400ex idle problems

Alabaster · #1 03-27-2011, 04:53 PM

Hi all,
I just bought my first TRX yesterday! I'm real excited about it and I got it for cheap because it's having some trouble running. It runs just fine with the choke on full but dies when I let the choke out past half way. It has a White Bros. exhaust with a K&N pod filter. I'm going to take the carb off and go through it and clean it good. While I'm in there I am going to verify the proper jets. Can anyone recommend what size jets I'm suppose to be using with my upgrades? Thanks in advance.

trx2fiveO · #2 03-27-2011, 05:34 PM

I would say with your set-up if it has a dynojet kit in it the main will be a 170 the Kehin hex jet equalivlant is 190, I would put in a 42 slow jet and set the air fuel screw at 2 1/4 turns out.

Alabaster · #3 03-27-2011, 06:52 PM

Yes, I verified just now that the main is a 170. Where is the adjustment nut suppose to sit on the jet?

trx2fiveO · #4 03-27-2011, 07:05 PM

when you re install that please make sure you clean it really good.. it's really durty. but to answer your question. If you screw that back into the carb then remove the bowl nut (17mm) put the bowl on the carb jus hold it up in place now look and see if the main is hanging about an 1/16 of so above the threads on the bowl nut. that's sufficient enough.

Alabaster · #5 03-27-2011, 07:29 PM

the air screw was only 1 1/4 turns out so I adjusted it. The slow jet was the stock #38. Could that be the non-idling problem? I'm thinking about taking it to a shop with an ultrasonic cleaner just because it is so dirty. Someone went through it before because the screw heads are all marred and the needle has been replaced. The float bowl O ring needs to be replaced too. Thanks for the help, bro. Any other advice would be appreciated.

trx2fiveO · #6 03-27-2011, 08:01 PM

the non idle issues is probably due to the slow jet being clogged but I would jump to a 42 that will help for easier starts. if you clean the carb make sure you remove any o-rings first.
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Alabaster · #7 03-27-2011, 09:11 PM

wow, so you think that it won't idle because of the slow jet? I'll get a #42 tomorrow then. I'd like to go ahead and get a new main jet too just because they are cheap enough and make such a big difference. You saw how dirty mine was. The head is all boogered up where the screwdriver slot is. I'll let you know how it goes. Thanks

trx2fiveO · #8 03-27-2011, 09:33 PM

The slow jet controls the idle circuit if it's clogged it wont idle unless you set the choke on a little.
I doubt you will find any dynojets in stock anywhere but you can get a Kehin Hex size 185 and you will be fine. just separate the jet at the 2 hex points that is an adapter for the slotted head jet. did you click the link in mt sig? I think you will enjoy it there too. we are new and trying to get some members. I rarely come here you got lucky..lol

Alabaster · #9 03-29-2011, 01:12 PM

Ok, I had to order the new parts, they had nothing in stock. I'm keeping the dyno jet but getting a new slow jet. Hopefully going from the stock 38 to a 42 will keep it from dying when I ease off the choke. I ordered a new O ring for the float bowl, too. I'll post again and update when the new parts come in.

Alabaster · #10 04-03-2011, 03:00 PM

Ok, I got the brand new perfectly clean #42 slow jet and installed it and got it all back together on the bike. It fires up like a champ on the cold start and runs great with no throttle needed at all for a bit. But when it warms up it dies, has a hard time firing over again, and when it does it blips and burps but won't fire up and run. Dang, what could I have missed?