Update on previous post

[coastie903]

Well, turns out the Blaster the kid sold to me wasn't a big bore at all... just a 67.5mm piston... but got a great deal on it nonetheless... anyways, he put a FMF Fatty pipe and a Powercore II silencer, reeds, oil pump blockoff and the overbore, and never re-jetted the carb. It was idling like junk, and didn't really have the power it should've. I ran a compression test this morning after warming it up a bit, and got like 107psi, so I know the top end is due. I'm going to try to get away with just a good hone, and a new Wiseco piston kit, since it's already .060 over. I also noticed a knock coming from the motor, although I couldn't quite pinpoint exactly where it was coming from. Anyone have any ideas as to some common causes of a knock, PIston slap maybe??And will a new top end and proper jets fix the problem? Any help would be great!

 

[stephen12091985]

yea it could be piston slap.you would have to bored it to the next size and get a piston to match

 

[rideyamaha09]

The noise you said could be piston slap, blaster engines are kinda noisy to begin with too. You might be able to get by with a hone, but it'd be best just to go up a size. You can pick up cylinders on ebay pretty cheap once you run out of room to bore yours anymore.

 

[sillykid]

noise may also be the slap in the crank rod when you pull your top end check for side to side play and up and down play

 

[Awk08]

in the rod.. there should be some side to side play, but little or none up and down

 

[coastie903]

Good to know guys! Thanks for the info, and I'm hoping to get the jug off this week at some point, weather and work depending. I'll update with what I find. Thanks again!