HI ZRWHAT,

What did Dryer's charge you to jet and dyno your raptor? I have been trying to get mine dialed in and I am getting tired of screwing with it. Thanks for your info.

Thanks KD

 

Hey Kevin. Dreyer's charges something like $64 for two runs or $96/hr. That's just to run the dyno, I do all of my own work, not sure what they would charge if you wanted them to change jets? Probably an additional $50-60/hr., whatever their shop rate is? I was there on a Friday and they weren't very busy, I got over 10 runs in and rejeted 5 times. I had more like 3hrs on the dyno, not actual dyno time, but physical time that my quad was mounted to the dyno for $96. One of the mechanic's Mark, ran the dyno and helped me get the Raptor dialed in. I can't count how many times I've had the carbs off, takes me about 20 min. to rejet. I would suggest doing it yourself, you will learn a lot more and be better off in the future if anything needs changed. I am sure Dreyer would do it if you've got the cash to throw away?

 

airraptor: That's what their dyno reads, have you had your quad dyno'ed? If not, don't you think it would be worth the money to know where your quad stands? I am happy with what I've built. I would like to see a so called 50hp piped/jetted/intaked Raptor keep up with my 686 with 50hp, it won't happen!

 

Couple of things here. The difference in Crank horsepower and RWHP should be no more than 5% on an atv. So 40hp at the crank would be no less than 38 at the wheels.
Anyway the key here is to baseline a quad on a dyno BEFORE mods are made, then test after the mods. The difference between the two will tell you if the money was well spent and everything is working as it is supposed to. I hope everyone realizes that no two identical stock machines will test or ride exactly the same. Hence the need to find out where YOUR baseline really is.

Denny

 

I always thought the differential between RWHP and Crank HP was more along the lines of 20%, where did you come up with 5%?

 

20%??? The difference bettween the two is only the friction loss in the drive train. Manual clutches don't slip and chains don't consume very much power.

 

Worn sprockets,worn or misadjusted chain, bad axle bearings,quad strapped down tight enough to cause chain to ride on rollers,worn or misadjusted clutch, etc, etc, etc these can cause 20% or more HP loss. Plus things I haven't even thought of.

My Raptor & other toys

 

"Moose" I'll stick will the 5% or less power loss. Anybody dynoing a quad with a bad chain, sprockets, or bearings is just wasting their time anyway. And a experienced dyno operator will not have the quad slipping on the rollers (what a poor excuse for lower than expected HP output!).
While we are on this subject not all wheel dyno's are created equal. Some just measure the time it takes to accelerate the drum from one rpm to a higher rpm. These dyno's are less expensive then dyno's that can measure "steady state" power output at any given rpm by using a water brake or electromagnet load.

 

Truckracer, I agree with you, I was just giving some examples of what could cause lower HP readings. I think a dry chain could cause almost a 5% drop so it wouldn' be hard to get a higher drop if your chain, sprockets, bearings, etc were just slightly worn.

 

The average loss to the rear wheels as opposed to the Crankshaft on a " Quad " is going to be 15 % to 20 % maybe even higher in some cases. Reasons: ( friction and drag ) crank to clutch, clutch to Trans main shaft, main shaft to counter shaft, hydraulic oil drag through every guar, oil drag through outer clutch basket, chain, ( especially if it's an o-ring chain ) rear axle bearing, rear axle seals, ( rear axle weight complete with hubs, tires & wheels etc.) rear break drag, wind resistance ( from tires ). I probably forgot a few things, but as you can see the list is long and costly to horsepower. But it is the best way to see exactly where you stand as far as final horsepower. If you check horsepower at the crank shaft you won't even be going through the Trans at all. Losses in the Trans and clutch alone can be 7% to 10% or higher. Just a overly tight Chain or as noted a dry chain can make a 2 to 3 hp difference. I have removed Amp Link's and made 3 to 5 more horsepower on 65 to 70 hp banshee's.