I have pulled the heads off of 2 different E81 engines. They both had the same size valves. The first was out of a 1981 Brat GL. It had the 2 extra 6mm bolts. The second was out of a 1982 Brat DL. It did not have the 6mm bolts. So, apparently the 2 extra bolts are not the final word on whether a motor has big valves or small valves. The valves measured 35mm exhaust and 40mm intake on both engines. Are these the big valves or small valves?  Thanks in advance for any information on valves sizes that anyone can provide.

IIRC big valve heads only came in '83 automatics, then every EA81 from '84 on.  I probably have that wrong, but nothing pre-'83 will have big valve heads.

83-on all have large valves. Regardless of lifter type. 82 and older all have small valves and solid lifters. 

 

GD

No idea of the difference between big and small valves measurement? I thought is was of little concern like a mm

Thanks to all for your responses. Does anyone know the actual measurements of the small and large valves?

Big valve:  41.3mm

 

Small valve:  39.6mm

Thank you john in KY for those measurements.  I agree with jono, not enough difference to get too excited about. 

It is the difference between 73 and 74 HP.