Raise the needle at least 1 notch & try a 125 main jet

 

[toymechanic.]

do you stil have the stock airbox? You might try putting it back on and see what happens

I still used the stock air box. I just put a K&N oem replacement in the stock air box! SO even with this I would need a bigger main jet?

 

[tconroy]

what about your adle adjusment screw?Have you checked for leaks around your intake boots.Will it idle smoothly?Did you set your floats properly?

 

[toymechanic.]

what about your adle adjusment screw?Have you checked for leaks around your intake boots.Will it idle smoothly?Did you set your floats properly?

As I mensioned before the Idle adjustment screws are 5 or 6 turns out and it was getting better the farther I screwed them out. I did not check for cracks on the boots when the carbs were off!

 

[tconroy]

Idle adjustment screw located in the back inbetween the carbs,not the air adjustment screws.Did you bench sinc the carbs when you had them off?check for leaks with wd40 around the intake boots and air chamber side of carbs also.You might have a cracked boot or bad o-rings in the intake.

 

[toymechanic.]

Idle adjustment screw located in the back inbetween the carbs,not the air adjustment screws.Did you bench sinc the carbs when you had them off?check for leaks with wd40 around the intake boots and air chamber side of carbs also.You might have a cracked boot or bad o-rings in the intake.

The boots are fine I just removed the carbs and check the boots.

I sychronized the carbs with a mecury balancer. Idle adjustment screw? do you mean the little knob between carbs two and three?

 

[toymechanic.]

Oh yeah BTW it idles smoothly!

 

[toymechanic.]

So with the dead spot between 1500 and 4000 RPMs. Does this all mean I need a bigger main jet or a bigger pilot jet. It doesnot cut out on top end. I feel the floats are set right, the idle is smooth, The passage ways are clean, and with the mixture screws 6 to 7 turns from seated is shimming the jet needle up going to solve the problem or do I need a bigger jet?

 

[jgordon]

So with the dead spot between 1500 and 4000 RPMs. Does this all mean I need a bigger main jet or a bigger pilot jet. It doesnot cut out on top end. I feel the floats are set right, the idle is smooth, The passage ways are clean, and with the mixture screws 6 to 7 turns from seated is shimming the jet needle up going to solve the problem or do I need a bigger jet?

With your air screws out so far it means you need...

Bigger pilot jet ( probably a 47.5 )
I would raise the needle 2 notches or shim up the equivalent
Probably around a 122.5 or 125 main

This depends on where you motor is at. Cam timing and such can change the requirements for your motor.

These are just suggestions. Jetting can get quite expensive if you have to keep buying jets as you probably already know.

 

[toymechanic.]

So with the dead spot between 1500 and 4000 RPMs. Does this all mean I need a bigger main jet or a bigger pilot jet. It doesnot cut out on top end. I feel the floats are set right, the idle is smooth, The passage ways are clean, and with the mixture screws 6 to 7 turns from seated is shimming the jet needle up going to solve the problem or do I need a bigger jet?

With your air screws out so far it means you need...

Bigger pilot jet ( probably a 47.5 )
I would raise the needle 2 notches or shim up the equivalent
Probably around a 122.5 or 125 main

This depends on where you motor is at. Cam timing and such can change the requirements for your motor.

These are just suggestions. Jetting can get quite expensive if you have to keep buying jets as you probably already know.

Jgordon,

My whole bike is stock with only 7785 miles on it the camshaft timing is as it was from the factory.

Do you really think I need to shim the jet needle and put bigger main jets in than the 115 it came with?

Gary

 

[hungryman]

You adjust the main with WOT runs. Once you get that, then you can tinker with the needle adjustment. If I remember correctly, Mikuni and a few other sites detail this procedure.

It sounds like you need to raise the needle a bit for sure.

 

[ccratin]

You shouldn't need a rejet. You should pull those carb intake boots and replace the o'rings. You may well be getting too much air. I didn't see if you have done a carb synch, but that's important. Do you have a better description of why you rebuilt the carbs? What was happening before? Did you ensure that you blew out all passages in the carbs and that they were clear? It often takes a small piece of wire to clean out everything. Soaking doesn't always get it all. You have to make sure that pilot circuit is totally clear and that the pickup hole is clear along with the rest of the circuit. The K&N stock replacement shouldn't require a major rejet if everything is as it was from the factory.

 

[toymechanic.]

You shouldn't need a rejet. You should pull those carb intake boots and replace the o'rings. You may well be getting too much air. I didn't see if you have done a carb synch, but that's important. Do you have a better description of why you rebuilt the carbs? What was happening before? Did you ensure that you blew out all passages in the carbs and that they were clear? It often takes a small piece of wire to clean out everything. Soaking doesn't always get it all. You have to make sure that pilot circuit is totally clear and that the pickup hole is clear along with the rest of the circuit. The K&N stock replacement shouldn't require a major rejet if everything is as it was from the factory.

I bought it on 10/01/05 and it only had 7785 miles, so that told me it sat allot and I right off the bat took them apart and soaked them. I beleive 100% that the passages way are clear. I'm going to replaces the K&L pilot jet from the kit and install the original factory ones because the K&L have a .135 of an in ch and the factory ones have a .0145 of an inch. wish me luck.

Gary

 

[jgordon]

Bigger pilot jet ( probably a 47.5 )
I would raise the needle 2 notches or shim up the equivalent
Probably around a 122.5 or 125 main

This depends on where you motor is at. Cam timing and such can change the requirements for your motor.



My whole bike is stock with only 7785 miles on it the camshaft timing is as it was from the factory.

Do you really think I need to shim the jet needle and put bigger main jets in than the 115 it came with?

Gary[/quote]

Just my opinion. Having to run with the choke on is pretty severe in my opinion so it sounds like it is running reeaaaal lean. That's bad for a motor. The suggestions that I gave you may put you over the top but it is a lot safer to work your way back down and lean it out. Make sure that you don't have any air leaks, all the holes in the carbs are clean and play with the pilot and the needle. I bought a brand new 1980 gs1100e and took it out to the track and ran 11.17's at a buck 18. My partner bought one a couple of months after I bought mine and I could not get his out of the 12's. I degreed his cams in and put his right where mine was running. Cams from the factory are off from time to time. 122.5's from 115's is only three sizes up. Do a plug chop.....Just a thought

 

[toymechanic.]

Bigger pilot jet ( probably a 47.5 )
I would raise the needle 2 notches or shim up the equivalent
Probably around a 122.5 or 125 main

This depends on where you motor is at. Cam timing and such can change the requirements for your motor.



My whole bike is stock with only 7785 miles on it the camshaft timing is as it was from the factory.

Do you really think I need to shim the jet needle and put bigger main jets in than the 115 it came with?

Gary

Just my opinion. Having to run with the choke on is pretty severe in my opinion so it sounds like it is running reeaaaal lean. That's bad for a motor. The suggestions that I gave you may put you over the top but it is a lot safer to work your way back down and lean it out. Make sure that you don't have any air leaks, all the holes in the carbs are clean and play with the pilot and the needle. I bought a brand new 1980 gs1100e and took it out to the track and ran 11.17's at a buck 18. My partner bought one a couple of months after I bought mine and I could not get his out of the 12's. I degreed his cams in and put his right where mine was running. Cams from the factory are off from time to time. 122.5's from 115's is only three sizes up. Do a plug chop.....Just a thought[/quote]

Jgordon,

I only need to use the choke to get going, once it is moving I can take the choke off. It doesnot cut out on top end, like it would if the main jets were to small.

UPDATE! UPDATE! tonight I put bigger pilot jets inAftermarket (45)s (their hole is a little smaller than .018 of an inch. Mixture screws out 3-1/2 turns. It help a little, then I shimmed the pilot needle about an !/8 of an inch. It got almost perfect. If I lug it around in first gear and let it get down 1500 rpms then I give it gas it just boggs, then takes off.

So does this mean I need to go bigger on the pilot jet.

Where to go from here!

 

[earlfor]

I agree, replace the pilots with stock mikuni pilots. Your bike is stock. Replacing the air filter element in the stock airbox with a K&N replacement would not require any jet changes or needle shimming. When everything else is correct, only then can you set up carbs. I would check voltage to the coils. It should be close to the same as battery voltage. I would also check resistance between the plug caps and coil resistance.
I would check ignition timing next. I would also disconnect the fuel line from the carbs and check for fuel flow by sucking on the petcock vacuum line to see if if does flow freely. Low battery voltage or a weak battery ground will also cause your problem.

If everything else is right, then it may be an induction problem.

Earl

I bought it on 10/01/05 and it only had 7785 miles, so that told me it sat allot and I right off the bat took them apart and soaked them. I beleive 100% that the passages way are clear. I'm going to replaces the K&L pilot jet from the kit and install the original factory ones because the K&L have a .135 of an in ch and the factory ones have a .0145 of an inch. wish me luck.

Gary

 

[toymechanic.]

I agree, replace the pilots with stock mikuni pilots. Your bike is stock. Replacing the air filter element in the stock airbox with a K&N replacement would not require any jet changes or needle shimming. When everything else is correct, only then can you set up carbs. I would check voltage to the coils. It should be close to the same as battery voltage. I would also check resistance between the plug caps and coil resistance.
I would check ignition timing next. I would also disconnect the fuel line from the carbs and check for fuel flow by sucking on the petcock vacuum line to see if if does flow freely. Low battery voltage or a weak battery ground will also cause your problem.

If everything else is right, then it may be an induction problem.

Earl


Can coil voltage and resistance to the plug give symtoms like fuel related problems?

 

[earlfor]

Yes. If your battery is low, going south, or has a poor ground, ignition voltage can be insufficient at low or even midrange rpm. If coils are out of spec, the same thing will happen. Flat spots in rpm, hesitation, fouled plugs inability to idle, frequently are an electrical deficiency. The weak link in the GS is not the carbs, its the electrical system and operating with 25 year old components and wiring. The order I trouble shoot in is to verify:
1. Battery is in good condition and holding voltage
2. valves are adjusted correctly.
3. compression
4. ignition timing
5. electrical system, coils, plug caps, voltage drop in the system
6. petcock operation and flow
7. charging system, stator output and R/R output.
8. Carb adjustment and synch, induction boot seals and airbox seal and filter.

Until the 1st 6 items are correct, its not possible to properly adjust carbs.
(if item 7 is inoperative, it would not have any bearing until the battery was exhausted to the point of lacking capacity and voltage to support electrical requirements.)

Earl

Can coil voltage and resistance to the plug give symtoms like fuel related problems?