Makita 6421 Build Problems

[I saw a lot]

The 6421 I picked up awhile back would race when started. Let a guy look at it (does small engines one the side) and felt it was a vacuum leak. Topend looked good so did more checking and I found the throttle cable was hanging up. Haven't run it much yet to see if it repeats or a one time problem. My guess it will act up again but we will see.

 

[trooney]

And thats why I was using rope, but I wasn't getting a solid stop with the rope I had, and I forgot I was given a plastic piston stop with my tool kit, so i gave that a try.

I haven't yet done a test yet. I need to find gasket material or rubber to block the intake and exhaust port. I know back when I worked on my muscle car, we use to spray carb cleaner around the intake or carb base gasket to find a leak. Not sure if a guy can do that with a 2 cycle motor.

Not ideal but it'll work in a pinch...

 

[..X..]

Well, I found my problem... Its the crankshaft seal on the clutch side.... I'm very surprised cause this is a brand new case half with bearing.... What are the chances of this bearing and seal bad being bad brand new? Any pointers on removing and reinstalling the bearing.

Thanks

 

[Johnmn]

Odds are the bearing is fine but it should be checked. I would guess the spring came off the back of the seal causing the leak

 

[..X..]

Update for anyone who has a similar issue in the future:


The vibration was from my clutch coming loose on the crank shaft, and the motor racing after I hit the throttle was my crank seal on the clutch side. Problem solved


Thanks for the ideas everyone!