Does this make any sense???

[hawk]

Since a simple compression test was bad I pulled the head and cylinder and the piston seemed looser than it should be.

Ran the numbers from the piston and it's a .75mm oversize but the guy said he had it bored .040 over which is 1mm right?

Did he install the wrong piston/rings??? The cylinder still looks like new with nice cross hatching from the honing. The piston and rings still look ok also.

 

[timsyfz]

Re: Does this make any since???

.040 should measure to be 67mm. from the sounds of it you may have a 66.75mm piston... Umm yeah it seems to be the wrong size piston for the bore.

 

[super noober]

Re: Does this make any since???

mabey he is just a moron and didnt know what he put in, mabey it is wrong. seems like the wrong piston would be bad, REALLY bad. lol

 

[hawk]

Ya, it's a 66.75 piston and you could lightly jiggle it around in the cylinder. I am 99.9% sure he put in the wrong piston.

 

[super noober]

a machine shop could tell ya for sure man. unless you just want to get the bigger piston and see whats up.

 

[timsyfz]

Who bored it?? Someone did it for you of for a previous owner?

Whenever I get a cylinder bored it becomes a process. I send the cylinder in to get sized, and then I get the next size piston bigger... Then I take the cylinder and piston back to the bore guy, and have them matched to the yamaha specs for clearances.

 

[hawk]

Previous owner had it done. said he had a 40 over big bore kit in it but seems to me like his engine guy knows nothing about engines. It also still had the stock jetting in the carb also.

I know some about engines but I will take it to a precision machine shop that builds racing engines to get their input. Course they may just laugh at my small 2 stroke when they build +1500hp BB racing engines lol. Hopefully they will plane the head for me also I:I

 

[yb200]

Who bored it?? Someone did it for you of for a previous owner?

Whenever I get a cylinder bored it becomes a process. I send the cylinder in to get sized, and then I get the next size piston bigger... Then I take the cylinder and piston back to the bore guy, and have them matched to the yamaha specs for clearances.

thats what i do also......take the piston and cylinder to someone and have then measured

 

[hawk]

Since the piston is def too small I went ahead and ordered the 67mm piston set from RockyMountainATV and will take it when it arrives and the cylinder and heads to the machine shop to have matched.

Wiseco Piston Kit Pro-Lite .040 (67 mm) - 2003 Yamaha BLASTER 200
Part # 1038400156

Question. How much can I have removed off the head and still run 93 octane?

 

[super noober]

Since the piston is def too small I went ahead and ordered the 67mm piston set from RockyMountainATV and will take it when it arrives and the cylinder and heads to the machine shop to have matched.

Wiseco Piston Kit Pro-Lite .040 (67 mm) - 2003 Yamaha BLASTER 200
Part # 1038400156

Question. How much can I have removed off the head and still run 93 octane?

i belive its .030, could be .035

 

[blasterfreek30]

^^yuppers that will keep ya safe on the pump gas