C650 Speed Verses RPM 0-35 mph

[Low On Cash]

Hey Guys - are there any threads on possibly modifying the clutch for "Increasing" the low end gear ratio on the 600S. Seems as if the engine is really turning much faster than it needs to when starting out and up to around 35 mph. After 40 mph things get right normal again. I was stuck in traffic moving slowly, it seems the engine is screaming for nothing.

When I got home, I found this graph and it actually shows that same area I'm referencing. You can see the engine is like turning over 4 grand at 2-5 mph when it should around 2000 just above clutch engagement. The curve needs to be more linear than it is, what was BMW thinking?

Mike

 

[Thom Davis]

CVT transmissions often require more rpm to "start" because the belt needs to grip the pulley and that won't happen at low rpm. Here's a link to more than you probably want to know. https://www.tandfonline.com/doi/full/10.1080/23311916.2017.1398299

 

[Low On Cash]

Thanks Tom - I just checked it out thanks.

The article is a bit generic and does not provide any answers why BMW ended up with this exceptionally high rpm at low speeds. Tooling around a town or in slow speed traffic the engine is just wasting power and fuel, because of a very non non-linear curve. This is the exact opposite of the Max, MP3 and many other scoothers who conserve rpm and fuel at low speeds where you don't need it. I'm sure someone has an update that smooths this sharp engagement curve out.

Thanks Mike

 

[Thom Davis]

Well, you might get more replies if you don't use "clutch" and "gear ratio" when talking about a CVT driven scooter. After all, no gears nor any clutch in the entire mechanism.

 

[Low On Cash]

Thanks for the reply - I know what your saying - but there is actually three clutches on the 650, the engine clutch and two variable clutches which change ratio. There is also a set of fixed gears in the main drive. I'm sure there must be hundreds of guys who changed out the clutch and sliders, hopefully they might weigh in to see if it helps with the high rpm at low speeds. Thanks

 

[Thom Davis]

Other folks have had similar irritation with the acceleration and have chosen to modify with a Dr. Pulley...and some have reported issues afterward but many have been happy. http://www.partsforscooters.com/169-406-Dr-Pulley-HiT-Clutch-302002-BMW-C600-C650-Maxi-Scooter

 

[Skutorr]

That's life with a cheap dry clutch on such a heavy scooter. The Tmax 530, KYMCO AK550, and Burgman 650 all have WET clutches and don't have that problem. (Piaggio even spent the extra $$$ and put wet clutches in their latest 350cc single-cylinder motor.) The ANCIENT Honda Silverwing 600 is the only other twin maxi that still uses a dry clutch, and it came out with it in 2001. BMW is just CHEAP...

 

[Low On Cash]

That's life with a cheap dry clutch on such a heavy scooter. The Tmax 530, KYMCO AK550, and Burgman 650 all have WET clutches and don't have that problem. (Piaggio even spent the extra $$$ and put wet clutches in their latest 350cc single-cylinder motor.) The ANCIENT Honda Silverwing 600 is the only other twin maxi that still uses a dry clutch, and it came out with it in 2001. BMW is just CHEAP...

Thanks for the reply - but its not the clutch, its fine. There's nothing wrong with dry clutches they have been working for decades. Besides, the bike only has 200 miles on it, all the 650's have high rpm at low speed for better off the line performance, however if your just tooling around town, or in traffic, you have to deal with the high rpm and noise. Sort of goofy to have the engine turning 3000-4000 at 10 mph.

Did you say BMW was cheap - LOL mine wasn't nor is the construction, it first quality!

Mike