Looking for some advice, yesterday it reached 41 degrees with not a smell of any cool air. I travelled down the M4 sitting on 100km's per hour and got off at the exit ramp. As usual I get a red light for around a minute then off we go only to have the bike start to pop and fart and surge and then stall. I coasted to the side of the road and started her up again but needed a fair few revs to keep it going. I travelled about five minutes further and made it home. Bike starts ok later in the evening. I have never experienced this before, could there be any damage and should I change the oil. Also, do you guys have temp gauges fitted and where?

welcome to the forum
what year bike? what mods?

The answer here is don't ride it on excessively hot days, its still an air cooled motor, l run an oil temp guage and an oil cooler , prior to fitting the cooler, oil temp on moderate hot days would run towards the 300 F, but with the cooler and l am moving at the legal speeds it runs at 270 F where the oil is designed to be. Ride it in the cooler parts of the day better for you better for your bike.

270F oil is still on the hot side of the scale.
Rode my SG in 40c here in WA last week, 120kmh for an hour straight, no oil cooler, oil temp never exceeded 230F, cooled off even more once I slowed going through towns and lights n shit. In moderate weather my oil temp rarely exceeds 200F, including town work
Your tune has a LOT to do with engine temps

I used to get the bike doing funny things after a run up from the coast on the freeway then hitting red lights within 30 seconds after leaving the off ramp. By the second set of lights a k down the road, it would ping and carry on, then after another few minutes of slower constant riding it would settle down again. I think it's just the residual heat from running at speed still coming out. You could try a higher octane fuel, or slow down a bit prior to your exit and let it cool down a bit while still on the freeway. Since it the speed limit was dropped to 80kph for roadworks a few k's before my exit, a lot of this carry on has now gone. You don't state what model bike it is, if it's a stocker, or if you came off a water cooled bike and this is your first air cooled big twin. I wouldn't lose sleep over it just yet.

It's most likely the EITMS system if it's a 2007 or younger

This system "drops out" the rear cylinder by stopping the fuel and sparks once the engine temp' sensor detects a given internal temperature

That has caught the riders of more than a few of the bikes I've worked on . I now switch it off as a matter of course when changing a bikes tune.

Several guys have called me " my bike's running fucked " or whatever, Caught me by surprise on my 2008 CVO Springer the first day I got it from compliancing/rego. So I fucked it off ASAP I got home.

From what I can gather it's really for " parade mode " in the US where you ride your Harley behind the "stick throwing" dolly bird at walking pace
You're fixated on her "pert ass" and the bike starts carrying on like a pork chop

For what it's worth my bike's oil temp in the oil tank sits under 200F or even less , maxing at 220F in traffic on a hot day . I have the push on "oil filter cooler collar " which works just as well as my plumbed in factory oil cooler on my previous bike at a fraction of the price and grief

Synthetic oil helps as well with heat dispersal

Why would you turn off eitms in the tune?! It's there for a reason

Thanks guy's for the responses. It's not until you read your responses that I can see there should have been more detail outlined in my question. My bike is a FXRS lowrider, 1991 model that I have owned for a while now. No mods to the bike, she is a stocker. Runs absolutely fine every time I take her out and to be honest I did consider trading it in for a 2014 fatboy but just couldn't bring myself to do so. Beagle, I think you are right with your response, the closer I got to the mountains the hotter the wind was and yes I made the error of maybe not slowing down a bit before the off ramp. I took her out for a run this afternoon and no obvious effects, the bike ran as it usually does. I do plan on fitting a temp gauge though as I really want to avoid that Oh shit, what have I done feeling happening again.

 So it's an early bike then , no ECM type reason !

Why switch off the EITMS ? The "reason" it's there is to cope with the high heat generated by the stock EPA approved fuel mixture as set in the stock ECM tune

Once you've pissed off the Catalytic converter (in the mufflers on most bikes ) and got a good tune in the ECM the EITMS is not necessary in my opinion , and all the times I've done it folks don't like the "dropping to one cylinder" effect so OFF it gets set.

Drifting from the Original poster's question now ! 

My old Evo ran 180,000KMs without an oil cooler. I live in North Queensland and rode it around Oz, out to Alice a few times, in all it saw plenty of 40+ degree days. I used only genuine Harley oil. When I replaced a rear base gasket at 145,000KMs the original honing marks were still visible.

You have to remember the earlier bikes all ran "cooler" from stock , that is Evos and 1450CC twincams

The 2007 and up 96/103 bikes run real hot as part of the emissions package the bikes are lumbered with from new

Fuel/air wise they are way "leaner" than early carby bikes

The slip-on oil cooler collars are on the oil filter obviously and don't impede air flow over the front cylinder at all

They're the best value for money , and slip right over black stock filters ( or chrome , but why bother ?)

Available on US eBay for Evos or Twincams and they WORK well

Dropped my oil tank oil temp' by 20F instantly on the first trial run ,  ( that's on my Temp' Guage dipstick ).

Had this same thing happen on my 97 Fatty on the weekend. Had a very fast run of about an hour down a freeway. Hit some heavy traffic and she was farting and carrying on. I thought I had run out of fuel and switched to reserve. After a bit of coaxing she was fine again and hasnt missed a beat since.