T20 Race Bike Woes

desmocat · Post by **desmocat** » Wed Jun 17, 2009 9:51 pm

So I think I'm cursed getting my T20 racer onto the track. Last year I got it finished but couldn't get the stock 24mm carbs to work, they were so worn that the slides would stick in the bores and return when I cloded the throttle. Not good!

So I pulled barells off, sent them to Scott Clough Racing to have new manifolds fitted to adapt to 28mm carbs from an RD350.

This past winter I put everything back together, rebuuilt the carbs, sorted out the electrical gremlins, then gave it a kick to get it started. It ran for a few seconds then stopped abruptly, almost seemed like it seized of got stuck, mind you this was at idle.

So I gave it a few more kicks, it wouldn't start. Checked the plugs, brillant blue spark with proper timing. Plugs smelled like race gas; I knew I was getting fuel int the cylinders. I even tried starting fluid, still no love.

I'm thinking this is a two stroke, if I've got spark and fuel it's got to run?

Then I kicked over my T500, noticed that it has way more compression.

Let's see; spark, fuel, what about compression? Took the plugs out again, stuck my thumb over the spark plug hole and turned the engine over. Right cylinder, yep there's compression. Left cylinder, ain't got no compression.

Aarrgghh!!! Pulled the exhaust head pipe off and looked into the exhaust port, I see scores on the piston. So I pulled the barrel off, and the piston AND the cylinder have two scores in them and the rings are smashed into the piston.

WTF would have caused this, it's a new engine with zero hours on it?

And there it was, lying on the transfer port area of the engine case...a piece of used safety wire. Looked like the tail of safety wire when you clip off the extra.

So I figure that somewhere in the past months when I had the engine apart I must of had some safety wire fragment fly through the garage and into the crankcase.

So now I'm going to possibly bore the cylinder out, get a new left piston, and split the case to make sure I don't have any other remnants lurking in the crank case.

Isn't building bikes fun!!!

johnakay · Post by **johnakay** » Thu Jun 18, 2009 6:20 am

Zook-e · Post by **Zook-e** » Thu Jun 18, 2009 2:35 pm

Air filters are your friend.

"We don't need no steenking air filters."

CJF · Post by **CJF** » Thu Jun 18, 2009 6:44 pm

Thats enough to make someone crazy!! Now i know why all those big time engine builders say to treat your shop like a hospital operating room when assembling an engine. An expensive lesson....but free for me

BTW...how are the new engine/carb changes working out for you on the T500 race bike?

H2RICK · Post by **H2RICK** » Mon Jun 22, 2009 8:59 am

I feel your pain, Ralph. I did a top end on a buddy's XR250 and I neglected to replace the wrist pin clips with new ones.....guess what.....one of them popped out and wrecked the piston AND the barrel. Since then, every top end gets NEW pin clips regardless. Grrrrrr.....