random surging (more like screaming) idle!

[Griff]

OK. Got my CA95 back together after having the cylinder bored .50 over, new pistons/rings and valves cleaned and lightly lapped.

The carb. was disassembled, cleaned and dipped last night and is very clean now.

My problem now is that the bike will start nice and easy (one kick) and settle into a good idle, but after 30 seconds or so (and every time) the idle screams to the moon. I kill the key before it can do any damage, but damn these things can scream!

I know when it runs out of fuel (by turning the petcock off) it does the same thing right before the carb runs out of gas.

One time I let it go for a few seconds and it seams to surge up and down a bit, but still stayed pegged up high. This happened before the rebuild too.

Any idea what's happening?

I'd hate for this to happen while in gear!....crash...

[mk2davis]

When I first got mine running the bike would seem to surge but it was actually the slide getting stuck in the up position. Same affect, and a bit startling when you are first getting it started!

You may just have an air leak. Did you check the condition of your gasket and mating surfaces?

[aaron7]

Mine was doing EXACTLY the same thing unless I choked it. It's an air leak somewhere. I didn't find the problem... changed the carb and it went away.

[Spokes]

The engine does rev high prior to running out of fuel. Not only on the cycle engines I know but also mower and two cycle engines as well.

So the clue is the engine is way leaned out. Being that the engine starts and idles nice, then revs means you have consumed the gas and may be sucking air.

The first thing I would do is start the bike and get a screwdriver on the pilot air screw. When the bike begins to rev, begin to tighen to enrich the mixture. If the idle is reduced. done deal. If not then,

Disconnect the fuel line to the carb, with a container ready, open the tank stopcock and allow the fuel to run out for 30-40 seconds. Is the flow slowing down? If no. Reconnect fuel line If yes, you have dirt in the tank reducing flow.

If no, check the float bowl for proper adjustment. I know for a fact that an incorrect float will flood out the carb or starve it.

Hope this helps.

[Griff]

Ahhh the float bowl...

I'm thinking that's where I may find my issue. I never checked it for adjustment (lazy I guess) and when I restart it after the over revving, it takes 3-4 kicks to get it to start (like its out of fuel).

I will check for sediment in the tank too, good idea. I totally rebuilt the petcock with all new parts, and it does flow well, but there could be crap in the tank.

Back to the garage...(hope the wife doesn't mind grease on the my Easter clothes..)

Thanks

[Sam Green]

With a straight edge, check the mating surface of the carb where it mates to the insulator. I've seen lots of carbs bowed at this place caused by previous owners over tightening them.

Sam.;)

[Griff]

Thanks Sam, I'll check this out. I actually remember over tightening it once and the slide didn't move very smoothly after, but it does now. I guess I could have bent it up a bit.

Also, could air leaks at the valve caps covers cause this too? I'm waiting for my new Viton ones to come in, so the cap o rings are a bit old and probably leak a bit.

Any other common spots for leaks?

[Sam Green]

Thanks Sam, I'll check this out. I actually remember over tightening it once and the slide didn't move very smoothly after, but it does now. I guess I could have bent it up a bit.

Also, could air leaks at the valve caps covers cause this too? I'm waiting for my new Viton ones to come in, so the cap o rings are a bit old and probably leak a bit.

Any other common spots for leaks?


Griff, over tightening the carb shouldn't affect how the slide operates, It just causes the surface to bow.
The valve covers can't leak air as the inside is allready open to atmosphere via the breather on the top of the cam box/head.
The valve cover seals irespective of how compressed they look rarely leak oil.
One of the only places that might leak and it is dificult to tell because there is a means of getting oil past it is the crank seal behind the genny.
There are two seals in there and a small hole which allows a small amount of oil past to lubricate the starter freewheel mechanism.
My motors don't run generators or starters so I run two aftermarket outer seals with the oil hole blocked, I still get a slight weep of oil getting past, not enough to worry about.

Sam.;)