Aftermarket Pipe cause surging at low rpm's?

[cd57078]

Hey Everyone,

I just bought a 2003 FZ1 and there is an aftermarket pipe and jet kit. I am trying to bring this thing closer to stock to maybe help it run a little better. Letting the clutch out in first and low rpm cruising it sputters pretty bad and thought maybe the pipe was the cause? I know that there could be many causes but I've searched and it seems a lot of people have had this problem with aftermarket pipes. So one question I do have is, can I keep the jet kit (i think it's stage 1) on there with the stock pipe? I have to admit I don't really know what jet kits do.

Thanks,
Chuck

 

[Pyrogenic]

What do you mean 'low' rpm? For a normal start - I need to go to about 2500 or so RPM. 4-5 for a a decent launch.

I have Ivan's and also a GYTR can - probably similar.

at about 4500 or so it really jumps up in power during a strong launch, which is where the kit really makes the difference.

 

[NJFZ1]

Hey Everyone,

I just bought a 2003 FZ1 and there is an aftermarket pipe and jet kit. I am trying to bring this thing closer to stock to maybe help it run a little better. Letting the clutch out in first and low rpm cruising it sputters pretty bad and thought maybe the pipe was the cause? I know that there could be many causes but I've searched and it seems a lot of people have had this problem with aftermarket pipes. So one question I do have is, can I keep the jet kit (i think it's stage 1) on there with the stock pipe? I have to admit I don't really know what jet kits do.

Thanks,
Chuck

Sure sounds like lean surging. Could very well be that the idle screws need adjusting or if the bike sat around for a while the pilot jets might be a little dirty.

 

[Pyrogenic]

That too - I know I fired mine up recently after sitting for a while, and it sounded like I was missing one complete cylinder... but it didn't work its way out until I ran it at high-rpm for a while.

 

[cd57078]

Well thanks guys, maybe i'll check out the carbs. I don't think it's been sitting all that long. I didn't notice it on the test drive because everything was like a new experience but now that I did, I asked the previous owner and he knew about it too (wish he woulda told me) and said he thought it was the pipe.

Oh and what I mean by low rpm is right after you let the clutch out which could very well be 4k, but I think a bit lower. This is just slow cruisin around town. If you "hit it" it's fine.

 

[lindy]

Sure sounds like lean surging. Could very well be that the idle screws need adjusting or if the bike sat around for a while the pilot jets might be a little dirty.

I go along with this.
For the original poster - lean means ... not enough fuel. Rich running means a little or a lot too much fuel. Both rich and lean conditions can create poor running conditions. But lean is more pronounced as a surging type affect. Rich is usually just a continuous "sloppy" running condition with missing and poor performance.
This is simplifying a kinda complex set of things but... if it helps.

Normally when a jet kit is installed, the new jets are larger - meaning they let more gas in - meaning richer running. But with a change to the exhaust - that changes running pressures that affect the need for more fuel -- again over simplification of a very complex set of things going on.
In any case - changing exhaust affects the amount of fuel required. The jets regulate that fuel. Larger = more fuel.
When this bike was modified with the exhaust change and fueling change (jet change) it would have been nice if the two components were matched. But that doesn't always happen - because many people don't really know what they are doing (to be blunt).

So... You really don't know what you have got - with the jets and exhaust. It doesn't sound like they are compatible. Or it could be like the previous poster suggested - that the carburetors are gummed up (dirty) and need to be cleaned. That could cause this effect that you see, also.

Idle jets ... possible. But the idle jets only work in the very low RPM range (idle range). But it would be worthwhile to investigate this - also would be the simplest. It's a good suggestion.

If you could find information on what jets were installed - compare these to the ones the exhaust manufacturer suggests for that particular bike - 2003 FZ1 - with that particular exhaust.

 

[cd57078]

Thanks Lindy, those are some good tips. It very well could be the idle jets as you mentioned. I have now put the stock exhaust back on and sadly there is no change. Also there is no change as to when the bike warms up vs cold. I think the surging is actually quite less when it's NOT warmed up. And just to clarify, the problem is right around 2,000 rpm's and keeps surging/bucking until about 3500. And this is only with just slow acceleration, if I go a little harder to doesn't really do it, at least not as noticeable.

One question I have is, with these jet kits, are they easy to remove and just get the carburetor back to stock?

 

[lindy]

First of all - my comments have been written assuming you do not know much about mechanics --- derived from your comments. So I am trying to explain some things simply - to give you an idea of what you are dealing with. If I am incorrect about your knowledge and you already know this stuff, please forgive me.
Your best bet is to find someone close to you who is very familiar with these issues.

The idle jets are separate from the main jets. Two separate sets of jets. The idle jets mix the air and fuel for very low speed operation (idle). the main jets take over above idle and supply the sir fuel mixture for higher engine speeds.

I have not worked on these carburetors personally so I cannot tell you what is involved in changing them. But to be clear - the changed jets from a jet kit would be the main jets - not the idle jets. The idle jets are adjustable by screws from outside the carburetors. One screw on each carburetor. You have four - one for each cylinder.

The more information you can provide -as to how the bike acts - at what speeds and under what conditions - like acceleration or steady or ... the easier it is to try to determine what is going on.

By what you just said in your latest message, it sounds like you could possibly have an air leak in a carburetor or two. Check the "tubes" going between the carburetor and the engine to see if they are not sealing correctly.
Also, you could try to spray some starting fluid around and on the carburetors while the engine is running - especially at an RPM when it is not running well. (you get it at the car parts store in a spray can) If the engine smooths out (runs smoother) when you do that, it is likely you have found an air leak. Then it is a matter of fixing the leak - relatively simple.

Try that - try the idle adjust screws - look online to find their location - go to FZ1 Gen 1 engine sites - look for carburetor photos/pictures/diagrams which show you were the idle adjust screws are. Turn the screws about 1/4 turn at a time and try to notice improvement or worsening. Remember your starting points. Try to do each carburetor the same. It is possible that someone has messed up and the idle screws are not the same for each carburetor. The engine won't like that. If that is the case you may have to stat the idle screw process completely over as I describe below --- to get all the carburetors adjusted the same.

If it gets really fouled up and running badly - and you are lost as to what to do with the screws - there will be someone on the board here that knows the carburetors and can help you get the screws turned to where they should be.
For most engines a good way to start - from scratch - is to turn the screw all the way in (that would be clockwise) until it stops. Don't try to force it when it stops. Then back the screw out (counterclockwise) about 2 1/2 turns. Do this for each carburetor. Start the engine - see if it will idle at all with it set like this. If it does idle - even if roughly, then turn the screws slowly out - maybe 1/8 turn each time. Make this change for each carburetor so that they all have the same setting. See if that improves the running. If it does repeat the process (another 1/8turn out). Continue until you can hear that the engine is starting to slow down with a little roughness. If you get to that point of it not running as well because of too many turns out - then start turning the screws in slowly until you reach a point where it is running the best. That is your best idle mixture point.

If, when you started this backing out the screws it only runs worse as you turn the screws out - then you start slowly turning the screws in - the same way by 1/4 turn or 1/8 turn segments. Then seek that best point as before. You can tell by the speed of the engine (it will come up to it's highest speed at the proper setting) and by the sound of the engine. It will sound best - at the other extremes it will sound labored or ready to quit running.

This is the general process for adjusting idle jets - but the guys on the forum can critique all this and set anything straight that isn't exactly.

Oh! For your information - as you turn the idle adjust screws out (counter clockwise), you are causing the jets to become "sort of larger" - flow more gas - which is richer. Rich means lots of gas... maybe too much gas. The opposite is lean - which is not enough gas.

Once you do this, of course, you will have to start considering yourself a mechanic! (kidding ...sort of)

More than likely it is something like an air leak or gummed up carburetors (and the guys can help you with what to do on this specific engine - since I have not worked on this one)......the carburetors may be gummed up from old gas and may have to be taken apart and cleaned. This is beyond you right now if you are not mechanically knowledgeable, as I have guessed.

You know, if the carburetors are gummed up you could just try adding a carburetor cleaner to the gas and drive it. After a while it could improve. You'll have to keep adding at each fill-up though - until you see it works or you give up because it doesn't. (Carburetor cleaner and fuel injection cleaner are the same stuff - and are at the car parts store. Either one is fine.)
There are other things -but not as likely as these.

Good luck with you conversion into mechanicing...

 

[cd57078]

Thanks a lot! I definitely appreciate the help. I'm not sure if I will attempt this or not, I've done a couple smaller projects like air filter replacement and oil changes but nothing like this. From what you said and the research I definitely think it's something with the carburetor. I may need to have them synced up.

 

[lindy]

Thanks a lot! I definitely appreciate the help. I'm not sure if I will attempt this or not, I've done a couple smaller projects like air filter replacement and oil changes but nothing like this. From what you said and the research I definitely think it's something with the carburetor. I may need to have them synced up.

These things really are not hard.
At least try the starting fluid spray. It's cheap at the store. Spray and see if you've got an air leak. It happens.
It sounds like the previous owner tolerated the engine not running too well, too.

If you've got some fears - look at some youtube videos. Try motorcycle carburetor idle jet adjustment. Or try just a generic idle jet adjustment procedure. There is a ton of stuff out there that is very helpful.