ISDE Aftermath
 

Hi guys,
I finally got my bike back from the ISDE and tore it down this evening. The piston seized in two spots on the exhaust side, right by the side exhaust ports. Must've been too lean on the needle, but I still don't get why it did it at the end of the day instead of the start.

The cylinder needs to be replated and a new piston and rings installed, but that seems to be the only damage. Bottom end looks good, same with the rod, head, etc. The question is, do I bigbore or not. I'm thinking of making it a 275...Opinions?

http://i33.photobucket.com/albums/d6...c/Cylinder.jpg
http://i33.photobucket.com/albums/d6.../Cylinder2.jpg
http://i33.photobucket.com/albums/d6...ac/Piston1.jpg
http://i33.photobucket.com/albums/d6...ac/Piston2.jpg

Looks a similar seizure to mine recently. I was running very lean in tight woods, when I did a more open Rally type event and it was held at constant speed a slight restriction in fuel flow pushed it over the edge.

As for 275 I'm the wrong person to comment - I have a 300 but would like a smaller motor. If I lived anywhere near you I'd offer to swap!

I think it was that deeper sand with the needle too lean that did it in. I used to ride in sand alot and we had to go up on the main also.

At the last minute, just before impounding in Chile, we jetted Brian Hasslen's 300 a little fatter then he was using on the test track in La Serena.

His 300 is a little less finacky when running rich, compared to how a 250 would run, and we decided it would be safer to run rich for the first day and adjust the jetting leaner later on if we needed too.

The first mistake a lot of Six Days "first timers" do is run too lean of jetting and over the year's, I've been to 12 Six Days, I've seen a lot of riders make that mistake and lean sieze.

A good Day-One Six Days approach is to run your jetting on the safe side, at least until you figure out how your bike is going to run using local fuels. The jetting track gets you close but there's no replacement for a couple hours in the saddle under race conditions.

From some of your more recent posts it sounds like your comfortable shooting for a silver medal this year ( in Greece ) and a little fatter jetting isn't going to keep you off that pace.

Hey Steve,
Lesson learned. Silver in Greece is my goal. I was on silver in Chile when my bike died and I wasn't overly comfortable in the sand or special tests. Greece looks like the terrain around here so hopefully I'll do better there.

I'm also still toying with tryiing the Romaniacs, but I gotta do a lot of fundraising to afford both races and a month in Europe. We'll see.

If your budget can afford it I'd go for the complete 300 stock cylinder, head and piston, that way if you need to do a top end either between or during Romanics or Six Days you'll be able to find parts.

I'll probably rent for this year's Six Days since I can easily bring my suspension, bars, etc from home to Greece (and possibly Romania).

I'm not sure if I want to modify the motor or not. It already makes good power (though it could make a little more in the open stuff) but I don't want to screw up the power delivery. Right now it's magic. It lugs down low as good as any thumper, yet it pulls hard all the way into the over-rev. It'd be nice to have a bit more meat in the midrange, but not at the cost of changing the delivery.

Isn't the saying go big or go home!.:D

No really , from the photos Ive seen of you, you don't look like you weigh allot and if you like the delivery of the 250 I would put it back to stock displacement.

I need the extra ooomph of a 300 to motivate my 225LB's with gear on, so I would personaly welcome more displacement.

Lets have a look at the underside of that piston. At this point i'm not totally convinced of the diagnosis, the reason being i dont see alot of damage at the exhaust side of the piston.I would want to know the existing piston to wall clearance before making assumtions.Ps Speedy will you keep the piston so that I can weigh it for a future registry?

I'll post a picture of the underside of the piston. My buddy thinks the jetting was fine, but that somehow the cylinder was suddenly cooled on the exhaust side (splashing water from creek crossings, maybe).

I'm planning on keeping the piston as once expensive souvenir from my first ISDE. And it's a reminder to triple check everything. Why do you want to weigh it?