Posts
545
Joined
2/1/2015
Location
Lakeland, FL
US
Edited Date/Time
10/22/2015 12:11pm
Hi , I read before about plating frame on this RM. Anyone have a picture or good description of what to do? Also,,any power mods for the engine? I have a DG reed cage on a 79 RM125. They where a casting that had short reed on top/ and I can see how to modify a stocker on RM250 to add another set as well...anyone done that?
Your KX needs it way more than the Suzuki
doing. I never saw any downside to that mod. To take full advantage on the 250/370
you need to cut the rear of the sleeve. I usually cut a large "thumbnail" shaped area from
the rear of the sleeve. the EC Birt cylinder a friend/coworker had done on his 78 250 had
a large slot milled/beveled through the backside for the 4 pedal setup.
Later I purchased an EC Birt 3 pedal billet reed (3 reeds on top), at the same time I had
my bike down for new mains etc. and noticed the areas in the crankcase by the reed area
had plenty of room to grind Boyesen ports (which I did), this setup worked REALLY well.
I suspect similar grinding to work well with the 4 pedal/stock mod & especially if the rear
sleeve is not cut. The cylinder porting is pretty modest and has a lot of potential, DG pipe
pulls better off corners and revs a lot quicker but not as much on top, they seem to like
more compression ( I ran a Webco head, the only Rm250 one I've seen ), did run the 79
OEM single ring piston "lighter) as well as the 79 second gear (same ratio but I broke 2
78 2nd gears when landing with throttle on, never with late version 79). Hope this helps, R.
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Luxon 4-Post Bar Mounts
$189.95 - $239.95
Free shipping: VITALMX
I have a 78 EC Birt rm125 engine,and it has a 3 pedal cage in it. Never seen one before or after. The DG Reed cage(R&R) I have on another 78 RM125 motor I found actually uses boysen 79 KX250 pedals. The thin ones fit the top side and clipped down shorter for stubby ones underneath. I think they added top end to the 125.
not the best description. Picture you have the cases apart and 1 half in hand,
set the cylinder w/o case reed installed. When you look at the area where the
cylinder sleeve & the engine case meet in the case reed area, imagine a nice
radiused port leading into the transfer port from the case area. Not really much
work on the cylinder sleeve itself but on the cases, I always put epoxy on the
outside of the case for good measure but never ground through. Hope that makes
sense, if not pm me & I will give you my cell phone# or help you with the mods,
pro bono.
If you have one of the old Eric Gorr mx handbooks, 95ish?, there is a pic on a
KX80? cyl where they grind a similar port on the sleeve itself. Its the same
except on the cases, basically reverse. But the mod I'm talking about would
be to the t of what you would get in 1982 if you sent an RM80 motor to R&D
racing (Rudy & Dean): case mods, blueprinted cyl, alignment pinned head &
they worked quite well.
PS. I think your 3 pedal is most likely the same setup I had, if I remember right, 1980ish
KX 250 reeds will fit it, should work well. There was an old MXA or Dirtbike arcticle that
EC did an RM400, article was called Project RM422, I think. Used a Maico 2mm larger
piston & the 3 pedal reed like yours. Cheers.
Post a reply to: 1978 C2 RM250 frame fix and engine mods?