300 won't idle. Please help!!

[stemplin]

I cleaned it up a little better and it does have the vertex name etched in the top.

I guess my question now is should I be ok replacing a vertex D with a Wossner C?

 

[Jakobi]

Well here's my thoughts on the matter.

The cylinder is stamped a B. Even with some wear it should be able to accomodate a C. As stated earlier there is only 0.02mm difference between each size. The Vertex is a cast piston. The Wossner is forged. Generally a forged piston will require a little more clearance by nature.

In my personal experiences with the A pistons I found the Wossner to be a better fit than the Vertex. I was comparing a piston with 75hrs on it to a new one though. Make of it what you will.

Unless if you are willing to go and have your cylinder measured up you are only guessing. I'd probably try and source a D quickly, but would also be comfortable ordering a C to drop in. If it felt loose I'd return in.

http://www.wossnerpistons.com/tech/piston-installation

 

[stemplin]

Put the Wossner "C" kit in and it fit like a glove but the problem is no better. I don't know what else to do.

There was a small amount of oily substance inside the ignition cover, could a leaking crank seal be causing these issues?

 

[Jakobi]

Ok. Update us on whats been checked/replaced again and what changes it has made.

Sounds like mechanically you might have a solid base to start with.

 

[stemplin]

The list of changes/updates is in my original post + the brand new top end. Nothing has seemed to help at all.

I did pull the crankcase drain plug but nothing at all drained.

I'm just not sure where else to look

 

[Jakobi]

Leaking crankcase seal on stator side would be causing a lean condition and a racing idle generally.

Did you investigate the choke assembly as described earlier? Did you drop a fresh plug in with the new top end? BR8ES work well and are much cheaper than the EG. Mechanically you have just about addressed everything so next would be investigating the electrical side further. Something I know next to nothing about.

 

[stemplin]

I was thinking the same thing on lh crank seal but what would account for the oily substance in there?

I didn't put a new plug in but the 1 in it only had 1 ride on it. I'll try that and then start looking into electrical.

 

[mrkartoom]

After reading everything through this thread my money would be on the right side crank seal. I've seen similar issues to what you are describing and you've ruled out about everything else. I think it would be worthwhile to do a crankcase pressure test.

 

[Jakobi]

whoa - just noticed this one. the choke has no effect? is the rubber bumper on the bottom of the choke assembly ok?

Has this been confirmed yet?

 

[stemplin]

No it hasn't. I've visually inspected right hand seal and saw no discoloration of oil in crank when I had the top end off.

I feel really stupid about this but I now suspect the spark plug boot. I hadn't noticed how loose it had gotten but feels like the rubber is really the only thing holding the plug. Would this cause the symptoms I've described?

 

[stemplin]

My bad on previous post. Choke has been checked and it does make a difference. It's just not a big one since it's running so rough already.

 

[Jakobi]

That was the next step. Electrical. Spark plug, plug cable, coil, stator, cdi.

 

[mrkartoom]

Sounds like you might be on to something with the plug wire. Take the cap off and make sure you have a good connection. If you have the length you can cut them back and re-attach the cap. If you have a high resistance connection it's possible you're not firing good at certain rpms. Maybe that would explain all the spooge. I guess if you were burning tranny oil you'd know it by the smell.

I had a plug wire shot on a bike once and I recall the bike just breaking up when I started to get on the gas. Otherwise it idled fine, so a bit of a different scenario. There were only a few strands of wire left at the plug connection and I was able to cut it back to good wire and all was fine.