probable carb problem, looking for some opinions.

Took the bike out and managed to get some good miles in finally this past week. Pulled the plugs to check for color, and cyl 1-3 are running lean indicated by the white plug insulators, cyl 4 is the coffee color which it should be. I have nice blue sparks on all 4 plugs when i pulled em and checked. the check the manifold temp with the hand method yields cyl's 1-3 are much hotter than 4, but 4 seems to be the plug thats running correctly. Which would mean that cyls 1-3 are running lean correct?

I have to go into work for a few hours, but after i am stopping to get some clear tubing to recheck the float height. I have messed with the idle air screws to seemingly no change. Is there a good amount of miles to run before i check plug color again? Was thinking it must be a problem with the pilot circuits as it runs great at 1/2 to wot. Just looking for some opinions, see if there's something i have not thought of.

Oh, when i pulled the plug wires off while the bikes running, there seems to be no change in idle when i pulled #4, but it idled like crap when i pulled #1, and is being shocked when you have the plug wire in your hand normal? I was wearing work boots and not touching the bike with any other part of my body......I have been shocked many a time in my day, but it seemed slightly odd. Thanks.

Haha, feels great dont it? :laugh:

Sounds like #4 is just not firing at idle.

yes, you can get a good shock just by holding the lead.

If you have stock airbox/filter and exhaust, then the stock mixture screw settings and fuel heights and plugs are perfectly fine.

Try this: Turn the idle down till the bike starts loping slightly (like its gonna stall), then let it idle a few minutes. Mist some water on the header pipes, and observe: If the water steam/vaporizes on a pipe, it is firing. If not, then you hav an issue that in most cases is improper vacuum syncronization, no spark, or no pilot mixture reaching cylinder, or terrible valve clearances.

Repeat the same setup with the bike idle set to 1500rpm, if all pipes steam/vaporise water mist, then you can eliminate the no spark and pilot mixture issues.

Fuel levels must all be the same, not necessarily perfectly spec, but it helps.

GL.

thanks for the reply. haha it felt just wonderful grabbing it, was a nice surprise this morning. I have a stock airbox, but theres a kerker 4-1 on it, the kerker muffler still has baffles and cone in it. I will give your suggestions a shot here after i get some dinner in me.

just went out and checked, water steams off the 1-3 cylinders but doesnt do very much off the 4th, turned the idle up to 1500 and pretty much the same result. guessing this might be more of an electrical problem than a carburetor problem, unless the idle/pilot circuit is really messed up on number 4. I believe the #4 plug is getting juice, that was the one i pulled and got a nice zap from.

sounds like a pilot circuit issue to me i'd be pulling the carbs and going through them for sure. if it was ignition it would be breaking up really at higher rpm levels

timebomb33 wrote:

sounds like a pilot circuit issue to me i'd be pulling the carbs and going through them for sure. if it was ignition it would be breaking up really at higher rpm levels

Bingo... most likely carb issue, as current must pass thru both 1 and 4 plugs at same time to produce usable spark.

Just to be certain of course, you can pull the plug and swap it with say #3 and retry test to confirm plug is good.

Pull carbs and pop off bottoms and pull pilots. A really clean pilot can be recognised as you look through it into a fairly bright light, you should be able to see the sheen off the clean taper inside it. SUPER CLEAN :laugh:

GL.

Thanks guys, heh kinda jumped the gun and just removed the carb bank. I did swap plugs before i started to take it off, same result. Thanks for the tip about making sure the taper is clear with a bright light. Appreciate the help.

Just finished putting things back together. No luck with cleaning the pilot jet out. Let the jet soak for a bit, blasted it out, ran a small piece of copper wire through it, blasted it out again. Still very little heat coming from the #4 cylinder, other 3 still instantly vaporize the water mist. only other guess i have is the valves....i dont believe ive got a small enough gauge to check it, so ill have to order one.

Did you check for vacuum leaks at the intake manifolds?
How about a compression test?
Did you do a bench clear tube test of the fuel levels?
Did you use a small wire gauge to bench sync the carbs so the butterflies/ or slides are even?
Then after a running carb sync?

I did a bench of the fuel levels, appears to be the same.
I used a similar method to check the slides with a small drill bit.
I just went to check something else before i got to the vacuum leak test, i pulled the pilot screw completely out of the opening and sprayed a few hits of carb cleaner into the pilot screw hole while it was running. I saw no change of engine rpm, although when i blasted it out with carb cleaner it sprayed out of the other holes.
Ill have to see if one of my friends has a compression tester i can borrow.
I gave the oil filler opening a quick sniff and didn't smell any gasoline though.

Did you check to see that the spark looked equal on each plug? Maybe its a bad coil wire or end?
Spray some carb cleaner around at the manifolds, that might show a vacuum leak.
Is the air system still hooked up? If so are the small hoses that run from the 1 & 4 carbs good no leaks?
Compression will tell the mechanical story, if a valve is tight you may have a burning of the valve face. I bought a starter shim kit for my 550 from K&L supply. Its cheaper to swap around, then order the couple of shims you need.
This won't cause your issue, but you should check the Ignition advancer, and lube it if not already done.

the jet may be clean but is the passage can you blow compressed air thru it cleanly the pilot circuit passage is very small and easy to plug up. even if you can see all the way through the jet it doesn't mean the passage isn't still plugged.