confused on piston # and also nuts coming loose.

[oachs83]

First off I rebuilt my 1986 R I have a good 10 hours on it and then it starting reving real high. I shut it down and noticed one nut that bolts the cylinder down was missing. I was about 100 yds from my truck so I raced it back and it started to vibrate the quad. I shut it down and now the two front nuts are gone and the rear ones were getting loose. First question is this a common problem and is there a fix? Second question I scored the piston but managed to keep the cylinder safe with a very light score that 600 and 1500 grit sand paper took out. I still need a piston though and ebay sells the cheapest for a 68mm bore. The number is Wiseco 526m06800 and some claim only fits 86 but Wiseco has the same part # for their 87-89 models as well. But Wiseco also has a 562m06800 for 87-89 that as well is a 68mm. So what is the difference in a 86 piston vs a 87-89 and why does Wiseco have the same part #'s?

[fearlessfred]

Originally posted by oachs83
First off I rebuilt my 1986 R I have a good 10 hours on it and then it starting reving real high. I shut it down and noticed one nut that bolts the cylinder down was missing. I was about 100 yds from my truck so I raced it back and it started to vibrate the quad. I shut it down and now the two front nuts are gone and the rear ones were getting loose. First question is this a common problem and is there a fix? Second question I scored the piston but managed to keep the cylinder safe with a very light score that 600 and 1500 grit sand paper took out. I still need a piston though and ebay sells the cheapest for a 68mm bore. The number is Wiseco 526m06800 and some claim only fits 86 but Wiseco has the same part # for their 87-89 models as well. But Wiseco also has a 562m06800 for 87-89 that as well is a 68mm. So what is the difference in a 86 piston vs a 87-89 and why does Wiseco have the same part #'s? no i have never seen the nuts back off .they must have not tightened proper. the 86 piston is a different animal than the later ones.does your piston have a window in it on the intake side and looking it to the intake side of the cylinder is it open or bridged .the cylinder should have a light hone done, and if that cleans up all the sanding marks u should be good to go with new piston and rings. ck the bottom end to make sure that u have not sucked dirt or sand into it

[oachs83]

You could say the piston has a window or some machining on kind of above and around the wrist pin towards intake side on both sides of the piston. Just curious why Wiseco has the same part # 526m06800 for 87 and 86?

[cdrookie]

the cylinder nuts coming loose is somewhat common when not using a head stay. torque them down with a little loctite and you'll be set, just check them every once in a while. when mine came loose i got away with just a new base gasket.

[fearlessfred]

Originally posted by oachs83
You could say the piston has a window or some machining on kind of above and around the wrist pin towards intake side on both sides of the piston. Just curious why Wiseco has the same part # 526m06800 for 87 and 86? dont know why, but thy are not the same

[methyman]

85-86 use 526M0XXX Piston size Go up to 69.50

87-89 use 562M0XXX Piston size Go up to 68.00

[oachs83]

Just look here. http://www.wiseco.com/ProductSearch.aspx

This is for a 87 250r and there is numbers that are a 526 and a 562.

[methyman]

This is a better link click to look

Piston Link (http://www.pistons-online.com/motorcycle2.asp?br=Honda&st=54&end=55)

[406Z26]

Maybe Dyslexia has a part in this.