Hey there folks -

I have a 2009 KLX 250 S. It has a Dyonjet fit and FmF slip on.

At 100 km/her (60 mph) - the engine is spinning at 7000 +/-. I am a 200 lb rider.

Red line is 10,500 - not sure when the limiter kicks in.

I just got the bike, not sure of the sprockets (gearing) has ever been altered. Assuming it has not, can any one comment on going down a few teeth in the rear and if that will give any more top end on the highway ? Would that make first gear too tall for trails ?

I do like 70% road riding, 30% trail

rob

 

Rob,
Stock gears are 14 up front and 42 rear.

The simplest and least expensive method is to change the front. One tooth up front is close to 3 on the rear. So a 15/42 setup would be very similar to a 14/39. This is a good way to experiment.

You may get more top end on the highway with a 15/42. Some riders do, but others say the bike just doesn't have the power needed to overcome wind resistance.

Based on looking at this: Gearing Commander: Motorcycle Speed, RPM, Chain & Sprockets Calculator
It sounds like your bike may not have stock 14/42 gearing if you're running 7K rpm at 60 mph.

Rev limiter should kick in at about 10.5K rpm.

 

Thanks for the info and the link to that site - based on a quick look - am I correct in that at 7000 rpm the bike - with stock gearing - should be going 114 km/hr ?

 

Based on my gearing spreadsheet I made for my 09, the bike has had a gearing change.

Actual peak power is at 8200 rpm (it will rev higher) and with stock 14/42 gearing with a 26" OD tire (probably small to average OD, a Kenda 270 is 26") the speed should be around 67 mph calculated at 7000 rpm.

If you email me I can send you my Excel spreadsheet. You find the tire OD and plug it in along with the rpm and you have the calculated speed. It's a good way to know what is happening when you do changes.

You could go to a 15T front/42 or 43 rear for all your road riding. It should still do okay on mild trails. If you are going to go more off road a quick change to a 13T and a minor chain adjustment and you're ready to go. I ran deep sand with the 13/43 and didn't have any bogging problem.

 

[QUOTE=robemac;512172

I have a 2009 KLX 250 S.
At 100 km/her (60 mph) - the engine is spinning at 7000 +/-. I am a 200 lb rider.

rob[/QUOTE]

Indicated or actual speed (GPS)? '09s usually show 10% high.

 

As speedo indicates - tires are Kendas front almost like new, rear center tread getting worn

I see that the rear is 43 tooth. Not sure of front, but after plugging the data into the gearcommander thing, it seems to fit that there is a 13 on the front with the 43 rear - why change both from stock, who knows...that scenario gives 103 at 7 K which is about what speedo says

 

Front is 14