runs lean but still gtg carbon on plugs

[rattman1]

Weird one here folks. 78 gs1000e with v&h 4 to 1 pipes, pod filters, jet needle clip moved from 3rd to 4th position. Mains bumped up one size. Also a new dyna ignition. Did this last year so I don’t remember the main jet size but it should not matter with my problem.

Biked ran fairly smooth last year and sat all winter and spring. Fired it up and got a tremendous amount of carbon on all 4 plugs. Put some sea foam in the tank and ran it a bit. Still nothing. Took float bowls off and cleaned out all main, needle, and pilot jets. (pilots were pretty trashed with carbon) and also reset the floats to about 17mm.

Tossed in some new plugs and took her out. She ran like a rocket for about 5 minutes before the carbon started building up on the plugs and she became sluggish. Closed the pilot screws from 1 turn out down to ½ turn out. Now on startup lots of backfiring… which means it is lean….. but then why the carbon on the plugs? Do I need to redo the timing?

Gtg frustrated so I called the local repair guy. He said that I needed to put the stock air box back on and that it would help the problem a lot. But I asked, wouldn’t that make the engine richer? He said something about the fact that the pods create too much (or maybe too little) back pressure and that that was my problem.

Any way… I was not having this problem last year after I made the modifications…. So I’m suspect of this guys advice…… so now I’m turning to the experts… YOU!

Thanks in advance!

[rattman1]

also wanted to mention.... the floats seem to be sticking cause im gtg intermittent majoy dripping out of one or two of the floats after i take her for a ride.

could that be part of the problem? sticking floats that is. and how do you get those buggers to quit sticking?

[Dave8338]

Gtg frustrated so I called the local repair guy. He said that I needed to put the stock air box back on and that it would help the problem a lot. But I asked, wouldn’t that make the engine richer? He said something about the fact that the pods create too much (or maybe too little) back pressure and that that was my problem.

Any way… I was not having this problem last year after I made the modifications…. So I’m suspect of this guys advice…… so now I’m turning to the experts… YOU!

Thanks in advance!

Hate to say it but it sounds like you may have a few issues (the bike). :-D
Did you leave fuel sitting in the bike over winter?
Have you checked the petcock to make sure that it is working correctly?
Have you adjusted the valves yet?
The "guy at the shop" is way off the mark IMHO, you are correct in that pods will make the bike run leaner, end of story.
It sounds like a combo of float/needle & seat issues along with a petcock that is bunk.
Check the petcock first...if it works correctly, move onto the floats. If their doing there job, it may valves out of spec. Let us know.

[Nessism]

Float bowls are overfilling which causes a rich condition. How did you measure the float height? They are supposed to be set at 24mm, not 17. You need to rebuild the carbs or at least figure out what it takes to get the float needles to seal.

[don_gibb6512]

You're on the right track with the suggestions given. Are you running the stock carbs? Check the valves and raise the float height. You mentioned you're running a Dyna S but do you still have the OEM coils? If so, that could be the problem. Check the resistance of your coils and if OEM, you may as well just swap them out for a set of green Dyna 3ohm. Sure won't hurt. Good luck and keep us updated.

[rattman1]

Thanks guys!

Ok first, I have one of those crappy pet cocks where you need a screw driver to turn it on or off. Are you suggesting it is not in the on position? Which direction should it be pointing to be on and how do i know if it is working or not? basically how do i test it?

I will reaadjust the floats to 24mm. read somewhere that 15mm was spec... not sure where. to adjust floats im just using one of those tiny metal slide rulers in millimeters that you get at menards.

you mentioned "seat" issues. sorry i'm a newb at engines. what is a seat and how do i test it?

not sure about the coils... they are whatever was on the bike when i bought it. the carb is stock.

the bike ran well last year after i made all of the modifications.... so i am going to start with the floats and go from there. i'll also get out the mercury gage and check the valves. i'm going to recheck the timing too.

thanks again guys!!!!

[Dave8338]

[quote=rattman1;689755]Thanks guys!

Ok first, I have one of those crappy pet cocks where you need a screw driver to turn it on or off. Are you suggesting it is not in the on position? Which direction should it be pointing to be on and how do i know if it is working or not? basically how do i test it?

Not sure on your particular petcock as I have a different style that actually says ON, PRI, OFF so someone else will have to fill you in there.

I will reaadjust the floats to 24mm. read somewhere that 15mm was spec... not sure where. to adjust floats im just using one of those tiny metal slide rulers in millimeters that you get at menards.

As far as the float height, this measurement can taken with the gasket on or off...looking at the 24mm height, that should be with the gasket off.

you mentioned "seat" issues. sorry i'm a newb at engines. what is a seat and how do i test it?

The seat is below the needle and can get gummed up to the point where things will still run but not seal.

not sure about the coils... they are whatever was on the bike when i bought it. the carb is stock.

If the bike hits on all four and it ran fine last year, not likely the problem...

the bike ran well last year after i made all of the modifications.... so i am going to start with the floats and go from there.

i'll also get out the mercury gage and check the valves. i'm going to recheck the timing too.

You lost me here, if you have a method that I'm not aware of, i'de like to hear it. :?

thanks again guys!!!!

[Nessism]

Thanks guys!

Ok first, I have one of those crappy pet cocks where you need a screw driver to turn it on or off. Are you suggesting it is not in the on position? Which direction should it be pointing to be on and how do i know if it is working or not? basically how do i test it?

I will reaadjust the floats to 24mm. read somewhere that 15mm was spec... not sure where. to adjust floats im just using one of those tiny metal slide rulers in millimeters that you get at menards.

you mentioned "seat" issues. sorry i'm a newb at engines. what is a seat and how do i test it?

not sure about the coils... they are whatever was on the bike when i bought it. the carb is stock.

the bike ran well last year after i made all of the modifications.... so i am going to start with the floats and go from there. i'll also get out the mercury gage and check the valves. i'm going to recheck the timing too.

thanks again guys!!!!

Measure float height from the carb body, without the gasket in place, to the top of the float just as the tang starts to depress the spring loaded tip of the float needle. The metal tab on the float interconnecting bracket should be close to flat with floats set to 24mm per spec for VM carbs (22mm for BS/CV carbs).

To check the petcock, pull the fuel line off and install a secondary piece of tubing dumping into some type of catch container. There should be three positions: on, reserve, and prime. When set to on and reserve there should be no fuel flow unless you suck a vacuum on the vacuum line. When set to prime fuel should flow all the time.

Good luck.

[SPARKSS]

The most important part of your post (to me) is the history saying that, with the same configuration, it worked correctly before (for a significant amount of time). Stop right there and ask what changed. Now I'll counter your assumption of a lean condition always causing the backfire and remind you that a backfire is a loss-then-regaining of ignition during which time fuel was still being added (thus the explosion happening not at the correct time or WHERE it should be......i.e. partially within the intake or exhaust system).

Sounds like you're trying to determine whether you have a fuel flooding or starving condition (dirt or gunk accumulated.......something that "changed") but don't overlook a change in ignition (system voltage even) being a contributing factor. Probably this isn't the case as you said it ran "like a rocket" but I've gotten fooled when new plugs covered up weak ignition temporarily. I'll assume you used the same plugs you used before and not a platinum type (another can of worms with many ignition systems).

Just food for thought

[rattman1]

ok.... i reset the floats to 24mm measuring without the gaskets. i recleanet the jets and changed the gas. i also set the pilot screwss back to one full turn from closed.

no change. it still loads the plugs w carbon in only a few miles. after about 5 miles, the bike barely runs.

interesting finding though. when i decided to empty the gas out of the tank and refill with new clean gas i set the tank up and put the hose inside of a gas can. no matter what direction i turn the petcock, gas continued to run out into the gas can.

could this be my problem? one thought though.... i had everything adjusted on the bike, reinstalled the gas tank, filled it with fresh gas and immediately took the bike for a run. did a plug chop about two miles away and had fouled plugs. was that enough time for a faulty petcock to cause a problem?

i read in other posts that perhaps i got gas in my oil. would that cause the symptoms that i am experiencing? if i remove the oil would gas be very noticeable in the oil?

i just don't think that this is a carb issue. i'm stumped! what would you guys do next? check timing maybe?

[t3rmin]

Gas dripping out is almost certainly not a float height issue. It's a float valve leaking or float stuck issue. Replace the o-rings on the float valve seats (cycleorings.com) and inspect the float needles for wear and the floats for smooth operation. Once the leaking is stopped, then move on to other troubleshooting. Don't waste your time until then.

After that, check on your petcock. You don't want the petcock leaking either, but properly sealing floats would make that basically a (short-term) non-issue, so start with fixing the floats!

[rattman1]

also...

with regards to the needle and seat.... how can i tell if there is a problem what should i be looking for?

is the seat simply the hole in the carb that the valve sits in or should there be something underneath the needle?

[t3rmin]

also...

with regards to the needle and seat.... how can i tell if there is a problem what should i be looking for?

You'll know wear when you see it. First the needle springy thing should still be springy enough to support the weight of the float when the carbs are upside-down. Second, the taper of the needle should be be uniform/straight. So far I haven't encountered worn needles, it's always been stuck floats or bad o-rings.

is the seat simply the hole in the carb that the valve sits in or should there be something underneath the needle?

Yeah, you're on the right track. The seat is a brass bushing thing which the needle seals against. It's pressed into the carb body and sealed with an o-ring. When that o-ring ceases to provide a good seal, you have a leak.

[Nessism]

interesting finding though. when i decided to empty the gas out of the tank and refill with new clean gas i set the tank up and put the hose inside of a gas can. no matter what direction i turn the petcock, gas continued to run out into the gas can.

could this be my problem? one thought though.... i had everything adjusted on the bike, reinstalled the gas tank, filled it with fresh gas and immediately took the bike for a run. did a plug chop about two miles away and had fouled plugs. was that enough time for a faulty petcock to cause a problem?

i read in other posts that perhaps i got gas in my oil. would that cause the symptoms that i am experiencing? if i remove the oil would gas be very noticeable in the oil?

i just don't think that this is a carb issue. i'm stumped! what would you guys do next? check timing maybe?

The leaking petcock will allow fuel to flow all the time which puts fuel pressure on the float needles - causing them to leak and overflow the float bowls. If the float needles are in good shape the amount of leakage should be minimal and not cause a problem...but, that is not typically the case with old motorcycles. It's hard to say how much leakage you are getting and where the extra gas is going. If it's going into the intake ports you will have a rich running bike. Most likely though it will only be one or two cylinders. Another kind of petcock failure dumps fuel down the vacuum line directly into the engine, often filling up the crankcase.

I'd say you should fix the petcock asap and try to figure out if the needles are leaking. You are going to have a difficult time figuring out what's going on mixture wise until you put these known problems to bed.

[t3rmin]

The leaking petcock will allow fuel to flow all the time which puts fuel pressure on the float needles - causing them to leak and overflow the float bowls. If the float needles are in good shape the amount of leakage should be minimal and not cause a problem...but, that is not typically the case with old motorcycles. It's hard to say how much leakage you are getting and where the extra gas is going. If it's going into the intake ports you will have a rich running bike. Most likely though it will only be one or two cylinders. Another kind of petcock failure dumps fuel down the vacuum line directly into the engine, often filling up the crankcase.

I'd say you should fix the petcock asap and try to figure out if the needles are leaking. You are going to have a difficult time figuring out what's going on mixture wise until you put these known problems to bed.

If he's fouling all the plugs, it's not going to be a leak down the vacuum line, but that's easy enough to check. And long term seepage past the needles isn't a factor when he's describing quick fouling and poor running.

If you leave the petcock on prime or it's leaking, and the float valves have a slight seep, you could eventually overflow. But that's not what's being described. That's why the floats are top priority. After all, while the engine is on and the petcock is getting vacuum, it's wide open and the floats are solely responsible for metering gas.