Backfire when letting go of throttle

[Derbs420]

I have a question that might have to do with my riding or the modifications I have done to my motorcycle.

Installed - K&N air box filter (Snorkel Removed)
- Two Brothers Exhaust

This setup was awful and made my bike backfire and cough whenever I let go of the throttle. Understandable from all the air intake. Then I brought the bike to a shop and had the Dynojet Kit installed for around $220, which I thought was a great deal. Using the 100's

However, when I brought it home and ran it the next few days later it still will backfire (not as much or often) when I release the throttle. Also when warming up in the morning the mechanic said with full choke it would stutter then rev really high with the install and in my case it will only rev to about 3000 after 2-3 min.

Few questions -

Is it that I am letting off the throttle to fast when riding? Or could they not have installed it correctly? When I looked in the box it still had the silver screw that you were supposed to drill into the carb and then screw it in. Is this the missing piece?

Any suggestions will help. Thanks!

[g21-30]

Originally Posted by Derbs420

When I looked in the box it still had the silver screw that you were supposed to drill into the carb and then screw it in. Is this the missing piece?

The screw is used to remove the caps, which cover the idle mixture screws. The caps are drilled with the small drill bit included in the kit and the screw is then used to remove the caps. The screw DOES NOT get installed anywhere on the carbs.

[Derbs420]

Good to know, as you can tell I'm not too knowledgeable about carbs and any info you can give me is appreciated.

So is this normal for it to backfire? What adjustments might I be able to make to the settings in the carb?

Repacking the exhaust? Reinstall factory air filter?

[Ken08Ninja]

The backfire is from the Kleen air system.
DIY: Removing the Kleen Air System H...s on a 08 250R

[almost40]

It will backfire a little especially if you run it hard. try not to have the throttle open at all when you hit the clutch. This will help alot but it will still backfire a little but dont worry about it. Remove the clean air system if you have one.

[Derbs420]

Thanks for the advise, I will also try removing the Kleen air system after work. Im just glad its not as big of a problem as I thought.

[almost40]

You should hear mine at the track. lol

[M-Oorb]

I have the full Area P exhaust and have left the Kleen air system in due to the fact of being lazy and loving a little back fire now and then...will this harm my bike in any way?

[Wes]

1. Backfires are not normal
2. Backfires are not good for your engine

I haven't played around with piping and jetting a -J or -K series bike, but what you have described is a lean-miss backfire.

Generally speaking, it is caused when the throttle is suddenly closed and the mixture is too lean to ignite in the cylinders. It winds up in the pipe, gets hit with the exhaust from a cycle which DID fire (probably the other cylinder), BANG! explodes inside the exhaust pipe.

You should be looking at tuning your carburetion to match your exhaust. You should also see if there are any tuneables with respect to your pilot mixture (EPA caps) and your coasting enrichener.

[almost40]

Not to start anything here Wes. You can tune your rear off if you please, but you will not get rid of the occasional backfire in the 08-09. I am 1000% sure my backfires have nothing to do with being lean. Im running a touch rich because I thought just as you did.
There is no harm in the occasional backfire especially off throttle. I will stipulate that if you are backfiring on throttle you have a problem no doubt. For those of you who are having a once in a while backfire off throttle dont fret. It will happen.

[kkim]

yep, the new gens have a kleen system which injects more air on throttle down situations to lean out the exhaust gases. if you have a stock exhaust system with the 2 cats in there, backfire doesn't seem to be a problem. (it's not a loud backfire, but more like popping on decel)

if you change out the exhaust and remove one or both cats, the extra air seems to introduce the decel popping.

[M-Oorb]

Kelly...is it ok to leave the kleen system in with an aftermarket system? I get the pop every once in a while(knew it would happn) and I like it
Posted via Mobile Device

[Nickds7]

Originally Posted by M-Oorb

Kelly...is it ok to leave the kleen system in with an aftermarket system? I get the pop every once in a while(knew it would happn) and I like it
Posted via Mobile Device

As Wes states above, back fires arn't the best for your engine. While I'm sure you could run it like that for awhile, its best not. Wonder if you could hook up a flame kit or something to fill that void, haha.

[kkim]

I tend to agree the popping is a sign that something's not right. I removed my kleen system and the popping stopped... haven't had any problems from removing it, that I'm aware of.

[almost40]

So Kelly, when you tach it in 2nd to 12000rpm and let the engine do the braking you dont get any popping?? I only get my popping when Im running the hell out of it at the track. If Im careful to make sure the throttle is shut before I hit the clutch for a downshift everything seems ok. During normal riding Ive never had an issue. Just when you run the hell out if it. Ive played with the carbs alot and never could get rid of it.

[kkim]

Kevin,

Nope. The only time I had popping is when I would cruise and let off the throttle at lower rpms.

No high rpm popping like you describe.

[Wes]

Has anybody talked to Area P about their setup and this popping? You'd think they would have bumped into it during development.

Does the Kleen system replace the coasting enrichener? If so, it might be interested to remove it, and add a coasting enrichener. The simplest way to accomplish that, I think, would be to pop in a set of -F bike carbs. That would also give you another set of needles to play with.

(The -J still uses CVK30s, right?)

Also, has anybody got any popping problems on a -K bike?

Wes

[Wes]

One more thing, have you guys dynoed your bikes with an EGA? Did you collect any data during roll-off?

Wes

[noche_caliente]

Kelly,
Will removing the kleen-air with the stock exhaust cause any damage to the cats?

[kkim]

Originally Posted by noche_caliente

Kelly,
Will removing the kleen-air with the stock exhaust cause any damage to the cats?

dunno.

[Derbs420]

I finally took off the kleen air system and the bike sounds great! I think if you have an after market exhaust and have the crackle when letting off the throttle, this is the mod to go with. I don't think the fuzz will be pulling you over for an emissions standards violation! haha

It doesn't take long to remove and now runs like a dream. Just make a quick run to a NAPA auto store for tubing and you will be all set.

[kkim]

cool... enjoy!

[TrueFaith]

As said earlier, a little popping on decelleration seems to be normal for the new-gens. I have air pods and a professionally tuned Area-P and I still get it occasionally, but only on hard decelleration when I'm more focused on the brake instead of the clutch or throttle.

[NaughtyusMaximus]

Originally Posted by noche_caliente

Kelly,
Will removing the kleen-air with the stock exhaust cause any damage to the cats?

I'm pretty sure I read on here somewhere that removing the kleen system will damage the cats on a stock exhaust. Pretty sure of course just means that I'm too lazy to search for where I read it.

[noche_caliente]

Adrian - I thought so too - if we're both thinking it, then we're probably right

[AnarchoMoltov]

Are motorcycles subject to state emissions testing, like the cars are??? I dont mean by being pulled over by a cop or any thing like that...But the same way we have to bring our cars in to be tested, do we have to bring in motorcycles???

[AnarchoMoltov]

Nevermind, just read motorcycles are exempt in Illinois..

[newgirlrider]

Remove your kleen air system and don't worry about it, all these new bikes have them or some form of it. I had to do it to my new concours14 the other day after installing my my muzzys. my old '01 yami roadstar had it too.
like somebody else said before it injects clean air into the combustion chamber on decel (popping sound) to help burn any lingering fuel to help with emissions. The popping was always there you just can't hear it with a stock pipe.

[AnarchoMoltov]

I removed my kleen air system the other day...hasnt backfired since...even at redline and completely closing throttle no popping, cracking, nothing..
a MUST DO D.I.Y. for aftermarket pipes..

[noche_caliente]

Originally Posted by newgirlrider

The popping was always there you just can't hear it with a stock pipe.

I beg to differ - I can very much hear it with my stock pipe, as can my husband when he is in the car behind me.... some are just worse than others

[kkim]

Originally Posted by noche_caliente

- I can very much hear it with my stock pipe,

you're the first I've heard about. are you sure you don't have an air leak somewhere in your exhaust system?

[noche_caliente]

pretty sure - my dad checked over it too when he was here back in May and said everything looked good too - and he rode it for about 60 miles for me since I was having trouble with the knee at the time... that was part of why I'm wondering if my jetting is just really off and part of the terrible gas mileage...

[kkim]

take one washer out... that's the only jetting change you've made, correct? IIRC, you have 3 in there now?

recheck the pipe/muffler junction for signs of a leak. also, check the mounting flange at the cylinder head/pipe junction.

[noche_caliente]

I have two washers atm - haven't done anything at the header... I think the perfect fix would be to just take the stocker off all together and put the area p on there, but it's hard to justify the expense....

I also wonder if maybe the dents in the can from where it slammed into the swing arm haven't affected how it functions and might be contributing?

[kkim]

check the header anyway. it could loosen or it could have been pushed out of place from your oops.

[NJD022588]

I have an Area P exhaust, Dynojet kit, and removed Kleen Air. Before i removed the Kleen Air i was getting alot of backfiring (almost every decel). After i removed it, it still happens but only when riding moderately hard. Does this give me any indications on now rich or lean my setup is?

[kkim]

what method did you use to tune the pilot/idle circuit?

[NJD022588]

For now, i followed the recommended setup by Dynojet for a stock airbox w/ removed snorkel and a full exhaust. That is: e-clips 3rd from the top, Dynojet #98 mains, and 3 turns out on idle mixture screws. I figured this would be a good starting point since there are other members on this board with the same setup and it is recommended by the company. Now, i am trying to find indications on whether i am rich, lean, or fine so i know whether i need to tune more, and if so, whether to go leaner or richer.

I seem to remember something about how the tach needle falls after revving, but cant remember any more about that. The bike feels the same in the low range as it did before, but mid and high range have a lot more pull. 10-13k is amazingly different!

[kkim]

http://faq.ninja250.org/wiki/How_do_...dle_mixture%3F

I used the alternate method in this link.