DR250...HP needed.

[UberTard]

No...this is not a DR-Z 250.

It's the old 1992 DR250. It has sohc and 4 valves. Air cooled. 6 speed.

Basic Dirt bike.

I just bought it and am refurbishing the whole beast while changing to SuperMotard trim.

1 thing. I need more power. It apparently has 18hp rating from the factory. I need a bit more. It revs plenty high ..it just doesn't pull hard enough on the way.

Plans are to check on the price of a slightly larger bore piston and little higher compression, but let's pretend that I can't get that stuff.

How much HP can I expect from the following mods.

-proper Port job

-3 angle valve job

-back cut valves (maybe 1mm bigger?)

-32mm flatslide

-proper exhaust system

-freer flowing air filter

Would someone who knows the bottlenecks of this engine please speak up.

Basically, I need to be able to pull harder than a Kawi D-Tracker. Then I'm happy.

Please help with any info you have.

Rob

[R_Little]

The pipe and jetting may get you 2 more hp. I did the same thing with my brothers old 250. What you really need is a 346CC kit from kientech.com

Will cost you about 1.5 times the price of the pipe.

[Irwin]

To be completely honest, the big bore kit is probably the best way to go. I've done most mods possible, it runs great but it's still a 250. More CC's are the real answer.

[UberTard]

Hmmm...it would likely be cheaper for me to just find a DR350 engine and slot that in ( I hear they are the same size).

I was thinking to keep it 250 though, maybe cloverleaf the combustion chamber and increase the compression to about 11:1?

Irwin, I would love to hear of any info and input you have on the DR. I'll definitely keep you guys informed on my progress and findings. Doubtlessly I'll need some advice on some stuff (electrics etc.)

[Irwin]

This winter so far has been very productive. List of completions.

The Kouba links were a breeze to install, installed the 1 3/4 inch lowering links. I had to compress the spring to it's tightest setting to avoid bottoming. Lowered front forks same amount and raised the handle bars using an additional set up top bar clamps flipped over, no cable adjustments needed. Supertrapp Stainless steel pipe added with 8 discs, the bike doesn't sound like a garden tractor anymore. Sounds nice. Opened the air box per Keintech's specs. Thank you Jesse! Purchased the ThumperTalk DynoJet Kit with the 140 main and the needle set on the 3rd from top position. Mixture screw 2.5 turns out. Bike starts much better and will pull the front tire in 1st with a quick roll of the throttle. Much torqier bike now. Thumper Talk is a great resource and I appreciate all the help.

Nice to find someone interested in the DR250, not too many of us around

__________________

1990 DR250S Dynojet, Supertrapp ........more

1974 Honda XL70

[R_Little]

I bet the 346 kit runs better than a stock 350 motor. It has higher compression and should rev faster due to smaller stroke.

[UberTard]

I'm not getting a big bore kit for a 1000dollar bike, just get a compression bump and displacement bump from a larger piston with a taller crown.

Instead of 249cc and 9:1 comp how does 270-290cc and 11:1 sound??

Also looking at carb options. need to ditch the CV carb.