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How to tell if an Air-cooled engine is getting too hot?

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Bhud
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Joined: 11 Oct 2018
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PostPosted: 21:45 - 23 Apr 2019    Post subject: Reply with quote
Riejufixing wrote:
Insufficient exhaust valve clearance causes that too (and retarded ignition timing, but is it adjustable on this engine?).


It isn't adjustable, but you can adjust it anyway, by widening out the holes for the timing disc's backing plate to let you rotate it a little. You wouldn't want to retard it any further though. With the normal timing disc, the engine is already retarded to fire at 4 degrees BTDC. This is so that it can handle low octane fuel without pinking. It's well worth it to advance ignition timing by 4 degrees, if you haven't already. The bike will then, very noticeably, perk up at 6k rpm. You can fit one of these and avoid drilling out your existing timing disc to achieve this:

https://www.ebay.co.uk/itm/Y003-YAMAHA-XJ600-DIVERSION-92-04-4-DEGREE-IGNITION-ADVANCER-ROTOR-YELLOW-ZINC/163622190567?hash=item2618a47de7:g:K-YAAOxywh1TCQvG
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adengtg
Scooby Slapper



Joined: 02 Sep 2017
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PostPosted: 23:01 - 23 Apr 2019    Post subject: Reply with quote
Riejufixing wrote:
I reckon it'll cook your 110C thermometer, as well as the Araldite.

If you want to stick something to something hot, then silicone adhesive (as in instant gasket compound, etc.) will withstand much higher temperatures than Araldite.

Why do you think your bike will suffer in a mere 23C ambient temperature? Say for instance it's OK at a cool 15C. If ambient goes up to 30C, you've still only added a sort-of-potential 15C to the running temperature, and in real life you won't even get that, since heat will dissapate faster from a hotter object.


Most of these cheap thermometers seem to have disply limits above 110. its only £3 so i'm gonna give it a try anyway
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Riejufixing
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PostPosted: 23:12 - 23 Apr 2019    Post subject: Reply with quote
Bhud wrote:
Riejufixing wrote:
Insufficient exhaust valve clearance causes that too (and retarded ignition timing, but is it adjustable on this engine?).

It isn't adjustable, but you can adjust it anyway, by widening out the holes for the timing disc's backing plate to let you rotate it a little. You wouldn't want to retard it any further though. With the normal timing disc, the engine is already retarded to fire at 4 degrees BTDC. This is so that it can handle low octane fuel without pinking. It's well worth it to advance ignition timing by 4 degrees, if you haven't already.

I don't understand that. Are you saying it already fires 4 degrees BTDC, and you can buy this disc to advance it further, so that it fires 8 degrees BTDC?
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Bhud
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PostPosted: 23:20 - 23 Apr 2019    Post subject: Reply with quote
Riejufixing wrote:

I don't understand that. Are you saying it already fires 4 degrees BTDC, and you can buy this disc to advance it further, so that it fires 8 degrees BTDC?


I described it wrongly.
In standard form, it fires at some point (n degrees) after top dead centre.
After the modification, it fires at some point (n degrees minus 4) before or at top dead centre.
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Sister Sledge
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PostPosted: 06:30 - 24 Apr 2019    Post subject: Reply with quote
Carry a slice of uncooked bacon to press on it?

Nah - think about Honda Cubs and how the engines get abused their whole lives and fail to die - should tell you something!

I won't worry you about your engine being red hot and still running but boiling the petrol above..
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MCN
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PostPosted: 16:19 - 24 Apr 2019    Post subject: Reply with quote
Sister Sledge wrote:
Carry a slice of uncooked bacon to press on it?

Nah - think about Honda Cubs and how the engines get abused their whole lives and fail to die - should tell you something!

I won't worry you about your engine being red hot and still running but boiling the petrol above..


Years ago on this very forum there was a thread about a few members cooking bacon on the zorst of their bikes.

All done in the name of domestic science.
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Fizzer Thou
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PostPosted: 22:23 - 24 Apr 2019    Post subject: Reply with quote
Bhud wrote:
Riejufixing wrote:

I don't understand that. Are you saying it already fires 4 degrees BTDC, and you can buy this disc to advance it further, so that it fires 8 degrees BTDC?


I described it wrongly.
In standard form, it fires at some point (n degrees) after top dead centre.
After the modification, it fires at some point (n degrees minus 4) before or at top dead centre.


WHAT!!!!

Why would any engine want to fire the air/fuel mixture after top dead centre?Or at top dead centre?There would be insufficient time for the flame travel to reach the outer extremities of the combustion chamber,to fire the complete air/fuel mixture and to achieve full burn Rolling Eyes

As an example my R1 fires at 5 degrees before top dead centre at 1100rpm but at 5500rpm the electronic advance goes to 55 degrees BTDC.

A weak ignition will result in poor combustion,excessive fuel consumption and engine damage.
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Bhud
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PostPosted: 00:37 - 25 Apr 2019    Post subject: Reply with quote
Fizzer Thou wrote:


WHAT!!!!

Why would any engine want to fire the air/fuel mixture after top dead centre?Or at top dead centre?There would be insufficient time for the flame travel to reach the outer extremities of the combustion chamber,to fire the complete air/fuel mixture and to achieve full burn Rolling Eyes

As an example my R1 fires at 5 degrees before top dead centre at 1100rpm but at 5500rpm the electronic advance goes to 55 degrees BTDC.

A weak ignition will result in poor combustion,excessive fuel consumption and engine damage.


My explanation was fucked up and wrong - ignore it.

What I should have said was, the ignition is retarded from the factory not to create optimum pressure at the optimum moment in the combustion chamber, in order that the bike can tolerate low
octane fuel, found in some countres, without preignition.

The 4-degree ignition advancer changes this so that the mixture ignites sooner. It's a well-known performance upgrade for this engine.

https://www.xjrider.com/viewtopic.php?t=8636
https://www.xjrider.com/viewtopic.php?t=106
https://www.xjrider.com/viewtopic.php?t=5214
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1198
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PostPosted: 12:54 - 25 Apr 2019    Post subject: Reply with quote
I wouldn’t worry massively. I’m pretty sure Yamaha know (roughly) what they’re doing. I don’t think it’s the first engine they’ve ever designed.
I wouldn’t hold the revs high in traffic just for fun, but who does anyway?
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Qyburn
Renault 5 Driver



Joined: 14 Jul 2017
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PostPosted: 13:09 - 25 Apr 2019    Post subject: Reply with quote
If it gets hotter than normal it will smell different, also maybe more clicks and pings while it cools down.
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Easy-X
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PostPosted: 13:53 - 25 Apr 2019    Post subject: Reply with quote
While air cooled engines are meant to get hot not all the cables, wires and pipes are so happy with extreme heat. Make sure everything is clipped away from the cylinder head and exhaust.
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Tdibs
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Joined: 16 Jan 2015
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PostPosted: 14:49 - 25 Apr 2019    Post subject: Reply with quote
It will be fine.

Ive only had mine cook pretty bad once or twice, after long stretches of slow filtering where you are not getting much air flow at the height of summer. You can smell it and it felt a little less responsive. Just got to keep moving Smile
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MarJay
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Joined: 15 Sep 2003
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PostPosted: 14:51 - 25 Apr 2019    Post subject: Reply with quote
In the manual for my Buell it just says "Try to avoid riding at parade speeds for extended periods".

This is a highly tuned Harley with one cylinder completely covered from the airflow, albeit with two enormous fans on each.
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NutsyUk
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PostPosted: 16:29 - 25 Apr 2019    Post subject: Reply with quote
Last summer when we had that heat wave, I was stuck in traffic at 35c ambient... My legs were getting properly cooked. I also was a tinsy worried about engine temps. but the light never came on so.... I guess it was ok :p

Apart from the second degree burns on my legs Very Happy
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Old Thread Alert!

The last post was made 4 years, 360 days ago. Instead of replying here, would creating a new thread be more useful?
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