How hot should it get?

[MarkCR750]

I have got a full fairing fitted and down pipes lagged, the tappet covers get too hot to touch after say 10 miles, is this normal?, I intend to fit an oil cooler but can't resist riding at the moment , I think we've got a probe thermometer somewhere in the darkest reaches of the kitchen cupboards, I was thinking of checking the oil temperature in the tank, does anyone know what the max acceptable oil temperature is for the 750 SOHC ?, cheers Mark.

[Green1]

I don't think I can touch the tappet covers when the bike is warmed up.
Air cooled engines tend to ping when there getting hot as you have a fairing I would run it on 20w50 and change it often probably no more than every 2000miles
In extreme cases the oil will smell burnt

[MarkCR750]

Thanks, I'm a bit paranoid about cooking the engine with that fairing fitted, I guess they run fine it places like Nevada with high ambient temperatures so I'm probably worrying about it too much, I changed the oil earlier today and what came out seemed fine, I'll get an oil cooler sorted soon.

[Bryanj]

Should be 1500 miles on any oil max not 2000

[K2-K6]

Don't think you could hold bare skin on any aircooled motor when up to normal operating temp, certainly around the cylinder head area.

Oil temp in degree C should be normal operation at 90, within an upper advised limit of 110 as I understand it.

It's quite possible that you're not running at elevated temp but if you want to measure it then put the probe in oil tank with it still running after getting it up to normal road use operating temp.

These have an oil cooler of sorts as the oil tank itself acts in this way albeit more limited than a cooler matrix.

Oil condition is everything when hot so keeping it fresh with no operational fuel dilution is the right way to go about running it in current configuration.

Changing the oil viscosity will give maybe nil advantage in these circumstances, you'd normally go up in viscosity if the bearing tolerances are greater than they should be i.e. too worn to maintain oil pressure. You may even get the opposite happen to what you want in that operating drag from increased viscosity marginally increases the temperature the engine runs at.

Towards an elevated \ excess operating temp,  you may get better protection by considered use of a synthetic based oil.

[Bryanj]

Forget synthetic for one of these

[K2-K6]

Apart from the standard issue clutch debate,  are there any specific reasons to sdvise against running synthetic?

[Bryanj]

Way over speced for these old motors and overpriced to boot

[K2-K6]

I agree completely with your cost argument as if you change it often enough then a lot of the claimed benefits for extended service intervals don't apply and the costs that go with them for a high spec oil can be avoided for these motors.

Buuuuut, your thinking about using a basic diesel oil to get the right spec for these caused me to further work through that path of logic and to try looking at some specs and usage for various different stuff I run and I've got to an asda supplied synthetic diesel oil of 5w 40 grade but with a VW spec 505.01 oil that is used in their PD diesel engines. This is specced to avoid very high camshaft operating mechanical pressures that those engines have and also support the elevated temp in the turbo casing and a certain amount of contamination from combustion blow by getting past the piston rings. Asda sell it at five litres for £20 so a reasonable cost.

In terms of the original question about high oil temp I feel it maybe a reasonable option if it does prove to be running a bit hot.

[MarkCR750]

Had a good ride out this morning, I think I was worrying too much, holding the back of my hand (the back of my hand is in calibration , yellow sticker in date) I can barely feel any radiated heat an inch and a half away, so I think all is well,  I'll still fit an oil cooler cos it can only be a benefit, and measure the oil temp, thanks for your posts .

[Greebo]

Mark

You could also use Motul 5100 10w50 semi Synth' [£30.00 quid on ebay],

I use it due to a recommendation by the guy who specialisers in re-building these engines, & I know these engines run hot even without a fairing, but you are definitely doing the right thing by fitting an oil cooler.

[MarkCR750]

I changed the oil yesterday, Halfords 10/40 semi synthetic motorcycle oil £21 5 litres not sure how good it is but definitely better than the oils the bike was designed to run on, I wonder who actually makes it?, the XJR got treated to 4 litres of castrol power 1 at £38, I had a look at the plugs on mine earlier, dark at the outer diameter and light tan electrode so pretty much perfect , good that yours is a lot nearer to where you want it.

[Johnwebley]

interesting subject,

  I remember when they used these motors (early 70's) for endurance racing,

  doing the 24hr Bol d'or,

 these bikes needed an oil cooler,24 hrs (if your lucky) flat out racing.

 are you guys going to ride that hard ? surely  in the UK,with an average temp of high teens,the oil will be comfortable,
also,will you fit a thermostat so the cooler only works when needed,?

I personally think over cooling the oil could do more harrm than good,

[Greebo]

interesting subject,

  I remember when they used these motors (early 70's) for endurance racing,

  doing the 24hr Bol d'or,

 these bikes needed an oil cooler,24 hrs (if your lucky) flat out racing.

 are you guys going to ride that hard ? surely  in the UK,with an average temp of high teens,the oil will be comfortable,
also,will you fit a thermostat so the cooler only works when needed,?

I personally think over cooling the oil could do more harrm than good,

#
Yes but after the race [thats if they made it the end] the Engines would be completely F*cked.

Better to be on the safe side ...

[totty]

I agree with the over cooling comment. According to a specialist oil blender I used to know it's definitely not the colder the better, 90 to 110 mineral, 90 to 130 with some synthetics is the range you want it to be in.

Personally I wouldn't fit a cooler without confirming one was required, and even then I'd use a thermostat.

I monitored the temps on my monkeybike, it can exceed 120 in extreme circumstances like sitting on traffic after running flat out on a 27 degree day, but it runs at 85 in normal conditions. (I'm not sure why I never monitored it on my 550, but I suspect it runs cooler)