from usa flattrack.com
To the best of my knowledge, Engine only:
Cams are the same.
All SR's and 1979+ TT, 1980+ XT used the 47mm intake valve. All the heads with the 2J2 valve have more fin area.
The TT/XT models used magnesium cases and covers.
The SR's use aluminum cases and covers
The 78-79 SR used a larger crank wheel and the case oil scrapper for these are clearance for the larger wheel.
In 1980 all models went to an oil pump with 5 bolts to address internal pump leakage.
The CDI's are different for 78-79 and 80-81 SR, The late XT's 80-81 CDI is different from both SR models. You can not mix and match between the CDI parts. They need to match to series.
The TT's were points only.
SR's used a banded clutch.
Transmissions are the same for all.
There were two different sized carbs used on the SR 34mm 78-79 and 32mm 80-81, both were pumpers
The TT/XT used a 34mm no pump carb.
I think that is about it.
Paul
This is my opinion only. The banded SR clutch is better, stronger and you do not tend to get the worn / spread aluminum clutch ears as quickly. Downside its more internal weight.
I run the 79 heavy crank on mine (its for sale in the classified section) Seems to tractor off the turns better. I also run a small PVL rotor not the bigger stock flywheel. Having said all that I know many that use the smaller crank with no issues.
Pete
is the usa j2j motor different to aust ones this is not the first time I have read the flywheels are bigger in the j2j (early pre80) sr500s
