what are the power gains?

[hondaracer_34]

does anyone have a duncan fatboy 4 exhaust on their 400ex? if so can you post a pic? and what are the power gains from this exhaust? thanks

[REDRIDDER]

hope this helps a little All Fat Boy 4 Exhaust Systems with FREE jet kit included with instruction packet

DRI offers a LIFETIME WARRANTY against defects in materials and workmanship on all Fat Boy 4 systems sold. Warranty is for original purchaser only and is non-transferable. Each system is supplied with warranty registration card that must be read, signed and returned to DRI

Optional Accessories
#FB4-4A250 $39.95 Bolt-On Turndown (required for spark arrestor usage).
#06-554 $17.95 Spark Arrestor Screen.
#FB4-RP-110 $20.50 Repacking Kit.
For additional parts see DRI price list for full listing.

Other Required modifications: K&N Air Filter, Carburetor Re-Jetting.
Larger C/S sprocket advisable in hard pack terrain or with 18" tires.
*On DRI Retail direct sales jets for stock OEM carburetors are supplied at no charge.

Performance: 20% HP Gain peak; 20 bike length gain in a 300 yard acceleration run, average.

Fat Boy 4 4-Stroke Power Exhausts are a proprietary product of Duncan Racing International, Inc. DRI is the sole manufacture and developer of this product. DRI has designed this product to be the top ATV 4-Stroke exhaust on the market.


Fat Boy 4 Features

CNC Bent 304 stainless steel headers, mid-pipes and tail sections. Standard finish; bright finish.

CNC machined stainless steel header flanges.

Custom designed .100" wall aluminum extrusion muffler body. Standard finish satin. Polished by special order.

Front and Rear End Caps CNC machined from 6061 billet aluminum.

Muffler mounts CNC machined from single piece of 6061 billet aluminum. Attached to muffler body by heli-arc weld.

O-Ring Seal at tail pipe to muffler joint.

All mufflers completely rebuild able and repack able.

Stainless muffler cores.

Optional (at additional cost) Bolt On Turndown; redirects exhaust fumes and noise toward the ground. Also required for use with spark arrestor. Attaches with 4 stainless screws (supplied) and has O-Ring seal.

All systems are individually marked with their own serial number.

Complete DRI Technical phone support for installation and carburetor jetting questions.

[hondaracer_34]

ok thanks for that...im probably going to get one soon...

[REDRIDDER]

no problem thats why were here.

according to that 20% you will get 5.44HP is that on a slip on or full?

[REDRIDDER]

full

[krt400ex]

Originally posted by FoxHondaRider
according to that 20% you will get 5.44HP is that on a slip on or full?


thats BS...im not talking about your calculations...im talking about the 20%. not witht eh 400ex...your not going to get a 20% gain.maybe with a cam and a pipe you will.

i think the yosh exhaust is better, and the full system from rockymountianatv.com is a hell of alot less expensive, and you dont have to buy the spark arrestor seperatly...comes with it

HMF full can guarantee 6HP with a full. The slip on is 4HP. They are cheap but the best besides curtis sparks

[krt400ex]

not true. talk to mobile dyno, he got only a half a horse more out of an hmf slip on with a correctly jetted 400ex and the airbox lid removed

[gcart2]

who r the 2 best all around racing companys out there? Duncan and sparks. they sell the best stuff. im sure lots of ppl are going to say im wrong but its plane to see they r the best. they not going to sell junk. sparks and Duncan throw darts when others shoot shotguns.... if u get that first try u r good. so fatboy and sparks exhaust r the best for racing. end of story =)

not true. talk to mobile dyno, he got only a half a horse more out of an hmf slip on with a correctly jetted 400ex and the airbox lid removed

krt400ex are you saying 1/2 more than fat boy 4? or 1/2 HP over stock?

[krt400ex]

Originally posted by FoxHondaRider
krt400ex are you saying 1/2 more than fat boy 4? or 1/2 HP over stock?


over stock. and actually, i think it was slightly more than that. he did a shootout against a WB full system and the hmf slip on actually made more power. ill see if i can dig up the thread

[krt400ex]

sorry, i got a little confused. the WB full made almost a half a horse over stock, the hmf slip on made slightly more than a horse over stock...and then if you added a properly tuned headpipe i highly doubt you will get more than 3.5 horse over stock...that is still a great gain, but not anything like 20%

http://www.exriders.com/vbb/showthread.php?s=&threadid=246519&highlight=mobile+dyno

HMF slip on adds 4 HP over stock white bros e series slip on is 2HP, yoshimura rs3 slip on is 3HP over stock. The best exhaust you can buy is curtis sparks which is around 5HP. Most companies lie saying 20% or 17% or however much HP. You have to rely on dynos done and at more that 1 place. I have seen 1 place do a dyno and then another place and come up with 2 different results. HMF won the dirtwheels slip on shootout 4 years in a row so far. Plus for $240 you cant beat it.

[hondaman440ex]

Anyone Know how much a pro-circuit t-4 full exuasts adds? Mine I spent over $600 dollars for!

[krt400ex]

Originally posted by FoxHondaRider
HMF won the dirtwheels slip on shootout 4 years in a row so far. Plus for $240 you cant beat it.


and it only made 2 hp more in their dyno runs 4 yrs in a row

I dont know about that I have the charts from those issuses and it wasnt the best but close to it. CT Racing & Curtis sparks came out on top with HP gains but HMF was just behind them. For the price to me you cant beat it.