09 drr50 dyno

[kfx450]

does anyone have an engine dyno run for this motor. I would like to see some hp vs rpm numbers. It has the stock clutching and razr cross rear tires. It has a bog in the mid range I am guessing it may be a carb issue but would like to know where this bike is making its power. tach says this bike takes off at 6000 shifts out around 8950 and is running top at 9050, this is with a 50lb rider. we are using a trail tech that has max rpm reading on it.

thank you
jayme

[srxmiller]

Machwon had a dyno run on here, 5/17 called 09 drx 50.

[kfx450]

that was a wheel dyno with no rpm numbers. since I am not putting it on a dyno right now, the motor numbers would help me figure out where this thing is making power

[bulldogfallon]

Your numbers seem to be in the right RPM range


I personally don't like the bigger cabr they come with...makes the power mushy (techincal term) to me


The smaller Sunworld/Mikuni card works way better IMO.

[machwon]

Here's the graph, 9150-9400 rpms. Keep in mind tachometers need to be calibrated as they are usually off by around 400 rpms and that can make or break how a motor runs. Why buy a pipe if the builder can't tell you what rpm to tune it too?

[kfx450]

thats why I was wanting to see an engine dyno.

[bulldogfallon]

If you have Razr Cross rear tires then you may also have the high speed tranny gears as well.

We had those units special ordered from the factory and they also changed some of them to the high speed gear set up...

You may want to look into this as well.

[kfx450]

I changed the rear tires when I got it out of the box. we are running harescrambles and my boy is by far the littlest so we put them on for the extra ground clearance. This bikes top speed is 28-29 mph. I am not sure if that makes it the tall gears or not. with him beeing 50lb it will break loose at anytime with this set up.

[kfx450]

put in a ztr 1000 spring and think it might have been too much. the stall is now 7000 and the bike is topping out at around 9800. we lost 2-3 mph but gained back shifting on the hills. can I get the rpms down a litle with heavier weigts or will this hurt something else.

[bulldogfallon]

Rollers weight set the shift speed so that is the perfect way to get the shift rpm down.

I would think 3.75 to 4 gram rollers with that spring


The stall is set by the clutch, but can be effected by a stiffer spring keeping the belt higher on the rear pulley.

This allows the engine to turn more rpms than the clutch due to the ratio of the front and rear pulley.

Ex)(hypothetical numbers used)

Front pulley ratio =19T sprocket Rear Pulley=38T sprocket

Ratio is 2 to 1......Well if the belt drops or sits higher on the rear pulley the ratio of engine to clutch rpms vary.


A longer belt can provide a higher stall if the belt sits up higher on the rear pulley

...too long can hurt you though

[kfx450]

alright now that the ztr has been in for a couple rides we are running about 8900 rpms a litle lower than I would think we needed to be at. spring must have broken in. Were can we get a smaller sliper sprocket? we ran in the mud today with the razr cross tires and by the end of the race the bike didn't want to climb the hills. it must not have been down shifting right but I think we may have more speed than we need for the tracks we have been running and would like to have more power on the hills.

[bulldogfallon]

I haven't seen an 18 slipper yet....go up on the rear sprocket.

We change our torque spring every race day

And use a practice clutch before the races.

Those rear tires in adverse conditions will kill that torque spring.

We tune for best performance last laps..

Perfect tune with fresh spring can leave you flat at end of the race.

[kfx450]

so for muddy conditions would I run a 1500 spring so at the end of the race it would still have some life?