I had my bike dynoed at another shop and it put down 189 hp. So the dyno operator postulated that the low numbers were due to the stretched swingarm with a longer chain that was not lubed properly. So he adjusted the roaring toyz swingarm back to the stock length and put on a used but still in good conditon stock tire and of course a proper length chain for the stock length swingarm and ran it on the dyno again and this time she put down 202 hp. But with this configurstion I could not keep the front-end down or the back tire would break loose, so I had the swingarm extended again as before and the shinko hookup put back on. The moral of the story is that she is faster even with lower dyno numbers with an extended swingarm and a sticky tire.

I'm surprised the numbers changed that drastically, but extended swingarm requires a longer chain. That chain introduces more parasitic loss through friction, and weighs more.

Frictional loss directly relates to the length of increase in chain. If a 100" chain causes 10 hp loss (this is just for illustrating the point..not actual number) then a 120" chain would cause 12 hp loss, given the same chain type and size.

Weight increases rotating mass, and also unsprung weight. The more something weighs, the more energy required to move it. Again, the energy required to move it is directly related to the increase in weight.

To answer your question abut speed, that's relative. At high speeds 202>189. In standing acceleration in a quarter mile, my guess is 189+6">202+0". The ability to put down all the 189 sooner is > having to baby 202.

I had my bike at the local shop for a repair. My bike made 205.9 stock length. I put a McIntosh 10 over arm on her, and Penski valved shock, rear Shinko 200 50. She pulled 199 on z dyno in absolutely the best conditions (temps, baro pressure). Because it was a "quick let's see" pull, I didn't hook up the sniffer and do a Torque pull read. I knew I would drop a few HP running the mc arm. Ain't no thing. On launch, you will make back those losses. I have to restate, I'm just an ordinary man on an extraordinary bike, so 6 hp ain't no thing.

* Last updated by: Wolfman on 1/24/2015 @ 4:55 PM *

I can believe that hp difference between stretched/stock wheelbase. But like Vic and Wolfman said, the bigger fact is you can apply a lot more of that power with a longer wheelbase and proper suspension setup than clutching through the higher hp to keep the front down at stock length.

Brock Davidson did some testing way back when he was building a 200mph kit for the gen1 14's, and found it took up 12hp just to push the bike's mirrors down the strip due to their drag coefficient at speed, so more swingarm and chain length/mass and weight would probably eat up that 12-13hp as well.

Leave her stretched if your drag racing, dont concern yourself with how much HP it's making so much as getting "usable" HP to the ground.

* Last updated by: Hellmutt on 1/25/2015 @ 3:33 PM *

This is very old news guys. Stretched bikes have always made less on the dyno and produced better ET on the strip. Yet another reason why dyno horsepower readouts are useless.

old news for sure, but remember some cats are new to this scene, and thats okay. I didn't know as much about any of this till I bought an arm and ran the set up myself.
reading and riding are two different things...

Lemme guess, you had a shinko hookup on your bike when you first put it on the dyno? It isn't the stretch that hurts your numbers, its the Shinko hookup. On average you lose about 20 horse on the dyno if you have a shinko hookup.

Lemme guess, you had a shinko hookup on your bike when you first put it on the dyno? It isn't the stretch that hurts your numbers, its the Shinko hookup. On average you lose about 20 horse on the dyno if you have a shinko hookup.

Old threads never die! Yes you are correct. I had a Shinko Hookup on.

* Last updated by: skewedTotheLeft on 6/2/2016 @ 3:03 PM *

Why? Does the Sinko tire slop on the dyno?

Even Shinko says not to put it on a dyno test

Its hard on the tire and the horsepower readout will be low. But only dummies take the horsepower readout and run with it. Worthless number.