08 Yamaha xt125r overheating

[Luckyfish13]

Hi people,

I've posted this on Yamaha club as well....

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

Went for a ride with the choke (enrichener circuit) on, came back temp was 105c....

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



Sorry for the essay lol


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Daytona 650
XT 125R

[AndyCF]

Still running weak maybe ? Remove plug and examine colour as a rough guide. Could be timing a bit retarded I guess too.

[Luckyfish13]

Plug actually looked best after the ride with the choke on.

Gonna pull the carb apart tonight hopefully the jets are clogged up...

Didn't know the timing could be changed? Isn't that all done by the ECU...it locates on the crankshaft end by the slot and key so can't be moved....
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Daytona 650
XT 125R

[AndyCF]

If the plug is about the right 'shade' when its got the choke on, it points towards a weak mixture as remember the mix is stronger with the choke due to the reduction of air.

Talking of air, worth a look to check you do not have any air leaks (carb to head area possibly)

I'm not 100% up on this model with regard to the timing, it probably is as you say fully locked however it would not be impossible for either the timing sensor to move or the actual CDI unit to be iffy but that does seem quite a stretch somehow.

Not a betting man but money is on weak mix from what you say... Hope that's a little bit of help anyway.

[Luckyfish13]

Thanks bud will defo look for air leaks again where the rubber intake mount is...also I re torqued the engine head bolts incase it was leaking there....

Was wondering...if the valves are out of time/adjustment would that cause overheating?

Btw the inside of the carb is frickin spotless
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Daytona 650
XT 125R

[AndyCF]

I'm not 100% sure on if valve clearances would effect overheating to be honest with you.

They could burn if the clearance is too small and you may get odd issues such as poor hot starting if the 'gap' has closed up (this is more apparent on engines with solid non adjustable tappets aka shims)

[Robby]

Check to see if you're missing the O-ring between the carb rubber and cylinder head. I've had similar symptoms on a 125 from that part missing (performance is OK, but running very hot).

[Luckyfish13]

Thanks all...defo will take a closer look tomorrow.

Also I should add I've ridden at least 300 miles before anyone says its cos of new rings wearing in...
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Daytona 650
XT 125R

[Luckyfish13]

Update...cleaned out all the jets and passages in the carb, all jets are stock sizes

After test ride she's runnning at 110C without the choke...
Plug looks like still slightly lean, but the insulator isnt bright white anymore...

I tried check for air leaks with wd40 and then easy start when the engine cooled down....I couldn't notice any change in idle with either....

Had sprayed all around the intake manifold and carb side of the rubber holder....and also the head gasket surface...

Anywhere else I should check for air leaks?

Also I checked the oil sump and strainer and there's no more metal particles from the break in of topend...but the thing is it's been worn it at over 100C....would this have any effect on overheating?


Cheers dears
____________________
Daytona 650
XT 125R