More Carb Issues

[HotRodYJ]

Seems like there are ALOT of carb issue threads, so I may as well add one more.

 

I've been wrking on my 83 which supposedly ran just fine a couple of years ago. I saved the bike from the scrap yard due to transmission issues. I upgraded to a 1300 trans and now trying to get the bike running. The carbs ended up being really really dirty, after going thru them a couple of times, the bike runs now, but I'm having an issue with a bad delay when I give it throttle coming off of idle, and then a very slow drop from 2500 rpm back down to idle. The carbs are really nice and clean inside, every passage seems very clear now. I did not mess with float levels, nor did I check them. I have sync'd the carbs using a carb stick and that went well. I did not replace anything, not even the diaphraghms because they look to be in excellent condition. The slides all dance about the same when the bike is running. No vacuum leaks at all that I can find. I've sprayed starting fluid around the intake boots and bottoms of the carbs and no leaks.

 

Any ideas of what to look for next?

[tazmocycle]

right beside the main jet tube sticking up in the middle of the carb, right next to it is another tube with a hole in it, did you see if it was open? i had to use a set of torch wire cleaners to get it open. it's about 1/32th of an inch hole, i used the smallest in the set and twisted it back and forth to i got it thru and then used the next in size and then the 3rd one to finish opening it up.

[MiCarl]

Your delay off idle is a symptom of a lean condition.

 

The slow drop from 2500 is also lean - likely a vacuum leak. Check out your vacuum lines, vacuum caps and carb holders for leaks. I spray a bit of starting fluid at suspect areas, some use unlighted propane torch, listen for rpm increase when you hit a potential leak.

 

**Don't use much of your flammable unless you like large fire balls.

[HotRodYJ]

Good ideas, but no go on either one. The hole in the metering blocks are all very open and clean. I can easily spray carb cleaner thu it and blow compressed air thru, no issues. They were plugged initially, but not now after going thru the carbs twice.

 

There are also no vacuum leaks at all. That's exactly what I did, spray ether on any and all possabilities with no diffrence at all.

 

What are the symptoms of bad diaphragms? Although they look perfect you never know.

 

How about the air cut-off valve diaphragms? What would a symptom be of those being bad?

 

What about leaking rubber plugs in the bottom of the metering block? Those are in pretty poor shape.

Edited October 25, 2012 by HotRodYJ

[GeorgeS]

Did you check the Intake manifold bolts, right at the cylinder heads. O-rings under there are known to leak. Only two Allen head bolts on each cylinder holding the Manifolds, onto the heads. They do come loose.

 

I remember one fellow said he replaced the O-rings, but still had leaks, and had to remove them again and apply sealant in addition to the new O-rings.

Well maby worth checking for.

[HotRodYJ]

Success!

 

Although no vacuum leaks could be found anywhere including around the intake boots, I decided to go ahead and reseal them anyway just to rule it out. Everything looked really good and put it back together with silicone to be sure. Still ran exactly the same, made no difference what-so-ever.

 

BUT, I did notice this time through that while running, only the right front exhaust pipe was hot. The other three pipes are dead cold. I stuck a new set of spark plugs in it this afternoon and after a few minutes going through the carb sync again, now she runs like she's supposed to. This is the first time I've ever heard this bike run (correctly).

 

Sometimes it's the simplest things.

[Venturous Randy]

Wow, a one cylinder thumper.

RandyA

[timgray]

A lot of us have discovered, that these engines, LIKE new spark plugs. It's either the really weak spark from the coils or just the temperamental design, but most times replacing the plugs is the answer to a lot of running problems.

 

My last bout with running issues was fixed with plug replacement. and I still cant figure out why. the old ones came out looking fine.