Help overheating cr250

[rick82cr250]

Hello all; Newbie here looking for some help. I own a 82cr250. Decent bike that i bought a month ago. The first problem I had was a inner waterpump seal leaking. Replaced seal and new waterpump. Took it for second test run and the y connector to radiator hoses busted (nice burn on leg). Replaced y fitting and installed a temp gauge where the hose leaves the head, also replaced head gasket. Piston and cylinder seem to be in good shape with not much carbon . Running 32:1. Now the problem is that I can start it and let it sit and idle for a good 10 minutes, then take a calm ride up and down the road and the gauge barely moves.(running it rich) The longer and harder I get into it the higher the gauge climbs. It will stick around 190 for a cpl of minutes then climb to 220, then continues to climb to 240. Now if you drop it back down to idle, the temp starts dropping back down to 220. I would greatly love to keep it under 210 and be able to lean it into the happy zone. I dont feel as if the radiators are clogged, since i have flushed about 2 gals of antifreeze thru them so far. And like I said earlier, the carb is running fat. I dont think its a air leak cause of how well it runs and idles. Even went as far as trying some of that antifreeze coolant to lower the temp. Rad shrouds in great shape. I dont think there is a lean condtion on top end either with having a wet plug. Thx for any suggestions.

 

[Pete Payne]

Couple of things, Make sure the jetting is close , i know you said the plug was wet , but is there any color to it ? Black=rich brown =OK white =lean.
If the plug looks OK then -----
I think I would get some automotive coolant flush and run it through it . I have seen some radiators be pluged up and do not show any sign of corrosion by looking through it at the filler neck .

 

[rick82cr250]

Hi Pete 1)As far as the jetting goes, I have no idea about it, havent touched the carb since the motor is so strong running. I do have a little concern about first starting up and seeing alot of smoke till she warms up. I figured it was ok since I'm running it rich cause of the weather conditions here(Florida). 2) I also thought about thr rads being clogged, but after running for a while and then draining coolant in a catch can, found no sign of dirt or debree. I preformed a search on overheating here and saw a product called Evans coolant, might check into that. This is the second plug in it since i owned it and starting to get black and wet. To affraid of leaning it and really frying the motor. What really upsets me is that I havent rode a bike for about 16 years, (use to run a honda 250r) and this thing really gives me chills when riding, even tho for just a cpl of minutes. I'm like a crack addict....gotta have more..:laugh:

 

[jrm]

I have an 82 CR250 that I race in AHRMA vintage MX. The radiators (and water pump) are a weak spot with age. You've already fixed the pump issue. My educated guess is that your radiators are clogged and need a trip to a radiator place to be rodded out and/or you've got a warped head/cylinder top and the head is not seating properly allowing exhaust gas to overheat your coolant. I'd replace the radiator cap for good measure too. Check the head/cylinder first. If they're in spec, replace the radiator cap. If it's still a problem, get your radiators cleaned out. One or more of these will fix your problem. Good luck.

 

[magneto]

What temperature does a correctly running 2 stroke run AT THIS POINT in the cooling circuit? Maybe you don't even have a problem.

The worst thing I ever did was to put an oil pressure gauge on an old Harley shovelhead...

 

[rick82cr250]

Thx for the quick responses. I agree with you jrm but the only thing that puzzles me is that the temp drops when you slow down, not a great drop, but I would think if the rads were in fact clogged, wouldnt the temp stay high almost like having a stuck thermostat? BTW, I ordered some of that Evans coolant to give a try. And the last confussing thing is that when i drained the rads, there was no sign of debree or corrossion. To answer your question magneto, the temp will keep climbing past 250 if I let it.

 

[magneto]

Is your gauge an internal type that could be blocking coolant flow?

Is your gauge accurate?

Does the system get hot enough to blow the coolant out past the radiator cap?

 

[rick82cr250]

Magneto; No its not blocking the flow, made sure of that when i installed it. It is a brand new sunpro temp gauge plus I have checked it with a handheld thermo gauge. I try not to let it get that hot to where it blows past the cap. The pressure was so great at one time that it poped the plastic y fitting and blew hot coolant on my leg.I wonder what most guys bikes run at for temp? I feel that keeping it under 210 is a perfect temp.

 

[magneto]

Are you running a 50/50 water/antifreeze mix? The more antifreeze you have in the mix the less heat energy it will transfer per degree temperature difference.

 

[jrm]

If it blew the "Y" fitting, it's a problem that no amount of cooling additives, mixture, etc is going to change. It has to be either a blocked rad or a a warped head. If you look at the '83 head, Honda changed the design considerably, added extra head bolts and rearranged the pattern, all b/c they had experienced some problems w/ the head warping and causing overheating. If the head warps, you'll get hot, pressurized combustion gas adding heat and pressure to your cooling system -- not a good mixture.

My rads did not look bad, but when one started leaking and I took it to a rad shop to be fixed, they found it was pretty blocked up. Getting the rads rodded out fixed about 90% of my issues. Getting the head trued took care of the rest.

Remember, 1982 was only the 2nd year for watercooled 250s from Honda. They were still working on getting the bugs out. Add 25 years of age to your bike and you've got some work to do to keep it running well.

 

[rick82cr250]

jrm, you were right. The rads were clogged up. I had them rotted out and I flushed the entire system again. The Evans coolant showed up today but I didnt put it in yet( didnt know if it was fix yet). I let the bike sit and idle for about 10 minutes and didnt even hit 190. So I took down the road a cpl of times and played with the carb to lean it out. ( I had it very rich) NOW I have a bigger problem! I have searched and searched, cant find anybody that sells big enough gonads to push this bike to the limit...lol So thx guys for all your help.

 

[jrm]

Glad you got it fixed. You're right -- the bike is very fast for 25 year old technology. The '82 RM250 was reputed to be "works bike" fast at the time, but my bike regularly holeshotted them then (I've owned the bike since it was new in 82) and still does today. It's a rocket.

The other weak spot, depending on how many hours you have on the bike, is that the rivets holding the primary gear to the clutch basket will eventually stretch and then break. The basket is no longer available. The fix is to take the basket to a machine shop and have new rivets made out of tool steel. You'll want to do this before the stock rivets break and do damage to gears, cases, etc. I got lucky -- when mine broke, the primary gear separated completely from the basket but there was no other internal damage.

 

[magneto]

Just curious... were the radiators stopped up on the air side (seeds, mud, etc...) or on the coolant side (crap in cooling system)?

Can an automotive radiator shop clean motorcycle radiators?

 

[rick82cr250]

jrm, Its so funny you said that about the clutch basket. When I changed my waterpump, went to start it and had nothing. Shopped all around for a used one. Then one day at a hardware store I saw some clevis pins and used those, worked really well. Magneto, the rads were stopped up inside and yes where Im at they car shop did it for me, just watch for his pig cause he will bite...lol

 

[rick82cr250]

Had a great day of riding finally!!!. Took it to the track made a cpl of slow passes and she got up to 210. Fattened it up and got to 190. Bike seems to be very strong and very low geared, running a 54:13. I bought a 14 just havent put it on yet. Even with the low gears the bike didnt stand straight up when I gassed it. Really liked the way it feels and handled. I havent gotten into the carb yet to know the jetting, but it seems to have a slight bog on the low end. Maybe jrm has some insight to that??

 

[jrm]

Mine was a bit rich with the stock jetting. I leaned the pilot and main one step each. Even with that, it's not really strong right off of idle -- it's always had the little flat spot just off idle you describe. I just use a little extra clutch work to get it out of turns. You could probably tune the flat spot out with some extra jetting work, maybe a different slide cutaway.