larky
New member
Sled: 1974 gpx 433f
with a 433 fan cooled engine( not the original free air)
had uneven compression reading so i pulled the head and cylinder. I found that something has scratched the cylinder wall in three places. I can think of only two things that could of happened. 1. someone put new rings on it after it had chewed up a ring and damaged the cylinder and piston crown (becuase the rings are still there and not broken up). 2. something fell into the cylinder and the plug was replaced and the engine was run. no matter what happened this is what i'm stuck with. i'm sure its pointless but ....does anyone have one of these cylinders?( pto side). I now the next step should be boring the cylinder but I've never had that done so I am a little ignorant about it. how deep a scratch is too deep to repair? can I do just the one cylinder? the sled is just a trail sled not a race machine, but i do have respect for these old girls and want to treat her right. but I'd also like to do it as cheap as possible( at this point you probally think I'm on crack) becuase I'm a stay-at-home dad and i can't expect the wife to foot the bill for my toys. so guys I'm looking for an education in this prosess.
any help is greatly apreciated
thanks, matt
with a 433 fan cooled engine( not the original free air)
had uneven compression reading so i pulled the head and cylinder. I found that something has scratched the cylinder wall in three places. I can think of only two things that could of happened. 1. someone put new rings on it after it had chewed up a ring and damaged the cylinder and piston crown (becuase the rings are still there and not broken up). 2. something fell into the cylinder and the plug was replaced and the engine was run. no matter what happened this is what i'm stuck with. i'm sure its pointless but ....does anyone have one of these cylinders?( pto side). I now the next step should be boring the cylinder but I've never had that done so I am a little ignorant about it. how deep a scratch is too deep to repair? can I do just the one cylinder? the sled is just a trail sled not a race machine, but i do have respect for these old girls and want to treat her right. but I'd also like to do it as cheap as possible( at this point you probally think I'm on crack) becuase I'm a stay-at-home dad and i can't expect the wife to foot the bill for my toys. so guys I'm looking for an education in this prosess.
any help is greatly apreciated
thanks, matt
deadsledz
New member
Sounds like you have an exciter 440 motor. I would start with a trip to yamaha.com they have complete diagrams with part #'s also. LOTS of vintage sites if you know #'s. If you can catch a fingernail in the groove probably need a bore job, you cannot bore only 1 jug,you will need to bore both and new pistons. Good luck, Steve