KDXRIDER.NET

If I wanted to ride my KDX on the road, what rpm should I shoot for at cruising speed (55) ? I'm thinking a little under when the powervalve kicks in, or right above it. I'm looking for the best gas mileage and least engine wear possible.

I'd love to know this too. Just got a 15t csprocket for this very purpose.

Sent from my SM-G900V using Tapatalk

Can't help you but you have to be thinking woods pipe and go for under the powervalve opening.

I have a 1997 220 and use a 15/45 combo. 65 mph is when the power valves is open. If you go much higher than that it struggles in 6th in a headwind or a bigger hill. I got over 7500 miles on mine. With the stock piston. I get around 40 mpg.

Personally on my kdx200 I just go up a gear to stop the powervalve kicking in. Keeps the revs lower too. I'm getting about 70 miles to a tank. Stock pipe with dep silencer. Riding at 30mph is tricky as she races so easy

220 running 14/45. Works great on the street and still rips in the woods.

kx200 wrote:I have a 1997 220 and use a 15/45 combo. 65 mph is when the power valves is open. If you go much higher than that it struggles in 6th in a headwind or a bigger hill. I got over 7500 miles on mine. With the stock piston. I get around 40 mpg.

40mpg ? how ? are you short shifting, being very easy with throttle, jetted lean ?




i've been running 15/47 on my 96 220, and the bike loves to cruise at 50mph, without the powervalve opening, and i only see around 25mpg at the best. getting into the pipe means terrible fuel economy, and much less comfortable cruising at steady speeds.

balance your tires, it makes a huge difference :)

I run stock 13/47 gearing on my '89 for woods use and for dual-sport use I just swap on a 14-tooth front sprocket. This way I can use the same chain. This gearing works pretty well on the road and pretty well in the woods. I had the bike up to around 80mph on the GPS before it fell off the pipe. It still works well for all but the most low-speed, technical woods riding, too.
I think my jetting is pretty spot-on and I get around 33 mpg on dual sport rides.

I always thought that if you held a 2 stroke at any RPM for an extended period of time, you risk damaging the motor (I.e. loosing your top end). Whenever I idea on the road I make a point to vary my RPM as I ride. Usually that makes rides above 45 MPH annoying and nerv racking (wondering if I am going do damage the motor). Is this nor true? Is it safe to ride for longer just under the power band?

I've heard that too, but not sure what the fundamental explanation is as to why it's "bad" on 2t engines to hold the throttle steady for extended time.


Sent from my SM-G900V using Tapatalk

I used to road race two stroke bikes and there used to be a CR500 getting round in a RGV250 frame. I asked a motorcycle mechanic that question and he said its the way they are jetted. They are supposed to go lean if head wide open for to long. Made sense to me as most my bikes had power jets for that. I like a good power jet, very adjustable.

Tioli wrote:I used to road race two stroke bikes and there used to be a CR500 getting round in a RGV250 frame. I asked a motorcycle mechanic that question and he said its the way they are jetted. They are supposed to go lean if head wide open for to long. Made sense to me as most my bikes had power jets for that. I like a good power jet, very adjustable.

So are you saying 2 stokes go lean when held open and that's why it damages the motor. Or are you saying you are supposed to lean out your mix when holding it open?

It's all in the tuning. 2 stroke boat motors are held at steady rpm sometimes for hours. It's not a 2 stroke problem.

You wouldn't want to lean out the mix though. Lean makes the most power but a tad rich is much safer for the engine. I may be wrong but I would think with conservative jetting (a little rich) you could run on the road for extended periods without problems.


Sent from my iPhone using Tapatalk

The way the mechanic said it indicated that it was what he was told, so when he said "suposed to go lean" it means MX motors are some how not jeted/carbed/timing/suited for road racing.

This was a confusing answer to me as I visulised the porting, pipe, carb and could not determine a reason why this would be so. Other than I was holding my moters pined for periods of time and had holed a few pistons. This all stoped when i got control of the timing and installed power jets.

Power jets are designed to work in the upper rev range.
Timing for road race bikes retard off aroung 10,000 to 12,000 rpm
Both will stop you holing pistons


Your average bike is never heald in that rev range for constant periods so this is probebly not a issue

It's all in the jetting. I can run my 3 cyl, 1100cc, 2 stroke JetSki's wide open for an hour straight.... if I want to burn 15gal of gas.

I agree jetting is key. Years ago many enduro/duelsport bikes were 2 stroke. Only problems they encounter was the EPA