Liquid cooled motors, discharging some fluid after a refill. Normal?

[Kenneth S (222)]

Hi Guys,
I have been working on my CR250RE, the Steam Train, and have fitted a brand new 1.4 radiator cap. I refilled the radiator right to the top, fitted the cap and started the bike. For the first 5 minutes of running, the coolant dribbled out of the overflow tube when I revved the engine. In total about 40-50ml of coolant came out and then it seemed to settle down. I imagine the coolant expands when it is heated so this is normal and there will always be an area of unfilled radiator at the top. Is this correct?

[Hoony]

Yes. (don't you love the short answers)

[Tony T]

I'll elaborate a bit. 
Exactly as you suggested, the liquid needs space to expand when hot, so you'll never keep the radiator completely full when cold. Unless the system has an expansion tank which is supposed to allow the coolant to escape into the tank when hot, then be drawn back into the radiator when it cools down. (Although the one on any of my Husky's never worked....  )
In short, keep an eye on the level, but I'd be confident that your cooling system is working correctly.

[Kenneth S (222)]

Thanks guys. Fingers crossed for this weekend. I have pulled the clutch case off this thing at least 5 times in the last 7 weeks since I received the bike!

[Simo63]

Kenneth.  I had the same issue with one of my CR250RE's a year or so ago, would spit coolant out when revved.  Simply put mate you've probably got a head gasket leak.  In my case the head was warped and allowed a small amount of blow-by on the head gasket.  Removed, checked and confirmed it was concave (they tend to do this due to the studs that hold the head on puloing it down on the outside and warping the head), resurfaced it, new gasket and no more problem.

Hope this helps.

Cheers
Craig

[Kenneth S (222)]

Kenneth.  I had the same issue with one of my CR250RE's a year or so ago, would spit coolant out when revved.  Simply put mate you've probably got a head gasket leak.  In my case the head was warped and allowed a small amount of blow-by on the head gasket.  Removed, checked and confirmed it was concave (they tend to do this due to the studs that hold the head on puloing it down on the outside and warping the head), resurfaced it, new gasket and no more problem.

Hope this helps.

Cheers
Craig

Thanks Craig, much appreciated. The case works fine thanks. Thanks for getting it to me so quickly.

[Kenneth S (222)]

Hi Craig,
The steam train reemerged at the recent Canberra race meet. On the Sunday morning before the racing, at 0 forking degrees, I took the head off and had a look at the head gasket. I think you were right. As a quick fix, I put some gasket goo in around the lip of the gasket, nipped it up to set, then tightened it down just before the racing and while it still leaked, it was not nearly as bad and I was able to get through the races. Thanks for the tip. Will resurface top and bottom and replace the head gasket.
Cheers

[Lozza]

check the top of the cylinder to they tend to sink around the exhaust port

[Kenneth S (222)]

The plot thickens. I saw a photo of a head for sale on eBay and noticed the coolant intake fittings looked to be larger in diameter to my head. This caused me to question my head. On closer inspection, I realised that a previous owner had crossthreaded and glued the wrong size brass inlet fittings to my head. As this bike is a new model to me, I was not familiar with what the stock head looked like. BigK was good enough to send me an old head he had kicking around for this bike and yes, I think this is the source of all the issues over the last 4 months. Surely this massive restriction in coolant flow would result in a huge increase in pressure, especially when I rev the engine, and the coolant was forced out at the weakest point. Fingers crossed, things might now settle down.

Thanks guys for all the tips. I have taken all the advice and along with BigKs head, surely I am close to solving this one.

Sorry Hardo but I think the Steam Train might soon be dead.

Old head on left, BigKs head on right

[Hoony]

Yep that shiny head is certainly BigK's .

[Lozza]

The plot thickens. I saw a photo of a head for sale on eBay and noticed the coolant intake fittings looked to be larger in diameter to my head. This caused me to question my head. On closer inspection, I realised that a previous owner had crossthreaded and glued the wrong size brass inlet fittings to my head. As this bike is a new model to me, I was not familiar with what the stock head looked like. BigK was good enough to send me an old head he had kicking around for this bike and yes, I think this is the source of all the issues over the last 4 months. Surely this massive restriction in coolant flow would result in a huge increase in pressure, especially when I rev the engine, and the coolant was forced out at the weakest point. Fingers crossed, things might now settle down.

Thanks guys for all the tips. I have taken all the advice and along with BigKs head, surely I am close to solving this one.

Sorry Hardo but I think the Steam Train might soon be dead.

I don't think that would result in a 'massive' increase in pressure, there would be passages that would be mich tighter than that in the cylinder. Compacting and slowing the water in the cylinder head is a good thing anyway. Most heads have a single 19mm or 3/4in outlet in them. Top of the cylinder not being flat has given me the most head gasket/o ring issues over the years.

[marshallmech]

hahahah good one Hoony

[Hardo]

Sorry Hardo but I think the Steam Train might soon be dead.

:'(
I sure will miss following that Steam Train... it has been my guiding light for 2 meetings !!   

[Kenneth S (222)]

A quick update on this one. I reassembled the bike the other night and took the time to use my torque wrench to tighten the head nuts. It took no extra time at all really, up until this reassembly I didn't have an original owners manual to tell me what the torque should be but I picked up a beauty recently so I had all the info at hand. After hand tightening them, I was surprised how much tighter I had to tighten the nuts with the torque wrench and realised that my 'mechanics feel' might have been a little too careful and I am quite sure that I didn't have enough torque on the head nuts prior to now. As these bikes are so old, I worry about over tightening things and I think this could have been one of the contributors to my steam train problems. Doh

[Kenneth S (222)]

Lozza, it seems you were spot on.

Blew 'another' head gasket on the weekend and did my best to keep it on the track with a makeshift trackside gasket courtesy of James Boags, Bob's gasket goo and the kind assistance of my old Manly clubmate from the 70s, Geoff. A stretch I know, but with only 3 lap races you don't know unless you try. No joy though as it blew on lap 2. The good news is that thanks to Ando & Middo, we might have finally got to the bottom of this. The barrel has been sleeved and it seems that after you sleeve them the sleeve settles and the outer barrel distorts just slightly. In some places, there is the faintest lip just barely noticeable between the sleeve and barrel itself. Not enough to cause such problems I would have throught but I am told this will interfere with how the inner rim of the gasket seals.

Off to the machine shop to have it shaved. Fingers crossed!