454 Thumper racing kit, best money I ever spent

[ktmwes]

After last weekends ride I was kinda disapointed with my dececision to buy another 400 instead of a 520, so after some soul searching and board searching I called Thumper racing and talked them into selling me there almost ready to sell 454 kit, which included a 11.1 to 95mm Wiesco pistion, special gaskit kit and cam chain rivit link. To save some time I bought a 520 cyl from my local KTM dealer instead of sending my cyl out to be bored and replated and had all overnighted so I could begin my journey deep inside a RFS motor (for me anyway) 7 hours later (that's a story in it's self) It runs! After a 3 hour ride today I can honestly say that's the best $575.00 I ever spent. I would have to say it's some where in the ballpark of 4-5 HP gain but the real gain is the torque, last weekend when coming out a turn in 3rd the bike would move briskly on to the next turn without much fuss or excitment, but now the front end starts to get light and/or comes up and the midrange is outstanding! it almost seems to have a "midrange hit" now and it still seems to rev to the moon. I have a PC T-4 exhaust with the 2" outlet (have a 1.5 ordered) and 14/52 gearing on a 02 400 EX/C. I do have to thank my local dealer for renting the cam chain tool to me and making me a great deal on the 520 cyl, he seemed as excited about this as I was!

Can't wait til next weekend now

Wes

 

[Moteaux]

Isn't nice when you spend your money well?!:) :) :)

 

[AFM744]

Wes-

I too am happy with my '02 400 EXC, especially now that I've ditched the G jetting for JD jetting. BUT... having ridden a 300 EXC for years I have a little remorse for not buying the 520. I'm kicking around Eric Gorr's 450 job, probably for when the cam seal pukes and I have to take my head up to OldStroker. Would you mind sharing what that cylinder cost you? Did you consider the 72mm crank too? Any reason you chose the Thumper Racing 454 kit (11:1 piston) over EG's 450 kit (13.5:1 piston)? Lastly, you never mentioned whether you changed the jetting either before or after the big-bore install.
Thanks!

 

[Bob Brooks]

Wes,

Congratulations! It sounds like you're real happy with the results! I'm very curious, how does your 400 compare power-wise to your 300, both stock and with the new big bore kit?

 

[ktmwes]

Originally posted by AFM744
Wes-

I too am happy with my '02 400 EXC, especially now that I've ditched the G jetting for JD jetting. BUT... having ridden a 300 EXC for years I have a little remorse for not buying the 520. I'm kicking around Eric Gorr's 450 job, probably for when the cam seal pukes and I have to take my head up to OldStroker. Would you mind sharing what that cylinder cost you? Did you consider the 72mm crank too? Any reason you chose the Thumper Racing 454 kit (11:1 piston) over EG's 450 kit (13.5:1 piston)? Lastly, you never mentioned whether you changed the jetting either before or after the big-bore install.
Thanks!

My biggest concern for the 11:1 piston was :
#1 I hate buying race gas
#2 My understanding is that the higher numbers contribute to easer stalling and harder starting.
#3 Reliability, Russell at Thumper told me they had been beating their test bikes like stepchildren for quite some time and no failures, that's important to me.

The cyl was approx $325.00 and the crank issue seemed too much like work and this was streaching what I felt comfortable with since the bike had only 2 rides on it, I was real close to just trading for a new 520 for the conveinence, but the extended rev range of the smaller engine seems more comfortable to me, there's nothing like just parking it in 3rd and riding your heart out! Yes I'm still high from last weekend's ride, oh yes the jetting was stock before and after.

Wes

 

[ktmwes]

Originally posted by Bob Brooks
Wes,

Congratulations! It sounds like you're real happy with the results! I'm very curious, how does your 400 compare power-wise to your 300, both stock and with the new big bore kit?

Thanks, I'm happy now, the power difference between the stock 400 and the 300 is more than most people will admit to, the 300 has more mid and top and is more violent. Last weekend I had the oppertunity to ride with the guy that purchased my 00 300 MX/C and normaly in the more open areas he can pull away but this time it was tire to tire and some instances I could pull away. of course this assumes that we are not talking about the first 20 minutes of "break in" time and the closely followed overshooting of turns and close calls associated with more than enough power:)

After the conversion I would have to say that they are real close or at the very least close enough. The width of the power band makes up for any differnces that might remain. The single most important issues to me is the ability to get the front end up to planeing speed in the sand and the ability to keep the front end light or lofted in the whoops/mud holes and the stock 400 was kinda scary in the whoops (better be pinned) Now it's fun!

Wes

 

[Strick]

Originally posted by AFM744
Wes-

I too am happy with my '02 400 EXC, especially now that I've ditched the G jetting for JD jetting. BUT... having ridden a 300 EXC for years I have a little remorse for not buying the 520. I'm kicking around Eric Gorr's 450 job, probably for when the cam seal pukes and I have to take my head up to OldStroker. Would you mind sharing what that cylinder cost you? Did you consider the 72mm crank too? Any reason you chose the Thumper Racing 454 kit (11:1 piston) over EG's 450 kit (13.5:1 piston)? Lastly, you never mentioned whether you changed the jetting either before or after the big-bore install.
Thanks!

I am going to pass out some inside info. Straight from the Horse's mouth ;)

The BOMB is the 453cc approach (454?). 400 motor with a 520 jug. In 2003 KTM will have a 450cc bike it will be the opposite, 520 with the 400 jug. My source said as far as seat of the pants testing the favorite set up was the 453 (454?). When my bike is ready for the 1st rebuild. That is the way I will go.

KTMwes I hope you don't mind me picking you brain a little later!

Eric also posted a comparision late last year on the GORR KTM 450 vs. a CRF. Guess which one he liked the most:eek: Hint: some color as a pumpkin!

 

[AFM744]

Strick, Wes, Eric, everyone else who knows big-bores-

If you can simply swap in a 95mm 520 cylinder to make a ~454, what do you do about the changed deck height? If the 400 cylinder is set up for a 64mm crank and a 520 for a 72mm crank, then tossing a 95mm 520 jug onto a 400 would leave you -4mm on the deck height, wouldn't it? Is the cylinder height the same for both motors (i.e. the conrod is 4mm shorter on the 520)?

Secondly, once I got my jetting figured out my bike runs great on 91 pump. I live close to a muni airport and have an account with ERC, so I have no problem with av/race gas, does Wiseco make a 12:1 piston or similar, something between the 3rd-world-gas 11:1 and the 115 oct. 13.5:1? Is stalling with the higher compression really an issue?

Lastly, what about Pro Circuit silencers? With a 1.5" tip will I get pinched up at Stonyford for CA noise violation?

Regarding comparison to my '96 300, perhaps either my new 400 is still "tight" or my 300 was jetted well, but my 300 was violently powerful on top, pulling 4th gear up the same long hills my 400 pulls 3rd. This is WITH the full JD/OldStroker jetting and AP mods. Don't misenterpret, I DO love this 400 though as it doesn't beat ME like a redheaded stepchild like the 300 did.

 

[Smitty]

Hey Wes, this is Mion. Sounds like you've got the hot setup now. Couldn't let Jim get up on you in the fast stuff anymore? We'll have to do some comparisons between the 454 and the 450. You riding the buddy race Sunday? Looks like I might Ironman it for the practice.

Hope this is the right Wes. :D

 

[Bud-Man]

AFM744,
Regarding the deck height issue: The new piston supplied with Eric's kit is 4mm taller. That is the distance from the centerline of the rist pin to the top of the piston is 4mm taller.

Strick,
Did EG post a dyno graph? I'm really interested to see it if so. I've seen a graph comparing a 400 SX, EG 450SX and a 520 SX. The 450 was roughly 6 hp stronger than the 400 and about 3 hp down from the 520 (peak). Unfortunately the graph didn't list what jetting the bikes were running so it's hard to say how our 400's would compare after the jetting changes. Also, I'd heard rumors that Dowd had riddent the factory 450 and wasn't happy with the power at all. I wonder if it's cause they are using a long stroke approach?

 

[pumpkin033]

Okay where do I get my big bore kit for my 400??

 

[Strick]

Bud - Man here is the post I am referring to:

http://www.dirtrider.net/forums3/showthread.php?threadid=29115

I think your comments on Dowd sum up the 450cc KTM. KTM, I have said many times, is the master manufacturer when it comes to utilization. Because the 450cc limit is exceeded by 3 or 4 cc's be going the 400 w/520 jug route, they settled for the 520 w/400 jug to arrive right at 450 (legal limit in '03). It is a shame, but that is my summation.

Strick

 

[ktmwes]

Originally posted by AFM744
Strick, Wes, Eric, everyone else who knows big-bores-

If you can simply swap in a 95mm 520 cylinder to make a ~454, what do you do about the changed deck height? If the 400 cylinder is set up for a 64mm crank and a 520 for a 72mm crank, then tossing a 95mm 520 jug onto a 400 would leave you -4mm on the deck height, wouldn't it? Is the cylinder height the same for both motors (i.e. the conrod is 4mm shorter on the 520)?

Secondly, once I got my jetting figured out my bike runs great on 91 pump. I live close to a muni airport and have an account with ERC, so I have no problem with av/race gas, does Wiseco make a 12:1 piston or similar, something between the 3rd-world-gas 11:1 and the 115 oct. 13.5:1? Is stalling with the higher compression really an issue?

Lastly, what about Pro Circuit silencers? With a 1.5" tip will I get pinched up at Stonyford for CA noise violation?

Regarding comparison to my '96 300, perhaps either my new 400 is still "tight" or my 300 was jetted well, but my 300 was violently powerful on top, pulling 4th gear up the same long hills my 400 pulls 3rd. This is WITH the full JD/OldStroker jetting and AP mods. Don't misenterpret, I DO love this 400 though as it doesn't beat ME like a redheaded stepchild like the 300 did.

The piston that comes in the "Kit" from Thumper is a custom Wiesco piston so I have to assume the critical wrist pin position is accounted for, any way the cyl is the same height and the piston comes all the way to the top of the bore. Come to think of it that may be why the Wiesco piston is a 3 ring piston instead of a 2 ring like the stocker, but I am not going to take it back out to look! Thumper also has a AMA legal 450 94 mm piston that is 13:1 for the moto guys.

My next project will be to start playing with the jetting, my hope would be that it would be somewhat easer than tearing apart a new bike!

My bike is pretty loud with the T-4 but I think it's still in the range of a stock CRF450.

Wes

 

[ktmwes]

Originally posted by Smitty
Hey Wes, this is Mion. Sounds like you've got the hot setup now. Couldn't let Jim get up on you in the fast stuff anymore? We'll have to do some comparisons between the 454 and the 450. You riding the buddy race Sunday? Looks like I might Ironman it for the practice.

Hope this is the right Wes. :D

Yep it's the right one, I hope you know it's all your fault, after I rode your bike on Sunday I had to do something, actually your bike just made up my mind. It's not the quick rever (is that a word?) that your Honda is, but it's closer to same mid range power. We where planing on going to Murray on Sunday, but the weather will make the choice for us. Jim will have to earn it now!

Wes

 

[Smitty]

I wondered if that test ride had anything to do with it. Truthfully, if those extra 50cc's make enough difference I could consider going back to a KTM in a year or two. But,................

See ya Sunday if you are at Anadarko. By the way, I got a tall seat made up and a set of low and back pegs on the way from IMS.