'05 Venom TRX501 Stock carb vs FCR44 Pump fuel

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mailman

Active Member
Apr 13, 2012
#1


Here is my before and after with the stock 2005 carb jetted right compared to a YFZ FCR straight bored to a 44.
I picked up 2 HP across the board as you can see which actually seems low. I also ran a max speed test up Olds to compare the 2 carbs in the same weekend. Max speed with the stock carb was 49mph and max speed with the 44 FCR was 52 mph!!! I thought that shows how big of a difference the carb can make.
My 2 dyno runs were not done back to back. The fcr was put on a couple of months later when the motor had more time on it so that could be why the difference isn't greater.

Motor: +3 hot rods crank unbalanced, CW BB kit, early hrc cam, venom porting, stock size valves in head, Rossier pipe, dyna box, Dasa intake + filter with stock snorkel and air box, 13:1 CP piston, pump gas, tps hooked up, etc.

The carb gives the bike better throttle response in the dunes. When racing the hill, the bike pulls much harder throughout the rpm range.

This stubborn s.o.b. finally hit 60HP with a very broad curve. I am lovin' this bike now.
 

ridingred

Active Member
Apr 12, 2012
#2
that is a nice broad curve! why is it so choppy through the curve? i'm used to seeing smoother lines. Might be a noob question, or maybe we are viewing a more detailed graph or something?
 

mailman

Active Member
Apr 13, 2012
#6
that is a nice broad curve! why is it so choppy through the curve? i'm used to seeing smoother lines. Might be a noob question, or maybe we are viewing a more detailed graph or something?
Thanks! The broad curve really makes it fun to dune and when draggin' the hill, the power output never really drops between shifts which I feel is a big advantage.

Choppy curve: It just seems to be characteristic of this dyno. I have many runs from many different bikes and they are look this way. It could just be as simple as the dyno tires we are using. The run times are much longer on this dyno to simulate the hill which may be causing these spikes to show up. Nothing to be concerned with though.
 

yfz450~bence

Active Member
Apr 10, 2012
#9
what do you mean longer run times? almost 60 at 8k is awesome! Only thing is if it didnt drop as much at 10k would be even better. Im sure its a fun ride:icon_cool:
 

mailman

Active Member
Apr 13, 2012
#10
Thanks yfz450~bence. It is a blast to ride.

We run on an automotive dyno so the length of the dyno pull is about 6 to 8 seconds. That is what I meant by a longer run time. Atv dynoes only have a run time of about 3 seconds for these bikes due to much lighter rollers.

This is a budget build. I only paid $275 for the porting and I think Venom did a great job! He promised me 10% across the board for a power increase and that is exactly what I got. I have dyno runs for this whole build. The dyno runs before and after porting were roughly 50 to 55. 5 HP gain for $275 bucks is a bargain. That is only $55 per HP gain. Where else can you get that?
I think I could go with larger valves, more radical cam, and more aggressive porting to get the top end to not drop off. I think there is enough of a broad curve for me to utilize. This 501 makes so much power down low that it isn't really necessary to rev the snot out of the motor. LOL
 

yfz450~bence

Active Member
Apr 10, 2012
#11
I didnt know it was a car dyno. cool. If thats the gains you saw from porting i wouldnt complain either:gr_nod:

Ive seen before and after of good known porters on raptors, and without giant valves and big ccs the gains from porting alone ive seen less than 10%. People really do fall for the poring should give me 20+ % alone. One builder claims 4hp with just a standard valve port, and at 64hp you do the math on the percentage. basically 10% is pretty good IMO