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High engine temps - what would you do?

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So this happened today....


Flying along, have been for an hour. Engine running well. Recent problems in the last month (all fixed) with the motor include welded exhaust crack (no issues since), pull starter fitted cos last one fell apart (classic polini), resoldered wires for earth (to cut motor) and resoldered CHT wires (wire carries power to the digital display gauge). Also changed bent paramotor mounts (attaches motor to frame). New spark plug recently too.


The CHT climbs to 230, (usually its 140 to 180). The red warning light flashes. I come off throttle instantly (now on idle). Temp rises to 330, 660, 880 over a min while on glide, then drops rapidly again to 140 to 180.


a little bit more throttle causes displayed temps to jump rapidly again. Then they drop. Engine feels fine to fly, no funny noises, good performance.

Do you:

Ignore gauge - its wrong probably cos the temps are ridiculous. This happened instantly.

Land immediately - requiring 40 min walk back to field with gear.

Fly to take off taking it easy on throttle and temps - less than 5 mins flying.


I'll post what I did and actual cause when people have had a chance to respond...

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If you solder a CHT cable you can get wrong outputs. A K-sensor works by measuring the resistance between different materials at different temperatures, so if you mix anything with the cable you can get funny results, correct me if I'm wrong. Change the CHT and it will most likely work.

I would ignore the CHT, fly back and land, remove the CHT, do the preflight check and launch again without the gadget.

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The Polini DRS is famous for giving incorrect readings and going wrong.. Broken wires one inch from the control box where they "join" to the main wiring loom. Why on earth they do that is a mystery!!!! also a join right where you wrist flex's... WHY??? 

Most of the DRS's we sell go wrong.. I always advise the PPG meter over the DRS as the failure rate is so low on the PPG meter and they give more info and have more channels.. 


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5 hours ago, admin (Simon W) said:

Hi, and welcome to the paramotor club :-) 

Maybe something like this would work in the courtyard? 



hi ill do as simon advised.. you also can get a larger container if needed. also chain the paramotor agianst the wall.added protection.if anyone wants something.make it really difficult for them.any any extras = prevention. ;0)

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Well I flew back to the field taking it mellow.

Landed and the engine did seem hot all over. Not sure if it was abnormally hot though, as I don't generally go feeling my motor all over after I've been flying. Spark plug looked fine - a bit of oil on it, and coffee colour on the white central area. The flash starter had fallen apart (again, I think this is the 3rd Polini flash starter to fall apart).

One of the starter pawls was jammed in the fins of the magneto cooling fan. I'm not sure if this had jammed the fan or not. I'm not sure it it could to be honest, but it is possible, and may have damaged the fan.

The temps on the CHT / Polini DRS took a while to come down, but did come down.

I've looked down the spark plug hole and the piston head looks ok to me (although I am no expert). Rotating the fan moves the cylinder head up and down - so presumably the fans OK. 

I looked up the melting temp of aluminium - about 660 degrees. Well there's no way the polini temp gauge is calibrated up to that range, and my engine didn't seize..

So it's either:

1. Faulty temp gauge.

2. Broken fan.

3. Something else running it lean?????


My plan is to get a new starter and then I can start it and run it to see if it's all OK. I'll let you know the final outcome, I'm hoping you are all correct at it's the temp gauge. All in all, a typical day paramotoring!

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  • 2 weeks later...

One simple check is to put your CHT into boiling water and leave for a few minutes checking the temps. 


You said... Rotating the fan moves the cylinder head up and down...??? I hope not surely you mean the piston ;-) 

Seeing a temp spike of 880 either means your About to blow a hole or the mix or something is seriously going or gone wrong or the DRS if starting to fail it self..  But this would on an EGT not CHT!!  Seeing that on the CHT tells me the DRS is failing...   I would advise either buying a cheap CHT and compare the two or Buy a PPG meter  or if you have a lazer temp gauge use that while running on the ground...   


If your struggling with Starter parts Feel free to give us a call as we have most pull start parts in stock for Polini ready for next day delivery.. 


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  • 2 weeks later...

Just to feed back, this was an error in the CHT. Basically a loose wire. If the polini DRS wire gets cut while in use the temps jump massively.


Also I fixed it and tried the putting the ring in boiling water - no temp change even after 5 mins. On the motor it worked fine though. Again I think this is because the cut thermocouple ring only works if you have a temperature difference across it (one hotter side eg cylinder head and one colder side spark plug).  Google seedbeck effect and you'll see why.


Also worth noting, taking the exhaust muffler off and looking in is a great way of inspecting the side of the piston head. I did this while changing gaskets recently. You get a much better view than looking down the spark plus hole and can also see the piston ring.


Thanks for all the advice.



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Sounds about right with the broken wire...  Normally the earth goes near the display where the wrist bends... 

Thats very strange the DRS's CHT wont register our PPG meters all come up to 95-100c in boiling water.. same with the WTS and EGT's 




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