I just can't figure it out.

I just got the throttle shaft seals today, and installed them. Went through everything, resync'd the carbs, and took it out for a ride. Same issue.

It will not idle down. I played with the idle mixture screws a bit, but still nothing. I just can't find the problem. It is running a tad rich right now, and seems to run real hot. I tried the propane test again and still nothing. I can get it to idle down if I hold the brake, and slip the clutch a bit, once it comes down, it will stay. But when I give it gas, it idles back up to about 3K-4K, and stays there until I brake/slip clutch. I did get it to idle down sitting in the garage, but when I let off the throttle, is it a gradual idle down, not a drop to idle.

I am running out of ideas. I have had the carbs apart and recleaned/adjusted/sync'd about 5 times, new rering, checked cam timing and valve clearances several times.

I just don't know what to do anymore.


Any ideas?

 

I bet you are excessively rich.
Pick the darkest plug, go in about 1/4 turn, and give it a little try. If it's better, pick the next darkest and give that 1/8 turn in.

My opinion is that the gasoline has SO MANY additives these days to make it burn better that a slightly rich engine with good compression will not show any significant color on new plugs for a long time.

It behaves JUST like you have the choke partially open (running rich)

 

I had one throttle blade not perfect and it was hanging up and making the idle run up to 4-5k I could push the throttle linkage down and it would settle down but I was also running rich and the extra air going around the blades made the RPMS hang too high. I think it was the #2 carb that was the culprit.

Just remember the blades need to be able to close completely so you can not see any light around them. If you see any light thats an air leak. I know its a big deal to pull the rack back off and use a penlight to look at the position of the blades.

Hope that helps.

 

I have almost the exact same issue, I know some of my spark plugs are very rich, particularly the 3rd, but I have to take the tank off because I accidentally screwed on the throttle cable holder in the wrong position so it's covering the mixture screw. I'm going to take the tank off this week and fix it so hopefully adjusting the screws will solve my problem once and for all and get rid of that unburned gasoline smell.

 

hey there, just browsed through your past threads. did you get your compression problems fixed or are they still low? have you set the float levels (wet) on the carbs? like MN mentioned have you checked the butterfly valves to ensure they are aligned/centered in the bores and moving freely? did you put them back in the same carbs they were originally? are you sure the idle isn't maybe set too high and the pilot mix too rich to run at an actual idle position? just throwing ideas out. sounds like you are close though.

cheers,

Trev

 

My thoughts would be: Binding rack or individual butterfly that won't close or not easily; float levels not set correctly; and sync. Or a really sneaky vacuum leak.

 

I was looking closely at it last night after the post, the #2 choke lever was pulling on the choke a bit. I gave it a "speed thunk" to make the fork loose on the choke, then resync'd the carbs. It seemed to help a bit when sitting in the garage. I will be taking it out today to see. If that doesn't work, I'll pull the carbs again and check the butterflies.

I keep everything in the original place/carb when working on them. I did the wet float adjustment, and all are good.

Compression issue - not real sure about. I am thinking it is a leak in the gauge. It is about 25-30 years old - I bought it from whitney when I was in high school. I can't see a new ring job with less than 100psi in all cylinders. (Heads lapped/checked - cam timing checked and rechecked.)

I'll keep up when I find a solution.

 

C21
I had a issue when letting off the throttle the revs were slow to come down.
Could it be that your throttle bodies are clinging onto the walls?
I hit mine with some 1600? grit paper ( the walls ) and now it motor brakes fine.
While you are in there you might as well blow it out with carb cleaner.

 

After the choke adj, it seems to work better, but not great. I took it out this morning, and it idled down quicker, and didn't really rev. A couple of times it would hang a 2-3K, but I would snap the throttle and it would come down.

I am going to run it for about a hundred miles or so, change the oil and go through the carbs again. I will it the slides and bodys with 1000 grit wet paper, and check the butterflies - recheck cam and valves, and resync.

I am thinking about jumping to 1 number hotter on the plug. Any thoughts about that. (It is my understanding the hotter the plug, the cooler the engine runs - don't quite get that) I did notice that the engine wasn't as hot today as it was the previous runs.

 

DO NOT SAND THE SLIDES they have a teflon-esque coating and you will damage it.

Polishing the bores is fine however; the finer the better. (Pun intended.)

 

Thanks for the slide info - I'll be sure to NOT sand them.