Thumper carb cleaning

[Da Baddest Mofo]

I've had my 450SMR for over 2 years now with roughly 40 hours. Runs good, but I started to notice occasional choppiness after a couple of sessions at Grange. I used to ride it almost every weekend, but now it sits in my garage for 2-3 months. Still starts OK. Valves are in spec, oil changed regularly, air filter cleaned, etc.

I'm thinking maybe I should finally clean my carb. Tried searching on Thumpertalk and KTMtalk, but can't easily find anything. Should be a simple procedure. Can someone post a step by step guide: preferably for KTM? Or I should just run one of those additives and it'd clean everything?

TIA,
Alex

[zman]

Take float bowl off
unscrew pilot and main
clean and re-install

They have good pictures and how to's
http://www.dirtrider.com/tech/141_0707_keihin_fcr_carb_rebuild/index.html

[Da Baddest Mofo]

So I should only worry about the pilot and main jets, nothing else?

[zman]

pretty much
But if you have a BOG on the throttle clean the accelerator pump
and the passages
DONT GET ANY carb cleaner on o-rings
it will mess them up , used wd--40 to clean them
as for the passages and jets
i use Carb cleaner , sewing needle and compressed air

Adjust the slack of the accelerator pump
and also adjust the air screw , different altitudes and weather conditions will also
make a bike sputter and bog , a few turns on the Air Screw will help

[Da Baddest Mofo]

Damn. Sounds complicated. especially the accelerator pump. I took the carb apart like you mentioned in the first post: removed the float, the main jet and both pilots. Do I need to disassemble it even more?

Can I use those compressed air dusters and what should I blast? Every orifice I see? Or just the 3 jets?

I did notice the gunk at the bottom of the bowl. Any carb cleaner from Pep boys can take care of that, right?

[zman]

Yeah Carb cleaner from Pep boys works
Blast air the the orifices with some carb cleaner
then follow up with air
make sure you clean the jets with carb cleaner , neddle and air

I wouldnt take it apart any more as it wasnt bad to start with

[Da Baddest Mofo]

No, it wasn't bad. I'm doing it mainly because I feel bad about my KTM maintenance. And have some free time.

[joe mamma]

I would also recommend trying some small allen screws to replace the brass ones that hold the float bowl on. At least on the jap bikes, the brass screws don't like to come off w/o a fight and always strip when they come off.

[Da Baddest Mofo]

Thanks everyone. Seems KTM's carb is simple enough: even the accelerator pump which is nothing, but a rubber membrane. Blasted it with carb cleaner, then compressed air from one of those office dusters. The bike seems to run fine.

[Nocontrol]

Thanks everyone. Seems KTM's carb is simple enough: even the accelerator pump which is nothing, but a rubber membrane. Blasted it with carb cleaner, then compressed air from one of those office dusters. The bike seems to run fine.

Carbs are usually pretty simple, but they are all pieces of shit. :fawkdance

I don't ever want to own anything with more then one carb on it.

[XR250rdr]

Make sure the AP rod isnt getting corroded. Sometimes they start to stick in the carb body after a couple years.