i'd love to get a couple dyno pulls under my belt, but i can tell you right now, that even though my greatest fault is perfectionism, until i can afford a climate-controlled workspace and the time to experiment, i've mostly given up trying to squeeze out that last drop of HP and torque out of my bike. reason being, my max pulls like a redbull-induced silverback in the early mornings, like a half-torn gazelle being chased by hyenas around noon-time, and like a charging african elephant stuffed with marula fruit in the late-afternoons to early evenings.
I assume this is some fermenting fruit which affects the pachyderms significantly?:rofl_200:
The thing you need to look-at, from being told by my friend who has many pulls under his belt, on a variety of bikes, is if the fuel/air mix shows well, then that is going to be an accurate figure,
on that dyno, on that day. Two bikes dynoed on different dynos on different days are going to be very different given the atmospheric conditions, including mean height above sea level, relative humidity, and temperature. As Sean mentioned, tire pressure, how tightly the rear was cinched-down to minimize drum/tire slippage, and even operator experience all will play a part.
I installed a used stock engine to avoid doing a case-split to repair a 2nd gear issue, and the bike was seemingly running very-well w/the replacement engine. When I took it to the dyno, it was to 'baseline' for discovering how-much mods affected the output. I had planned a new full 4/1, Dynojet Stage 7 complete kit, COP's, and a DYNA 3000.
The bike on 3 pulls did 109+ RWHP, which I thought was OK, not outstanding but a known starting point. Then leaving the dyno shop, I lost a #3 cyl big-end conn-rod. It didn't break, but it had ~2mm extra-play! (on tear-down) So I had to split the cases after-all. I ended up rebuilding my original engine (I had it done at Under Pressure, Dania Beach FL) and installing an undercut tranny my machinist friend cut for me. That included a new head job, which actually was in pretty-good shape, saving me from replacing valves, seats, or extensive additional machining. He did a 'clean-up' surfacing of a few thousandths on the heads' mating surfaces.
Now, I am "dyno-adverse!":rofl_200: The bike is running well, it pulls well, doesn't overheat, and I have surprised some late-model sportbikes who wonder, "how is that old crock able to stay w/me?":rofl_200: No, it's not the world's fastest, or worthy of any accolades, except that it's
mine, and is running reliably, is safe, fun to ride, and it makes me smile every-time I ride it, which it did before, but it now has given-me a greater perception of delivery of power, but without quantifying the enhanced power via a dyno set. So-what? Yes, a good engine should be-able to survive some dyno pulls, but stung-once, I am not going to run a dyno again. It works for me, the way it is, and I can live w/o a slip of paper squiggles, especially if it means a $2K rebuild (I know it shouldn't, but it did this one-time for me).
So, my advice is, if you are thinking of installing a used engine, take the time to open the cases, and inspect and measure your clearances on the main bearings, and the conn rod big-ends. Do it for peace of mind. And, if you're wanting to dyno-thrash your bike, doing it
before the runs may save your engine expensive repairs. :confused2:
If you're happy w/the way your bike runs, don't get too hung-up on trying for some ego-feeding dyno numbers. Enjoy it for what it does for you in daily use. If you really want to see what changes did, run it at the strip before and after, and a rev-limiter and shift light would help to preserve your engine, and optimize your bike's performance.
unk:
