GRiSO gets lazy in the heat. How come?

With the onset of cooler weather I've been reminded of one of my GRiSO's less charming quirks and would like to ask if anyone here has any clues which may help solve it.

In the summer time when the ambient temp gets over about 25 deg C, the bike is noticably slower and more breathless; over 35 she is so wheezy that I take pity on her and catch the bus instead..
When winter rolls around and temps drop below 25 there is a noticable difference; the bike is more powerful, engine crisper.
At temps under 15 the thing is an absolute rocket....well lets not get carried away; but the contrast between winter and summer running is hugely noticable so much so that I can hardly keep myself off the bloody thing in winter!

Riding the bike in the cold puts a huge smile on my face and i'd like to keep it that way when things warm up again so any ideas where I should start looking? The bike really does need a service (my limited foray into GuzziDiag has told me the bike needs TBs balanced and TPS reset) but would that help this apparently heat related issue?

Its worth mentioning that the engine pinks a lot through the mid range in the hot scenario but the issue vanishes completely in winter and the engine runs flawlessly (i always use 98 octane juice).

Ive trawled various forums looking for clues but apart from volumes on pinking there doesnt seem to be anything on hot/cold running performance. I know air is less dense when its hot but surely that couldnt be resposible for such a difference in performance?

Any input greatly appreciated,
Thanks!

TB's out of balance can cause pinging, and when the ambient temps are up, the engine will run hotter and the fuel correction tables will lean the mixture further, exascerbating the issue.

Once you've got your TB's balanced, if the problem is still there, there may be an issue with the temp sensors, possibly causing the ECU to lean the mixture more than it should.

Warmer less dense air is supposed to be compensated for in the air temp-pressure table of the engine map i.e less fuel is injected when the temperature rises to maintain the required air/fuel ration, normally 14.7:1.
It doesn't help that the air intake is close to the engine because the air box recieves even warmer air from the engine at slower speeds.
You could try turning the lambda off and/or resetting the TPS and seeing if that helps. Normally the change in fueling shouldn't make too much difference to the performance.

Can I have a look at it? It's definitely not normal.

Pete

Air cooled engines, less powerful with hot temp??
Hell yeah!!! Every one of them. It's the nature of the beast...

Your bike might have a TB issue but it will NEVER run as strong as it does when it's 15C or lower, despite how well tuned your engine is.

No but it shouldn't be gutless!

Pete

Thanks everyone for the input,

Re; the hot/cold ambient air thing; I know it makes a difference however Ive never ridden a bike with a more noticeable difference than this one; new old, carbed, FI- this is the worst and considering the technomological aids this one has over for eg. the Pantah, you would surely expect less impact if anything? Which makes me think this is a condition that can be improved.
Regarding the TB- i mentioned it as a potential issue because it hasn't been done to my knowledge (I'm the 2nd owner) however audibly there doesn't sound to be any major imbalance however I'm showing my ignorance here because i don't know how out of balance it needs to be on these new fangled things to make a difference.

Pete, thanks for the offer, I'm planning on getting it serviced in about a month so will tee something up then. Having a decent service sound about the best/only starting point for attacking this issue!

Ill have to wait for summer now before I can do anything serious about it anyway! In the meantime I'm going to enjoy the shit outta it!

Thanks again- and lets resume this thread when things start getting toasty again. Cheers!

How about rather than risking serious engine damage due to chronic over fueling which is what it sounds like to me why don't you take a day off and ride up here so I can have a look at it? I can't say what the problem is without looking at it but it doesn't sound either right or difficult to fix.

Pete