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Discussion Starter #1
Here is the best power curves of the stock 39mm carb and the new 44mm with rat Stack from Chris aka sredrum!! Thanks again Chris!

Build is a 554cc Outlaw KTM Thumper Racing big bore kit, 807 cam, Ron Woods intake, stock head, stock lower end, stock head pipe with FMF slip on.

B)

 

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Nice, results are similar to what ive seen. Little bottom end loss with big topend gain.
 

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Discussion Starter #3
Nice, results are similar to what ive seen. Little bottom end loss with big topend gain.
Yep... same as all my testing with the yfz. I thought maybe with the 99mm bore in this it may not have had as much loss on bottom.... but I guess there was. Still nice gains up top. I think porting is the limiting factor as well as pipe choice. We did dyno test it with the slip on off and just the header pipe..... any one care to see that graph? Goes to show what flow does.
 

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Throw a hmf full system or ct pipe on there and i bet it would have about 3whp more up top.

post that other graph

What ron woods intake is on there? For the yfz? I almost put one on my sx. Looks to fit for sure
 

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Discussion Starter #5
I think he is looking at the CT pipe. Not to many options for the Outlaw 450mx-er though...

Here is the graphs with A/F. Best power curves for the 39mm, and 44mm with Venom Rat Stack liked different A/F's..... we did not re jet for the header only "drag" pipe....

 

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Discussion Starter #6
It was for a YFZ yes.... but we had to cut off the smaller carb side of the tube as the Rat side of the carb was bigger then that side of the tube.... it also needs a 250r K&N filter....



 

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Thanks for posting those, the thing was way lean with just the head pipe, so more power was there if you jetted it,
 

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Discussion Starter #9
IMO 42mm would be a good compromise.

Way lean yes.... but some times lean is more power and by making it richer into more of a safe zone the power drops off. Either way we were testing to see where the upper rpm limits were... and the rear canister is definitely holding back the flow in the upper rpm range. This motor with a regular pipe likes to be a little richer then the standard 13.5 range, from what we've seen.

I think we're going to make a custom pipe for his style of racing.... and see where that gets us.
 

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make some inframe duals and ill buy a set or a set that runs close to the frame on the out side like the barkers i had on my 660
 

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Discussion Starter #11
make some inframe duals and ill buy a set or a set that runs close to the frame on the out side like the barkers i had on my 660
What motor cc size is yours? And is your the Outlaw 450mx-er with the swing arm, or KTM model all together. I ask because this is the Outlaw mx-er with the swing arm, and they put the battery and starter solenoid off the inner part of the sub frame and there is not much room. However Kevin, the owner of this bike, likes the idea of duals. :p But he also trail rides.... so we haven't figured out exactly what we'll make yet.
 

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mines a outlaw525 but i think im moving the battery to the front like on my wifes 525 irs
so then ill have plenty of room i have a extra set of pure polaris duals i was thinking of finding some one to make head pipes to run into these cans
 

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Terse I think I still have more pics from that day in Ks.. What did you end up drilling the leak jet out to if you remember? I dont remember hearing it pop on the dyno as the rpms came down.
 

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Discussion Starter #14
Terse I think I still have more pics from that day in Ks.. What did you end up drilling the leak jet out to if you remember? I dont remember hearing it pop on the dyno as the rpms came down.

Got more pics huh? :D

I think it has a #35 or #40 in it, but I think it is a #35 of the two. This KTM carb had the leak jet blocked off, with a leak jet with no hole in it, and when this was the stock 450cc and with this BB kit, it had a nasty stumble off idle worse then any yfz I've ever seen. So I looked and it was blocked off so way to rich A/P.... so I leaned it out with a leak jet from my jets. Seems to work very well.

Also on the dyno in KS. it had the 39mm carb. I don't think Chris did anything special to the leak jet, or air jets in this carb either.
 

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Has anyone dyno'd a 41 or 42 mm carb to see if there is a bottom end loss?
 
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