Kawasaki Ninja Forum banner
1 - 20 of 26 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter · #1 ·
I am a noob here and also to all this motorcycle exhaust stuff so please be gentle.

I was planning on getting a slip-on for my 09 ninja 250, but noticed that a lot of the manufacturers "highly recommend" that you re-jet after installing their cans, which I have no idea how to do. I also read Redrider's step-by-step on the needle shimming, which I am embarrassed to say seems like too tall an order for something like me to do. :'( (Not that I'm retarded)

So my question is; do any of you guys know of manufacturers who make slip-ons geared to the stock fuel specs that wouldn't require any other modification? Or would those products not even be worth my purchase?

Thanks in advance.
 

·
Registered
Joined
·
274 Posts
yeah, I can relate. I'm learning all this too but my problem is that I bought used 08 Ninja 250 that already had an AWESOME Two Brothers exhaust on it, but i know nothing about the previous owners and very little about the bike's history. So it is in the back of my mind wondering if they did what they needed to do (jetting and whatnot) when they installed this slip on.

How will I ever know? Can my mechanic tell if this was done? What if it was not?

so many questions. Crappy weather this week is making me stir crazy. Want to get on my bike and ride !!!
 

·
Registered
Joined
·
124 Posts
yeah I installed. Its the coolest exhaust system Ive seen on the net. You can actually open and close the can for top and bottom end. And for the guy who bought the used 250 I dont know what to tell you about your question?
 

·
Registered
Joined
·
267 Posts
BTW shady lane is no guy, haha.

not sure what to tell you about that shady. does your bike backfire often because that could be a sign that it is running too lean as a result of the slip-on being installed without any fuel modification.
 

·
Registered
Joined
·
277 Posts
You SHOULD re-jet or at the very least shim after most mod's you make to the intake or exhaust side of the bike. Slip-ons, full exhausts, K&N slip in or the R-0990 would all greatly benefit from a jet kit.

Yes, your mechanic should be able to tell if the bike has been re-jetted. The DynoJet kit comes with an adjustable main needle, larger jets, and it comes with the drill bit to change the air-fuel mixture screw.

You ideally would re-jet the bike with the HR-1 as well.

The only bikes that don't need to be re-jetted are the lucky SOB's that have the Euro fuel-injected bikes.
 

·
Registered
Joined
·
274 Posts
dknollRX7 said:
does your bike backfire often because that could be a sign that it is running too lean as a result of the slip-on being installed without any fuel modification.
Oh Crap, it does backfire, um sometimes. Like when I let off throttle or sometimes on a downshift. I told my friend it wasn't backfiring, it just gumbles a bit. Guess I will have dude at the shop check that out. Thanks Guys!
 

·
Registered
Joined
·
5,695 Posts
Shady Lane said:
dknollRX7 said:
does your bike backfire often because that could be a sign that it is running too lean as a result of the slip-on being installed without any fuel modification.
Oh Crap, it does backfire, um sometimes. Like when I let off throttle or sometimes on a downshift. I told my friend it wasn't backfiring, it just gumbles a bit. Guess I will have dude at the shop check that out. Thanks Guys!
I'm sorry, but I have to disagree here... If the bike's exhaust is popping when coming off the high RPM's, you're running just a tad rich... Remove one shim, or lower the needle one notch, if you have a dynojet/similar needle. You could also try screwing the air/fuel screw in about a half turn...

So many things to farkle with! :D

good luck.
 

·
Registered
Joined
·
267 Posts
how do you figure....not trying to be argumentative, just curious. as I understand it, the backfire is caused by a predetonation which is also referred to as a knock. this situation occurs when the temperature in the combustion chamber surpasses the flashpoint of the mixture (a/f) and therefore ignites the mixture before it's predetermined time (power stroke via the spark plug). excessive temperatures are usually caused by a lean condition rather than a rich condition as the fuel actually cools the combustion chamber. I have seen misfires (no detonation at all either premature of from the spark plug) caused by a rich running engine, but not backfires. again, that's just how I understand it. let me know if you know something different that I may not.
 

·
Premium Member
Joined
·
6,846 Posts
Remove your 'Kleen Air' gear and you wont get a backfire on decel, it draws air into the exhaust system to lean the gases out to pass emission testing.

Backfires occur under both conditions, lean or rich. Its incomplete combustion that causes the backfire.

Felix







 

·
Registered
Joined
·
5,695 Posts
Excellent point DK, and Felix, you be right as well... This is where I think we're running into a communication issue, let me try and clarify:

Backfire: A piston igniting Before Top Dead Center, BTDC, and actually driving the crank in the opposite direction as the engine should turn... Bad news on timing.

Knock: Anytime the fuel ignition doesn't correspond to, or is initiated by the spark plug. Over-compression, hot embers in the cylinder from carbon deposits, etc... Usually results in a back fire.

"Popping": When an internal combustion is running rich, and has excess, unburned fuel going through the engine and into a hot exhaust, and actually "exploding" in your exhaust. This is usually diagnosed if the engine runs fine and strong under hard excel, especially in the upper rev range, but starts "popping" when you come off the gas. More pops the harder you return the throttle to neutral. This is hard to explain without a video.. Damn I have to get a camera, and please bear with me. I really want to figure this out, so we have a good frame of reference for the future.

This, I think, is what Angel and Shady are speaking of. It can be remedied various ways, but what it comes down to, is the carbs don't correspond fast enough to the engine, and extra fuel is drawn through the engine. The exhaust is hot, and fuel eventually burns up in the exhaust. It's not necessarily a bad thing, nor will a little of it hurt your engine. If you come of the exhaust and your exhaust sounds like a machine gun, take it to somebody who can massage the carbs a bit better... Lean out the bottom end, and prolly top end, and adjust the needle accordingly to get a good balance.

DK, I especially want to thank you for the way you approached this discrepancy between you and I. I like, so many on here, are just trying to help, and I think (but what's my opinion worth?), that you are an A-spec example of a good communicator. This is my take on the situation, but I'm not an authority either, so what do you think of this? Where do we go from here to keep clarifying?

Oh, Shady and Angel, speak up. Is the "popping" what you ladies are experiencing? Help us out.

dknollRX7 said:
how do you figure....not trying to be argumentative, just curious. as I understand it, the backfire is caused by a predetonation which is also referred to as a knock. this situation occurs when the temperature in the combustion chamber surpasses the flashpoint of the mixture (a/f) and therefore ignites the mixture before it's predetermined time (power stroke via the spark plug). excessive temperatures are usually caused by a lean condition rather than a rich condition as the fuel actually cools the combustion chamber. I have seen misfires (no detonation at all either premature of from the spark plug) caused by a rich running engine, but not backfires. again, that's just how I understand it. let me know if you know something different that I may not.
 

·
Registered
Joined
·
274 Posts
ok, just got all caught up on the conversation and my head is spinning a bit. First of all, Thanks for all the information dudes.

I'd have to say its more of popping. Like I said, I denied it when my friend called it a backfire. And it is when I roll off the throttle, and sometimes on the downshift. But it's not major like a shotgun firing, like I have heard some bikes do.

I have a call in to my mechanic guy, to ask him if he noticed if my bike was jetted or not.

I mean, I love my sweet azz exhaust, I just hope the person who put it on (aka, previous owner who wrecked the bike) is not a total idiot and did it the right way. Guess we will find out soon.

Thanks again - will keep ya updated on what mechanic dude says.
 

·
Registered
Joined
·
267 Posts
I think we're all right Spooph! The backfire can be caused under a lean or rich condition just like felix said. Just like you said I think it was all a communication issue. Thank you by the way. Like you said it's nice to be on this forum and be able to express differing opinions without being called out or made to feel inferior or stupid. Here we can actually express our views and ideas about a certain topic and talk about the results logically and in an educated manner to actually reach some conclusion that makes sense...so thanks to you Spooph.

I think the big issue is that there are many different terms for what could be occurring and they are all very similar with only slight differences. As you stated before, the spark occuring BTDC tries to drive the piston in the opposite direction (or moreso hinders the ability of the crank to turn freely and thus robs power). This also occurs when a knock occurs or pre-detonation. PRE-detonation happens before the disired spark (BTDC) and works against the power stroke. Predetonation is usually caused by a lean condition or possibly and EGR issue (although I'm not sure if bikes even have EGRs....I wouldn't think so, but I have no clue). A lot of times that knocking or predetonation will make a popping sound (kind of like a bag of popcorn in the microwave). haha, my RX-7 used to do that because of a weak air pump.

I totally agree with you about the unburnt fuel igniting in the hot exhaust. I had forgotten about that, but thanks to the mighty Spooph I now remember. I don't really have much experience with bikes (should be getting mine on 4-11, red 250R...first bike) but this doesn't happen too often in cars...especially fuel injected ones. I have heard of this condition on some rally cars like STis and EVOs where there's another component....I can't remember exactly but I think it's called and afterburner valve or something like that. I can see it happening with bikes though as the higher rpms and more exhaust pulses will raise the temps higher and with the less accurate carburation, fuel adjustments don't happen as quickly. I can see how if you were hard on the throttle in the upper rpm range and let off really quickly this backfire could occur. So I guess what I'm trying to say is that I'm not certain who is right, but you definitely have a valid point. Let's all take a moment to thank Spooph, haha. Thanks again for the kind words Spooph and for not taking anything personally when I had questioned you. Like I said I was just trying to clarify and I think we were just experiencing a communication issue. Now hop back on Cherry and take her for a spin.
 

·
Registered
Joined
·
274 Posts
You are all so cute. Its nice to see respect among each other. From an outsider and newbie opinion, the more heads we put together on these issues, the more complete the discussion is. We all bring some different knowledge and experiences to the discussion.

I'm loving learning from all you you. I'm not a gear head yet, but maybe when I grow up. lol. Right now I am a novice and appreciate all the knowledge everyone here has to offer.

Thanks.
 
1 - 20 of 26 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top