Engine breathing

[Ken.Wallington]

Are there any mods or points to bear in mind when building a 500cc short stroke regards letting it breath properly?

I've seen some picture of engines with breathers added to one of the rocker covers.

Thanks

[nevhunter]

Don't enlarge the ports. The exhaust valve is already too big in the early 500's. Short stroke engines don't suck air in as well as longer ones and your port velocity will be lower. They rely on revs to get the extra power. so you might have to work on the cam and follower profiles. If it is for a trials type bike then that may not be necessary or beneficial as you want torque and response at lower revs. I am considering building a 500 trials motor with the shorter stroke 350 RH steel flywheels myself, so I'm interested in what you have in mind. Nev

[Ken.Wallington]

Will keep you posted. That's exactly the bottom end I'm using. With an XT350 piston and pattern short stroke barrel and head.

[nevhunter]

Thanks Ken > I will look forward to it. Nev

[Ken.Wallington]

New big end, small end made to fit Yamaha piston, things are progressing

[nevhunter]

Where did you get the head and barrell castings? nev.