Bonneville America Forums Forums Technical Forums Performance Mods Dyno Information

Having just done a Freak and rejetted my 2004 790cc Speedmaster my seat of the pants Dyno says that is the best it has ever gone.

Now I think I should have a Dyno done to see if I am right.

We only have one Dyno in town and seeing that what I know about running Dynos could be written on a postage stamp with a paint brush, help is needed.

I was going to the guys workshop first to talk to him about what he does.

As a lot of you guys have been through the Dyno routine before, what questions should I ask him.

Please bear in mind folks I have only ever seen a Dyno on Youtube.

Can somebody tell me in laymans terms what happens exactly.

It depends on the dyno operator. If he knows his stuff about your(our) fuel delivery system, mainly the carbs (keihin).It will take him less time to dial your bike in. Time is money!

Frank,

I'm in the same boat as you. Youtube only. If I was getting it done, I'd make sure they monitored the air/fuel ratio out the exhaust to show if you are running lean or rich. Max horsepower and torque are expected.

Find out if he charges by the hour or by the run. If by the run, see where you are rich/lean and adjust accordingly on your time (main jets, needle height, pilot jets, idle mixture screws, etc). If by the hour, you could let him do the work, if he has the proper jets in stock.

most all of the operators know plenty .. best to smile .. laugh .. let him/her do their job and enjoy the experience ! i too was a bit excited and anxious ...
but w/ no balance pipe installed. was able to get the most out of it.. allowed us to seperate the clyinders for A/F info .. have fun.. just let them do their thing .. a print out will be provided.. and explained in detail.. congrats ..we cant wait to hear/see the results. !

Not all have a sniffer , make sure they have that to determine your mixture. Also make sure it is long enough to go past the crossover pipe to get a good reading. If you still have baffles or a cat then you can't put the probe that far in. He should also monitor head temperature. If you want to make adjustments be sure to tell him that, some will put the bike up there do 3 runs and that's that. Just hand you the paper read out.

let him do the job get a print and ask for advice.....mine dyno man is doing racing japanese bikes on daily basis but his advice was spot on and second visit in his place showed that

I found out today that the guy who does the Dynos in town has a Dyno for cars.

But he rigs it up for bikes will it work alright for bikes.

I am going into town on Monday morning so I will pay him a visit and ask him the questions that have been suggested to me.

The nearest dedicated Dyno for bikes is 125 Klms. away.

When I look at other riders dynos that I have seen on the site I have noticed that some are lean, some are rich.

I know the optimum is 13.1, but if that is not acheivable is it better to be rich or lean.

I would prefer it to be on the rich side, specially for an air cooled motor (yea,and oil cooled).

If it were me I would ride the 125 KLM's to a real motorcycle dyno. That's only 75 miles each way. The nearest good motorcycle dyno operator that I know works about 65 miles from where I live, and I've gone there 5 times while changing pipes, removing my air box, etc. A good dyno operator will save you time and money, and a dyno operator who works primarily on cars just doesn't have the same knowledge and feel that a motorcycle dyno operator will have. 75 miles each way is a nice ride and in my opinion well worth the time.

I would go slightly rich if I had to go one way or the other. Lean will run hotter and can burn a valve, rich can wash away lubricant and foul plugs as well as contaminate your oil. Burning a valve or washing away lubricant are at the 2 extremes. Other damage can be done too but those are the most common from the 2 conditions. Slightly either way won't hurt anything but slightly lean will blue your pipes and slightly rich can do the same from unburned fuel.

We're now straying off the dyno subject a bit, however if the bike (carbs, that is - as a general rule Yanks don't say "carbies") is tuned for the so-called "optimal" A/F ratio in cold/cool weather, it will, as a general rule, automatically run on the rich side in warm/hot weather. The converse is also true - set the carbs up to be "spot-on" in warm/hot weather, & the bike will run leaner in cold/cool weather.

Apparently I was given bum information. The guy in town had a Dynojet Dyno for bikes. Problem is he went out of business 2 months ago. So it looks like a 125 Klm. trip to Hervey Bay. At least the bike will be warmed up when I get there. From what I have found on the Internet he has been a Dynojet owner for 6 years and does a lot of race & drag bikes. He actually owns a drag bike that he has been very succesful with.