carburetor issues

has anybody come across this before? I took the carbs off AGAIN, and found the needles in the slides were all different. they moved down in the plastic retainer. I pushed them all back to where they bottomed out to the plastic and then turned it 1/4. it seems to be good now. one was down pretty much, so I think that was my slight backfire problem. as far as my hanging idle problem, I took my brass plugs out so I could get the mixture screws out and I found one at 1 1/2 one at 2 1/4 one at 2 and one at 2 1/2. ya think it was set this way from factory, or did they move through the years. waiting for my new jets. should come today. even though I found all my exhaust valves to be on the tight side, I think I'm going to slap it back together and fire it up. I'm thinking the thicker oil (20-50) might have something to do with valve clearance.

 

The needles are supposed to have e-clips on them to keep them from moving. they should have a small spring with a plastic spacer on top to keep downward pressure on the needle. I don't think oil thickness has anything to do with tight valves.

 

you must get the valves in spec before you can do any carb tuning.

FU

 

Oil will have no effect on the valve clearance. Did you check them cold? I mean stone cold, hasn't been started in min 24 hours? If the valves are tight, your other tuning efforts are wasted.

 

valves it is. my needles do not have a circlip nor did they ever. they have a small round plastic piece that the needle pushes into, then the spring fits over that, and then a cap with a 6mm allen head goes over that and screws into the slide.

 

Valves must be out in spec:

Needles - if the collar is sliding, slide it down far enough that you can wedge a utility knife blade into the slit to expand it a hair. Slide the collar back up. Repeat if necessary.

Mixture screws- base setting is 2.5 turns out. From there, colortune, temperature tune, or plug chop tune to dial it in. Your settings were done at the factory, but now the bike has many miles and years on it. Thorough carb cleaning, then base settings, and bench sync, then running sync/colortune to dial in again

 

You have so many different threads going in this issue..... Condense them into one. It will be easier to read through and keep track of what's been said or done.

 

Good morning hogfiddles! We have a 1981 maximum 650. When we purchased it 15 years ago the only way to start it was choke on and NO throttle. Hit the throttle and die. Once it was warm and the choke was off it ran ok a little over idle. It sat for 12 years then my son rebuilt carbs, cleaned out tank, etc.. He drilled out plugs and adjusted all the same. ( still have all old adjustments documented. If it sits for a few minutes it will start for 2 seconds then die. Only wat to start is sticking fingers in carb and slightly raise the needles by fingers. Once running must rev to keep running. The slides feel like they are chattering on top of finger. They will never raise up. If you remove fingers it will eventually slow and die even though holding the throttle open. I read your response about many same issues but can't seem to find one that describes our issues. Can you please help? Thanks

 

if you have to lift the slides to make it run you probaly need to revisit the cleaning out of your enrichment circuit and its passages as well as the pilot jet circuits. they are what starts the motor and keeps it running at idle. your slides do not do much at the lower rpm.
you should also check the diaphrams at the top of the slides for little holes or rips. slides need to be polished to make them move freely and pass the clunk test which can be seen in the Church of clean thread.

quoting from the talkin-tech-various-thoughts thread
The pilot fuel circuit is active from idle up to about 2500-3500 rpms, and at about 3000 rpms the main fuel circuit starts becoming involved, and by 4000+ rpms the main fuel circuit is responsible for about 80%+ of the engine's fuel supply conditions.

read the following links
look under plug chops for an explanation of how the 3 circuits work and when in the carbs
http://www.xjbikes.com/forums/threads/talkin-tech-various-thoughts-on-various-issues.14608/

the church of clean Must reading
http://www.xjbikes.com/forums/threads/in-the-church-of-clean.14692/

naked carbs for understanding the circuits in photos
http://www.xj4ever.com/inside your carbs.pdf

and secret life of carbs
http://www.xjbikes.com/forums/threads/the-secret-life-of-carburetors.14751/

and a pdf on rebuilding
http://www.mtsac.edu/~cliff/storage/gs/Mikuni_BS-CV_Carburetor_Rebuild_Tutorial.pdf
great reading

 

Thanks for the quick response. The diaphragms are new. Are there any diagrams or pics of these passage ways? I worked on these things in the 70's. The slides were connected to the cables. No vacuum! My son 31, disassembled, cleaned, removed the plugs and jets. He soaked and then blew air through the passageways. He did say after cleaning the tank and putting new fuel he did get a little junk past and found some in the carbs. Maybe it could have gotten in these passage ways. Not sure if we back out adjustment screws to 2.5 turns. We set them at 3/4 to start.
He did use the cleaner and finish inside the tank before starting.

 

Read the church of clean and the secret life of carbs front to back. Bith of thise threads will answer most of your questions.

Unless your son removed the throttle shafts and the throttle shaft seals before soaking the carb bodies the throttle shaft seals are now toast and will need to be replaced. It is also imparative that the air jets get put back into the proper places. If he used the Hyanes manual as a guide then he put the air jets in backwards since the photo in that manual is mislabeled.

If there was still crud in the fuel tank that found its way into the carbs they will need to be cleaned again.

I suggest starting your own thread rather than hijacking this old one. You have much more work to do than just getting the carbs clean in order to get your machine back on the road.

 

the naked carb link and the pdf tutorial i posted for you have the photos you are looking for.
2.5 turns is where you want to start. slides are all vacccum in your xj

 

Thanks, just finished looking at it. Now I more understand how it works! One more question, if the tank is removed and replaced with a small tank ( for working purposes) and the vacuum line to tank is plugged will this cause issues?

 

If your tank is off and you're using an auxiliary fuel supply that is hooked directly to the carbs, you MUST have a cap on the vacuum port on the manifold boot. Otherwise you'll REALLY have a vacuum leak!

 

Right! I've got it plugged. The intake boots were very dry and started some cracking. He sprayed with silicone until it quit absorbing. I don't think there is a vacuum leak but maybe there is one somewhere. Only way I know how to check is spray with Carb cleaner while running and listen for an increase in rpm. I think after reading we'll adjust the valves and try again. I, assuming the valves can be adjusted cold. Any other words of wisdom?
Thanks

 

Valve clearances must be checked cold.

http://xjbikes.com/forums/threads/airhead-valve-adjustment-with-pics.14827/

 

Thanks, that makes it easy. Wish all tutorials were like this!