Bonneville America Forums Forums Technical Forums Performance Mods Dyno test results

Had my bike put on a dyno today.

54 hp
45 foot lbs of torque

I have removed one baffle on each side of the exaust, and removed the snorkle from the air box.

The test showed I am running a bit lean, and I need to rejet.
Now my question is what size are the stock jets in a BA, and what size jets would be recomended for my set-up.

Any help appreciated, Thanks.

stock pilot 42
stock main 120

I would go up on the main jet to 130 (or possibly 128)
& leave pilot jet stock

Stock jets are 120 mains and 42 pilots. With your setup, I would say 130 mains if you put in a Uni or K and N filter and stay with the stock pilot. About 3 to 3 1/2 turns on the mixture screw should do.

Oop's, I should have read all the other post' first, and I wouldn't have had to post.

Oh, OK cool.

Thanks

So you have a 54HP bike that is rated to be 62HP. Torgue seems right.

Pat, can you explain this one when you come on.

I was looking at the graph from the dyno, and according to the operator the carbs being lean caused an erratic line that wavered up and down between 4500 and 6500 rpms.
Seat of the pants feel... felt stronger with the mods definitely, but can feel it get weak at full open throttle.

I never did get a dyno before the mods, but maybe I should have.

I don't think it was putting out no 61 hp, even though thats what Trump advetise's it at. Maybe they exagerated it a bit.
Or maybe I got fuel delivery problems. I don't know, now I'm confused.

I was just curious, removing one baffel and the snorkels would not reduce you by 7-8 hp. just the snorkel removal should give you some push not take it away, the same with the baffel removal. Lean? Well, the advertised rating is factory settings. I wonder if Mr. Triumph is telling a little fib in advertising.

The difference in the horsepower figures is probably due to the factory measuring at the crankshaft and the test here is at the rear wheel.

My .02 worth.

Dan

How a dyno is operated can make quite a difference in HP readings.

From my life-long best friend, who sometimes operates the (car engine) dyno at a race engine shop in Tiffin, Ohio, and from my own experience at a circle track engine shop in Phoenix, AZ (where they have a very nice dyno room), I've learned that the way the operator loads the engine during a "pull" can very the results.

Generally, a dyno operator usually ends up overloading the engine during a dyno run. That is, he sets the water brake to hold the engine at the various rpms a little too long. This does several things, including showing more HP on the print-out, and causing the engine to seem a little lean. Circle track guys are notorius for doing this. Drag guys aren't much better, either.

A faster accerating rate should be used, as it approximates the real world more than a heavily loaded, slow accerating rate does. Some engines rev up faster than others, for a variety of reasons, including - lighter crankshaft, flywheel and other moving components - or more spark timing advance (more is almost always better!). This faster revving rate, "a good thing", would not be obvious with an overloaded run.

Another problem with dyno runs can be the operator's set up in the computer that records the various output of the sensors. That computer can be programed to fudge the numbers by whatever amount the programer wants. Ten percent is not uncommon to add to the stock readings.

NOTE: I'm not talking of adjusting the computer results to an STP day here. (STP means Standard Temperature Pressure.) Doing that type of adjusting gives a baseline so that guys can compare their results meaningfully with others.

All of what I'm talking about here is for crankshaft HP testing. As DanB notes above, a chassis dyno will show lower readings because of driveline losses between the crank to the wheel.

That would make sense. Never thought a chain drive would loose that much HP to the wheel from the crank but could be the operator too. Strange thing is the torque is right

pretty sure some gets lost in the tranny

Frank

The 61 BHP (62PS DIN) rating is at the crankshaft. 6 to 10 HP loss to drivetrain drag is normal.

What grump said...
And the 130s sound right on too.