yz250 starting issue

[240Fun]

So a friend of mine decided to go buy a 2001 yz250 bike and took the guys word on how well it ran the guy had the been riding it when he got there and he said it ran great when he got it home it wouldn't start so he brought it to me to take a look at the intake boot was cracked and the gaskets on the reed spacer was leaking so all that is fixed now tried to do a leak down test and it will hold air for about 2-4 mins ie pump it up and it takes 2-4 mins to leak out all the air I did a compression test its about 155 psi the PO said he changed the pilot jet to a bigger size I'm guessing to compensate for the air leaks so I got my friend buying a new stock OE pilot the only thing done to the bike is a pro circuit pipe and silencer
Are there any common places for these to leak air I'd rather not have to pull the whole engine apart to find the leak but I think it's gonna come to that

 

[speedyslyder]

155psi is low...my 93 yz250 stock had 190psi even after it threw a bearing up into piston and head.Perhaps it might just be the gauge you are using but..if it is correct that is to low

 

[Larry's Shee]

Ha Ha, leak testing a PV engine is a PIA. Maybe the great and mighty can shed some light on it

89 Rm I recently did the trans vents up through the PV, so you don't know if the "leak" is crank seal, case, or normal leak from PV/ex. I did find leak at reed gasket and tiny case leak that I sealed from outside with 3bond.
Had a screw at PV cover leaking even with new gasket, and can't get at it with cyl on eng
Close enough for the girls I go with

 

[240Fun]

i might see about borrowing another compression tester the one i have i bought off of Ebay probably not the greatest quality but when i built my blaster KOR told me i should see 160 psi on my BBK and it came out right on the money and i have to say if it is low on compression wow it's a pisser to kick over i've learned don't do it in a sneaker or you'll end up with a sore foot

i'm gonna take a look at the carb and see if the PO put it back together right as well i got a feeling that he was tinkering with it

 

[speedyslyder]

it could just kick hard from worn parts.

research what the compression should be for your bike
all i know is it is not 155psi