Rm85 blows o ring

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9/4/2018 4:34 PM

Why does my rm85 keep blowing the inner head o ring it has blown it 2 times I bought a Chinese carb a pwk28 replica and after that it keeps blowing the inner o ring and the cylinder gets flooded with coolant I put a bigger inner o ring that I cut to fit and used some gasket maker to keep it in place and I also put a new keihin pwk28 I need to wait till the gasket maker dries but I doubt it’ll work can someone help me please

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9/4/2018 8:20 PM

If you are cutting orings to make them fit that is part of your problem. If OEM orings keep blowing then I would bet you have some damage either on the head or cylinder surface causing this problem. Might need to find a machine shop that can clean up both surfaces for you. It doesn't have anything to do with the Carb.

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2018 KX450F
2005 KX250
2003 KDX 220
1984 KX 80
1982 RM 80
1980 RM 80
1977 XR 75
1969 Honda Mini 50

9/5/2018 10:29 AM
Edited Date/Time: 9/5/2018 10:30 AM

OEM rings are needed, you can't cut them, and you can't use gasket maker. Make sure the head is flat and not warped. The carb is not the issue I don't think.

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9/5/2018 4:33 PM

I checked the water pump and it was moving freely so I opened the clutch cover and the water pump shaft was missing a clip the holds it in so when the engine was running the pump wasn’t working do you think that would be the problem to the melted o rings?

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9/5/2018 4:45 PM

Richard Aira wrote:

I checked the water pump and it was moving freely so I opened the clutch cover and the water pump shaft was missing a clip the ...more

Yes, no coolant circulation = overheating= melted oring...I would search for the missing clip, don't need that in your bottom end. Use only Oem orings, no cutting or using sealant...check your head & cylinder top for warpage, if they got hot enough to melt your orings, they may need to be resurfaced.

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9/5/2018 5:09 PM

Ok thank you I just bought a whole pump kit and the o rings I looked fore the clip but couldn’t find it I drain the oil yesterday so I’m guessing it already came down

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9/10/2018 2:09 PM

I put the clip on and it spins but the o ring keeps melting

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9/10/2018 4:07 PM

Check some basic things. Is your plug the right heat range? (I think it should be a BR10EG.) Is your radiator full of coolant?
Is there a kinked radiator hose or any blockage in the hoses? Blockage in the radiator? (You should be able to pour water right through these.)

When you have a completely cool engine, try running the engine and remove the radiator cap. You should see the water moving through. DO NOT OPEN THE CAP WHEN IT IS HOT!

How about other things to overheat the engine? Is your rider more than 120 pounds or so? riding in severely hot weather? Deep mud or sand? All of the above?
Is your jetting too lean? (White spark plug?)

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Braaapin' aint easy.

9/10/2018 4:48 PM

Has the right plug there’s no blockage the pump works fine

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9/11/2018 5:07 AM

Run the correct oring before wasting time on anything else ?

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9/11/2018 7:54 AM

Possibly a warped head. A sheet of glass, fine wet sandpaper and figur 8 movement can show warp and fix it

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9/11/2018 2:00 PM

OK, so if the water pump works fine and there's no leakage, we need to focus on something else.

X2 on making sure the head is flat. You may also want to remove the studs from your cylinder and check to see that the top is flat also, using the same method Lumpy outlined.

Make sure you are using the correct o-ring. You didn't mention your model year, but all models back to 1991 use 11147-03B00 (inner) and 11148-03B00 (outer). I always put a thin slime of grease on them to keep 'em pliable. Make sure you torque the head nuts in a star pattern and keep them at the same torque.

Try running richer jetting and/or race gas to keep the temps cooler. It may help. You might also check to see that the timing has not been advanced.

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Braaapin' aint easy.

9/12/2018 8:42 AM

Falcon wrote:

OK, so if the water pump works fine and there's no leakage, we need to focus on something else.

X2 on making sure the head is ...more

sometimes when assembling the O ring will be slightly larger than the machined groove so it pops out before putting the head on and like you I use a tiny layer of grease in the groove to hold the O ring in place.

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