If the manufacturer supplies the engine with an oil cooler, it needs an oil cooler. Otherwise not, unless you have made significant power-related modifications. Air-cooled engines are designed to run hotter than water-cooled engines, but the rules for oil temperatures are the same for both engines. YOU may be uncomfortable at the higher engine temperatures but the engine has been designed with adequate materials and thermal expansion clearances to run just fine.

From the engine point-of-view, you should expect to see indicated oil temperatures between the gauge midpoint and three quarter mark with occasional excursions to full scale. That’s how the manufacturer selects the gauge mid-point. If the oil temperature is too cool the oil viscosity is higher so you will loose power due to pumping losses.

From the oil point-of-view, you need to maintain lubrication and a high enough viscosity when hot to produce an adequate oil pressure. If the oil temperature is too hot, the oil oxidizes and breaks-down more quickly.

That’s why you should run a synthetic oil, to give you a safety margin against oil breakdown. A regular oil will begin to lose its film strength at temperatures above 220°F (105°C), while most full-synthetic oils can be safely used at temperatures as high as 300°F (150°C) before lubrication-related damage becomes a concern.

As a rule-of-thumb your oil temperature should be kept below 240ºF if you want to change petroleum-based oil at the recommended intervals. For every ten degrees above 240°F, cut your oil change interval in half.

Race car builders usually design for oil temperatures between 230°F and 260°F in order to get the best power. Above that range, engine reliability and oil life becomes a factor in racing.

As mine was designed with out a cooler and is still the standard 583cc, i'll continue running mine as it is. Just change the oil as and when.
Be handy to fit a temp gauge which I hope to do when I get the 916 tacho to work, then I can fit the housing from the 916 to mount both of them.

Note that the DP oil cooler for the Multi 620 is different to that for the Monster. I think it is just the hoses and stuff as it mounts up behind the point at the front of the fairing. However, the kit is not available yet - mines been on order since September 04 (when I ordered the bike), and no sign of it yet.

Multi600, did you need to change the exhaust pipe to fit that belly pan, or was it made specially to fit ?? I want one.......

I would agree with you... but how would you explain that my 620 Sport is fitted with an oil cooler and Ian's one isn't. Mine is a French model, and his is a British one. I agree it's always raining in Britain ( :lol: :lol: :lol: :lol: ) but I think the average temperature is almost the same than in France... What do you think ?

We have a saying here.

"The French copy nobody and nobody copies the French."

But the oil of the French guy's bike just stay around 105°C after a race :D