INTERESTING heat-related phenomenon?  By  oldchopperguy (Read 884 times)

Cyborg55,

Absolutely on the money!  Have a bone on the Old Chopper Guy...

My old Kymco has had a one-tooth-upped final drive done by the original owner for highway use.  That upped her top-speed from the shop manual listed 67-mph to over 75 while still retaining decent acceleration.  However, "Minnie Mouse's" top-speed and cruise is noticeably faster during this 100 degree weather.

Just goes to show HOW much these CVT trannies affect the performance of our scoots.  Being an old-school biker, I have over 50 years riding Harley, and other choppers and cruisers.  When I went with a Chinese 150 scooter eight years ago, I thought I'd have a hard time "transitioning" from manual shifting to the "twist-n'-go" CVT.

Turned out to be the opposite.  In ONE DAY I was completely comfortable with the CVT and really would not like to go back to manual shifting again.

When I was young, an engine putting out one horsepower per cubic inch was considered super-hot.  An Italian-built Harley 250 Sprint got around 15 hp out of its 15 CID 250 motor.  And it won races!

My outdated Kymco 250 puts out over 19 hp from its 15 CID.  Even Chinese 150's squeeze around 10 hp from their 9 CID.  This would have been RACING performance in my youth.  Horsepower is not a problem with our scoots...

Granted, the CVT transmission DOES lose a LOT of top-speed in scooters compared with a solid-hookup manual tranny and chain-drive... But... The ease-of-operation, convenience and simple maintenance makes up for it.

On my old 150 I obtained a LOT of improvement in performance by tweaking the variator.  This surprise "hot-weather-hop-up" tells me my 250 will also respond to similar tweaking.  Considering the small-displacement scooters (300cc and smaller) I would not potentially compromise reliability by modding the engine, but rather spend my time and money tuning the CVT.

Even the teensiest change in belt-movement in the variator, and just WHEN the movement takes place, makes for REAL changes in performance: totally different from clutch-n'-gears bikes where the final drive is "etched in stone" save for changing final-drive-sprockets.

My old mind is thinking I should be able to duplicate this surprise performance by playing with sliders in the variator.  I've heard great things about Dr. Pulley sliders.  The secret will be getting the right weights.  The 250's with more hp and torque are a little more forgiving than the 150's, but the weights still must be correct.

I found that SO true with roller experimentation in my 150.  Original "performance" was a top speed of about 48 mph, with poor acceleration.  Switching to 11 gram rollers gave INCREDIBLE acceleration and hill-climbing but a top-speed of only 45-mph at 9,500 rpm!

Replacing with 12 gram rollers gave me a top speed of 65-mph at only 7,500 rpm, but with zero acceleration...

I finally mixed 3 ea. 11's and 3 ea. 12's for effectively an 11.5 gram mix.  THIS did it!  GOOD acceleration, and a top-speed of 62-mph.  THAT is about as good as a 150 is going to get...  Unfortunately, still not enough to keep up with changing traffic, which prompted me to trade it on the old Kymco.

The Kymco could still use a little more "go" so when I can, I do want to try sliders...

At any rate, it is very likely we can improve overall performance of our scoots with simple and affordable changes to our "twist-n'-go" trannies.

Ride safe!

Leo in Texas

It's been hot here too.... When it's over 100 out, I just don't ride. It's just too uncomfortable AND unsafe with the helmet and all the gear, when it's that hot. It's just too easy to get dehydrated. Especially with my stop and go commute and my 1500cc goldwing (about 900lbs). Just be careful, carry water and take frequent brakes. There is nothing worse then finding your legs all wobbly and weak when you are at a stop light.