Scored cylinder: What happens if I don't replate or hone my cylinder?

Chris Long

Member
Jan 17, 2005
33
0
I'm doing a topend on my wifes 2000 RM80. It ran excellent, but needs to be done. I pulled the jug and just above the exhasut port is some vertical scoring. 2 of the scores I can feel with my finger nail. I have a new Weisco and ready to re-assemble but am concerned about the score marks. What could happen if I just clean it up real good, leaveing it as is and put it back together?

Thanks for your advice, Chris
 

Rich Rohrich

Moderator / BioHazard
LIFETIME SPONSOR
Jul 27, 1999
22,839
16,904
Chicago
As long as the plating isn't torn worst case is probably just ring seal at that point. The problem with a poor ring seal on the exhaust side is it runs hot already and it's the major thrust face so lubrication is really put to the test there even with a perfect seal. A poor ring seal will tend to blow combustion heat past the rings and vaporize the oil on the cylinder wall, which increases the chance of seizures if it's run hard. If the bike is just plonked around it's much less likely to be a problem.

If you pop the exhaust off once in a while and inspect the piston through the exhaust port you can monitor it's health reasonably well.
 

Chris Long

Member
Jan 17, 2005
33
0
I got the cylinder at the machine shop right now and he said this is an old school cylinder 2000 RM80 before plating and can be honed ($15) or bored .1 over for $45. Should I do it?
 

Chris Long

Member
Jan 17, 2005
33
0
I'm taking my machinists advice and believing him that this cylinder is not plated. I thought all 2 strokes were plated (sleeved). Not this one evidently.

Anyways, he said the the scoring was bad, so I'm doing it right and boring it a tenth over with a new weisco piston to match. The machine shop is charging me $60 for the bore and $100 for the top end and gaskets. I also had the head resurfaced as some radiator fluid was getting by and I could smell it in the exhuast. Thats what originally made me pull the head apart was a pressurized cooling system and sweet rads smell in the exhasut. Thanks guys. I hope my wife will thank me but I'm sure she's rather have some new jeans for the money.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
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Merrillville,Indiana
Ditch the jeans and get her some pink racing pants! 00 rm80 should have been plated, stock. Someone could have put an iron liner in it. If they did it should be obvious from where it got pressed in.
 

Rotorranch

Member
Feb 10, 2007
436
0
whenfoxforks-ruled said:
Ditch the jeans and get her some pink racing pants! 00 rm80 should have been plated, stock. Someone could have put an iron liner in it. If they did it should be obvious from where it got pressed in.

Beg to differ WFFR, but if you look at the fiche for the '00 RM80, you'll see Suzi shows OEM oversize pistons, therefore, it's not a plated bore. :) If I hadn't looked, I would have also thought it was plated.

Rotor
 

Jasle

Sponsoring Member
Nov 27, 2001
1,358
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a whole bunch of 2 strokes were not plated...but sleeved is a different type of situation all together. don't get them mixed up. sleeving is actually putting a sleeve inside the stock cylinder. plating is a very thin coating inside the original cylinder.
 

whenfoxforks-ruled

Old MX Racer
~SPONSOR~
Oct 19, 2006
8,129
2
Merrillville,Indiana
Somewhere around 00 they plated the 80 bore, on some models at first. Over seas in particular. Wiseco offers a pro lite piston. They have an asterisk for the coated bores.
 

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