I think I have an air leak but can't find it...

[SpenceDawg]

So I was riding today, when all of a sudden my engine got incredibly loud and started making that slapping noise. I realized my exhaust pipe had started to hang loose, so I pedaled it home and tightened those bolts so the pipe is sealed to the block again. However, when I started riding again, it was still making that sound as if it was getting too much air, and when I hold the clutch in, the engine starts to rev like crazy.

Now I know this means I have an air leak, and it's not the exhaust pipe being loose, so what could it be? I checked to make sure the carby is attached tight, and it's not that either. What are some other places I could look, before I start pulling it apart. This block is only a month or so old and I'd rather not start moving things around just yet if I don't have to. Thanks!!

 

[sp1ke]

head

as your exhaust came off ur engine took in too much air reved up and got hot check your head for leaks and skim it to make sure its not warped

 

[FurryOnTheInside]

".... when I hold the clutch in, the engine starts to rev like crazy."

Well I haven't started my engine yet but I have always read that you can pinpoint the location of the vacuum leak by aiming carb cleaner/ cold start/ flammable liquid at places between the carb and cylinder. The place where it changes anything in sound/rpm is where your leak is.

 

[crassius]

yes, but I prefer to spray water to find leaks

 

[FurryOnTheInside]

yes, but I prefer to spray water to find leaks

For safety? Avoiding dripping on a hot exhaust or whatever?

 

[crassius]

yes, and I always have a water spray bottle handy to cool running, stationary motors anyway

 

[SpenceDawg]

head

as your exhaust came off ur engine took in too much air reved up and got hot check your head for leaks and skim it to make sure its not warped

That sounds like its probably what happened, how should I go about checking my head? If there is a leak or a warp what can I do to fix that?

 

[Frankenstein]

That sounds like its probably what happened, how should I go about checking my head? If there is a leak or a warp what can I do to fix that?

First place the head on a digital or analog spectoral analyzer to find the warp degree. Then turn the head around and shave off just enough metal with a razor blade in the opposite direction of the warp degree.

When flat, reassemble.

Gillette makes a nice 4 speed shaving razor, you can go all out and get the 5 speed blades with the automatic reverse but I don't think the shave is any closer or better. Dollar store has plenty of disposable single speeds if you're looking for a quick fix.