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cylinder head 1984 rm 125
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Author:  harmen [ Tue Oct 09, 2012 1:45 pm ]
Post subject:  cylinder head 1984 rm 125
hello,

i have a question about the cylinder head of my 1984 rm 125.
I've got two of them, one with the code: E1 on top of it and one with E2.
now perhaps one of them is from a 1985 rm 125 but i don't know for sure.
they are different, the 'hole' in the E2 head is bigger than in the E1 cylinder head
(i don't know what is the name of that hole, but i mean the space above the piston)
can anyone give me advise about which one i should use?
i tried the E2 one but the engine will start very difficult then, so it's perhaps the wrong one.
thanks in advance..

harmen
Author:  harmen [ Fri Oct 12, 2012 3:05 am ]
Post subject:  Re: cylinder head 1984 rm 125
hello,

the bike still didn't start with the E1 head
but today i saw that one connector of the ignition was connected wrong.
when i fixed that, the bike started after two times kicking..
so i think the E1 head is the proper one, with the the E2 head it would only start after very much kicking

but then i have another question:
i have an oversized piston in my bike, do i have to make the hole in the cylinder head bigger?
i have a 56mm piston now and the stock one is 54mm, so do i have to make the hole in the cylinderhead 56mm?

harmen
Author:  GSjimmy [ Wed Jan 09, 2013 11:19 am ]
Post subject:  Re: cylinder head 1984 rm 125
The "hole" you are reffering to is the chamber area of the head. The dome area of the piston is a match to it. Since the "E2" head has a noticabily larger (you can see it) surface area, it has in effect lowered your compression to just barely enough to allow the bike to fire. You could verify this by CCing the heads, but I think you have the question answered already. I'd just use the "E1" head and call it done.

Jim
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