'82 550 LTD carb issues... I'm at a loss.

[apbling]

OK, I have tk22 carbs on my 550 LTD. I started it and it started kind of hard and ran rough. I realized that the #4 cylinder was not firing the pipe was no getting that warm. I've been fighting this for a while, but I do believe that under throttle the #4 fires because the I do have power under throttle and the pipe is warmer.

I have cleaned the carbs spotlessly, adjusted the air/fuel air mixture screws to 1 and 1/4 turn out, checked compression (good at 150 psi), checked spark, swaped plugs and plug cap/wires.

Here are my findings:
The odd part is that I can back the air/fuel mixture screw all the way out and all the way in, makes 0 difference on #4 carb. I do this on any other cylinder and it affects the idle bigtime. At idle I pull the spark plug cap off and no change. I do this to any other plug and I kill the bike. I pull the vacuum cap off the carb manifold and nothing... I do this to another and kills the bike. I took the boot off and put my hand over the throat of the carb and the cylinder started to fire. I sprayed a very small amount of carb cleaner into the carb manifold and get an RPM change, so I have tentatively ruled out compression and spark. I sprayed carb cleaner all over and no RPM change.

Something seems to be wrong with this idle circuit... I can't imagine what though because I have tried everything. The plug is not wet when I pull it, so I think it's just not getting gas on idle.

FYI, stock air box and pipes.

I am completely stumped on this one...Can anyone give me any help on this one?

[OneShadeOfGreen]

It's most likely the pilot-circuit on that no.4 carb, either the jet or drillings, it needs carb-cleaner squirting through the pilot-jet, air-jet and pilot-outlets then blasting with compressed-air.

There are loads of posts/threads on here about the same or similar problems, not always possible to see the problem so even though you think everything is clean...............

Make sure to check the float-height before reassembly.

[apbling]

Thats what I assumed, and I used compressed air, carb cleaner and alot of cussing to clean them all out. It is definitley, for sure clean. The air comes in through a small hole in the throat, it easily comes out the jet in the bowl and the where the mixture screw goes. I also checked float height. Still no dice. I thought that height looked a little low (my picture in my book is iffy at best), but it was actually a little bit higher than the other 3 carbs (that are running fine).

Would it be possible that the seat is damaged on the air/fuel air mixture screw? So I would be getting so much air through there that it's barely getting enough fuel?

[OneShadeOfGreen]

Sorry, i never read your first post closely enough, just had a couple of pints for the first time in a couple of months

It's possible that there might be too much air allowed past the screw but you'd probably see damage to the screw-tip if the seat were butchered.

Aah, gotcha, these have the air-screw up near the inlet, not a mixture-screw
into the inlet bore. have you checked the o-ring is sealing?

Have you definitely found that air/cleaner will come out of the pilot-outlet or progression drillings on the engine side of the slide?

Have you checked if the slide is sat correctly compared to the other three, might be a venturi issue.

Don't forget if your float-height is higher than the other three then the fuel-level will be lower (if that's what you meant).

Sorry if i'm talking rubbish, best get me head down and try again the morra.

[apbling]

Hey, no problem... about to do the same thing. It's been a while, so I'm thinking it'll be an early night... anyway

Yep, o-ring is actually new... and I swapped the screws between the others to see if that made a difference.

The slide is good to go. Sits evenly with the others, moves freely and good.

I was referring to fuel level, not float height. The fuel level was actually higher, so I lowered it to match the others and the spec.

now that you mention it... The air comes into the small hole on the airbox side of the carb... goes through the passages (and the screw) to the pilot jet... but I never followed it from there. It needs to route back to the throat somehow... on the engine side of the slide.

I never thought of this... I hope this is my issue... feel dumb and excited to give it a shot tomorrow again.

I just wish I could get a good picture of my carb air/fuel flows. Once again the fearless clymer manual doesn't have a good diagram. My OEM 750 LTD has a great one that would be of good use.

[apbling]

Figured it out!

The pilot passage to the throat of the carb is plugged... well it passes SOME air, but not as much as the other ones... problem is its in such a god forsaken place that I spent hours today with air and carb cleaner and I can't get it to clear out.

I'm gonna to try boiling it in lemon juice...

If not maybe see if a local shop can throw them in a sonic cleaner.

Anyone else have any advice? Its in a part where it makes a 90 deg turn and theres just no way to snake a carb cleaning tool into it.

[OneShadeOfGreen]

What more advice do you need, if boiling/soaking doesn't clear it then an ultrasonic-bath should sort it out

If it's a blocked drilling a good soak for a few hours is usually the answer.

[650hardtail]

ive found some small gauge stranded copper wire can be used to clear the passages..
do it carefully

[apbling]

I'll have to try that. I actually really screwed myself bigtime last night. I was using a dental pick to try and clear the jet out... and you might have already guessed it, I broke the tip off in the opening of the passage. So now I have a plugged passage from hell and a tip of a dental pick stuck in the opening in the throat of the carb!

I just can't imagine what the heck in is in there that the air, carb cleaner and lemon juice didn't get it out. Whats odd is that you can shoot it with carb cleaner and try to get the torch tip cleaning tool in there... then shoot it with air and if seems like things are getting better.... so you shoot some more carb cleaner and torch tip cleaner...then shoot it with air again and it actually gets worse. It's like whats in there keep flopping around, but doesn't actually come out.

I'm tempted to just get a set of parts carbs off ebay or something and just replace that #4 carb.

[jtcNinja]

Probably the easiest thing to do is just replace the carb as you said. Can you get the dental pick out but blowing air through? or does it look like a lost cause?

[apbling]

Yeah, tried the compressed air... 180 psi wouldn't move it. It's wedged in the opening of the pilot circuit and throat of the carb, but there is no good way to actually get close to it.

I'll keep trying to get it out, but even then I have to get the original pluggage out! One positive thing is if I get a set of parts carbs, I can maybe get a choke mechanism with no broken doors and actually have a working choke!

[OneShadeOfGreen]

I can maybe get a choke mechanism with no broken doors and actually have a working choke!

Oooof, them bloody things, pain in the arse

Probably flaking varnish blocking the drilling.

Maybe a pencil-type butane torch will get both the blockage and the broken tip v0v

[apbling]

Good news! I got the stupid dental pick tip out. There is a local shop here that does good work and the guy tells me he can unplug it for me... I'm thinking it might be worth the $10-$20 to just have him do it.

I am second guessing those choke doors now... They are notorious for breaking off and if I find a set with all four of them, I run the risk of them coming off. Maybe I am better off just toughing it out.

I do have a "manual" type of choke aka stuff a hankerchief in the intake to the air box

[OneShadeOfGreen]

I read somewhere once where someone had done a mod for the choke-flaps, no idea where i saw it now mind.

[apbling]

Actually, I found it over at KZ rider. I don't go there much...not sure why, I guess I just don't.

But some guy on there fab'd up some replacement doors. He never replied how they worked, but I thought I would try it. I grabbed some 0.01" and 0.015" stainless shim stock from work and I'll try to cut some new doors since my choke still has the springs and pins.

[apbling]

OK, so when I pull these carbs all apart, I needed to drill out two bolts on the rod connecting to the throttle (it operates the mechanical slides). Problem is the bolt is discontinued by Kawie. It's a M5x14, but it has a countersunk head (shape like a cone). Anyone know where to find something like this besides the obvious hardware stores and Fastenal (they actually don't have one)?

[Bill Frazier]

You can get a 5x16 flat head in either steel or stainless at www.boltdepot.com and use as is or file or grind it shorter.

[wmgeorge64]

OK, so when I pull these carbs all apart, I needed to drill out two bolts on the rod connecting to the throttle (it operates the mechanical slides). Problem is the bolt is discontinued by Kawie. It's a M5x14, but it has a countersunk head (shape like a cone). Anyone know where to find something like this besides the obvious hardware stores and Fastenal (they actually don't have one)?

Try your local Menard's, the one here in Ankeny IA has lots of metric in plated and stainless. Plan "B" can you find a M6x14? Get a metric tap and the correct drill size for the tap, once again I think Menard's will have. If you are in Wisconsin should have lots of Menard stores....

[apbling]

wmgeorge64 - funny you mention that, I just moved back to WI (my home state) from Oskaloosa, IA. I worked at the corn milling place down in Eddyville.

Anyway, I'll check Menards out. I'd hate to have to tap out the carb mechanism though. I actually found something interesting. There is a guy on Ebay that makes the polished stainless bolt sets for bikes (he's actually not far from here) and I think he may be able to get me exactly what I need. Plus I'm thinking of buying the bolt kit to kind of dress up my bike a little bit.

I'm worried about the thread pitch though. It looks like an M5 always has a 0.8 thread pitch, but I'm worried this bolt might be unique and have a different pitch. Anyone have any experience with these thread pitches?

[wmgeorge64]

I would do the re-tapping as a last resort. Anther thought is. can you find a SAE or US standard screw that looks like it would work? If so, get that one and re-tap to standard SAE.... I noticed my side cover screws are now 1/4-20 US thread instead of whatever metric the PO lost. I changed all my screws for the seat mounting and side covers to stainless and Phillips head. Much easier to work with than cap or Allen head on the road.

My son has worked at the Eddyville plant as a union pipe fitter / welder in the past. Small world.