2002 cr250 pinging and surging issue need help

[Funnyguy]

So I rebuilt my cr250 the end of last season because I swamped it out in a massive mud puddle, new honda crank and bearings, wiseco piston kit...

I've broken in the engine correctly last season and it ran good for maybe 1 ride last year and it has developed a low RPM pinging and surging when stopping. Started last ride of last season so got the bike home and checked slow jet in carb, sure enough it was clogged so I thought I fixed it once cleaned. Now fast forward through the winter to last weekend, 1st ride of the season, same problem. I checked the slow jet, clean. Reeds look good, only thing, I might replace the air boot and reed cage gaskets but not convinced that's the problem.

Has anyone here had an air leak at the air boot or anywhere else? What would be causing this lean condition? It seems lean at low rpm but rich everywhere else. The plug was black. 

I need some advice, maybe air leak at left crank seal? What am I missing? 

Thanks for any advice.

[Br0ck]

So I rebuilt my cr250 the end of last season because I swamped it out in a massive mud puddle, new honda crank and bearings, wiseco piston kit...
I've broken in the engine correctly last season and it ran good for maybe 1 ride last year and it has developed a low RPM pinging and surging when stopping. Started last ride of last season so got the bike home and checked slow jet in carb, sure enough it was clogged so I thought I fixed it once cleaned. Now fast forward through the winter to last weekend, 1st ride of the season, same problem. I checked the slow jet, clean. Reeds look good, only thing, I might replace the air boot and reed cage gaskets but not convinced that's the problem.
Has anyone here had an air leak at the air boot or anywhere else? What would be causing this lean condition? It seems lean at low rpm but rich everywhere else. The plug was black. 
I need some advice, maybe air leak at left crank seal? What am I missing? 
Thanks for any advice.

You got old gas in it? That might cause pinging.

[Faded]

Pressure test it to find out if you have an air leak or not, you can search for the ‘how to’ on here if you’re not familiar with the procedure. If the left side crank seal is good (it should be if you replaced it in the rebuild) then the other areas to look closely at is the reed cage gasket and @ the base gasket where it mates to the case halves (front and rear). 

[Into the sunset]

Re-torque the cylinder bolts. Remove the carb and set the float height. Clean the whole thing with Hondaline carb cleaner. Replace carb make sure the carb bands are straight and snug. Loosen and retighten the reed cage bolts in a cris cross sequence to the proper torque.

 A big problem area for an air leak is the air boot to air box seal. The seal was weak new and after all the years since it left the factory it won’t be any better. A company called MX bones sells kits on eBay that solve the problem. I highly recommend you get one. 

[Azrael888]

MX Bonz

[arthur6]

It sounds like the rebuild didn't go too well. You'll get more experienced each time.