Why can't I get my RM80 to stop dripping coolant?

[Chris Long]

I have a 2000 RM80 that runs extremely good, but whenever you rev it or ride it the way it should be ridden, it spits coolant out the overflow. It will not run dry but will spit enough out till you see the water level is below the top of the core when you check it after it cools.

I have done all the following:
new waterpump, gaskets and waterpump seal
new 1.1 radiator cap
straightened radiator fins
used Water Wetter and distilled water for coolant
Running 28:1 mix with Octane
BR10ES plug

Does anyone have any idea's? Could it be jetting...running lean? Any other thoughts as what it could be?

Thank you

 

[husabutt]

Losing a little coolant now and then should not cause you any grief. If it just bothers you to no end try a few of these ideas:

Use a 1.6 radiator cap. Be careful removing it. There is a reason stock bikes come with low pressure caps and being sued is one of them.

http://www.pitposse.com/ourahipr16ra.html

This will probably do ya. You can also:

Install a coolant overflow bottle.
Run Evans coolant
Make sure your crankcase oil is filled to the maximum level.
Your gas/oil ratio seems too rich. More gas and less oil helps cool the engine. Use a leaner mixture.
Make sure your hoses are not collapsing due to wear. replace them with good quality hose.

 

[griffbones]

Make sue the head gasket or head o-rings are not leaking. If they are leaking, the pressure from the piston (combustion chamber) can pressurize the coolant system and push the coolant out the over flow.

 

[Chris Long]

I may just go with a bigger cap. Thats a good idea.

As for the head o-rings, its funny you mention that becasue when I got the bike for cheap becasue it didn't run, that was the reason. The head gasket had lost its seal and shot all the radiator fluid into the exhaust as well as pushed coolent right out the tube. I changed that and torqued it to spec so I don't think that could be it this time. I actually think this bike may not like to have coolent full to the radiator cap. It spits out till its just at the top of the core or a little below and never goes below that. I don't notice the bike overheating persay becasue it runs good and deosn't feel excessivley hot and when I never hear radiator fluid boiling. I guess I will just watch it, but if anyone else has any .02 I'd love to hear what you think.
Thanks, Chris

 

[jason33]

try "bleeding" the air out of the system
it could be building up pressure from air ,and not enough fluid

 

[SHSPVR]

You may want have Cylinder and Head check warp you can do this your self with a can of gray spray primer and 320 girt wet/dry sandpaper and if it is warp then have it resurface at your closest Bike Machine Shop but it also possable you could have hair line crack and you could have that check at any Machine Shop that know how to do aluminum cylinder and head.