YZ80 Top End
- Thread starter felt5063
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riderdadof4
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- Dec 30, 2005
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gotta disagree get a yamaha one! I have found clymer and haynes to miss things (remove A - remove B remove C hey wait I can't take C off till I take this off grrrrr) either the guy taking notes is missing it or gets deleted in editing somehow? worth the $10 extra to know it's right!flattie said:
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- #5
I tried getting a manual for the 94; however, niether company makes them for this year. I called every place on the web and also checked both manuals web sites for a manual. I gues I will need to check with Yamaha direct. One question I do have is do I need to hone the cylinder?
riderdadof4
Member
- Dec 30, 2005
- 32
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honeing depends upon condition sometimes you do, sometimes you don't! If scratched or scruff marks may need to be replated. sometimes marks are only alum deposits from the piston and will come out with honeing. It really all depends on what condition it is in, but has a rule do you have to hone EVERY time you do a top end no! .felt5063 said:
riderdadof4
Member
- Dec 30, 2005
- 32
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check this thread guess there a differant therory on honeing
http://www.dirtrider.net/forums3/showthread.php?t=127046
my budddy who raced m/x in late 70's, now is the head mechcanic for a sea doo race team and is part owner in a repair shop said told me only hone when needed, I never know "when needed" so take it my clys to him when doing top ends and if it needs it he hones it, if it doesn't he just hands it back to me a says good to go. but these guys in this thread said to always hone to remove glazing I'll have to ask him about this I'm going to his shop tommorow to learn how to rebuild a crank while he does my son's kx 60!
http://www.dirtrider.net/forums3/showthread.php?t=127046
my budddy who raced m/x in late 70's, now is the head mechcanic for a sea doo race team and is part owner in a repair shop said told me only hone when needed, I never know "when needed" so take it my clys to him when doing top ends and if it needs it he hones it, if it doesn't he just hands it back to me a says good to go. but these guys in this thread said to always hone to remove glazing I'll have to ask him about this I'm going to his shop tommorow to learn how to rebuild a crank while he does my son's kx 60!
The breakin procedure is another of those controvercial issues. But don't let the details worry you too much, as you are dealing with a mass production engine, and not a highly precise machined part.
When you look into the cylinder, there should be cross-hatching marks. Overlapping swirls that are unmistakable.
These little lines need to be there. And when we rebuild, we need to make sure that all the contamination and crud are out of the little nooks and crannys that are on the walls and in the swirls.
A ball hone is used often to clean up the walls of a cylinder. But, you can also use a green Scotch-Brite pad and some elbow grease.
What you are wanting is the cylinder wall cross-hatching to be consistant from top to bottom.
After cleaning vigourously with the pad or a ball hone, take a clean rag with some pre-mix on it and wipe the walls down. You want to repeat the cleaning procedure until the rag comes back completely clean (no black carbon) after wiping.
I personally never use a ball hone. A ball hone will NOT hurt the cylinder walls in any fashion. They are way too tough for the ball hone to do damage. I simply have some reasons that I only use an abrasive pad like Scotch-Brite. I won't go into why I don't do this here, as it shouldn't matter in your situation one bit.
It is possible for a mass production motor to be way off. In fact, the cyliner can be slightly egg shaped. And if this is the case, you will see evidence of an inconsistant pattern on the piston and walls. If you see a scar or some sort of rub marks on the walls, you may have a deeper issue. You may need remachining.
Im my experiences, an 80cc two cycle that is as old as yours will have some major problems, as kids tend to ride the hides off of them. Be certain to get a Yamaha manual and take measurments of all the parts as you go. Find something that is out of tolerence according to the manual, and you need to replace it before going further...or else try to get lucky...and maybe Jr will end up with a new scoot. :)
When you look into the cylinder, there should be cross-hatching marks. Overlapping swirls that are unmistakable.
These little lines need to be there. And when we rebuild, we need to make sure that all the contamination and crud are out of the little nooks and crannys that are on the walls and in the swirls.
A ball hone is used often to clean up the walls of a cylinder. But, you can also use a green Scotch-Brite pad and some elbow grease.
What you are wanting is the cylinder wall cross-hatching to be consistant from top to bottom.
After cleaning vigourously with the pad or a ball hone, take a clean rag with some pre-mix on it and wipe the walls down. You want to repeat the cleaning procedure until the rag comes back completely clean (no black carbon) after wiping.
I personally never use a ball hone. A ball hone will NOT hurt the cylinder walls in any fashion. They are way too tough for the ball hone to do damage. I simply have some reasons that I only use an abrasive pad like Scotch-Brite. I won't go into why I don't do this here, as it shouldn't matter in your situation one bit.
It is possible for a mass production motor to be way off. In fact, the cyliner can be slightly egg shaped. And if this is the case, you will see evidence of an inconsistant pattern on the piston and walls. If you see a scar or some sort of rub marks on the walls, you may have a deeper issue. You may need remachining.
Im my experiences, an 80cc two cycle that is as old as yours will have some major problems, as kids tend to ride the hides off of them. Be certain to get a Yamaha manual and take measurments of all the parts as you go. Find something that is out of tolerence according to the manual, and you need to replace it before going further...or else try to get lucky...and maybe Jr will end up with a new scoot. :)
