Engine misfire under light load

[89stroker]

Hoople,
I was at the dealership and asked what he had used to check for the intake leak. He used Brake cleaner, says that it works best out of anything they have ever tried and doesn't hurt any paint, etc. I know other guys that use it as well but I was out of it when I was checking for leaks.

"After I had my TFI for about a year I was experiencing the same problem as you describe. I called Dobeck and talked to the guy there. He had me do a couple of things to the TFI module like richen the green poteniometer up a smidge. That didn't fix the problem so I called him back a couple of hours later. He told me to box it up and send it back. He sent me a new one out as soon as he got the old one. I put the new one on and problem solved. They are very easy to do business with both before and after the sale."

Retrop, my problem want the TFI unit, I had an intake leak to the rear cylinder.

 

[Hoople]

He used Brake cleaner, says that it works best out of anything they have ever tried and doesn't hurt any paint, etc. I know other guys that use it as well but I was out of it when I was checking for leaks.

Thanks for getting back with the info but we really need to know which brand of brake clean because some brake cleans are flammable and some are not. Most parts stores carry both.

Earlier you had said your engine stalled when he hit the leaking seal. That makes me think it was a non-flammable spray. In the past, whenever I have hit intake leaks with a flammable spray, the RPM would increase (unless the hole was SO big you flooded the engine-- in which case you could almost hear the leak).

I am also starting to think the size of the leak plays a roll in the results also(?) and wonder how big your leak was. It couldn't have been too big of a leak because the IAC had enough steps left within it's adjustment range to make the bike idle correctly. On a large leak, you would run out of IAC range.
Thanks again.

 

[89stroker]

He said a non flammable spray, did not say which brand but I will ask him when he gets back from Sturgis as he left yesterday. When I checked with carb cleaner, I did once get a slight increase when I sprayed on the rear flange once, but couldn't get it to do it again.

 

[Retrop]

WD-40 works too. Cheap, inexpensive, readily available and most importantly it won't harm paint.

 

[Hoople]

WD-40 works too. Cheap, inexpensive, readily available and most importantly it won't harm paint.

I never used it. When you hit the air leak with WD-40, does RPM go up or does it cause an engine stall. Does it make the exhaust start smoking from burning the solvent?

 

[Retrop]

I never used it. When you hit the air leak with WD-40, does RPM go up or does it cause an engine stall. Does it make the exhaust start smoking from burning the solvent?

I have never had an air leak that was sufficient enough to stall when it sucked in the WD. I suspect if it were that bad, the motor might not even start up, but, never the less. When you squirt the WD and it finds a leak, there is a definite change in the exhaust note. No billowing clouds of white smoke. I seem to remember that the MOCO offers what looks like a small cylinder of propane that has a flexible rubber hose on it that allows the mechanics to deliver a small "whiff" of propane to the area around the intake manifold. When the propane is ingested the motor probably speeds up. I think I saw a picture of it in a service manual a few years ago. It reminded me of a freon sniffer that air conditioner mechanics use to find a leak. Once again, I am just thinking out loud here.