Originally Posted by
Motu
I have a new plan,deep in the shit,the fertility of my brain plumbs new depths.I'm gunna make an XT500!
An XT600 is 95mm x 87mm,an SRX 600 is 96mm x 87mm,an XT400E is 87mm x 67.2mm....I have a 97mm piston.I'm going to use my 67.2mm crank,and just put the 97mm top end on,making a short stroke 97 x 67.2 motor - Mr Skid and I worked it out to 495cc,pretty close huh?
Now,the complications.....the cases will still need machining for the bigger sleeve,so I still have to strip the XT400,can't just slap the top end on.It will lower the compression with the shorter stroke...is this a bad thing? enough to notice?....I will do some measurements.I could put the big sleeve into my 400 barrel,and use the 400 head,same size ports,but smaller valves,but this will raise the compression....by how much? more calc required.A jetting nightmare with carburettors with unavailable jets.
I like the idea,no big cubes is a let down,but a short stroke big bore is an interesting idea....grist for the mill in my brain....
I've worked out the formula for maximum piston speed that i was telling you about - should be able to model the piston's travel on a sine wave, and differentiate to work out the redline based on the stroke. That doesn't take into account whether you'd get valve float or something other nasty at high revs.
The XT tacho only goes to 9k rpm though - you might need to fit an Apexi monsta tacho to the Renthals..
As for jetting I reckon it's going to be enough of a mutant to justify dumping the YDIS carbs.. Didn't one of the SRX sites suggest that the carbs from a gpx250 would bolt up happily to the manifolds?
We're all fucked. I'm fucked. You're fucked. The whole department is fucked. It's the biggest cock-up ever. We're all completely fucked.
-Sir Richard Mottram
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