Doing engine over haul

[nd jat]

Well I ordered the parts to over haul the blasty motor. The rod crank bearing was shot. Has any one ever seen this in a motor? Not sure how long the motor ran this way. Last time I rod it died while I came to a stop to listen to a noise that it seemed to have just started making. I cranked it over by hand slowly and could hear cluking in the motor, so we pulled it home and took a look. This is what I found.

bottom of the crank rod

the bottom of the case. ouch.

crank rod bearings?? needle bearings, none that can be seen in the bearing cage.
I'm also putting new rings in to the motor too. Compression was around 90 psi. It was a good starter even that low. Thinking this is the first rebuild on this motor, has stock piston. The wear is really low on the cylinder also. But found out I need the main crank bearing also will need to order new ones, plan on replacing both even thou one is locked up. Looks like it got rusty not sure where the water came from to make it rusty.

 

[nd jat]

Update got crank and bearing will be installing them soon, just whating on seals and rings now.

 

[quam]

yeah, i've seen a blaster case trenched outlike that from the rod before.....
man, if you're gonna replace the rings i'd recommend just boring up a size and replacing the piston.
if your compression is that low, then it's not just the rings that have worn, the cylinder wall has worn too. that means that if you reuse the stock piston w/ new rings, and go to hone the cylinder, you're increasing the size of the cylinder even more.....this will increase the play between the piston and the cylinder. on a 4 stroke, it's not as big of a deal, but a 2stroke has ports on both sides. this meands that the piston will flap around and the skirt will catch on the ports (mainly the exhaust port). then you're looking at a chewed up piston and splitting the cases again to clean all the metal bits out of the crank chamber and bearings......
i know cuz i've been there!

 

[blasterman87]

yeah ive seen it before also, a blaster i baught awhile back was being ran with a mixture of 50:1 with weed eater oil...

 

[nd jat]

Well I know that stock pistons are sh*tty but the rings had .48 to .5mm gaps, The piston has hardly any visible wear. The cylinder is still in spec to the manual for a stock bore, I really don't see the need to overbore it till need be. I do plan on getting a wisco piston in the future. I'm not planning on racing the blaster, thou I may be bit in the butt with the piston later if not replaced by then.

 

[blasterman87]

it will run, and have more compression than it does now it just wont have the potential compression with a new bore, its not hurting anything by going this rout it should run you just fine i would put it together and do a compression check to be sure you should have around 130-135 stock

 

[nd jat]

Well she runs....!!!! The compression is far better than before. Wish breaking in the motor wouldn't take so long. So far it does seem to have more ughff at the bottom range after a couple of days easy riding. Should be fun to ride this summer!!