Carb diaphragms & cute little pinholes

[Bob]

Okay, I know pinholes wiill affect performance. Quick question: just how do they affect performance? Reason I'm asking is I have found two diaphragms each with a pinhole. Just wondering if these are causing the symptoms my bike has or if I may need to look further. Symptoms: starts & run fines until after about 3 miles, then acts like it may be flooding. Can usually get it to run okay for another short distance, but then it's yuckkkk. I am in the process of repairing the diaphragms.

[TopCatGr58]

Hey there Bob,

They could be!? The vacuum slides are pulled up under throttle load and vacuum load to allow more air to mix with fuel, however if there are holes in them, then they won't slide up enough, causing less air to be allowed in, possibly excessively richening your mixture?

I was surprised though, when I had my intake filters off, and was running the bike just to see the action of the slides. Under a very slow increase of throttle and no engine/wheel load, the slides essentially didn't move up, cause there wasn't enough differential vacuum, the carbs were able to feed the engine the proper mixture of air/fuel with very little increases, up to 5-6+krpm!?

However, if I cranked the throttle from idle, they would be pulled up briskly and even bounced a bit before the engine revved up and the pressure equalized and they came back down!

BTW, give us some more details about your bike, how it's behaving , how it behaved before misbehaving, work done to it, type of intake/exhaust, etc., then we can have more info to make our "Guestimations" of what could be wrong!? :P
T.C.

[dbag51]

bob, I had a similiar problem with my xs, after cleaning the carbs, and going for a test run, it ran fine until I parked for a while. upon starting up, it ran really rough and lots of black smoke, as it would if flooded out. upon further checking, I found three small pinholes in the floats. After repairing them with a soldering gun, and reassembly, and installment, the bike ran fine! your bike may have similar holes and filling the floats with gas, dropping the floats down and flooding the engine. just a thought. I found them using near boiling water, and immersing the floats. the holes would spew out a stream of bubbles. this may be way off, but it is worth checking out! dbag51,an old claude guy!

[Bob]

Thanks guys. Found a couple of things after posting and reading the responses. Float bowl #3 was dirrrrrrrttyyyyy. Also found the air lines that used to go to the factory airbox just hanging out in the open, so put little filters on those lines..don't know if it will help, but it sure can't hurt. Gonna check her out Monday & see how she does....hope I don't have to walk home (lol). If the problem is still there, then I'll check out the float suggestion, dbag51. kewl, finding someone on here from--at one time--Claude. Been through there a buncha times....friendly people there.

[pgg]

Pinholes made my bike lag and flutter on light unloaded throttle at high speed.

[Geezer]

Re: Carb diaphragms & cute little pinholes

Originally posted by Bob
Okay, I know pinholes wiill affect performance. Quick question: just how do they affect performance? Reason I'm asking is I have found two diaphragms each with a pinhole. Just wondering if these are causing the symptoms my bike has or if I may need to look further. Symptoms: starts & run fines until after about 3 miles, then acts like it may be flooding. Can usually get it to run okay for another short distance, but then it's yuckkkk. I am in the process of repairing the diaphragms.

Wash the diaphram in soap and water. Let them dry over night and then fill the holes with YamaBond #5. A few hours later they'll be as good as new.

Geezer

[skids]

TC, if you really want unobstructed viewing, remove the bank-o-carbs, hook a shop vac to the carb outlet, and watch the slides rise. They do rise to about the half-way point quickly, then rise more gradually the rest of the way. It probably prevents a overly rich mixtures while accelerating at higher throttle.

Originally posted by TopCatGr58
Hey there Bob,

They could be!? The vacuum slides are pulled up under throttle load and vacuum load to allow more air to mix with fuel, however if there are holes in them, then they won't slide up enough, causing less air to be allowed in, possibly excessively richening your mixture?

I was surprised though, when I had my intake filters off, and was running the bike just to see the action of the slides. Under a very slow increase of throttle and no engine/wheel load, the slides essentially didn't move up, cause there wasn't enough differential vacuum, the carbs were able to feed the engine the proper mixture of air/fuel with very little increases, up to 5-6+krpm!?
(snip)T.C.