dtr 125 water splashing out

[lee125]

the bike is 1994 yamaha dtr 125.ok about a week or so ago i skimmed the barrel and head and fitted a new head gasket since doing this i have been on the bike 2 times for about 4 -5 hours each time and now as soon as you hit powerband the coolent just splashes out of the back of the bike near the expansion tank or it is coming out of the expansion tank one of them anyway if you dont let the bike hit powerband it is fine and nothing comes out does anyone know what could cause this as it is really annoying me know cause while owning the bike the cooling system has never worked properly it has always done this or overheated any help will be much appreciated thanks
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cbt passed 01/07/2006 bike:92 dt 125 and 96 honda cr 250
theory:PASSED! A2 test:PASSED 08/11/2006 restricted to 33bhp for 2 years

[shager]

you ave got air in the water drain it and use coolent, or there is to much water in

[lee125]

also the power valve has been fully opened so your going along then it kicks in all of a sudden and then you are off.
____________________
cbt passed 01/07/2006 bike:92 dt 125 and 96 honda cr 250
theory:PASSED! A2 test:PASSED 08/11/2006 restricted to 33bhp for 2 years

[lee125]

any ideas? please i really need to fix it
____________________
cbt passed 01/07/2006 bike:92 dt 125 and 96 honda cr 250
theory:PASSED! A2 test:PASSED 08/11/2006 restricted to 33bhp for 2 years

[Finglonga]

[lee125]

i thought it might build up more pressure in the cooling system as it only does it when in powereband
____________________
cbt passed 01/07/2006 bike:92 dt 125 and 96 honda cr 250
theory:PASSED! A2 test:PASSED 08/11/2006 restricted to 33bhp for 2 years

[sickpup]

Sorry mate but still sounds like the same problem. You did use new gaskets didn't you?

[lee125]

[Robby]

Sounds like the head gasket has blown again.
Did you skim it yourself or get it done by a shop? If you did it yourself and it was your first attempt, you could have done a shit job of it.
You say you used a new gasket, so this should be ok.
Did you tighten the heads bolt down in the right pattern using a torque wrench?

Also is there anywhere else in the system that a DT125 can pressurise the cooling system?

[lee125]

[lee125]

also i have taken the head of yesterday and the gasket doesnt have a hole or anything in it so it hasnt blown.
____________________
cbt passed 01/07/2006 bike:92 dt 125 and 96 honda cr 250
theory:PASSED! A2 test:PASSED 08/11/2006 restricted to 33bhp for 2 years

[Robby]

It doesn't have to have a hole - but I would at least expect a scorch mark or some discolouring where the gases have leaked into the water jacket.

You shouldn't even consider do a job like this without a torque wrench. They aren't very expensive, you should get one.

Any other modifications to the bike like a big bore kit?

In your shoes I would be rebuilding the engine again, using new gaskets and being sure the head and barrell are perfectly flat. Then when you fill the cooling system make sure you fill it, let the bike warm up on tick over with the radiator cap off so that the thermostat opens, top up the rad as necessary, then switch off, let it cool down, check the level again, and put the rad cap on.

Also worth getting a new cap, just in case thats part of the problem.

If its still pressurising the cooling system after all that, I'm short on ideas. Maybe the barrel gone porous, but thats unlikely.

[lee125]

[Robby]

Well the scorch on the head is probably where the gasket blew, so you need to do a decent job of skimming it this time and torque the head down probably.

The thermostat regulates the temp of the engine. No therostat will make it run cold. You should get one when you get a torque wrench.

[lee125]

ok will do thanks for the help
____________________
cbt passed 01/07/2006 bike:92 dt 125 and 96 honda cr 250
theory:PASSED! A2 test:PASSED 08/11/2006 restricted to 33bhp for 2 years