79 GS1000L backfiring, sometimes r-pipe smokes at start-up

[gwhunran]

Have made quite a few changes to the bike lately and took it for a more lenghty ride on Wednesday and had quite a bit of backfiring from the right side pipe only. Today noticed quite a bit of blue smoke also from the right side only, until it warmed up. The backfiring happens mostly when coming off the throttle sometimes not very loud, sometimes very loud approaching gun shot loud.
The bike runs smoothly throughout the throttle range with plenty of power. I have not noticed any oil usage although I haven't put too many miles on it since it was changed and before changing no appreciable oil usage. The problem I was having with the misfiring/sputtering around 3700-4000rpms is now gone.
The changes that have been made in the last month are: Dyna ignition, coils and wires, Dynojet kit, K&N pods, the headers/pipes are MAC 4-2 turnouts.
I am still getting pretty poor gas milage- around 25mpg. I am not seeing any gas leaking. My driving is a mix of 55mph to 65-75mph driving in fast commuting traffic with occasional faster burst to get by possible threats.
Any thoughts on what may be happening with the the backfiring/smoke/poor gas milage?

Thanks,
Richard

[gremlin]

check coil connetion and spark plug wires. also pull the spark plugs to see if one is starting to fail. for that side. if thay all check good it may be just one carb starting to clog.

[KEITH KRAUSE]

Burning oil is going to interrupt good combustion. Hard to say if you have a compression, weak spark (shouldn't be because of new ignition/coils) or too much fuel problem, or a combination of.
Generally, the big backfires are caused by raw fuel passing into the header. The fuel collects until it ignites/fires all at once. Big bang. Raw fuel can pass/collect due to weak spark, too rich of mixture, or poor compression simply screwing up the combustion process.
As for too rich of mixture, if that's what it is, at what throttle position does the problem show and what is your jetting set up? (Main jet size, jet needle e-clip position and pilot jet size? Also pilot fuel screw and side air screw settings?)
Are float levels set and carbs VERY clean?
I can suggest settings that would be close if needed and would at least eliminate a rich mixture as part of your problem.
Have you checked compression?

[duaneage]

Could be an Intake valve guide seal. IF a seal tore or failed it would allow air into the engine upon deceleration that would contribute to a backfire and allow oil into the engine. Pull plugs on that side and find out which one it is , the oil should be present on the plug.

Leaks at the exhaust port of the head can allow air to enter the exhaust pipe, igniting blowpast gas in the muffler. This would not explain oil use and mileage but then again you may have two problems.

If the proiblem lies with the bore tht the vacuum petcock is hooked to that could be another problem. A leaky diaphram is allowing more gas to go into the engine wasting fuel and washing oil from the walls. Check the petcock vacuum line for liquid fuel.

[gwhunran]

Have not had a compression check. The bike has massive amounts of pick-up/acceleration. Could I have a compression problem and still have great acceleration/pick-up/ available power?
The bike does not smoke all the time. It is pretty rare, othter than when first cranking cold. However a couple of times it has smoked after initial cranking and some warm-up. For example: Saturday, I was showing the bike to a relative, I cranked it and took it around the block and returned home about 1 minute. The bike was smoking when I returned. I took it around the block again, returned home, no smoke. I took the bike to work on Sunday, temp low 30's F on the way out, low 40's F on the way back. No smoking either way, very very infrequent "popping"/mild backfiring both ways. I took the bike to work Monday. Temps upper 50'sF on way out, low 60's on way home. A little more popping/ mild backfiring today, more on return trip than outbound trip, only thing different was ambient temps. No smoking after initial warm-up.
Jetting and carb info:
I believe the installed main jets from the Dynojet kit are 138. I am not 100% sure as I am not where I can look at the package. The needle clip position is exactly in the middle. The kit did not include pilot jets, so the pilot jets have not been changed, don't know if they are stock or not. Don't know the number of turns out on the pilot fuel screw or side are screw. The bike starts and idles great. The carbs are synced. The float levels are set at 23 or 24mm as per a procedure put out by a GS Resource member on this forum. All floats have even range of motion with no binding. The petcock does not leak when the tank is removed from the bike. The carbs seem clean but have not been dipped.

[KEITH KRAUSE]

If compression is low in any cylinder(s) you won't be able to tune well. Having said that...
Your bike is giving mixed signals, both rich and lean. 25 mpg isn't acceptable, that's rich. Decel' pop is a lean condition. Different throttle positions can give rich and lean symptoms.
Before re-jetting, some basics should be done to make the re-jet easier. If you decide to skip some, you can have problems and can't necessarily blame the jetting.
In your case, I'd be sure to check compression. If good, I always make sure the carbs are completely clean and all inner o-rings are good. Float levels are adjusted to .94" or very close to, manifolds and their o-rings checked/replaced, with the pods...REMOVE the two floatbowl vent lines and leave the ports open, carbs must be bench synched followed by a vacuum tool synch. Before the vacuum tool synch, valve clearances must be between .03 and .08mm. Also before the synch, be SURE the ignition timing/advance is spot on. Use a gun instead of a static check. Your electrical system is new and should be otherwise good. Use NGK B8ES plugs, gapped correctly. I suggest new exhaust gaskets for any new pipe. Any decel' pop could be a leaking header.
For jetting, you have to test at minimal, 1/3 and full throttle positions to see what each jetting circuit is doing. Chop off and read. From my experience, your jet needles e-clip should be set at position 4 from the top as a good starting point but test at 1/3 throttle first for a couple miles. Be SURE the two plastic spacers are re-installed on the jet needles. The thicker spacer goes above the e-clip, the thinner one goes under the e-clip. The 138 main jet should work fine. The stock pilot jet should work with correct pilot fuel and air screw adjustments.
Start by adjusting the pilot fuel screws (underneath) out to about 1 1/2 turns. Seat them LIGHTLY when counting. If the sharp tips break off in the carb body, you're screwed. Fine tuning/testing these will almost certainly be needed later. For the side air screws, adjust them to 1 3/4 turns to start. Then warm up the motor completely and set the side air screws using the highest rpm method. The bike should idle at 1,000rpm. Starting at any carb, slowly adjust the screw to hear maximum rpm. Fine tune the setting, then re-set idle to 1,000 with the idle adjuster knob. Repeat to each carb. Then vacuum synch for best performance and to get accurate plug reads.
If all the above is done, the bike should run well with no backfiring and only minimal decel' pop. The only adjustments you may need would be to the jet needle and some minor fuel/air screw adjustments. Of course, if the jet needles are re-set, the bench and vacuum synchs must be re-done. The bike should also average around 35 mpg in the city if you don't open it up constantly. 40 or better on the highway.

[gwhunran]

update to previous

I have made arrangements to get a compression check, and borrow a timing light, but have discovered something else in the meantime. The number three header is cooler than the rest. I can almost hold it bare-handed after the bike is warmed up. The rest are very hot . Pulled number three plug out and reattached to wire--getting good spark. However, it and spark plug #2 make a clicking sound when moving them around outside still attached to the wires bike running and #1 and #4 do not make this sound doing the same thing. This test was performed at a bike shop with the service manager. He said it was electrical problem related to "short" involving coil for #2&3. The coils were changed a few weeks ago, along with the wires, and a DynaS ignition.

My main question is, does what the service manager said, sound right? Or could the clicking sound-plugs 2&3, mild backfiring out of right pipe-cylinders 3&4 be caused by timing being off, or poor compression, or something else entirely.

[drewshotrodding]

the coils fire at the same time between that coil change your wires around and see what happens and do the same for the spark plugs if that don't work the carbs are dirty or there is some thing missing out of them on the gs 1100 they have a rubber plug pushed into the idle jet hole inside the bowls if the are not in there it wont work right /////Don't put your hands on the pipe get a spray bottle put just water in and spray it on the header and you will see it come off fast or not at all try this at differnt rpms and see if that pipe fires in if it don't than check it some thing to make that carb fire like starting fluid I check mine with that cheep autozone carbcleaner than the carbs have trash in there

[jimg]

gwhunran
Pulled number three plug out and reattached to wire--getting good spark. However, it and spark plug #2 make a clicking sound when moving them around outside still attached to the wires bike running and #1 and #4 do not make this sound doing the same thing. This test was performed at a bike shop with the service manager. He said it was electrical problem related to "short" involving coil for #2&3. The coils were changed a few weeks ago, along with the wires, and a DynaS ignition.

My main question is, does what the service manager said, sound right? Or could the clicking sound-plugs 2&3, mild backfiring out of right pipe-cylinders 3&4 be caused by timing being off, or poor compression, or something else entirely.

First, testing spark with the plug laying on the head will only tell you if everything is working, not how well. Under compression, that spark plug may not be firing or not firing well.

It sounds to me like you have a leaky plug wire(s). That clicking sound could easily be spark jumping from a plug wire to ground somewhere, even inside the coil. I suspect this is what the service manager meant by a 'short'.

It may not do this with the plug out of the cylinder since this would be the easiest path to ground. With it back in the cylinder, the spark may be finding another, easier, path to ground than the plug.

I would try swapping coils and plug wires to see if the problem moves.

[KEITH KRAUSE]

Yes, the clicking sound with no plug attached, would have to be arcing between the plug leads and the frame/ground somewhere. Replace them.

[gwhunran]

I will take the tank off this weekend and troubleshoot the wires to and from coil(2&3). The wires and coils are pretty new. When doing the previous troubleshooting with the plugs out/wires attached, running the motor, I think some gas has gotten into the crankcase. The level in the sight glass is a little higher and removing the oil fill cap and smelling inside, I detect a slight fuel odor. Would it be normal for gas to get into the crank this way. The motor was ran for less than a minute total doing the test. I did not notice the oil level change until I had driven the bike home from the shop, a total of about 10 miles. I did not notice any change in the way the bike was running. The oil is synthetic.

[KEITH KRAUSE]

If the petcock diaphragm is failing, gas can get through by way of the vacuum line to carb #3 and enter the crankcase with the bike running or just sitting.
A failing petcock will also allow gas to enter all carbs. Any carb can then leak if the float valve is not sealing well.

[gwhunran]

With the tank off the bike, the petcock does not leak at all. If it was failing wouldn't it leak then as well?

[KEITH KRAUSE]

With the tank off the bike, the petcock does not leak at all. If it was failing wouldn't it leak then as well?

The petcock diaphragm/spring assembly can fail in a couple of ways.
Just sitting, the petcock can allow gas to pass through. Running or sitting, the petcock can allow gas to enter the vacuum line.
You can also accumulate gas in the crank with a good petcock.
If one or more float valves isn't sealing well, the gas still in the line and carb passages (after turning off) can leak past these valves and enter the crank. After a few times, the smell/amount of gas would become obvious.

[gwhunran]

I managed to correct the "coil/wires issue yesterday, but #3 pipe is still much cooler than the rest. Decided to take the bike to the shop as I am not confident about fooling with the valve adjustments. When I took it in the compression was checked, values as follows from 1-4: 110,110,140, and 140. Also found the intake boot leaking at number 3 carb. Mechanic said I needed a new boot. Are these still available new? If so where? And new boot O-rings will be needed too. I have seen them mentioned in other post but don't remember where they got them.