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Discussion Starter #1
Hello all. I'm a long time reader, first time poster. My wife and I are avid riders on both dirt and pavement. For the dirt, she rides the TW200 and I ride a CRF230F. I saw a 1991 TW on craigslist for cheap and decided I buy it, steal the tires for my wife and resell it. It needed cosmetic work, so I figured I'd pretty it up and maybe make a profit. Well... I don't think that's going to happen. The clatter I thought was cam chain or valves is something more. I'd like some opinions on whether or not I need to tear it down further after I replace the piston and rings - and maybe the cylinder. It kind of sounded like it had a rod knock, but the rod and wristpin feel solid. That's a chunk missing from above the top ring.



 

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If the rod is tight you'll be alright. It may have been in need of new rings for a looooong time to cause that chatter. That is a strange place to have a chunk missing from. Check the cylinder and make sure the bore is even all the way up. If it's good, you could probably get away with honing and replacing the piston and rings with the same size. If not, it's time for an over-bore. Shouldn't cost too much to have it bored out. How many miles are on the bike?
 

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Kwizard said:
Come on now; you already know that answer. Bite the bullet and get after it. You'll be the better for it. Sorry about your motor.


OK, 1 vote for tear it down!



I went out to remove the piston and noticed the wristpin had actually migrated over the circlip and was pretty much welded to the piston. I think that's the cause of the noise. I don't feel any slack on the big end of the rod and after I hammered the wristpin out, the small end of the rod looks OK. I think I'm going to wing it. I assume it's supposed to be a floating wristpin - haven't looked in the manual yet.
 

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Discussion Starter #5
If the rod is tight you'll be alright. It may have been in need of new rings for a looooong time to cause that chatter. That is a strange place to have a chunk missing from. Check the cylinder and make sure the bore is even all the way up. If it's good, you could probably get away with honing and replacing the piston and rings with the same size. If not, it's time for an over-bore. Shouldn't cost too much to have it bored out. How many miles are on the bike?


Odo shows 8,000 or so. I like your opinion
The cylinder still has the crosshatch pattern except a little at the bottom that will hone out. It WILL hone out...
 

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Discussion Starter #7

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Discussion Starter #8
If anyone cares, I put the piston and rings in and she runs great. I did some cosmetic work and some other repairs, so she'll make a nice bike for someone.















 

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Make sure that oil pump is working and the bike has the correct oil filter. Break her in like she was new again. I wish I could direct you on which break in style to use.



Lots of opinions out there (almost like an oil thread)




http://tw200forum.co...6/ShowPost.aspx



http://tw200forum.co...0/ShowPost.aspx



http://www.mototuneu..._in_secrets.htm



Turbo break in for older bikes 1960-1980's (I used this style on my 70's xl175)



Don't worry about honing the cylinder as it's entirely unnecessary and will in fact hinder the bedding in of the new rings.



Assemble the cylinder & piston dry then button it all up, ensure the timing is dead nutz.



Change the oil (duh) and fire it up, the _instant_ it starts, run the engine up to your normal maximum cruising speed, RPM's_do_not_ vary the engine speed for one full minute, you _MUST_ use a watch with sweep second hand as time will slow down on you, this will be the longest 60 seconds of your life, trust me.



After 60 seconds, shut it off and allow to cool fully (hours) before re-starting and setting idle adjustment as needed.



That's it! you're done and not only no more smoke but higher compression too. enjoy.



Oh, yes, here's the highly technical factory taught way to test for bad piston: Drag your fingernail around the sides, near the wrist pin and if the lines there catch like the grooves on a phonograph record would, it's junk.







http://www.dansmc.com break in style

On one hand, if you run the bike too easy, you run the risk of the cylinder walls glazing over and then, maybe, never seating properly. On the other hand, if you run the bike too hard, you run the risk of engine seizure. I suspect, that even if you do glaze the cylinder walls over, if your run the engine hard enough and long enough, the rings will seat. However, this may take a thousand miles, or more, to do.



So what's a biker to do ? Well, a compromise is in order. This is what I do with a freshly rebuilt engine. It will work on new engines too. On a straight, deserted road, I put the bike in second or third gear and accelerate with wide open throttle to about one or two thousand RPM BELOW red line. I then shut the throttle and coast down, in gear, to two thousand RPM or so. I then do it again. I do this about ten times. Then I ride around for a while at an easy pace. I do this several times, if possible. This seats the rings without overheating the engine.



I would continue to do this during the entire break-in period. If you are doing any freeway riding. That is, running long periods of time at a steady throttle setting. I would also add this. Shut the throttle off and then on again, very quickly, every three or four miles. This tends to draw more oil up on the bottom of the piston, lubing and cooling it. On a freshly rebuilt engine, I like to change the oil and filter at about two hundred miles and then every thousand miles thereafter. On a totally new engine, I change the oil and filter at one hundred fifty miles, three hundred miles, six hundred miles and twelve hundred miles. After that, change the oil and filter every one thousand miles.
 

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Discussion Starter #10
Make sure that oil pump is working and the bike has the correct oil filter.


Already done. Oil pours out of that port on top of the head and it has the same filter my other TW has, so I assume its right.
 

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Discussion Starter #11
Kwizard said:
What happened to that piece of missing piston ring?


There is no missing piece of ring. The picture makes it look that way because the piston smashed the ring into the groove.
 

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Hey Ishootstuff,



I have my own tale of woe and I hope it comes out as good as yours. I do have a question for you though: does the new wrist pin slide into the new piston easily? I had to drive out the old wrist pin on my bike and I assume that it is not supposed to be that tight.



Good job on the rebuild and a fine lookin' Tdub.
 

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Hey Ishootstuff,



I have my own tale of woe and I hope it comes out as good as yours. I do have a question for you though: does the new wrist pin slide into the new piston easily? I had to drive out the old wrist pin on my bike and I assume that it is not supposed to be that tight.



Good job on the rebuild and a fine lookin' Tdub.


I had to drive the wristpin out too, but no, it's no supposed to be that way


It's a floating design, so the wristpin should be allowed to move and is held in place by the circlips in the piston. It shouldn't be loose though.
 

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I had to drive the wristpin out too, but no, it's no supposed to be that way


It's a floating design, so the wristpin should be allowed to move and is held in place by the circlips in the piston. It shouldn't be loose though.


Thanks for the help, I appreciate the info.
 
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