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I have an 86 250r fourtrax and would like to know what exh port and transfer port timing should be. It has a prox cylinder 270 kit with stock stroke . Just wanted to check and see if I could get a little more out of my wifes quad. I have a banshee and it made a night and day difference on that. Thanks
 

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I certainly don't have the expericence that a lot of builders on here have... so you can take my 2 cents worth for what it is...


A lot of what you set the port timings to probably depends on what pipe you are running.....

But having said that, on my 250R, OEM cylinder, I have had pretty good results running 194E and 128T timing when combined with the ESR11 in-frame center mount pipe and CR ignition.

If you are wanting someone to port it for you, I'd recommend Nate McCoy (more-torque) on here. He'll treat you right and does excellent work.
 

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Well, I could write a book here but will keep it fairly simple. I am assuming you want an overall bike to deal with. Being a small displacement motor I would not go over about 192 on the exhaust. If it is the bridged exhaust port, keep it closer to 190 and widen and square up the tops of the exhaust ports and open the subs up some and square them up. More exhaust area will pick up top end but also help keep some midrange if the port timing is kept low. The transfer number of 128 is good enough, no real need of going much higher there. I would concentrate on a good dome design and compression numbers. Match up the exhaust flange to the cylinder and also the intake manifold to the reedcage. The little things help out more than most people think. Hope that helps, Bubba
 
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