engine id

[larky]

hope this is in the correct forum. I'm trying to identify the engine that is in my sled. the sled is a 1974 gpx 338 but the engine is a 433 and is fan cooled not free air. the fan is on the flywheel and not belt driven. the id tag has come off and the only numbers i can see on this engine is on the clutch side cast into the jug and it says 433 wb. trying to do a rebuild and need to now what it is. i did a compression check and the right side is 120 psi and the left side is 90 psi. also is it nessisary rebuild both cylinders or just the side that is low.

thanks for any help
matt

 

[SpartaSXr]

Motor

Should be S433 or Y433 on the fan housing also. If it an S the motor is a 73 GP433 if it is a Y the motor is a STD 433 motor from either a 433E or a Widetrack sled same year. Pull the jug and see what is wrong. You will be replacing the base gasket for sure and the head gasket. Check for ring problems and pray the jug is OK.

 

[YamaChris]

You can check the vintage area also. There might be a little more traffic for your questions as you tear into it.

 

[larky]

where on the fan housing is the numbers, the tag is missing, should it be stamped in or something? to the best of my ability from comparing on the yamaha web site it could be a GP 433 or a TL 433. but just a quess. thanks for the help guys. I'll post more when i get into it
matt

 

[larky]

bump...

 

[SpartaSXr]

Motor

The numbers are stamped into the fan housing. If there are no numbers on the fan housing then the motor came out of a Sno Jet. They had the same motor but had different covers. The numbers were on the upper side of the fan cover near the coils.