Overheating.....new waterpump or radiator??

[1promodfan]

O.K. so I've got my bike finally running right. But now its overheating. We usually go riding a couple hours from here in the dirt, but when I ride at home its in the sand. So my question is, do I need an oversized radiator?? Or could it be my waterpump?

If I make 3 good passes racing, I have to stop and let it cool. Yesterday it got really hot once, and the last thing I want to do is burn up my new cylinder. I tried water wetter and its no better......:confused:

[86 Quad R]

as a general rule the carb needs to be jetted differently for sand as opposed to regular trails ect ect. hows the plug color after plug chops? what compression are you running and what fuel? are you running scoops?

[regg187]

a 310 with a lot of compression, might just need to go to an over size radiator. I know the last thing YOU want to screw with is your jetting again, but might it be a little lean, adding some to heat problem?
I've always assumed water pumps work or don't. Most get replaced because of leaking seals, not poor performance.

[1promodfan]

Originally posted by 86 Quad R
as a general rule the carb needs to be jetted differently for sand as opposed to regular trails ect ect. hows the plug color after plug chops? what compression are you running and what fuel? are you running scoops?

The plug looks really good. My compression is 173......I've been running 110 race fuel, although I still run regular pump gas at times too. I have the pump gas dome. And yes, I have rad. scoops.

[1promodfan]

Originally posted by regg187
a 310 with a lot of compression, might just need to go to an over size radiator. I know the last thing YOU want to screw with is your jetting again, but might it be a little lean, adding some to heat problem?
I've always assumed water pumps work or don't. Most get replaced because of leaking seals, not poor performance.

Yea, my jetting issues have been a nightmare. But, I did try to fatten up the main, and it still overheats.

[86 Quad R]

what ratio of water/coolant are you running?

[Tommy Warren]

I don't know 250R's but it sounds like lean jetting or a faulty thermostat.

[deathman53]

I had mine running hot all the time. Nothing with jetting solved it, different domes, different water pump, radiator, nothing solved it. It turned out that the intake boot carb-cylinder had a crack in it. 250r's don't have a thermostat.

[Tommy Warren]

Originally posted by deathman53
I had mine running hot all the time. Nothing with jetting solved it, different domes, different water pump, radiator, nothing solved it. It turned out that the intake boot carb-cylinder had a crack in it. 250r's don't have a thermostat.

told you I don't know 250R's:D

[1promodfan]

Originally posted by deathman53
I had mine running hot all the time. Nothing with jetting solved it, different domes, different water pump, radiator, nothing solved it. It turned out that the intake boot carb-cylinder had a crack in it. 250r's don't have a thermostat.

Hey deathman, how did a crack cause it to over heat?? I have noticed a little gas residue on my carb. You might be on to something, I'd like a little more info. on this.

[86 Quad R]

hey 1promodfan, do a leak down test on the system. there is a possibility that you may be getting intermitting air leak somewhere. juss a thought. :cool:

[deathman53]

the rubber on the intake had a crack in it, when I took it off, I could see it. It would allow air to suck in, causing a lean condition. What happened was I had crank case seals leak and caused the top end to overheat. At this time, the esr330 seamed to always run somewhat hot, compared to my stock top end. Tried everything, nothing got it lower. After the crank case seals replaced and top end re-bored and re-built. It still ran hot. I then thought about the airbox-carb intake, no cracks. I eliminated everything and replaced the other intake for a joke, it worked. I ran it the next weekend, fouled 2 plugs. I leaned the needle and dropped the main over the next week, I ended up with a 180, this was from a 205. I used several new plugs to get the most accurate reading.

[Aceman]

I run an Afco on my high compression 310 with Engine Ice. It doesn't see over 180 on the 70-80 degree days when I'm out duning. I'd have a hard time believing a stock rad could keep it under 200 degrees in those conditions.

You need to be running a temp gauge if you're not already so you can keep a good eye on it. Watching the overflow isn't the right way to fly.


Originally posted by deathman53
the rubber on the intake had a crack in it, when I took it off, I could see it. It would allow air to suck in, causing a lean condition. What happened was I had crank case seals leak and caused the top end to overheat. At this time, the esr330 seamed to always run somewhat hot, compared to my stock top end. Tried everything, nothing got it lower. After the crank case seals replaced and top end re-bored and re-built. It still ran hot. I then thought about the airbox-carb intake, no cracks. I eliminated everything and replaced the other intake for a joke, it worked. I ran it the next weekend, fouled 2 plugs. I leaned the needle and dropped the main over the next week, I ended up with a 180, this was from a 205. I used several new plugs to get the most accurate reading.

Wouldn't a leakdown test have caught that immediately? A little crankcase pressure and some Windex takes the guesswork out of it...

I never really liked the guess-and-replace method myself.

[deathman53]

I never did a leak-down test, that was my error and thinking about it, I don't know why I didn't.

[norcalduner]

What type of front bumper are you using ? I had an AC racing on my 310pv and temps hovered around 220 when I was braking the motor in during a trail ride. I then decided to remove it that same day and rode the same trails. Well, guess what? My temps went down and settled to around 180. So the problem in my situation was not enough airflow thru the rad. Hope this helps.

[1promodfan]

Originally posted by Aceman
I run an Afco on my high compression 310 with Engine Ice. It doesn't see over 180 on the 70-80 degree days when I'm out duning. I'd have a hard time believing a stock rad could keep it under 200 degrees in those conditions.

You need to be running a temp gauge if you're not already so you can keep a good eye on it. Watching the overflow isn't the right way to fly.

I do have a temp. guage, thats how I know its overheating. I'll probably average between 200-225 degrees, and I've seen it get a lot higher......which then I pull the kill switch.

[1promodfan]

Originally posted by norcalduner
What type of front bumper are you using ? I had an AC racing on my 310pv and temps hovered around 220 when I was braking the motor in during a trail ride. I then decided to remove it that same day and rode the same trails. Well, guess what? My temps went down and settled to around 180. So the problem in my situation was not enough airflow thru the rad. Hope this helps.

I believe my bumper is an AC racing.......hey at this point I'll try anything. From 220 to 180 thats a BIG drop. I'd feel safer even around 190-200.

[deathman53]

what bumper are you using, AC regular or Stadium bumper? The stadium bumper is open and has a place to put a number plate, screen or leave it empty. If you have the regular with that screen-like center, it could be blocking air-flow. I seen it happen with bling-star bumpers, replace it with a open design bumper and temps dramatically fall.

One thing that none has said yet, is your radiator damaged or clogged with dirt? If so, replace it. I had a 250r that ran hot, a good part of the fins were bent. Or remove it, clean and run it under a sink backward of airflow, until you can clearly see light through it. In worse cases, take it to a radiator shop to be cleaned inside and out. My hybrid some years ago, ran hot, I removed the radiator and cleaned it real good, solved the problem.

[1promodfan]

Originally posted by deathman53
what bumper are you using, AC regular or Stadium bumper? The stadium bumper is open and has a place to put a number plate, screen or leave it empty. If you have the regular with that screen-like center, it could be blocking air-flow. I seen it happen with bling-star bumpers, replace it with a open design bumper and temps dramatically fall.

One thing that none has said yet, is your radiator damaged or clogged with dirt? If so, replace it. I had a 250r that ran hot, a good part of the fins were bent. Or remove it, clean and run it under a sink backward of airflow, until you can clearly see light through it. In worse cases, take it to a radiator shop to be cleaned inside and out. My hybrid some years ago, ran hot, I removed the radiator and cleaned it real good, solved the problem.

I have no idea which one it is.......you can look at my pic, maybe you can tell which one I've got. It has the screen in it.

I checked my rad. and to me it looks pretty good. Sure it has bent fins, but I cleaned it the best I could. I can see light through it, and I sprayed it with the water hose just to see if water would pass through it easily.

[norcalduner]

I suggest just riding the bike without the bumper and see what happens. I am almost positive that is your problem. Then you'll know to get a bumper WITHOUT any type of screen.

[86 Quad R]

Originally posted by norcalduner
I suggest just riding the bike without the bumper and see what happens. I am almost positive that is your problem. Then you'll know to get a bumper WITHOUT any type of screen.

thats why i like me "OLD SCHOOL" bumpers. :D

also: take the rad out and flush it with that stuff the a/c repair man uses to clean the grills on a/c units. that stuff is bad a z z. :cool:

[EXtreme-]

I've been thru all this before. They run hot....plain and simple. You need a big rad and engine ice. With that, we run both motors, long and short rods, at 180 during normal trail conditions. But as soon as we stop to shoot hillclimbs and fool around, it runs up to an easy 225 if you're not paying attention. They need lots of airflow....bottom line.

[regg187]

a leak down is a great idea especially on a new untested motor. that being said I don't believe that would catch a bad intake rubber though. they usually bolt a plate over the reed opening and plug the exhaust port and pump in the air through the spark plug hole, at least the ones I have seen and done did it this way.


gas on the front of the carb might mean fuel mixture blowing back , but the reed valves are supposed to stop that from coming out intake manifold, but you never know!!

[regg187]

straighting your bent fins, though tedious might help because with that motor you should need every bit of your cooling area working. smashed and bent are 2 different things bent/ fix smashed/ be careful not to cause a leak when straightening
use something with a plastic point to help straighten the fins, metal to metal could cause problems

[1promodfan]

Originally posted by norcalduner
What type of front bumper are you using ? I had an AC racing on my 310pv and temps hovered around 220 when I was braking the motor in during a trail ride. I then decided to remove it that same day and rode the same trails. Well, guess what? My temps went down and settled to around 180. So the problem in my situation was not enough airflow thru the rad. Hope this helps.

Hey norcalduner, I knocked out the screen in my bumper and took it for a test ride and it ran cooler.....about 20 degrees along with me redoing my intake boot


Originally posted by deathman53
the rubber on the intake had a crack in it, when I took it off, I could see it. It would allow air to suck in, causing a lean condition.


Hey deathman, I took my intake boot off and made sure it was on tight. Between knocking out the screen and redoing the boot it dropped about 20 degrees.

Thanks for all the help. My next move is to put in some engine ice. The other day after riding about 25 minutes in would overheat up to 250 degrees........today after riding for the same amount of time it might have hit 220 degrees or so. And thats in the sand. So I know (hope) once I hit the trails it'll drop to a normal riding temp.

[C-LEIGH RACING]

:eek: Now have you got that temp gauge in the bottom hose ???.
Neil

[1promodfan]

Originally posted by C-LEIGH RACING
:eek: Now have you got that temp gauge in the bottom hose ???.
Neil

No its in the hose coming off the head going into the radiator. You have anymore suggestions Neil??

[Aceman]

Originally posted by 1promodfan
today after riding for the same amount of time it might have hit 220 degrees or so. And thats in the sand. So I know (hope) once I hit the trails it'll drop to a normal riding temp.

That's too hot for my tastes. I shoot for longevity and reliability and lower motor temps are a part of that. I like 180 or less ideally.

Engine Ice might help a little, but I'd put an Afco on it and be done with it. I run 150-180 all year long on trails or sand with my 310 and that's pushing it hard when I'm duning.

[C-LEIGH RACING]

Originally posted by 1promodfan
No its in the hose coming off the head going into the radiator. You have anymore suggestions Neil??

Guess who, with all the 250Rs they have had over the years, never bought one of those high dollar aftermarket radiators & had 310 up to 410cc engines.

That engines heating cause somethings wrong with it & could be a number of things causing it.
A simple thing like the end of the impellar worn off just a bit & the coolant wont flow like its suppose to.

Do you know what heat soak is, thats what happens when your riding hard & then stop riding & no air is flowing through the radiator.

How that new ESR cylinder is cast, being as thick as it is around the exhaust port area & NO coolant circling around the port tunnel, will cause high heat on the exhaust side.
That cylinders solid cast from the side down on each side & under the exhaust port as well, so only coolant to cool the front of the block is right above the exhaust port & very little at that.

Pro-x cylinders, the coolant goes full circle around the exhaust port, thats why it has those two allen set screws in the base.

You got to do some more checking.
If them wheels aint moving, cut the engine off.
Neil

[Honda 250r 001]

so are you saying that the pro x 310 cooling jacket is a better design? i knew i did right by choosing the more experienced pro x. Anyway. Have you ever rigged a fan to work on the trx 250r neil?

even if your not moving, the radiator still helps cool the coolant correct? What do you do in the slow technical trails?!?!? lol

[Honda 250r 001]

Originally posted by Aceman
That's too hot for my tastes. I shoot for longevity and reliability and lower motor temps are a part of that. I like 180 or less ideally.

Engine Ice might help a little, but I'd put an Afco on it and be done with it. I run 150-180 all year long on trails or sand with my 310 and that's pushing it hard when I'm duning.

the only time mine gets hot is when im trail riding. But how do you keep yours so cool? I think i might replace my impellar to see if that helps any. Maybe i will have my radiator cleaned also.

[C-LEIGH RACING]

Originally posted by Honda 250r 001
so are you saying that the pro x 310 cooling jacket is a better design? i knew i did right by choosing the more experienced pro x. Anyway. Have you ever rigged a fan to work on the trx 250r neil?

even if your not moving, the radiator still helps cool the coolant correct? What do you do in the slow technical trails?!?!? lol

Compairing the Pro-x cylinder casting to the new ESR cylinders, yes, there is a bit of difference in how the coolant jacket is formed from one cylinder to the other.

All of the Pro-x cylinder casting from the 250 to the 410, the coolant circles the exhaust port at the front. The ESR, coolant is only at the very top above the exhaust port.

Never used a fan, but my 250Rs only race TT or some MX during the off season.
If the bikes not moving, no cooling air is passing through the radiator so heat just keeps building up.
Cold absorbs heat, so as the cool air passes through the radiator fins it pulls the heat away from the coolant.
Neil