milled case??

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#1
I replaced the cases on a 99rm125, It apears the used **** cases may have been milled down??? The piton hits the head and locks it right up. It loks like the pison comes over the top of the jug about 20thousands or so. I put all my stock gut out of old case in there. is there a way to measure how much is milled and get a coustom gasket to compensate??? Thanks for any help
 
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#2
Measure exactly the distance from the bearing journal to the gasket surface for the cylinder. Check it against the old set. Mate an old and new case together and measure the distance.
 
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#3
Read Eric Gorr's book, in the section on RM 125s he gives you the year that Suzuki changed rod leghths.
 
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#4
The motors all togather, its just a back yard bike for my nephew. Dont really want to tear it appart or go buy a book ill never need again. We dont race, just ride the feild behind the house. . Does anyone know If milling the top of the case is done or Is it possible I bought a case set for a shorter rod motor??? Or how I can tell the year of the cases from The number on them. They both start wih f114********. Thanks for any help or opinion. I need all I can get these days.
 
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#5
hi, could you not just either use 2 headgaskets to increase the piston to head clearence or if you measure the amount exactly that the piston sticks up from the barrell then get the head modified by a tuner to cut into the head and give the proper clearance.

p.s. sorry dont know if that year rm125 has a actual headgasket or not (o-rings?). if it doesnt im sure the latter method would work.
 
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#6
steve.emma said:
hi, could you not just either use 2 headgaskets to increase the piston to head clearence or if you measure the amount exactly that the piston sticks up from the barrell then get the head modified by a tuner to cut into the head and give the proper clearance.

p.s. sorry dont know if that year rm125 has a actual headgasket or not (o-rings?). if it doesnt im sure the latter method would work.
Thats what im thinking. Need to know for sure that the piston is supposed to only come up to flush with the top of the jug. thanks for the advice, thats my plan.
 

Rich Rohrich

Moderator / BioHazard
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#7
If you raise the cylinder to obtain squish band clearance in .040"-.055" range you'll be safe.
 
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#10
i would personally add a base gasket than a head gasket for some reasons.

1) a base gasket it cheaper.
2) If you change the base at the same time you can check everything and make sure the piston, ring, bearings, etc..... are within specs.
3) the base gasket is under alot less pressure than the head and adding a second base is better than adding a second head beacause the amount of pressure in the head may leak.
4) There may be some cooling issues( dont know if ur bike is liquid cooled) Coolant may leak in the pasages of the head gaskets.

Those are just some of the reasons i would add only a base gasket.
 
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#11
The bike is liquid cooled with o-rings up top, I wouldnt be afraid to add a few base gaskets. I just need to know how to measure the clearance up top. I dont want to end up with super hi compression and have him burn it up.
 
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#13
Rich Rohrich said:
Ok I did the search thing. I know very help full info out there.
I just came in from my garage I have a negative squish. I tried using 3 base gaskets and it still hits. I figured if I could get it to not hit ,then measure the clearance with the solder then I may be able to have the head cut. I have a friend that manages a machine shop and also is a flattrack racer. He knows how to modifiy stuff and has lots of cool tools!!. any how , I still want to know why this is happining. Should the frame and case numbers match?? and is there a way off the case # to tell the exact year. I have the # off both cases. The origonal is f114 152830 and the ones I have togather now is #f114 149483 thanks again for all the help.
 
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#14
if you have tried 3 base gaskets and the piston hits the head then the piston must protrude above the cylinder(when using 1 base gasket) by a lot more than 20 thou? perhaps you could have a custom base gasket/spacer made that would provide enough clearance? this could be gauged by assembling the cylinder on the cases with no base gasket then measuring the piston protrusion. this amount would be the required gasket/spacer thickness. alternatively if you have this problem due to a milled cylinder you could always try to find a used one on zbay etc..
 
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#15
Ok heres my plan. Measure from center of crank to top of case deck on both cases, subtract the difference and see If commetic can make me a thicker base gasket. I hope thats no to much $$$$ . I really dont want to go thru looking for a different case. Then if I close I can adjust the squish the rest of the way with a head mod.. What do ya think?