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FCR39 MX Help Please

10 replies to this topic
  • killa09DRZ

Posted March 19, 2010 - 06:49 PM


I have a 2009 DRZ400sm with a MRD/SSW exhaust,3x3, and just installed the fcr39mx kit from TT. I did the o-ring mod aswell. I did forget to order the extended fuel screw so that wont be here until sometime next week.

The carb swap was a breeze and the bike started right up. I followed the directions for the initial tunning. After my first ride I noticed a slight bog with the initial take off with light throttle. I also noticed on decel the popping from the exhaust was bad.

So I took it apart again(really wish i had the extended screw at this point) and from the mixture screw being 2 turns i turn it out to almost 3 turns. The bog got alittle better and so did the popping on decel but both are still there.

I know some popping is normal but this is more then I had with the stock carb w/JD kit. I did not have the bog as well. I know this is a sign of being on the lean side. Just wanted some help on what to change or adjust to help smooth it out.

The WOT does feel great and is a big inprovement over the stock jetted carb. But I know there is more in the set up and with alittle help I can get the most out of it.

I am at sea level btw.

Thanks in advance for any help!

  • suzuki sm nut 123

Posted March 19, 2010 - 07:10 PM


try adjusting your squirt timming , a 1/4 turn out at a time . adjust test adjust

remember the first setting so if no improvment or gets worse you can go back

  • killa09DRZ

Posted March 19, 2010 - 09:04 PM


Thanks for a quick response. But I'm new to the bike carb thing. All my other bike were fi. I can rebuild a car carb with my eyes closed. Can someone explain to me which screw is the sqirt timing screw. Thanks!

  • chrisf608

Posted March 19, 2010 - 09:27 PM


What jetting did you use? EMN.

  • Dr Honda

Posted March 20, 2010 - 03:34 AM


Thanks for a quick response. But I'm new to the bike carb thing. All my other bike were fi. I can rebuild a car carb with my eyes closed. Can someone explain to me which screw is the sqirt timing screw. Thanks!

When you did the O-ring mod... you pulled it over a little arm with a screw in it. That screw controls the timing on the accelerator pump. Turn it in 1/2 a turn, and see if the bog gets better. I'm not using the TT kit FCR39... but I turned my screw in an extra 1 1/2 turns from where the last bike liked it... and my bog is non-existent.

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  • William1

Posted March 20, 2010 - 03:46 AM


I'll add, the popping is normal for a non-cv type carb without a coast enricher.

You should set the fuel screw for the best idle and leave it be. Do not try and adjust it to affect a problem that it is not intended for. Fuel screw is for idle only!

  • killa09DRZ

Posted March 20, 2010 - 04:40 AM


I used the jetting that the carb came with and the emn needle. I will try the sqirt screw today and see what happens. Once the extended scree gets here I can set that better. Thanks again

  • killa09DRZ

Posted March 21, 2010 - 03:24 PM


Ok the part throttle bog is basically gone. But I had to turn the mixture screw back in a 1/2 turn because the bike was dieing at idle with it being 3 turns out. But the popping on decel was better.

Now that the mixture screw is 2 1/2 turns out the bike idles fine but the popping got worse again. Is there a way to help this or should I just get used to it with the fcr and mrd exhaust?

  • William1

Posted March 22, 2010 - 03:00 AM


Get used to it. Popping is a fact of life with an open pipe.

  • xr50kidx

Posted March 22, 2010 - 04:53 PM


killa 09 drz show some pics of your bike the guys here would love to peep it,...

  • killa09DRZ

Posted March 24, 2010 - 01:36 AM


Will have some pics up this weekend. As you know NYC weather sux the last few days.

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