Sm250 road gearing

[Niall-griffiths]

Hi. 2002 gas gas sm250

I seem to have a very close gear box on this your in 6th pretty fast and the rest of the gears feel so close together can anyone tell me if his gearing is low down or not. Bike does about 85-90mph in 6th

13 front and 42 rear ?does that sound low ?top speed seems more than high enough but box seems so close together

 

[WAZ]

The 2003 parts book I have shows a 42t sprocket for the SM, so looks like you've got the standard gearing. I've tried 44t-35t on my 300 with RS125 wheels, and so far the 35t makes most sense on the road as it allows you to cruise at 70mph just under the power band in top. I may try 14-40t next.

 

[slocalspode]

The 2003 parts book I have shows a 42t sprocket for the SM, so looks like you've got the standard gearing. I've tried 44t-35t on my 300 with RS125 wheels, and so far the 35t makes most sense on the road as it allows you to cruise at 70mph just under the power band in top. I may try 14-40t next.

14-40t is what I am using on my '98 EC250SM. I like it. It will cruise just
below the power valve opening around 50-55 MPH. It is still not good for
the highway (freeway) speeds here in the US. 65-70MPH is required if you
do not want to be a rolling road block. For secondary roads and canyon roads
it is just about perfect.

 

[Niall-griffiths]

The 2003 parts book I have shows a 42t sprocket for the SM, so looks like you've got the standard gearing. I've tried 44t-35t on my 300 with RS125 wheels, and so far the 35t makes most sense on the road as it allows you to cruise at 70mph just under the power band in top. I may try 14-40t next.

What was top speed on the 35 mate? Did you loose much of th snappy power and wheelies on throttle ?

thanks for that slocalspode do u notice the gears are very close even if u go much taller ??

 

[slocalspode]

First is rather tall. Got to slip the clutch for the first 20 feet at launch.
After that I do not notice much change in the spacing (between) gears.
Just more speed in each gear when it's time to shift.
I did it for a more relaxed cruise speed from 45-55 MPH. Another benefit is
much improved gas mileage. I did a +100 mile ride and had ~1/3 of a tank
left. I do have a ~3.7 gal IMS tank though. And I ride like a grandma. I do
not care much for wheelies or top speed. It is all about the corner speed and
conservation of momentum for me.
cheers,

 

[stian]

Im on 13-40. Only been to around 60-75kmh due to missing reg plate. For my part, I like more 14-38.
More linear power, high speed low rpm. Also like long gearing on wheelis.

 

[motopsycho87]

My SM 300 conversion tops out at 96 if I remember correctly, the idea is to have fun with the power, not just seek the highest speed possible !

 

[stian]

My SM 300 conversion tops out at 96 if I remember correctly, the idea is to have fun with the power, not just seek the highest speed possible !

Not what I said either. With low gearing you get more linear power delivery, and also low rpm in higher speeds (110-120kmh). For those of us who commute to schools/jobs this is quite good. Also I hate stressed engines over longer times.

 

[Niall-griffiths]

My SM 300 conversion tops out at 96 if I remember correctly, the idea is to have fun with the power, not just seek the highest speed possible !

Of course I know this its just nice to be able to sit at 70roughlty without screaming what gearing does your 300 have ??

 

[motopsycho87]

I know my knobbly gearing is 13-52 and am using the same chain. I think I've got 14-48 or 49 for SM. I'm going to assume you've not found the gearing calculator floating about the net? Input all the gear ratios and revs etc and it spits out max speed in each gear.

 

[WAZ]

http://www.gearingcommander.com