bike is poppin an sputtering

Hi i am new here an just pick up a 81 maxim 550 took the carbs out and got it clean at a shop, they told me it didnt need rebuild. I put the carbs back on an try starting it but it wont start, then i spray on gas in the carbs an it started right up. Then i took it for a ride an it pop an sputter at low rpm but when i give it full thorttle it runs ok. I an not runing a air box and have open headers do i need to get my carbs rejetted? thanks.

 

popping at low rpms is a symptom of running lean.

no air box and open headers will make you run lean.

your plugs are probably white.

yes, rejet.

 

thank for the info is there a website that can show me how to rejet my bike? and where can i buy the jets at?

 

All you have to do to rejet is pull the carbs, remove the float bowls and unscrew the old ones and put the new ones in. With open headers You'll probably have to go to 125 size or bigger jets (if you are running pod air intake filters). Jets are easy to remove and install. Finding the right ones aren't.
Take this advice seriously. It's coming from hours on here, hours working on the bike, and hundreds of miles... oh yeah, and around $1200 at shops... reinstall an airbox or you'll never have it running right.

 

High_Octane:

You night as well know, ... right up-front, ... Bikes which have been altered with Headers and Pod Filters may be impossible to Fine Tune to a point where they perform without sacrificing some performance within the Power Band.

Constant Velocity Carbs are impossible to Dial-In to peak performance when the INTAKE and EXHAUSTS are not regulated.

With your situation you have to protect against running the Engine: CRITICALLY LEAN.

Before you do anything else, ... you should remove your Spark Plugs and examine them.
Look at each Spark Plug's Center Electrode.

More specifically, ... look at the Very Top of the Ceramic surrounding the Center Electrode.
Use a Magnifying Glass.

IF ... you observe hairline fractures or any deterioration or damage to the Ceramic where it surrounds the Electrode, ... You need to to take measures to avoid doing serious damage to your Engine.

 

Rick is as right on as you'll get on here. It is a huge disappointment... trust me... to find out that the cool looking pod filters and the race boat sounding exhaust is going to make riding without problems impossible.
It's a 550 and if this is your first Yamaha xj 550, you are in for a treat if you go as far back to stock as possible. The bike has really smooth throttle response, insane power band for a 30 year old little 550, and I have taken mine from Burlington to Oshkosh wisconsin and back on the interstate 3 days in a row and it barreled through that like a beast.
I have done the trying to improve performance on this bike. Then almost took it to the salvage shop due to the headaches and frustration trying to dial it in caused. It's peak performance comes stock. That's it. Otherwise you'll spend money in the thousands and have not much at all to show for it.
If you get an airbox i can tell you how to put it back in without removing the engine or lowering it. It's a task and you'll bust your knuckles but it is worth it.
The stock jet size is 112.5. If you find good headers and a good, stock collector, I'll be jealous. I have a Mac 4 into 1 and even with re-installing the stock air-box and jetting DOWN to 115 (2 1/2 sizes larger than stock) I am very unsatisfied with it. But it's better than open, free flowing exhaust (which I also tried with the pods). Now I am on a mission to get a decent stock exhaust back on the bike.
Good luck. Seriously. If you do the hunting, you can find what you need for cheap. And a lot of guys here know these bikes inside and out.

 

feeling creative

 

thanks for the info guy.

 

A few guys, on here, have designed PVC Intake Air Reduction "Manifolds"
They made a Manifold that feeds ALL the Carbs through ONE Pod.

I think some have been very successful engineering this Mod to reduce the Cubic Feet Per Minute of Intake Air to a level that is very close to the Design Parameters.

But, I don't remember if they were running 550's.

 

ok i just install the 125 jet an took it for a test ride rode good till 4 grand now it seem like its getting to much gas start to bog out. I am going to try smaller jet see if i can get it to even out. Do i have to change the intake jets to? i am guess the bigger jet is the exaust and the smaller one is the intake correct me of i am wrong. Another question am i suppose to run the bike on pri or the on position? sorry for the question i am new to working on bikes thanks.

 

The big jet is known as the Main jet, and the little jet is known as the Pilot jet.

You need this. You also need a service manual or two, and to read Chacal's catalog, and everything RickCoMatic has ever posted.

Sorry, but you also might want to brush up on the basic mechanics of a gasoline engine, because NOTHING in a carburetor has anything to do with exhaust (except being part of the whole system, of course).

You should be able to run with the petcock in the "ON" position. If you can get gas in "PRI" but not "ON", there is something wrong with either the petcock or the vacuum connection.

 

+1.
I don't know rick personaly, but I've followed his
advice as a member and for a long time before that,
and it's always been right on the money.
He's not about ego-he's just right, so take that for what it's
worth.
As for my 2 cents; do as day7a1 suggests and learn as much
as you can about how and why this motors work. Most of what
you need is here.
Good luck.

 

thanks alot on the info i am new to carburetor i use to working on fuel injected cars and this is my first bike i ever work on that has a carburetor.