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Discussion Starter #1
Hi im working on a friends 660 raptor kept blowing 3 head gaskets so he gave it to me to fix i usually work on 400 and 450s. starts up fine blows white smoke. So i took it apart the cam was messed up and head no oil to cam and head gasket blown. So i found a head head yamaha check it out and resurfaced head found out oil pump was bad so replaced oil pump and check outconecting rod no damage to rod. But cylinder bad too so new fresh cylinder and piston with rings install refresh head and timing chain installed. Adjust valves and she started up ran fine. Drove it on my trails no problem went to start it up the other day. she head hard time starting on compression stroke and i noticed bubbles coming threw radiator after doing leak down test. Now idk much on raptors so i hoping it just didnt do sumthing right but i follow a yamaha book. So if anyone has a idea let me know thanks
 

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Hi im working on a friends 660 raptor kept blowing 3 head gaskets so he gave it to me to fix i usually work on 400 and 450s. starts up fine blows white smoke. So i took it apart the cam was messed up and head no oil to cam and head gasket blown. So i found a head head yamaha check it out and resurfaced head found out oil pump was bad so replaced oil pump and check outconecting rod no damage to rod. But cylinder bad too so new fresh cylinder and piston with rings install refresh head and timing chain installed. Adjust valves and she started up ran fine. Drove it on my trails no problem went to start it up the other day. she head hard time starting on compression stroke and i noticed bubbles coming threw radiator after doing leak down test. Now idk much on raptors so i hoping it just didnt do sumthing right but i follow a yamaha book. So if anyone has a idea let me know thanks
I'm more into Raptor 700's, but this may be true for the 660 too. ALWAYS use a factory head gasket. The 'Cometic' brand has a high failure rate.

On another note, the water pump seal could be leaking into the motor.

WELCOME TO THE FORUM.
 

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Discussion Starter #3
Its a factory head gasket from yamaha and i did a leak down test and air bubbles coming from radiator so it b a head gasket leak
 

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660s can be finicky with head gaskets. Some times you have to use new bolts. Studs are expensive but it allows you to use a more torque. Sometimes you need to pull the cam cover off and re torque the bolts.

I use a Cometic EST head gasket with studs in my raptor.
 

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I may be getting older, but I refuse to grow up!
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Its a factory head gasket from yamaha and i did a leak down test and air bubbles coming from radiator so it b a head gasket leak
Did you retorque the head bolts? Factory head bolts are usually a one time use, but most use them more than that. A stud kit may be about $100 and can be torqued about 10% more.

Verify the head and cylinder are totally flat. Even new parts can be warped. Lay the gasket on the head and the cylinder and make sure the water passages are completely covered.

Note; FYI, the 660 head and valve cover are matched and should not be interchanged.
 

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Discussion Starter #6
I retorqued the head bolts befor they stayed in spec but i torn down to head gasket looks like the bolt that holds the cylinder broke and it was new bolts and cylinder so looks like that could b a problem and might need to mske sure the cylinder is good
 
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