RM250 or 370 head?

[Quicksilver]

Is Suzuki casting number ISZZ 241 an RM250 or 370 head? Other ?

Cheers.

[VMX Andrew]

sorry to hijack this thread....but i was wondering if any of you know if i can fit an RM370 motor in an RM250 frame same year model..ive heard whispers it can be done but i thought id ask the pros first..reason is i know where there is a cheap 250 for sale and a 370 motor laying on the ground at a mates place...cheers

[Quicksilver]

I know wheres theirs a RM370 roller, so if you dont use that engine id certainly be very interested.

[Lozza]

Wouldn't looking at the bore size make it obvious  

[Quicksilver]

Nope. 

[Doc]

measuring the bore size or head gasket ID should..the rm250's were 67mm bore the 370 were 77mm.

Andrew, yes the RM370A-B/400C will bolt into the RM250A/B/C frames..only mods you may need are the rear of the exhaust 

[VMX Andrew]

thanks doc for the good advice...your a champion...no better still your a LEGEND...

[Quicksilver]

Thanks Doc..
It messures up at 82.98 maybe 400 or 465?  Its not the same to look at as the head that was on my old RM500.  The only info I have to go is "RM" written on the head with a paint pen. At least now I know its not 250 or 370.

[Doc]

  no legend Andrew, I have a 250C frame here that I'd planned my spare 400 going into when I get the time I best be absolutely sure before I state a definate..I'll go dig it out now and try it for size 

80mm is 400C/N/T Quicky (if only suzuki had made a U model between the C and N could have been amusing) the C has a round recessed gasket and the N and T have a surface gasket with 6 holes to fit over the studs.

Andrew, just double checked and it's all good in the engine/frame department..I doubt you'd even need to modify the rear exhaust mount as the 250 looks the same as the 370's.

[Quicksilver]

Thanks again Doc. Your a top man. 
I have an RM400 N or T head then. I'll be racing back out their in morning to see how much of that bike might still be laying about.