RM-250-A barrels

[huskibul]

    ,so crs/rms what was the  diameter of the crankwheels? so i can check against my A, are you certain they were both an A and a B? (just like to be sure)   if so i could get a B/C crank and rod and B/C barrel/head/piston  if i decide to go that way,otherwise it's A gear all the way,thanks guys for the input cheers

[pmc57]

I have an RM 250A motor in my RM250B plus I also have a spare A motor built with B cases so the cases are interchangable.
I've used Wiseco TS250 pistons in both and they perform well, they're available up to 72.00 mm (2mm o/s) in 0.5mm increments, only thing you have to do is dress some of the skirt away at the transfer cut-outs to clear the crank wheels when it goes to the bottom of the stroke, just a couple of mm off the corners usually does it.

[huskibul]

  hey pmc'thanks for that, it's not a case of the A crankwheels  fitting in the B case's,it's a case of the B crankwheel fitting the A case's,(check the post with the 125 crankwheel diameters)all the other gear is compatable i know,the 250's maybe as crs/rms said ,the same diameter , but i need to be totaly sure ,if their like the 125's,it could be a costly arse up    ps it's not a problem it's a build and it's interesting

[crs-and-rms]

ive measured two A cranks and two B crank wheels i measured with digital verniers as my micrometers only go up to 100mm so not as accurate as micrometer would be  all  four are between 112.60mm and 112.70 mm in dia hope this helps i would just get a A crank ive seen so many on us ebay

[huskibul]

   thanks for those measurements, the whole point of the exercise was to see if i could use a B/C barrel on an A set of cases,as i dont have a barrel/head ,i know there 's A barrels on fleabay but their's more B/C barrels and more B/C everything else (pistons etc) hence the reason to think about doing the shift,to summarise unlike the 125's it looks like you can use A/B/C parts in either A or B/C cases as long as you use the corresponding crank(bottom pin location is different,giving 64-70mm strokes)another reason that could persuade me is the B/C has a broader power spread(long stroke)the older i get the more i like that thats, for the input guys ,shout ya a beer one day