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blowing head gasket


fastbob
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Can anyone suggest the best way to confirm that a liquid cooled bike has a blown cylinder head gasket ? The bike is an ER5, but thankfully it isn't mine . My current thinking is that combustion gasses are pressurising the cooling system which is causing coolant to spew out of the reservoir overflow. BUT , I haven't actually seen the bike yet so it might just be connected up all wrong . Thoughts welcome.

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The usual check is to see if the coolant pipes pressurise from cold. Usually when cold they are not are pressure - which only builds up as the coolant gets hot. If the pipes go hard as soon as the engine starts then the coolant system is being pressurised by the cylinder pressure.


You can also check the coolant for combustion products.


Or you can do a leak test - you need to rotate each cylinder in turn to the point where the valves are closed - remove the plug, place an airline into the hole and apply moderate pressure. See where it leaks out.

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Thanks for all the replies. I've been to see this ER5 this morning. I've had a good look with the tank off and there was nothing obviously wrong such as coolant pipes wrongly connected. Interestingly, the owner had fitted a rad cap with a temperature gauge. Anyway, we started the engine and warmed it up . It didn't like having the choke taken off but when I put it back on the revs went really high so I couldn't find a sweet spot where the bike was at a medium fast ( ish ) idle . Eventually it settled down to a idle without choke . After only two minutes the coolant temperature had climbed to 100 ° . I removed the rad cap and there were no bubbles but then the level began to rise rapidly so we shut it off . Then we started it again with the rad cap back on while keeping an eye on the coolant level in the expansion tank . After another two minutes of normal idle speed the tank filled right up and over flowed . Ok so there are two possibilities here to my mind . A. The coolant is boiling B. The heat has opened up a warp in the head allowing combustion gasses to seep past the head gasket and pressurise the cooling system . I guess that only a proper top end strip down would answer this for sure .NOW here's the bit that puzzles me . Bearing in mind that this engine was only running for 5 minutes at the most the heat coming off it was tremendous . The owner had told me that he had had the exhausts glowing red in the dark just from balancing the carbs . When I put my hand a foot away from the tail pipe it was like a blow lamp . ( we compared it to my ER5and mine is only luke warm after five minutes ) So regardless of what's going on with the head gasket, what on earth would cause an ER5 to generate such tremendous heat so quickly ? What I'm trying to do is work out the order of cause and effect here . Sorry for the long post but I've never felt so much heat coming off an engine in my life .

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Id look at lean mixture and retarded ignition timing


Bit deeper would be cam timing and valve clearances.


What's the story behind it,was running ok until carb balancing?

 

Yes , apparently so .

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If the cooling system is airlocked, or the circulation has failed due to a mechanical issue, then the engt WL get hot very quickly.

 

I'm sure it would but I was genuinely shocked at how much heat this thing was producing especially out of the tail pipe . Bear in mind that an ER5 does have cooling fins as well . The owner told me that he had the exhaust glowing red so that's not caused by a cooling failure. I can't imagine what I would have to do to get an ER5 to run that hot . The main needles are not adjustable and the pilot air screws being a bit out would surely not cause this . He said the bike was doing 100 mph so surely the cam chain can't be out by a tooth. The trouble is ,I could probably figure this all out if it was my bike and i had a week or two but I was just dropping by in case I could spot something obviously wrong.

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Thanks once again, I reckon it all points to a leaking head gasket. If anyone's that interested, this is a good read with a happy ending . The symptoms are very similar to what I saw today anyway. https://www.perthstreetbikes.com/forum/showthread.php?t=180046

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https://www.ebay.co.uk/p/Bt-1-2x50ml-Combustion-Leak-Tester-Kit-Co2-Fluid-Head-Gasket-Test-Block-Car-14e/527962631


Cheap and quick tester, put liquid in and then the bung in place of radiator or expansion tank cap and run bike, if liquid changes colour you've got combustion gas in coolant.


Sounds to me like that is cause too, combustion gas which by nature is hot would heat coolant up quickly so would see ridiculous temperatures.

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This doesn't sound like a leaking head gasket but you cant be sure. It sounds like a couple of problems.


The lean mixture and advanced ignition explain the heating. Normal mixture ignited properly advanced will begin its burn before top dead centre and the mixture is still burning by the time the exhaust valve opens but most heat and power has already been extracted by the piston and most of the heat is removed by the cooling system.


When you retard the ignition you begin the burn too late theres not as much power extracted by the piston and the mixture is still burning strongly as it enters the downpipe. This explains the glowing downpipe. A lean mixture burns hotter than normal mixture and adds to this effect. The excessive heat in the downpipe then heats up the exhaust. This all happens very quickly.


The coolant issue appears to be unconnected and possibly caused by an air pocket trapped somewhere. The water level will behave normally until the air in the air pocket heats up it then expands and forces the coolant out of the system.


The fact that the level remains stable until hot and then a lot of coolant is forced out suggests that this is happening. on the other hand if the burning mixture is bathing the exhaust ports and heating them much more than normal then a local hotspot might superheat the water at that point causing local boiling and then coolant ejection, this might indicate a poor or malfunctioning water pump.


I would have the timing and the mixture looked at and at the same time have a pressure test on each cylinder. After that have the cooling system looked at and the thermostat replaced. It is possible that a malfunctioning water pump that is no longer pumping or a malfunctioning thermostat has not shifted an air pocket. So the water pump may have to be swapped.


Basically there is so much going on that a mechanic is probably required to get the bottom of it.

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I quite agree, the only way to get this thing sorted would be an investigative strip down . I am more than capable of carrying out the work and my knowledge of the ER5 is excellent but it is not my bike . I was just paying a visit to an ER5 forum member in the hope that I could spot something more obvious.

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My guess.......knackered water pump (sheared drive?). Think about it - no circulation of water, coolant stands in water jacket then boils, causing system to pressurise and forcing coolant into expansion tank. No cooling = running very hot. Was the bike OK before fitting new rad cap with temp gauge? Could anything have fallen off new rad cap and jammed pump impeller? Fins on er-5 are decorative and I reckon would not aid cooling. But just my guess.

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My guess.......knackered water pump (sheared drive?). Think about it - no circulation of water, coolant stands in water jacket then boils, causing system to pressurise and forcing coolant into expansion tank. No cooling = running very hot. Was the bike OK before fitting new rad cap with temp gauge? Could anything have fallen off new rad cap and jammed pump impeller? Fins on er-5 are decorative and I reckon would not aid cooling. But just my guess.

It's was certainly on my list of possibilities and you're quite right, any small object dropped into the filler cap would quickly find it's way to the impeller . As far as I could tell though the coolant was circulating . As I say , the guy was really just seeking reassurance that he hadn't missed anything obvious. He did have reasonably good grasp of what was going on so its pretty much up to him now .

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Does the new rad cap actually open at correct psi as standard .

Why did they change cap ?

Has the bike had a history of cooling issues ?

Have you or they ever had the bike running correctly .


its hard to adjust timing significantly on a bike engine to such a point it runs without conflicting in other areas .


kawasakis can get red headers if left on choke too long very quickly

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Does the new rad cap actually open at correct psi as standard .

Why did they change cap ?

Has the bike had a history of cooling issues ?

Have you or they ever had the bike running correctly .


its hard to adjust timing significantly on a bike engine to such a point it runs without conflicting in other areas .


kawasakis can get red headers if left on choke too long very quickly

 

That's a very good question, I think he bought the new cap AFTER the over heating problem so that he could monitor the temperature. Up until he balanced the carbs he had been riding it without being aware of the over heating problem. He only noticed it spewing coolant when he was running it stationary.

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can i suggest you test this rad cap temp guage..ie boil a saucepan of water and see what temp it reaches..

if its a cheapie i doubt if its calibrated and psi rated

I'll pass your suggestion on . I haven't heard from the owner since the weekend. The chap wasn't too well and he's got a bit on his plate right now apart from motorbikes .

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can i suggest you test this rad cap temp guage..ie boil a saucepan of water and see what temp it reaches..

if its a cheapie i doubt if its calibrated and psi rated

I'll pass your suggestion on . I haven't heard from the owner since the weekend. The chap wasn't too well and he's got a bit on his plate right now apart from motorbikes .

i hadn't realised it was you who had posted the original post .... thought it was one of those bloody fly by night newbies

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can i suggest you test this rad cap temp guage..ie boil a saucepan of water and see what temp it reaches..

if its a cheapie i doubt if its calibrated and psi rated

I'll pass your suggestion on . I haven't heard from the owner since the weekend. The chap wasn't too well and he's got a bit on his plate right now apart from motorbikes .

i hadn't realised it was you who had posted the original post .... thought it was one of those bloody fly by night newbies

That's alright, I was just trying to help out a fellow member of the ER5 Forum who happens to live not far away from me . As I say , give me a week with this bike and I'm pretty sure I could sort it out but in a few hours I could only guess . It's the tremendous heat that this engine generates that was the biggest surprise. Regardless of whether the cooling system works or not this thing is like a blast furnace .

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