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Author Topic: 1982 RM 125Z exhaust and mods  (Read 3159 times)

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Offline NoMuff2Tuff

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1982 RM 125Z exhaust and mods
« on: May 25, 2014, 05:44:54 PM »
I'm building a 82 RM 125 to do some vintage racing and looking to get some more power out of it. I plan on some cylinder work, boyesen reeds and bringing the piston to head squish clearance down some since stock it is .080". I also have a 35mm PWK air striker I may try. This year head has the full hemi open design with no step and I'm not familiar with this design. As for the exhaust I'm only able to find DG available pipes, so the question is, is the DG pipe any good for these older RM's or just better to run the stock pipe ? Any do's and don'ts on engine modifications would be appreciated !!!!
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline TMKIWI

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1982 RM 125Z exhaust and mods
« Reply #1 on: May 26, 2014, 10:29:39 AM »
Nice bike. I have a 84' and have the full DG system. Seems to perform well but I havn't compared it back to back with the standard system.
Set your quish to 0.8 or 32 thou. I didn't do any port work except to clean them up and case match the halfs. Am also running the Boyesen power reeds. Bike is not lacking power compared to other bikes in the class, Pre 85 125.
I am running the 34mm carb as well.
My next mod will be to remachine the head to except o-rings instead of the head gasket. I did this to my 84' 250. Makes removing the head an easier job and you don't stuff a head gasket each time.
The bike loves to rev to the moon and the sign off is quite abrupt, but you learn where it is and it's easy to keep in the band.
There is a build thread on here on the bike.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline TMKIWI

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1982 RM 125Z exhaust and mods
« Reply #2 on: May 26, 2014, 10:49:29 AM »
BTW. The 82' is a full reed motor which the 84' is not. You have the better motor for sure.
I would love to find an 82' motor for my bike.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline NoMuff2Tuff

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1982 RM 125Z exhaust and mods
« Reply #3 on: May 26, 2014, 12:42:36 PM »
Thanks for the tips and I'll try and search for the build up!!! What 34 carb, jetting and needle you are running ? I sent the cylinder out to a guy who knows 2 strokes pretty well to analyze and plug in some port timing numbers just for fun and right off the bat he saying transfer port volumes are too big but the heights looks good. This is mostly a fun project to tinker with and see what I can get out of it. Building them to me is just as fun as riding them.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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Offline TMKIWI

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1982 RM 125Z exhaust and mods
« Reply #4 on: May 27, 2014, 09:19:05 AM »
I am running the standard Mikuni. Will have to find the jetting I am using. Writen down somewhere.
« Last Edit: December 31, 1969, 04:00:00 PM by ' »
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