I will be having another look at it tomorrow as well as pop the cylinder off and see what I can see. I'll report back what I find...

Thanks Peter. I also found a place to turn me up a new head gasket if need be to get that squish right, so with any luck it'll be a goer in a couple of weeks.

Can you use that gasket paper? I figured it was just for oil jointing surfaces, not for the heat of a base gasket?

Very cool!

http://www.raceface.mx/

Thanks for the offer, but I am flying to Maryborough and it's just a practice day. Unless you were planning to be there on the day? Mind you, I am thinking about trying to get along to a BMCC dirt track day at some stage too...

Yep. I have sussed out a local company and will email them for a quote on what I need and will report back. My plan is upgrade the software, go to a new webhost (local) and do some integration if possible.

Saw a pic of Troy at the Ekka I think... maybe that's a clue?

Steve, I am hoping to be there to check out the practice day on May 12. I've asked Dave McDowell to see if anyone would be willing to lend me a bike to do a few slow laps.

Good plan Lozza, it's what I'll do. Thanks fore the thoughts re squish - I was clearly well off the mark. That's why I am not an engine builder I guess...   

Yeah Firko, I didn't follow Lozza on that one. Good point Head, I'll check that out. Re ultra wide squish, does anyone know correct squish clearance for the RM? I did some research and found that around 1.3mm (.040") should be a fair middle of the road number for a 250 2T. Is that not correct?

In the absence of any good idea why things are as they are, I want to fiddle base and head gaskets to get correct squish. I needed to know deck height so I had a baseline compared to my situation. But I also need squish clearance.

The obvious question Geoff. Sadly no, I don't have the old piston! But I can say that the new head and base gaskets are OEM, and that the gaskets on the bike when I got it are definitely thinner (ie used) than the new ones. The piston is, as SON notes, the correct piston. The old piston and combustion chamber were seriously beat up as something has been in there while the engine was running.

One curious thing about the bike is that from when I bought it (and I have done no more than maybe 2 hours on it), it has always run strangely - it will not rev freely, sounding like it is strangled or something. Yet on the bike it revs out OK, though without any noticeable 'hit'. I am wondering if the piston has always been close to the head and the new piston etc has just slightly exacerbated that situation. The bike itself is a bitza of sorts and I have no idea of its history.

Anyway, the main thing I wanted to learn is the correct deck height so's i can adjust gaskets etc as necessary.

Oops, what I meant was, get an IT guy to help me upgrade the existing system and fix the problems! Once I find someone and get a quote, I may need to call for donations to help fund it.

I have a strange issue with my RM250T - the new piston contacts the head. On checking, I can see that the piston top edge is about 1mm proud of the cylinder gasket surface. With a single standard head gasket the piston contacts the head, with two gaskets the squish clearance is 1.37mm. I have no idea what the standard clearance should be, but 1.37mm would be in the ballpark. A head gasket is 1mm thick. So, right there, it looks like the 1mm that the piston clears the cylinder by is the problem. I am just trying to confirm if in fact the piston edge on an RM250T should be flush with the cylinder surface. Anyone?

Yeah it IS playing up. I was contemplating trying to migrate to a different system but am not savvy enough. I am thinking of hiring an IT guy to help me do it. Stay tuned.

Cheeky or not Nathan, I'm with Bill. That KDX is a brilliant little bike and really ticks the boxes for me. And so much better looking than the real KDX175.

Yep, great issue!

Hmmm... I had a Supertrapp on my HL500 and it was a fairly short one. No internal baffles in that one, just the centre bolt and the discs. Whether though it's the shorter one is uncertain but I think the muffler was sourced when the bike was built around 1978 or so.