How to know if head o-rings are bad?

[rablack21]

How can you tell for sure if your head orings are not sealing like they should? How do you tell for sure if you are leaking coolant into the combustion chamber or if combustion pressure is going into the cooling system?  

I am battling a problem once again that I battled last year and somewhat ignored. My ESR310 pv runs great, but it gets too hot while running, like (215-225). Last year, I ran straight water, coolant boost, and kept the main jet a little rich and it seem to keep the temp to about 215-220. This winter I swapped it to water/antifreeze mix. When I got it out this year and ran it some in the woods, then temp is creeping up pretty high pretty fast, I think because my engine is producing more power because of the new carb I got. So I think my problem is not longer being "masked". Any way, last night I drained the antifreeze and put straight water and coolant boost back in it and will run it today to see if it still gets hot. I also swtiched to higher compression and race fuel last year, which I also thought would help with the cooling.

I am wondering if it is somehow the head orings even though I have replaced them early last year when this problem first arose. I am out of ideas though. Everything else seems to be fine. I have a new aluminum radiator, doubled water pump last night-working fine, no leaks, exhaust smells normal, tried 2 new radiator cap-no difference, sprayed starting fluid around engine-no leaks.

I have run out of ideas on this issue. Anybody got any?

[Skeans1]

You might try pressure testing your cooling system for lose

[havinnoj]

I've never had a bad o-ring or noticed symptoms of them going bad.. since they're $1 to replace - it never hurts to put new ones on.  Doesn't sound like you're running lean but you're running pretty hot.  When was the last time you replaced the piston, checked the rings, and checked the tolerance to the bore?  If it's been a while, it could be piston slap.

[rsss396]

For the orings you can pressurize the cooling system and see if it leaks down any, autozone and advance auto normally has these test kits but not sure if they have the adapter to fit our radiator caps.

[rsss396]

For better cooling have you ever thought of trying a fan on the radiator, but obviously this only works with the stock ignition with its lighting coils.

On my snomoquad adding a 7" fan on my radiator dropped temps at least 30 degrees, with all the big bores out there somebody needs to come up with a kit to add to the 250r because as HP increases so does the load on the cooling system

[rablack21]

I've never had a bad o-ring or noticed symptoms of them going bad.. since they're $1 to replace - it never hurts to put new ones on.  Doesn't sound like you're running lean but you're running pretty hot.  When was the last time you replaced the piston, checked the rings, and checked the tolerance to the bore?  If it's been a while, it could be piston slap.

OJ, you might be on to something. I have been secretly suspecting this in my mind, but didn't want to say unless someone brought it up. I has been quite a while since I have replaced the piston or the rings. I am hearing quite a bit of noise coming of the engine right now, even while idling. But I don't know what piston slap sounds like or it's symptoms, so I wasn't sure how to diagnose that. I have enough hours on it, that it should be time for new rings, but not quite enough for a piston. What are the symptoms I should be looking for and could piston slap cause the engine to overheat like I am seeing?

[rablack21]

For better cooling have you ever thought of trying a fan on the radiator, but obviously this only works with the stock ignition with its lighting coils.

On my snomoquad adding a 7" fan on my radiator dropped temps at least 30 degrees, with all the big bores out there somebody needs to come up with a kit to add to the 250r because as HP increases so does the load on the cooling system

Yes, I have definitely thought about it. It is probably something that really needs to be developed pretty soon. But we need to figure out a way to utilize this with a cr 250 ignition since that will be the future of our ignitions.

[rsss396]

There are cr250 lighting coil kits that may have enough juice to run just a fan, but they are aftermarket stators so we all know they can be hit or miss with reliability.
The other option is to run a Vortex ignition with the stock stator, or if you are really brave ther are a couple programmable ignitions that are designed to run off 12v and you can combine the ignition and fan on the same circuit with a small battery, these are really small dry cell batterys and would make the circuit more stable

[havinnoj]

OJ, you might be on to something. I have been secretly suspecting this in my mind, but didn't want to say unless someone brought it up. I has been quite a while since I have replaced the piston or the rings. I am hearing quite a bit of noise coming of the engine right now, even while idling. But I don't know what piston slap sounds like or it's symptoms, so I wasn't sure how to diagnose that. I have enough hours on it, that it should be time for new rings, but not quite enough for a piston. What are the symptoms I should be looking for and could piston slap cause the engine to overheat like I am seeing?

I was having a hard time describing it but this definition sounds about right "hollow, muffled, bell-like sound."  If it's more of a ticking/clicking sound it may be a bad crank bearing.

[rablack21]

I was having a hard time describing it but this definition sounds about right "hollow, muffled, bell-like sound."  If it's more of a ticking/clicking sound it may be a bad crank bearing.

Actually, that description sounds about right. It does sounds like that. What are the symptoms of piston slap other than the noise. Will it cause overheating? Could it cause other issues? idling problems? combustion issues? engine to raise rpms? I'm just spitballing here, I don't really know. Those who know, fill us in!

[Jerry Hall]

Check your temp gauge for calibration

If your o-ring is bad, compression will leak into the cooling system and over-pressurize the cooling system. The radiator cap will prevent over-pressurizing the coolant system by allowing pressure and coolant to escape by way of the over flow line on the radiator cap. If you are not loosing coolant your 0-rings are probably ok.

Most overheating problems are the result of insufficient air flow THROUGH the radiator or a plugged radiator. Remove the radiator cap and look at the tubes for deposits that are visible through the cap hole. Look at the front of your radiator for damage from gravel and mud peening the fins over or a radiator that has the fins full of mud or debris. Make sure that your air scoops and rubber scoop on the bottom are present and properly orientated. Many of the aftermarket grills, bumpers and number plates hinder the air flow THROUGH the radiator. The 250 R will not tolerate very many seconds of running around in 1st gear without overheating.

[havinnoj]

Actually, that description sounds about right. It does sounds like that. What are the symptoms of piston slap other than the noise. Will it cause overheating? Could it cause other issues? idling problems? combustion issues? engine to raise rpms? I'm just spitballing here, I don't really know. Those who know, fill us in!

The noise typically is louder on start-up and decreases as the motor warms up.  The added heat that is generated by the piston "slapping" can cause a loss of power.

[rablack21]

Check your temp gauge for calibration

If your o-ring is bad, compression will leak into the cooling system and over-pressurize the cooling system. The radiator cap will prevent over-pressurizing the coolant system by allowing pressure and coolant to escape by way of the over flow line on the radiator cap. If you are not loosing coolant your 0-rings are probably ok.

Most overheating problems are the result of insufficient air flow THROUGH the radiator or a plugged radiator. Remove the radiator cap and look at the tubes for deposits that are visible through the cap hole. Look at the front of your radiator for damage from gravel and mud peening the fins over or a radiator that has the fins full of mud or debris. Make sure that your air scoops and rubber scoop on the bottom are present and properly orientated. Many of the aftermarket grills, bumpers and number plates hinder the air flow THROUGH the radiator. The 250 R will not tolerate very many seconds of running around in 1st gear without overheating.

Jerry, Thanks for the response. I have checked a few things that your mentioned. I checked my temp gauge with an IR thermometer. The temp of the head and the upper radiator at the inlet appear to collaborate the temp of the gauge. The inside turbolators are very clean, no corrosion, no build up. The external fins are also clean with VERY FEW of the fins bent, as this radiator is still fairly new.

I am losing a bit of coolant, especially as it goes over 210. It's not spewing, but it is dripping a little at a time. I don't have an overflow bottle, just a hose ran down pointed at the top of my pipe so I know when it is leaking.

The place I am riding it is pretty narrow and slow. Mostly 1st and 2nd gear stuff and using the clutch. Then when I get in the small clearings, I will hammer it as fast as it will go until I reach the next tight area (about 10-15 seconds).

I have a big race coming up this Sunday and am trying to figure out this problem before then. My new carb is running great, but this issue has crept up again from last year. I have some new piston rings and gasket kit/head orings on the way now, but won't arrive til Friday.

Does this sound more like a piston slap problem or bad head oring problem? I can do any check pretty quickly as long as I know what to check. I don't really have any way of pressurizing the coolant system to check for leaks. I will rig up something if that is what an comes down to.

[rablack21]

I just want to make sure there is nothing wrong with the motor before I decide how to remedy this issue. If there is nothing wrong with the motor, then the only way to add more cooling to the engine is to increase cooler size, change fin pitch, increase air flow across fins. This is the part I'm good at. I just want to make sure there is nothing actually wrong with the motor first.

[C-Leigh Racing]

Heres something you might want to check, the tips of the water pump impeller blades, making sure they are not worn down on the ends.
Sometimes when a pump shaft bearing goes out, it will let the shaft & impeller move in & out & when it does, the impeller will rub on the steel defuser & wear the ends of those blades.
Once the worn out bearing & seals are replaced, the pump is back to were it is suppose to be sitting, except the ends of those blades are sitting to far away from that defuser & the impeller cant flow the coolant like it could when those blades are sitting close, so you end up with less coolant flow afterwards.
Old as all the 250Rs are these days, theres probably quite a few worn out parts we are still using, that are causing some of the hard to figure out problems some are having, but that dont know theres anything is wrong with those parts.

A radiator cap left loose or not on at all, will run a 250R hot quick, so it is important that cap is on & sealing so to hold back some pressure.