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1987 Rebel 250
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147 Posts
Discussion Starter · #41 ·
I really doubt the valves are burnt.. Don't know why you feel they are without proof..
There are Used and New P&C sets for sale on eBay which will likely solve your compression problems.
That cylinder that's at 115 dry had the exhaust disconnected for years (by PO), so I assumed that since the psi remained low even after adding oil to the cylinder, that it just be more than the rings leaking, and that's it's probable (given the above) that the exhaust valve could be burnt. I'll be happy if I'm wrong. I really don't want to replace valves.

Partzilla has the gen1 and gen2 cylinders as different part numbers, so I thought those eBay kits wouldn't work. I was even thinking about going with the 280cc, but that seems like a gen2 part as well. I guess I could swap the top end to gen2 and that would work.

I'm very open to suggestions. Called tons of shops, and no one is willing to touch my bike......
 

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1987 CMX250C AC
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3,411 Posts
imho you should disassemble the engine first to discover what is needed..
1st generation has different cam, lobes were ground differently and slightly higher rise which I believe is responsible for increased horse power over 2nd gen Rebel.. 2nd gen head is a downgrade

Differences in cylinders that I have noted 1st gen used 4 dowel pins and 3 stud gaskets

While the 2nd gen cylinder used only 2 dowel pins and no stud gaskets..

1st gen members who have ordered Head Gaskets have received 2nd gen gaskets.
Two of the head gasket holes are too small to use 2 of the dowel pins which can be discarded..

unproven Big Bore cylinder may be a waste of money and you won't hear from Elchico as he was able to get himself banned within 3 weeks of joining..
 
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Registered
1987 Rebel 250
Joined
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147 Posts
Discussion Starter · #43 ·
imho you should disassemble the engine first to discover what is needed..
1st generation has different cam, lobes were ground differently and slightly higher rise which I believe is responsible for increased horse power over 2nd gen Rebel.. 2nd gen head is a downgrade

Differences in cylinders that I have noted 1st gen used 4 dowel pins and 3 stud gaskets

While the 2nd gen cylinder used only 2 dowel pins and no stud gaskets..

1st gen members who have ordered Head Gaskets have received 2nd gen gaskets.
Two of the head gasket holes are too small to use 2 of the dowel pins which can be discarded..

unproven Big Bore cylinder may be a waste of money and you won't hear from Elchico as he was able to get himself banned within 3 weeks of joining..
That was very helpful. I really appreciate it!

Can I ride the rest of the season with low compression? Or should I tear it down as soon as I can?
 

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1987 CMX250C AC
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3,411 Posts
If you have sealed exhaust leak the you can only damage the pistons and cylinders while riding.
you can replace P&C with new 2nd gen style or used 1st gen P&C for less than $100
so ride til it quits if you wish.. keep your eye out for deals on cylinder and pistons while you ride..
 
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