went to the dyno and...

i have a 508 yfz with a sparks big core, a pro design pro flow kit, a gytr jet kit, a dyna cdi, and a 11:1 cp piston, and i hit...a whopping... 40 hp with 33 ft lbs of torque what the f*!k happened??? mine you i am running irazr tires and tire balls but damn!!! i am thinking of going to a 12.5:1 piston when i had it at a stock bore it only hit 34.7 hp. i think its a combination of low compression and heavy rear tires. any info would be great!

[Quad Boy 660r]

Yeah, most 450s w/ big bores run high comp pistons. Yours is probably more reliable though.

What size are your rear tires.

Jetting????

20/11/9

[DirtDevilBT]

Lets see a graph and a/f graph too. A 508 seems like it should run better than that even with low compression. I dunno though, lets see a graph.

[Eddiesanders250]

I would think it would be putting out more, but what do i know about thumpers lol

nevermind the lind going down across the graph the torque is the other line.

http://www.imagestation.com/picture/sraid200/p37ca90e7dad0e46c3c302af9165435a2/f05c49c1.jpg
http://www.imagestation.com/picture/sraid200/pc3e790534511f76293d0e9a69b5c5d71/f05c4af6.jpg

[bwamos]

Originally posted by raptor0443
i have a 508 yfz with a sparks big core, a pro design pro flow kit, a gytr jet kit, a dyna cdi, and a 11:1 cp piston, and i hit...a whopping... 40 hp with 33 ft lbs of torque what the f*!k happened??? mine you i am running irazr tires and tire balls but damn!!! i am thinking of going to a 12.5:1 piston when i had it at a stock bore it only hit 34.7 hp. i think its a combination of low compression and heavy rear tires. any info would be great!

1) Knobbies really hurt the dyno reading. It's not the weight. They add slip and extra resistance all at the same time. You need a good set of street/slicks on there for a good dyno run. I'd say you're easily loosing 4hp+ because of the tires alone.

2) was the dyno a cart/atv dyno? Others will have heavier drums.

3) have you had any head combustion chamber work done? That can help out the HP a lot.

it was an atv dyno, and no i haven't had any head work done, i will have to wait until next year to do that. but i am put ing in a 13:1 piston in it and a hotcams intake cam this weekend and i'll see what that does.

[DirtDevilBT]

Don't spend anymore money until some bigger valves and major portwork is done. Are you running the stock cams? If you are that's also where you are losing a LOT of power.

Get yourself:

a pair, or one, cam
bigger valves
good portwork
heavier valve springs

Leave the piston alone for now and see the numbers fly off the chart.

is there someone who has heads already ported to where you can just send them your head as a core and they send you a already ported head???

[EX_Junkie]

Wow. I'd try running it with some tt tires. My piped and jetted yz400 hybrid but down 43.7hp

[machwon]

Raptor0443, I've seen very similar results from a TRX520 kit, only 40hp without the slicks and no big valves. Like mentioned before the slicks will get you at least 4hp, but the big valves and cam are important for the rest (mid 50's hp). The port work is really not that big of deal, they do need to unshroud the large valves though.