Does weather change performance a lot

[phatboy]

scoot didnt feel quite right today, power is down, worse acceleration and top end lost about 3-4 mph

i was hoping to be done with tweaking the scoot for the summer so before I tear into it again i wonder if its just weather

last week was 85-90 F and dry out and the performance was great

today it was 65 F and humid I want to say 65-70% humidity

i wouldn't think weather would matter so much but these scoot engines are pretty simple not like a car with fuel injection so i could be wrong. what do you think, from those who ride more than i do.

[Vivo]

Cooler temps makes our scoot perform better...

[XR100]

My a50 loves hot weather, she doesn't care for the cold very much.

[phatboy]

My a50 loves hot weather, she doesn't care for the cold very much.

yeah it seems opposite of what should happen, but mine ran great in the hot temps last week

could it have something to do with better fuel atomization when its warmer?

[ScooterCommuter]

You'd be amazed how little a change in the environment can throw off the tuning on these little 50cc engines. Here in MN where the range in temps over the year is so huge I kept a "winter jet" and a "summer jet" for the carb. It would begin the riding year (which for me, counted as "once the morning temps are mostly into the high 30s and there's no fresh snow or ice on the roads) with the winter jet but as the weather warmed up it would start to run rich and I'd switch to the slightly leaner summer jet, reversing the swap to finish out the year as it cooled down. As a rule of thumb I usually made the swap the weekends where we switched between daylight saving and standard time.

Now admittedly it's kinda an extreme situation here, there is only one other place on earth with as wide a temp range between summer and winter as MN has - and that's Siberia!

[tortoise]

Enricher switch.

"Why does the engine need a lot of fuel to fire when it is cold? For a fuel mixture to ignite, it needs to be made up of very tiny (atomized) particles of fuel suspended in the air. Cold fuel tends to stay in big drops which don't ignite easily. Also these big drops tend to cling to intake walls. So in a cold engine, a lot of the fuel doesn't atomize correctly and is just wasted. Therefore you need more fuel to start with to make up for these losses, and assure that enough of it is atomized to give you a mixture which will ignite properly. As the engine warms up, atomization becomes much better and more complete, so less fuel is needed to create the proper air/fuel ratio" . . source

If the engine is broken-in (oil drain pan glitter has subsided), might also consider using a more slippery engine oil such as Delo 400LE.

[blue]

In my scoot I just up the jet in the cold and down size in the wormer weather.

[phatboy]

almost 80 F today and the scoot is better almost back to tip top power i had on a 90 F day, still a couple mph off

its weird the weather effects tune so much, must be these scoots are so low powered compared to other vehicles you really notice

think i will upjet its usually not 90 F here

just curious what is the range for winter and summer jets you guys use. like are we talking 5 point difference, 10 point or what.

[ScooterCommuter]

I used a 2 point diff between winter and summer, IIRC. Plug chops showed about the same color and the scoot ran fine

[LoveMyKymco]

I travel to the mountains often for motorcross and we do 1/4" drilled holes covered by tape or a bolt inserted coupled by different air filters soaked in filter oil at various levels. This can be used for the same concept.
Saves a lot of time rejetting. Colder weather means more O2 in the air so you need a bigger jet, me personally Id rather run a little rich than lean half the time. The more air in the air, ha, the less power you will make with the same size jet, cooler intake temps aside from the cooler weather.

[LoveMyKymco]

Also you can advance your timing more in the cold, if you do that that is. Those 72cc kits arent that much stronger than stock and I think a 105 jet may be too big, especially with that cam. I run the Hoca 50mm/82cc kit with the A9 and I run a 38 pilot and 105 main with a performance intake,an open uni air filter, and "performance" exhaust.

[phatboy]

Also you can advance your timing more in the cold, if you do that that is. Those 72cc kits arent that much stronger than stock and I think a 105 jet may be too big, especially with that cam. I run the Hoca 50mm/82cc kit with the A9 and I run a 38 pilot and 105 main with a performance intake,an open uni air filter, and "performance" exhaust.

I'm running stock CDI with wire cut, can't change timing, was thinking about CDI with adjustable timing but i need a DC CDI they cost a lot more

Does seem like it would be rich but the plug is tan colored may even be on the lean side

I got my air box and the exhaust drilled out the scoot is a lot louder than stock

im running the stock head probably higher compression than aftermarket heads wonder if that makes a difference in air fuel ratio.

[LoveMyKymco]

The 72s were made to run the stock head, you would actually gain a lot of top end with the bigger higher flowing head but not necessary.
Anyone can change their timing by removing the woodruff key or modifying it.