5 replies to this topic

[OrangeBleeder TT Newbie]

Hi I am new to the forum an I just got another bike I got a pretty much bone stock beside the handle bars an a pro circut pipe 2002 KTM 400 MXC. I live in texas an it is warm here all the time an right know I am fixing the bike up to get it trail ready again. The guy who had it before me did not take the best care of the bike all the oil filter an oil screen bolts an plugs were stripped out got that fixed then I changed all my fluids an filters an greased everything. so now I am have some air/fuel problems the bike starts up just fine but it is back firing when I come of the throttle so I got a new carb rebuild kit just so I can freshen everything up to make sure it is in good shape. I am wondering what a good jetting spec may be? That an I am also wondering if their is any upgrades that I want think about doing to improve the ride. I pretty much ride woods an trails an that is it. I just got a new chain, sprockets, radiator guards, skid plate, new fuel tubing an a new tire from my work.

[BDM TT Silver Member]

OrangeBleeder, on 03 February 2012 - 03:35 PM, said:

so now I am have some air/fuel problems the bike starts up just fine but it is back firing when I come of the throttle so I got a new carb rebuild kit just so I can freshen everything up to make sure it is in good shape. I am wondering what a good jetting spec may be? That an I am also wondering if their is any upgrades that I want think about doing to improve the ride.

Sounds good. If it is otherwise running well the backfire on trailing throttle is likely caused by leaks in the header at the head flange to header joint. Can be reduced by sealing with high temp sealer but will not hurt anything as is. And/or could be a partly clogged pilot jet. There are some motor updates (might be a sticky at the top of the forum) which are not expensive but good insurance and some suspension work can make a big difference.

Bruce

Edited by BDM, 03 February 2012 - 06:04 PM.

[djchan TT Silver Member]

Great bike. I have the same year EXC model.

You'll have to do something about the fork springs/valving to ride it though. It's brutal in stock form. I upgraded my springs to .45s for my 200 pounds... would even like a set of 48's. Added SKF seals with my fork service and changed the valving to "fabtech stack 1" standards. No more stiction and it's relatively plush now. Just now buying a set of fork subtanks (used of course) to complete the picture.

I also added a "powernow" mod for enhanced lowend grunt and a gen 2 FCR carb cause the internal o-rings were shot in my gen 1 carb. Runs like an absolute top. Don't believe the people who say they require a lot of work and break down a lot. They're tough as nails.

Good luck - you'll love that bike.

[ktmwade TT Bronze Member]

when it comes time to freshen the piston/rings/topend, take a look at the 453 kits from Thumper Racing. I had an 02 with the 453 kit and it was one of my favorite KTM's owned. I always said the 453/400 is the best engine KTM never made

[OrangeBleeder TT Newbie]

Thanks a bunch for your reply's. I am goin to get it all tuned up this week I will let you know how it turns out.

[OrangeBleeder TT Newbie]

Well guys my bike has been runing great but i think i am going to be getting ready to upgrade to 453 kit i am really seeking out more bottom end out of my motor an i am approaching time to do a valve job too. So i was wondering what else i should plan on replacing while i have my motor out. but i am planing on doing a EBC dirt cluch an the 453 kit and i was wondering if any one has used the Boyesen Quick shot III? but i am unsure of what else needs to be done while i am inside the motor to get it to perofrm where i need it to. the type of riding i do mostly is wood trails an some enduro racing.


Thanks

Michael