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06 trx450 won't idle without choke need help please

9K views 21 replies 5 participants last post by  Nate35 
#1 ·
Hello I am new here and can't find anyone with this same problem so I'm hoping to get some help.
I recently installed a jet kit along with a new exhaust and filter. There is two issues I am having one is the idle will go up and down...vacume leak I assume?

Second the bike will not idle without a choke. With the choke on it idles where it should higher then a standard idle. As soon as I put the choke off it dies right out. I did hold the throttle to keep it running at a very low rpm and it was popping quite a bit. It performs well everywhere else from 1/8th throttle to wot just will not idle without the choke. I have tuned the idle adjustment and the fuel screw it runs better now but still won't idle.

Any help would be much appreciated thank you!
 
#4 ·
What jet kit and jet sizes? Needle clip position? Air box lid on or off? Did you install a new crush gasket on the header? (Possible leak)
 
#5 ·
Sadly its a dyno jet ket with a cj128 main (converts to a 138 for keihin). Kit said to use that one for under 3000 ft elevation. Needle is in the 3rd position and air box lid is currently on. The header is fine that's something I looked for as soon as it was installed. Iplan on looking at this tomorrow as I just got done putting a new frame on my grizzly.
 
#6 ·
I just read (downloaded) the instructions for the stage 2 kit for 06-14 trx. It says install the needle on groove 4 from the top. Also says to remove the airbox snorkel.
I had some issues with a Dynojet kit as well. Let's just say now I have the HRC jet kit installed and all is well.
 
#7 ·
I assume you have a full exhaust and not just a slip on?
I remember I had issues with popping on decel too. I was able to fix it by installing a 55 leak jet.
s far as the idle, make sure you don't have a vacuum leak or something somewhere? Make sure the carb boot(s) is fully secured/sealed.
 
#8 ·
So I decided to experiment. The bike ran fine with the pipe and filter on and stock jetting so I went back and same problem. This leads me to believe a blockage in the carb. I didn't have time today so I will clean tomorrow and see what happens.

Since it ran without the jet kit with no issue that I seen would it be OK to just leave it stock jetting then?
 
#9 ·
Slip on or full exhaust? Slip on you may be ok, but full exhaust you need a rejet from stock.
 
#10 ·
1. Remove dynojet kit and throw away
2. Take entire carb apart, accelerator pump, bowl, etc. Spray out every hole you can find, remove jets, clean with air, remove float and check float needle.
3. Put keihin jets in, HRC jets will work great
4. Remove airbox lid
 
#11 ·
So I had a blockage in the pilot jet cleaned it all up and went to start and....

The up and down idle is gone, but it still will not idle without the choke. The idle is higher with the choke on like expected. No miss no popping sounds great. As soon as the choke comes off it shuts right down.

I saw that the insulator from carb to engine is worn down ( the rib inside is half gone) I ordered a new one so if there is an air leak there will that cause it not to idle? Any other ideas?
 
#12 ·
Did you try moving your clip on the needle to the 4th position from the top like Dynojets instructions say? If it's still on the 3rd, maybe it's possible it's resting too low and blocking fuel flow from the slow jet, which affects idle. That would explain why it only idles with the choke on(creating a vacuum to draw in more fuel).
Dynojet instructions:
http://www.dynojet.com/pdf/Q118.pdf
 
#14 ·
I had the same issue with mine and all I needed was a bigger pilot jet. Also don't be afraid to mess around with air/fuel mixture. These carbs are very hard to get tuned correctly. Like I said, bigger pilot jet should do the trick. Stock is a 42 so if you go up to a 45 (like I had to) it should work great.
 
#16 ·
Like I said, throw away the dyno jet, it will not run properly with it in there no matter what ya do. Once that issue is fixed, then try and jet it.
 
#18 ·
Main jet will be 162, leak jet (located in the bottom of the float bowl) gets a #55, replace needle-needle clip goes in 3rd spot from flatend of need (can tune further to 4th spot).Turn the accel pump out 1 1/8 turns from stock. Fuel screw 2 turns out from all the way in.

You can get the entire jet kit from woodward, he is a site sponsor:http://www.trx450r.org/forum/93-engine/177346-hrc-jet-kit-instructions.html

Here, this post has some videos further down on the page http://www.trx450r.org/forum/93-engine/177346-hrc-jet-kit-instructions.html
 
#20 ·
When you say "idle screw" are you referring to the fuel screw located on the bottom of the carb or are you referring to the air/fuel mixture knob on the right side up under the front plastic? A lot of guys on here use "idle screw" to describe either. Plus if you are referring to the air/fuel mixture knob that just simply controls the amount of air entering the carb mixing with the fuel which changes the idle. Most people think it literally controls the idle speed when it just regulates the amount of air.
 
#21 ·
Idle knob as in the one up top. This is all the way in and still won't idle. I have been trying to adjust Tue fuel screw also but doesn't do much. Granted this has all been done with the choke on so its more then likely way off. Pilot jet did help though as it did the idle for a little without choke, but very very low.
 
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