Vintage Dirt Bike Q & A

Due to the problem in locating a suitable piston for my 81 CR450 I am considering fitting a CR480 barrel and piston to the engine. This will entail a little work to open out the crankcase mouth to suit the wider cylinder liner of the 480.
I have posted this proposal on the Red Racer forum and have found a difference of opinion if this conversion is feasible.
The barrel can be made to fit with a little work but is the crankcase strong enough to take the extra load?
I am wondering if anyone out there has any views on this subject or has actually carried out this coversion.
I have a 480 barrel and head that interestingly was fitted with a thicker head gasket than standard, approx 1mm thick.
Obviously this would lower the compression ratio.
Would this thick gasket be required if a CR500 piston is used.
Any ideas?
Cheers,
Neil

Hi ,cant see no problem with fitting the 480 cylinder, i know that they made a mugen kit that made the 450 into a 480 and the cylinder head compustion chamber is almost identical between the mugen and 480. should not be a problem with crank as these remained the same. hope it all works out ok. jonathan

i've had my 450 cylinder bored to fit a 480 piston. it runs pretty good. the head gasket will have to be changed for the bigger bore. i used the 450 head .the cylinder sleeve is fairly thin but i've seen thinner . i,ve got a 480 engine and i didn't see a whole lot of a difference in the cylinders.