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Help w/ XS400 engine modifications

13766 Views 7 Replies 5 Participants Last post by  Sidney Franklin
Anyone modify an XS400 for improved performance? Are cams available? Any OEM parts that are common? Does an XS500 engine fit?

Thinking valve job, and mill the head for a little more compression. Aftermarket Trumpet slip-ons, new jetting. Nothing crazy, just a little more power.


Sidney Franklin
Bloomington, IL
1 - 1 of 8 Posts
Yeah, what he said. Putting a hot cam in an otherwise unchanged engine is not a good thing as cams, carbs and cans all go hand in hand. Most street engines are tuned for good mid-range performance, but if you go popping in a hot cam that wants higher revs to perform, you lose all power as now the motor has the wrong cam in it to perform in the low to mid range, and the carbs and exhausts are too small to make it breathe on the top end. The dude is right, get the boring bar and punch it out, go up a bit on the carbs and open the exhausts up a little. I ran a 750 Triumph Trackmaster on the dirt track circuit for a couple of years, and the engine was bone stock, but with 34mm Mikuni's (stock was 32mm), and a set of Supertrapps. If I had been running a lot of 1/2 miles, a set of different cams would have been called for so it'd wind a little more, but for the short tracks, nobody beat based on power (they beat me because they were better).

1 - 1 of 8 Posts
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