Bonneville America Forums Forums Technical Forums General Tech dyno run last night 136whp

On all of my dyno runs, we never just go shifting through the gears like that. Just 3rd gear from about 2500-3000 rpm to redline.

the dyno guy said i had a min speed (50mph) and a max speed (100mph) he said to get up to the min and then open it up to 100mph then let off and what is this arkansas rally u speak of

Arkansas Rally

And maybe it was 4th gear, because that sounds right about the speeds, but only used one gear to get the power line

My SM with stock bore makes over 60 RWHP and I got a bunch of crap about even that. I won't post my numbers again since I was told by a few on here my numbers are impossible even though there were a couple others who said they were about the same as me. 135 HP isn't gonna happen but I bet it felt great while it lasted!

I've seen a couple on here that were in the 60's with stock bore

With a properly adjusted limber chain and correctly inflated tire, 60 HP at the rear wheel translates to 68 - 75 HP at the crank. On a cold dry day with properly tuned intake and exhaust, you can get that from a stock displacement engine.

Now, as for the 136 reading. Some dyno's have too many adjustments for the operator to fiddle with. On the newer ones, you can adjust for altitude, humidity, etc to get a reading that can be close to what you would get at sea level with standard temperature and pressure. On some, you can also dial in a drive train loss 'fudge factor' that might give you a rough estimate of crankshaft power IF it is set correctly.
So, I'm thinking the dyno wasn't setup correctly, but it seemed to be more accurate on other bikes because they had under inflated tires, incorrectly adjusted belt drives and cold, heavy transmission oil, all factors that will result in low readings.

well about a year after i got the i dyoned it and it came out 51hp and it was bone stock

Maybe in a sea of Harleys he was having a bit of fun with the Trumpet owner...

Ya know my buddy has a 1200 sporty, had the dealership do pipes, efi, and intake, dynoed it at like 85hp...something like a 25 hp gain over stock.

Is that possible?

In these days of legislators fancying themselves to be engineers, it is easily possible. 1200 is roughly 74 cubic inches and the blockhead design is said to be more efficient than the older engine, yet I was getting close to that from my old '76 Ironhead XLCH and that was only 61 cubic inches.

it just seemed like a large increase considering the numbers that bore jobs add to our bikes. And then I seen the new thunderbird numbers compared to this little sporty and what the hel?

Open up the breathing and (in some cases anyway) fix the valve timing and you can get similar changes, or even better, from Triumphs. Even the little 883 has catalytic converters in the exhaust, so they can start off with decent valve timing. The whole thing is pumping enough air through the engine and getting the mixture down to around 12.5:1 like it aught to be to produce optimum power.

it pssed me off cause I was running with him the same at first and then he went to the dealership and came back pulling away from me and driving my rev limiter crazy