IT/YZ 250D pre78 project

[Paul552]

Did you tig weld it? (the nice pipe)

I have seen a few done with oxy (fusion weld)

[head]

Yes, that was my first pipe with the Tig, I have made some with the oxy in the past. If you get yourself a #6 tip the oxy works well. Tig worked well also. Was down to about 15 amps for most of it.
Cheers Neil

[Lozza]

It was 786mm

How hard are you going to rev it ? That TL will give peak power at around 13,000 rpm.

[head]

Only playing with you. 1020mm

[Lozza]

That will still be a tad peaky 1150mm would be peak at 8500rpm

[head]

I worked it out for 8000rpm peak power. The cylinder has fairly long duration on exhaust port.

[Paul552]

I worked it out for 8000rpm peak power. The cylinder has fairly long duration on exhaust port.

Did you also modify the ports?

[head]

Yes the cylinder has been modified.

[Lozza]

I worked it out for 8000rpm peak power. The cylinder has fairly long duration on exhaust port.

Port timing is irrelevant the pipe decides when peak power is.

[head]

Yes I understand that, but don't you use exhaust timing to work out tuned length. If you do not now the exhaust duration how can you work out a length for pipe. What formula do you use Lozza?

[OverTheHill]

bought an IT400 motor from a wreckers many moons ago & fitted into a DT250 monoshock frame to go vmx-ing, used a pipe that should have been ideal off something like a 400-465 it or yz but was terrible [all top end, dangerously high rpm for an old shitta]. Found someone had-had a good play & it had 192 degrees exhaust duration so in desperation i added 100mm to header pipe [took a guess as couldn't find my 'graham bell' book] & transformed it luckily. [pages all fell out of both my graham bell 2 stroke & 4 stroke books in the end].

[head]

After a few initial dramas I finally got a decent ride on it today. Power seems good, with a good strong surge. May try and lighten the IT flywheel a little bit. But other than a bit of fiddling i think it is ready to race.

[Ted]

It certainly looks ready. Fantastic job buddy. Now pull your finger out and do the 465 before them gears rust away.

[TM BILL]

That looks great  i envy talented people who can build a bike like that and even design and build their own chambers 

[oldyzman]

10 out of 10 for our effort on the pipe. Hope it works just like it looks.