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OK back story, we race an 09 in a 4 wheeled vehicle so don't have the whole bike. Recently we broke the nipple off the water pump, some may have seen that post. We didn't know we did it and he went out for the next practice and over heated it to the point of shutting off. We have had issue with loosing water every since not in the oil and couldn't tell if it was smoking. We pressurized the system and found a couple leaky hose clamps and tightened them thinking that could be our problem. Went back last week and now as soon as he gets on track and accelerates it blows water out of the overflow, we don't run a catch tank. Back to thinking a blown head gasket now. We tried pulling the thermostat and still did it. Sone read that pressure from the cyl compression is getting into water jacket and over pressuring the system does this sound right? Oh and no water in oil, pulled the head and I see no rust in cylinders or where water was traveling across. The gasket was coming apart so wondering if it could be passing between. So with all that:

1. Is there a tolerance foe a warped head? Sitting head on glass there is one area that is about .014 gap.
2. Could a blown head gasket put pressure in water system under acceleration and make water push out over flow?
 

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Yes there is a tolerance to warping in the head, i cannot remember what it is just now and being away from home i cannot check the manual, however you can download the workshop manual from this site.
Yes a blown gasket can and normally with G3 blows direct to coolant system and yes that causes pressure enough to lift the radiator cap and dump your coolant. My assumption based on your post is, on the G3 head there is always from the factory a concave area in the middle of around 0.1-0.05mm this probably what you are seeing, these heads don't tend to warp much really. However this negative situation should be resolved into a positive by skimming the head 0.4mm and fitting a cometic head gasket of 0.45mm increasing your power and response. Your removing the valves to have the head skimmed so do some mild porting as per the racing manual and have the valve seats cut. At this stage you may well think fuck it im doing it now so i will spend extra and have some performance cams as well, if so now is the time to fit heavier valve springs for that. If you want advice on cams in that head for a kit car i can help. The by the book method is to get the head pressure tested even though the symptoms don't indicate that. If its the head leaking normally you can see a hairline crack on the face of the head from outer jacket to the inside of the timing tunnel (cam chain). I hope this helps.
 

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Discussion Starter #3
Yes there is a tolerance to warping in the head, i cannot remember what it is just now and being away from home i cannot check the manual, however you can download the workshop manual from this site.
Yes a blown gasket can and normally with G3 blows direct to coolant system and yes that causes pressure enough to lift the radiator cap and dump your coolant. My assumption based on your post is, on the G3 head there is always from the factory a concave area in the middle of around 0.1-0.05mm this probably what you are seeing, these heads don't tend to warp much really. However this negative situation should be resolved into a positive by skimming the head 0.4mm and fitting a cometic head gasket of 0.45mm increasing your power and response. Your removing the valves to have the head skimmed so do some mild porting as per the racing manual and have the valve seats cut. At this stage you may well think fuck it im doing it now so i will spend extra and have some performance cams as well, if so now is the time to fit heavier valve springs for that. If you want advice on cams in that head for a kit car i can help. The by the book method is to get the head pressure tested even though the symptoms don't indicate that. If its the head leaking normally you can see a hairline crack on the face of the head from outer jacket to the inside of the timing tunnel (cam chain). I hope this helps.
All that sounds fun but sadly we have rules that say motor has to be stock and checked then sealed by a competition motor builder.
 
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