Rd250 vs RD350 Jugs

[soonerbillz]

Are RD 250cyliners the same as RD350 except for the bore?
I have set and was interested in using them for a build but was hoping I could just get them bored to 350.
Thanks.

[m in sc]

liner isnt thick enough to do that. you'll hit transfer port.

[stresa]

And they have a different height as the piston pin to crown height is different on the RD250 and 350 pistons.
It is not possible.
Regards Uwe

[m in sc]

good point on the piston/jug height. I forgot about that.

[stresa]

Fahron in the UK does conversions of the jugs but then you have 370ccm as he overcome the piston crown height with the 66mm piston of the DT175. But he uses new sleeves in that process.
Regards Uwe

[soonerbillz]

Sounds like it ain't worth a problem.
Yeah guess I'll just hunt down some RD350 cylinders and go from there.

[Vintagetz]

Some DT175 pistons don't have the ring pins in the right location for the RD boost/transfer ports. 

I run blaster pistons in my race bike. The pin is about 4.8 mm higher and they weigh significantly less than the stock RD pistons.  The higher pin position helps to relieve the pressure on the skirt a little (which is good for wear)

A very cheap way to hop-up for a 350 is to use 115mm rods, and blaster pistons and a 400 cylinder.  The Exhaust and transfer port timing on a 400 has more duration because it is designed for a longer stroke.so it is like spending $$$ on a full port job, you can widen it a (full race width is 70% of bore)

To make it work with the 350 stroke you have deck the top down and if I remember correctly you may take some off the bottom.  I mapped it out in cad before I did it, someplace I have all the specs.   Any machine shop can do the work with the specs.  It will give you a VERY lively - hot 350. at a very reasonable cost.