Power of 250 ccms...

[Mikkel]

Hi guys,

I was wondering if anyone else had an interest in helping compile a thread of dyno charts/results for 250 ccms so one can get an idea about what is achievable with these little engines.

I was out at Ruapuna today where BEARS had a race meeting. Graham from Harris Pipes had brought a dyno on a trailer along (he'll be at the March Hare as well btw.) and I thought I'd chuck my wee '89 ZXR250 on it.

The bike is supposed to put out 45 hps at the crank - on the dyno I saw 37.5 hps @ 16,500 RPM and ~13.5 lb-ft @ 14,000 RPM. A run without the muffler gave about 1.5 hps along the entire rev range (and sounded insane).

I'll attach scans of the dyno graphs when I've been by a printer.

[The Pastor]

good idea, i want to get my bike [mc22] dyno'd when its ready to run again, I hope it puts out around 40-45 hp (ive modified it slightly)

[Subike]

Mr Harris pipes and his trailer will be at the march hare next weekend
I saw you little Kwaka doing its thing today, pretty tidy result.
Give it a tune up this week, with some fresh plugs, and a clean air filter, you might just see that 45hp on the dyno next week end
Of course you are going to the march hare arnt you?

[FJRider]

"CLAIMED" power at the crank will be more than at the back tyre. HP is ALWAYS lost in the drivetrain

[Mikkel]

Mr Harris pipes and his trailer will be at the march hare next weekend
I saw you little Kwaka doing its thing today, pretty tidy result.
Give it a tune up this week, with some fresh plugs, and a clean air filter, you might just see that 45hp on the dyno next week end
Of course you are going to the march hare arnt you?

Cheers mate! I won't be making the March Hare I'm afraid. Got other things planned for that weekend (very busy time at the moment).

But yeah, I might go and see Dyno Kyle about the bike at some point - but most likely after I've had either the muffler worked on or a new muffler made. I doubt I'd be able to get more than 40 out of her without doing radical stuff like getting custom cams - and I'm not interested in that seeing as the bike is running really well as it is. Besides, it's a 250 it'll never be *fast* anyway

There are also something to be had by making a custom exhaust system all the way - but spending upwards of $2,000 on a $6,000 bike is overkill and would perhaps gain me 5 hps tops.

"CLAIMED" power at the crank will be more than at the back tyre. HP is ALWAYS lost in the drivetrain

Indeed - a power loss of 10-20% from crank to tyre is to be expected for a chain driven bike. Some loss in the gear box, some to overcome the rotational inertia of the wheel, chain, sprocket, etc.

In comparison one can expect upwards of 45% power loss in a 4x4 drivetrain for a car... (~15% for FWD - ~25% for RWD).

[jcupit69]

Hey, have a look at:
http://www.factorypro.com/dyno/true1.html