Ton up SR250: 100mph, 100kg, 30hp


Over 1,000 Posts
Big news! I got the engine running! Even before the end of the month of July! However, failure ensued right away.

All things considered, the first start went ok. It is always a process to go through and make sure things are right and I was not sure how it would go. But I did manage to start the bike and it sounds great. Reading a post from this thread a few pages back, I mentioned oringing the copper head gasket... I should have done it. I was convinced this is why the head gasket leaked and have therefore handed the cylinder in to a specialist to do the work. He only works when the weather is bad because he lives on a boat and lives the good life (actually an awesome role model!). So, we'll have to see when I can get the engine back together. I say I was convinced because I now think it was something else. Notice in the attached image the leakage is clearly around the dowel area of the gasket/cylinder. I think the dowel stopped the head from being able to be pulled against the gasket and cylinder. Now that the head gasket is 0.5mm thinner than stock, the dowel is 0.5mm too long. It makes sense but it was something I hadn't even considered (duh) when putting the engine together. I thought the dowel fitment would be a relatively loose fit in the vertical axis and there would be enough clearance. Obviously I was wrong. Anyway, I have ordered some new dowels and will file one down removing 0.5mm of material.

The good thing with this process was that there is good spark, the kickstart assembly works, the head was getting good oil flow and the whole package seems to work. I actually rode the bike up and down the street a few times before calling it a night and man it pulls! It is somewhat aggressive and feels more like my 500. This is when I discovered the second issue that needs to be solved... The clutch slips like crazy, even with new clutch plates and heavy duty springs. To remedy this, I have now ordered an XT250 6 plate clutch (instead of the SRs 5) and even harder springs and will even use spacers with those. Hopefully that helps! Any tips from you lot?

If anyone is interested, I made a start up video. It is not super gripping but at least you get to hear how it sounds at the end:


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Over 1,000 Posts
While I have been waiting for parts through this project and especially recently waiting for this engine work to be done, I have had a pet side project on the go. A problem I had with the last SR project was finding mirrors that looked good. The same problem was encountered with this bike... So I decided to develop my own design to test and potentially bring to market. See attached some of the prototypes and the first machined prototype. The mirrors are to be used for 'under arm' use - you look behind you along the side of your body and under your arm rather than over your shoulder. This way the mirrors can be much more compact and closer to the bikes centre line - so they do not 'protrude' too much. They are very light and very small at 50mm diameter. Not the most practical no, but very much good enough to see what is coming behind you and keep an eye on things. I have had mirrors set up like this in the past and thought it worked well enough.

The final product would be supplied with proper mounting bolts as well - not the horrible ones in the pictures. The extension bar is supplied to be able to clear the switch gear (not needed in all cases) and to get the right rearward angle on the mirror.

What do others reckon?


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