kmx 125 pressurising cooling system

Beamexican · Borekit Bruiser Joined: 09 May 2009 Karma :

Alright lads as per the title my bike appears to be pushing air into the cooling system, If I run the bike without the rad cap on I can see it pushing air up out of the system, ive just rebuilt the engine and I've bled the system several times, squeezed pipes etc.

Am I right in thinking that it could only be the base/headgasket or am I missing something glaringly obvious, everything is torqued up according to the manual and this didn't happen the last 3 times I built this engine

Any help would be much appreciated as Im getting a bit fed up now.
Rick

HD · World Chat Champion Joined: 16 Dec 2009 Karma :

What is actually happening? Are there just a few bubbles as these could be caught in the system and when fluid is pushed around they are released.

Or is it a constant flow? And are you sure you are bleeding it correctly?
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Rusty '02 Vito Camper + CBR600F3

bennell09 · Renault 5 Driver Joined: 12 May 2011 Karma :

Don't forget there is a bleed screw south of the spark plug on the head, make sure you have bled from that screw if you haven't already
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remember if it is more than two strokes its just masturbation

dangerousdave · Traffic Copper Joined: 22 Apr 2011 Karma :

have never run the engine without the radiator cap so can't say i've ever noticed any bubbles when the engine is running. Possibly a few bubbles trapped in the system which then circulate when the water pump fires up.

are you leaking any water from anywhere around the cylinder? Does the fluid level drop after riding it ?

is the bike overheating ?

If no problem with either then you should be fine.
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1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50

stevo as b4 · World Chat Champion Joined: 17 Jul 2003 Karma :

It won't be the base gasket, as the KMX doesnt drain down from the barrel to the water pump through the crank cases like alot of 2strokes do. It has a much better system IMO of taking the coolant via hose straight from the cylinder barrel to the pump, which eliminates one possible source of coolant leaks/ gasket breach.

Id say it has to be Head gasket related or cracks or damage to the head or barrel in the area of the coolant passages. Was it an OE or a pattern head gasket?

Beamexican · Borekit Bruiser Joined: 09 May 2009 Karma :

Hd if I rev the bike with the rad cap off its actually spitting water out the the top, i've bled the system correctly several times in the last 2 days and multiple times before that and never had a problem before so cant see there being air in the system,

Dangerous dave I always run the bike without the rad cap the first time I start it after bleeding to allow any air bubbles to escape and yes the bike does overheat ad its loosing coolant out of the overflow pretty fast when the rad caps on.

Stevo its a pattern gasket, these have always been fine before, I should really have bought a genuine headgasket but having just shelled out for a crank rebuild, mains, topend etc my wallet was hurting, starting to think it must be the headgasket.

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

stevo as b4 · World Chat Champion Joined: 17 Jul 2003 Karma :

On a positive it wont take long to whip off the head and check everything out. The pattern gasket might have been a faulty item from new, not to say that pattern gaskets are not good quality, but id always use OEM for a Head gasket personally even if all the other gaskets were pattern items.

Check the head face with a straight edge and feeler guage, and if it is warped you should get away with a light skim. Id also check for corrossion of the water jacket holes in the head and cylinder barrel. It's possible that you have got a crack in the head or deck surface of the cylinder.

karthead · Trackday Trickster Joined: 01 Apr 2012 Karma :

Beamexican · Borekit Bruiser Joined: 09 May 2009 Karma :

Gasket faces were spotless and comp test was 150 psi, seems odd that the head would be warped as Weit was fine before I had to get the crank rebuilt.

RS1Banger · Scooby Slapper Joined: 08 Oct 2004 Karma :

Just had same issue with a tdr125
I fitted a new head gasket and it still pressurised the rad Confused

Whipped the head off, got out a sheet of glass and some sandpaper, the outer edge of the water jacket was sanding, but not the inner cylinder to water part, it was slightly concave and not pressing firmly on the inner part of the gasket, carried on sanding for 15 mins till the inner part was sanding up too, refitted and all was well, fingers crossed, so far Smile

karthead · Trackday Trickster Joined: 01 Apr 2012 Karma :

Beamexican · Borekit Bruiser Joined: 09 May 2009 Karma :

Got the barrel and head machined as the barrel was warped and only sealing around the outside and the head done to match, all sorted now as the barrel was useless in that state.