Motor races - air leak/no compression and scoring.

GoldenMotor.com

DuctTapedGoat

Active Member
Dec 20, 2010
1,179
10
38
38
Nampa Idaho
My motor just started racing the other day. I'm super upset about it. :(

I swung by my buddies house to use his compression tester, and lo and behold - a whopping 80 PSI. So I'm thinking, bad rings, blown head gasket and got them on order (taking all my cash till payday). I dropped a teaspoon of marvel into it to be sure and that got me a few cycles of compression, so it's leaking like a stuck pig, though I don't know if it's crank seal, bottom gasket, head gasket or rings.

I popped the top to take a look and things are looking really good for being ran hard for almost a couple years. There's some scoring on the wall in a couple places, not too severe, but really anything is severe. It will need to be polished up nice and bright, but that's easy enough.

Buddy mentioned to me that I should crosshatch the cylinder, but I don't know how well this all aluminum block will take that.

I'm going to have to WD test it tonight or tomorrow, probably tomorrow.


Though, once I realized it could be a crank seal, I decided that I'm just going to order a new motor - though GasBike and KingsMotorBikes are the only places I saw that sell em. So, it's about the same price to get a top end and bottom end from Bicycle-Engines.com, maybe even cheaper.

So, with that coming in a few weeks, I'm transportationless.

I will be ordering a full top end rebuild kit for it on pay day as well, and my current motor will get worked on. i plan to port it and polish it, replace every gasket on the thing, clean it top to bottom. Then I'll have a good backup ride, and maybe even convince my girlfriend to start riding, as all the parts I've got is about 20 bucks away from being a complete kit.
 

GearNut

Active Member
Aug 19, 2009
5,104
11
38
San Diego, Kaliforgnia
I am sorry to hear of the demise of your main mode of transportation!
I cannot recommend honing any chrome lined cylinder. The best (worst?) I have ever done on a re-ring is gently scuff and de-glaze the cylinder with 2000 grit wet/dry sand paper.
Yes, I used water with a drop of soap while wet sanding it, and yes I washed the living begesus out of the cylinder afterwards. The chrome is only 0.010 thick at best, so you want to preserve the thickness of it as best as you can.

Edit: if you are going to hop up the new engine, do it right and upgrade all the bearings, studs, seals, ect. too.
 

DuctTapedGoat

Active Member
Dec 20, 2010
1,179
10
38
38
Nampa Idaho
Seals came in yesterday, so I got to work on it. The original seal was split into two pieces, so it was seriously toasted. Got the new one dropped in easily and it's running like it used to. Except now it's got new rings and a new head and base gasket.