New bike (2001 drz-s made supermoto) problems backfire on decel, carb help?

[cambam41]

hey i recently bought a 2001 drz converted to sm, has 3x3 mod, yoshi rs-1 and fcr carb possibly jet kit? (i think they are standard with an aftermarket carb). i love the bike so far but the previous owner said the carb might need cleaned. the bike pops and backfires on decel or even sometimes one backfire when i upshift. sounds almost identical to this video------->

  I was just wondering how difficult it would be to "clean" the carb or whatever it is i need to do, a list of what i'd need, and so on. thank you so much for your help i hope to get this fixed soon ?

[38super]

Sounds like my bike.

[OhioYJ]

Do you have a picture of y our carb? We need to know what carb it has first (Slant FCR / FCR MX).

 

It is possible to tune out almost all deccel popping, but without knowing exactly what carb it's hard for us to tell you where to start.

[IRON MAIDEN]

That's nothing! You should hear one with an MRD/SSW exhaust. 10X the decal pop! I love it. Wakes up the drivers around you in traffic!!!

Sets alarms on. Scares young children. lol

[npm]

Sounds pretty much like my bike with the FCR-MX on it.  A properly jetted DRZ will pop or burble on decel.  Possibly your Yoshi just makes it a bit more noticeable?

 

Anyways, if you do tackle the problem you will first have to take the carb off and verify the current jetting before people on here can help much.  Taking the carb apart is not difficult but there are a lot of small parts to misplace and re-assembly errors to make if you haven't done it before.  

[Rukix]

If your using the stock Mikuni 36mm CV carb, found on the s or sm model and have modded the intake or exhaust at all you will need a rejet. try getting a 25 pilot jet it may fix your issue. The stock is 22.5 I believe. Also see which slot your needle is in. There is a forum with a lot of info for jetting this stock CV carb to your elevation.

 

If the popping on decel sounds just like that, it sounds slightly lean to me, I am currently experimenting with a Mikuni tm-40 flat slide and I had a similar popping until I went up to a 27.5 Pilot jet. If you have never opened your carb up, make sure you don't lose any rubber gaskets, and inspect the CV boot on the top for any tears. Get a can of carb cleaner and some compressed air (if no compresser, a can from your local computer store will work) spray the jets and blow them clean, as well remove any tarnish from the float bowl and insure your float isn't binding. When I first modded my DRZ (pre-major engine work) I ran a 155 Mail jet and a 25 Pilot Jet, Needle in the middle (JD jet kit blue needle) 350 ft above sea level, (3x3 and full pipe) It ran great, no popping, light brown coloured spark plug, big difference.

 

Good Luck, feel free to ask any more questions. 

Edited April 28, 2015 by Rukix

[npm]

If your using the stock Mikuni 36mm CV carb, found on the s or sm model and have modded the intake or exhaust at all you will need a rejet. try getting a 25 pilot jet it may fix your issue. The stock is 22.5 I believe. Also see which slot your needle is in. There is a forum with a lot of info for jetting this stock CV carb to your elevation.

 

If the popping on decel sounds just like that, it sounds slightly lean to me, I am currently experimenting with a Mikuni tm-40 flat slide and I had a similar popping until I went up to a 27.5 Pilot jet. If you have never opened your carb up, make sure you don't lose any rubber gaskets, and inspect the CV boot on the top for any tears. Get a can of carb cleaner and some compressed air (if no compresser, a can from your local computer store will work) spray the jets and blow them clean, as well remove any tarnish from the float bowl and insure your float isn't binding. When I first modded my DRZ (pre-major engine work) I ran a 155 Mail jet and a 25 Pilot Jet, Needle in the middle (JD jet kit blue needle) 350 ft above sea level, (3x3 and full pipe) It ran great, no popping, light brown coloured spark plug, big difference.

 

Good Luck, feel free to ask any more questions. 

In the original post he stated he has the FCR carb.  

[Rukix]

Missed that sorry.

[atarijedi]

I have a similar issue, sometimes it sounds like a machine gun, lol.

 

I'm currently running a #45 pilot jet, and after doing some reading and conferring with Mike at Jets R Us, I am going to try running a #48 Pilot Jet (Slow Jet). If it still sounds the same, I will then try an ACV (Air Cutoff Valve).

 

That said, you will never get rid of the decel popping though, there will always be some if you have an FCR and a slip-on like the Yoshi RS series (I have an RS2).

[707LAKE]

i got absolutely 0 pop @ 45/160(recomended for my area/temp/elev) fcr slant, but that setup i could turn the fuel screw in to 0 turns out..and it would still run..so i changed it

 

i switched to 42/155 and i get pop now, but it runs better,fuel screw @1 3/4turns..no where near the pop in video though

 

turning the fuel screw 1/2 turn either way will make my current setup into a full auto AK47 lol

Edited April 29, 2015 by 707LAKE

[///Z]

That's nothing! You should hear one with an MRD/SSW exhaust. 10X the decal pop! I love it. Wakes up the drivers around you in traffic!!!

Sets alarms on. Scares young children. lol

I wish i took a video of my exhaust before I jetted it and did the 3x3. it runs so lean and it's so amazing lol. It's the main reason why I love carbonated bikes. You don't see any FI bikes doing this. It still pops and banks but not nearly as much as before.

[OhioYJ]

i got absolutely 0 pop @ 45/160(recomended for my area/temp/elev) fcr slant, but that setup i could turn the fuel screw in to 0 turns out..and it would still run..so i changed it

 

i switched to 42/155 and i get pop now, but it runs better,fuel screw @1 3/4turns..no where near the pop in video though

 

turning the fuel screw 1/2 turn either way will make my current setup into a full auto AK47 lol

 

If your PAJ is tuned correctly for your pilot circuit the popping will go away. Without going rich on the PJ. The entire system needs to be tuned together to eliminate the popping. The FCR-MX responds the same way as well.

[Kev650r]

My fcr pops on decel without the acv installed but it is a nice growl with no popping if it is installed. You will lose a small amount of engine breaking with an acv but I think it's worth it. And idle will not be constant sometimes with the acv in but like I said I think it's worth it. Just set your a/f screw with the acv then re-install it.

[monkeypooop]

That's nothing! You should hear one with an MRD/SSW exhaust. 10X the decal pop! I love it. Wakes up the drivers around you in traffic!!!

Sets alarms on. Scares young children. lol

had my bike for 2 days with the SSW pipe and i have done all three! kinda felt bad for the kid, looked like he pooped his pants.

[monkeypooop]

My fcr pops on decel without the acv installed but it is a nice growl with no popping if it is installed. You will lose a small amount of engine breaking with an acv but I think it's worth it. And idle will not be constant sometimes with the acv in but like I said I think it's worth it. Just set your a/f screw with the acv then re-install i

noob Q for $100 Alex, Whats an ACV?

[Kev650r]

Air cut-off valve aka coast enrichener. It cuts off air to the pilot circuit when you close the throttle. This causes a rich condition in the pilot circuit. Which stops the lean pop on decel. Hope this helps. Some carbs don't even have them.

[atarijedi]

I put a #48 PJ, up from a #45, in my FCR and the popping largely went away.