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Luckyfish13

Xt125r overheating bad!

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Hi people,

I've been creeping round the forum for ages but never needed to post, thanks for all your ideas before and hopefully someone has some yamamagic tips lol....

 

bought a non runner 08 xt125r, did the top end rebuild using all genuine parts...

the barrel was within spec and not warped.

only thing I noticed was the second ring gap was about 0.05 mm too small, but hey I installed it anyway....

had reset the carb to stock settings...

new oil...

she fired up straight away, 75psi compression, but after going ride for about 5 mins it felt crazy hot so came home checked temp it was 130C....

now ive set the pilot mix 2.5 turns out, moved the throttle needle up to rich out the mix, after the test ride temp was showing 120c, so improvements but still too hot.

theres no air leaks

air box is standard

oil is changed after every test ride (probs cos 120c absolutely destroys it)

Engine starts pinging after it's been running a couple minutes, or when temp reaches around 70-80C

any ideas why she's runnning soooo hot????

 

Sorry for the essay lol

 

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Hi LF

I don't know what the compression should be on your bike, but my two stroke DT175 makes more compression than 75psi, I seem to recall I checked it just before xmas and I think it was around 90 psi min and 110 psi max depending on how warm the motor was,

So although somthing else may be making the motor warm, I think your bikes compression may be too low,

Aj

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Is your thermostat working correctly?

 

Sent from my E6553 using Tapatalk

 

 

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Is the temp gauge working correctly.

Oil should handle 120 deg, turbo's can glow cherry red and  oil runs through them.

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Ok I assume the bike is water cooled ? if it is check the water pump is working correctly the rad is not blocked ristricting water flow, the thurmostat is working and all hoses are free and not blocked, if it still over heats you will have to look at the water ways in the barrel etc, oh and has it got a fan ? is that working ? good luck and I hope you find the problem, and as somebody mentioned the compression seems a bit low there might be gasses leaking in to the block ?

Keith.

 

 

 

 

 

 

 

 

 

 

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Thanks for the replies, didn't get notifications for some reason....

my bike is air cooled so no coolant, thermostats, radiator etc..

temp gauge is a cheap eBay uv laser thing but I check d it with boiling water it said 100C...

compressoin I know is low, but as long as she fires up I think it's fine? Maybe less compression means a worse seal...so more blow by increasing crankcase pressures?????

thing is I used to have a Honda vision scooter was fuel injected I know but that used to fire up every time at 40psi...but is it something I should be worried about? Maybe get a leak down test done?

 

Last night I cleaned out all the carbs and checked for air leaks again....everything seems fine even the head gasket seal is not leaking....she's still runnning 110C...all jetting is standard....really dunno where to look now...

maybe yellow pages for a decent mechanic lol

Ok I've  just clocked onto the workshop forum thread...should I repost? Or not...

not very good at these forums...

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erm, for an aircooled engine its really not that hot.  Watercooled engines run around 110 to 120 deg c, water will certainly boil off my TDR engine when its wet, not that that happens outside of a hosepipe generally. Aircooled engines will go well over that, their designed to.

I think your worrying over nothing, when aircooled bikes overheat badly in my experience they usually cut out from fuel vaporisation. Unless she is pinking really badly. And by that I don't mean pinging as she cools down.

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really? I've had a few 125s never felt heat coming off the engine...on the old Cg (bless) I could comfortably place my palm on the cooling fins for at least 10 seconds even after a 'spirited' ride....

never had a yammie tho and worse thing is I don't know how they should run...if u reckon it's no problem then hey....problem solved lol

 

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Wow, no way i'd touch an engine with a bare hand. I can recall leaving skin on my dads old cb100. If that helps.

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Air cooled, well the only two things I can suggest it to make sure the fuel mixture is not to weak and check the timing, it will run hotter if it is retarded or running weak, otherwise it might be as others have said you have nothing to worry about.

Keith

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