Setup Issue with FCR39MX Carb

[myetman23]

Hi all, today I installed the TT FCR39MX kit on my 03 Drz400. It all went as smoothe as it could go, until I started it up. The bike has a very rough idle and most time stalls when idling and needs to be cranked over much longer to start it up. The idle screw is turned it pretty much all the way, which is where it will idle the longest. If I back it out it'll stall pretty much right away. I took it for a short ride and it seemed to work ok, it pulls much harder than before, as it should. I guess my question to you is what can I do to make the bike run smoothe at idle/lower rpm?

The bike is an 03 drz400s with 3x3 mod, holesawed muffler end cap, and aftermarket filter, riding at sea level @ about 10-20 degrees Celsius.

Jetting is 80 starter jet, 160 main jet, 200 main air jet, 45 pilot, 2.25 turns out on fuel screw, EMR needle in the 3rd notch, with o-ring mod done.

Thanks in advance!
 

[myetman23]

I should also add that the pilot air jet is removed.

[William1]

Check for vacuum leaks.

[myetman23]

Thanks for the reply! A vacuum leak never even came to mind to be honest. I thought it would've had something to do with the fuel screw or the EMR needle, since the EMN needle is recommended. I guess I can't totally rule that out yet either, but I'll have a look tomorrow and see if I have any leaks.

[myetman23]

Just for an update, I was playing with starting the bike again today. It will start on choke most times, but to get it to start without the choke requires a twist of the throttle. As long as I keep revving the engine it'll stay running, but as soon as I take my hand off the throttle the bikes dies within a few seconds.

[taldrz]

If it idled better with choke on then idle circuit too lean. No comment on your combo as I have no experience with it.

[mickeydee]

I would check your pilot circuit, you may of plugged up the pilot jet or pilot air passage.

[myetman23]

So I went out today to mess with the bike a bit more, I took William1's advice about the vacuum issue. I turned the fuel petcock to prime and voila! The bike will idle without dying and without the choke on. It's still not 100%, I still have some tweaking to do, but at least it idles and is rideable now.

[Mad Dogg W]

So I went out today to mess with the bike a bit more, I took William1's advice about the vacuum issue. I turned the fuel petcock to prime and voila! The bike will idle without dying and without the choke on. It's still not 100%, I still have some tweaking to do, but at least it idles and is rideable now.

 

Your '03 has a vacuum petcock ? I must have it wrong but I thought the VP was introduced in '06 or '07...... Hinsky (Greg) had a similar issue last year, maybe he will bump in and say g'day some time this morning   ?

Edited September 22, 2013 by Mad Dogg W

[myetman23]

It does indeed! First time I saw one actually, I was looking for the "off" on the petcock when I was removing the tank to install the carb, but didn't see one, so I just pulled the fuel line off to see what it was gonna do, and it did nothing! As it was supposed to lol

I don't know what my vacuum issue is yet, I never got too Indepth with it today, I was just happy enough to hear the bike idle.

[Mad Dogg W]

In regards to the petcock, vacuum issues are often related to the line running from the head not sealing properly or the actual fuel valve failing but what I think William1 is referring to is the bell mouth, air box and inlet manifold seals.....

 

That said, if running on prime has made things better then it is likely your fuel valve that is amiss.

Edited September 22, 2013 by Mad Dogg W

[myetman23]

Still not being satisfied with how the bike was running, I went ahead and ordered the R&D fuel screw from

TT, and the EMN needle from Jetsrus. When I removed the stock fuel screw from the carb, I noticed that the small tapered tip was not on the stock fuel screw, then I started to worry! I looked inside the fuel screw port, and sure enough the tip of the fuel screw was stuck inside the carb! Luckily, the FCR splits into 3 sections, so I took it apart and was able to get at the other side of the fuel screw port, and even better I was able to push out the cracked tip with a thumbtack without damaging anything else.

So after installing the remote fuel screw and EMN needle, the bike runs and idles great! And no more issue with the "on" and "prime" position on the petcock. I'm very pleased with the upgrade now, but not so pleased with the guy I bought the carb from.