I have a 98 300 xpress and It is starting to get low on the compression and is hard to start when hot. So I want to take advantage of the winter to redo the top end. And I thought that anything I could do to the top end while it is apart to give this thing some more horse power would be great. So my question is what is the max safe bore size you could go on one of these. And If I went max bore what else would I have to do like jetting or anything. Also is there any cons to doing this besides having to buy a new jug next time it needs rings and a bore job. And what is the factory bore size is it 75.00mm.

 

On a 2 stroke you do not want to do the max bore on it. You just get what is need to bring the cylender back to good condtion. If you want to incress the power you can have the head shaved .20 off. Get it ported an get a good pipe for it. Not sure if they have one for it but a 250 pipe might fit. If you bore it to max bore an it leans out or have any problem where you need to rebore it you will need to buy an new cylender so just go .10 or .20 on the bore.

 

I have a dynoport pipe for a 300 express for sale! It really made my 300 come alive in the mid and top end.I had to calm it down because my wife rides it now. I also have the main jet for the carb too. Private message me if your interested.

davey