sieze/unsieze/rattle/wtf?

[Joeschmo]

ok so i have an old it175 and the other day i was riding it at full rpms and it siezed up on me... when i had gotten it home i put oil down the cylinder walls to hopefully unsieze it. It did unsieze but then whenever it started up it would have a terrible rattle in it. I lost about alot of compression and is now down to around 60. i took the head apart and the piston rings werent broken and it look okay. there are a few scraps on the walls but not big gashes or anything. i dont know what it could be new piston and what is it also worth fixing? Oh and also the piston moves side to side quite a bit as well when we took the head off.

 

[nickyd]

the cylinder/piston are scored - more likely than not you'll need a new piston and possible a bore on the cylinder depending on how bad it is

 

[Colorado]

You'll need a hone and rings at least, again, depending how bad it is. The piston moving straight side to side on the wrist pin isn't necessarily bad. If it rocks laterally (twisting it instead of straight side to side) your wrist pin and or bearing are probably shot.

You're more fortunate than I am. When my IT400 siezed at high rpm the connecting rod broke below the wrist bearing and made another rotation on the crank, blasting straight forward through the cylinder sleeve skirt and both halves of the case.

 

[Joeschmo]

Okay so it ended up being both the bottom and top end all at the same time :bang: I dont know how this is possible but it was the connecting rod that went and same with the piston

 

[Colorado]

Okay so it ended up being both the bottom and top end all at the same time :bang: I dont know how this is possible but it was the connecting rod that went and same with the piston

How do you mean, 'it ended up being'? If the con-rod went you shouldn't have been able to start it at all after freeing it up --- it wouldn't move the piston to create a compression stroke or turn the crank from the combustion fire.

Bummer, anyway! Sorry to hear it! From your list of bikes I see that was your newest one --- like me, you ride old iron.

I was fond enough of my '77 IT400 that blew everything but the transmission when the con-rod broke that I bought a '78 with no compression and a wicked piston slap. I thought it was just a bore and fresh top end, but turned out to need a whole replacement cylinder as a previous overbore was done out of square somehow (amature machinist, or something). Between the bike, bore (used cylinder) and some miscellaneous parts I've already got about US$600 into it, and it's an old bike. Something else could go next.

But the ITs are really cool! I've got an old KDX as well, and it is more advanced technology wise, but those old Yamahas have a different kind of cool. They were the first REAL Japanese competition enduro bike, and ruled the roost in their time. I can't seem to kick the habit.

 

[Joeschmo]

Yah i know im really tempted to fix it aswell can you rebuild a connecting rod by yourself or should you get yamaha to do it they told me its too hard to do i think they might have said that because i am 14 and just might want an extra buck but i donno i trust the people there and i like learning new things so i wouldnt mind doing it myself but dont have access to literally anything...

 

[Colorado]

Yah i know im really tempted to fix it aswell can you rebuild a connecting rod by yourself or should you get yamaha to do it they told me its too hard to do i think they might have said that because i am 14 and just might want an extra buck but i donno i trust the people there and i like learning new things so i wouldnt mind doing it myself but dont have access to literally anything...

You'd need someplace good to work and a lot of tools. Or money. Time's worth something too. You could replace a connecting rod and bearing, but you'd want to measure everything before you bought any parts.

 

[Joeschmo]

okay well i dont really think that it is the connecting rod because arent they supposed to have like a hair bit of movement in them. mine has that and wouldnt the motor be siezed period like it wouldnt move at all if it is that.? because it does move not freely but it will when you kick it over i really think it is a bearing but wouldnt not having to take the bottom end apart if i dont need too

 

[Joeschmo]

okay so it was the crank thats what it really ended up to be because it goes almost an inch up and down. so now my next question is would an it200 or 250 motor fit in an it175 frame?