Carb Balance and problem solving (pic heavy)

Lately my XJ600 has started running a little rough. Not as smooth as it is usually, and getting more and more reluctant to start. Also the revs would not drop quickly on a closed throttle.
The last straw was on my run home from work yetserday, the bike was a complete pig to start and would just not run cleanly. It would still pull to about 110 mph but was very "thrashy", so some investigation required.

Hope this helps some of you guys.



Judging by my problem, there is too much air getting in somewhere, so first thing off with the carbs. Release the four clips on the intake rubbers, and the four clips on the airbox rubbers. undo the mounting bolts on the airbox to aid removal. Remember to unclip the throttle cable (see above) and choke cable if your model has one.

I recon my problem is with the intake rubbers, so I need to remove them

WARNING As so has been rightly pointed out, be very careful removing the inlet rubber bolts. They can become seized in the head and there is a huge risk of them snapping requiring proffesional work to remove them. proceed with caution. Try to remove them if they come out easily your lucky. if they require moderate pressure proceed with caution, if they require huge amounts of pressure stop before anything catastrophic happens. If you are not confident with your abilities have a professional take a look for you. WARNING



each of these are different, so work one at a time. First thing though, the vacuum pipes have to come off



with the first rubber off remove the old gasket carefully and clean the surface



Genuine gaskets are quite expensive so I cut my own from quality gasket paper, using a surgeons scalpel. The trick is to use an old gasket as a template. Put the gasket paper on a wooden board, lay the template gasket on top and draw around it using the scalpel. (do not be tempted to push to hard, or you won't achieve the correct shape) draw around as if you were using a pencil. it will take a few passes to cut the gasket out, but it will be correct.



now to fit the gasket I use this stuff,


it's easy to use, and easy to remove.

run a bead around the surface of the rubber, and then smooth over with a finger



fit the gasket, and add more compound the the other side, now refit to the bike, using thread locker on the bolts, and torque the bolts up carefuly.

one of my rubbers had severe cracking and I suspect that this was the source of my probs, so this was replaced for a new one I had in the garage.

with all four rubbers inspected and with new gaskets, time to look at the airbox. one thing that annoyed me about mine, is that it never seemed to sit right on the carbs, so I removed the rubbers from the box.



And steeped them each in a cup of boiling water for a short time (this should allow them to return to their original shape)

with all four done, I reffited the carbs, and everything now sits up nice and tight



refit all cables and it's time to move on to carb balancing.

for this your going to need a carb tuner, long screwdrivers, and a remote fuel tank.



The carb tuner has four steel rods that give a reading when pulled under vacuum. each rod has it's on take off pipe, which fits to the corrisponding intake rubber. they fit to the brass vacuum take off's on the inlet rubbers



the tuner hooks over the left bar. now rig up your remote fuel tank (mine is an old cement mixer tank fitted to a tripod) and your good to go



To balance the carbs you work in pairs, using the balancer gauge.

I do the right pair, then the left pair, then balance them both together.
there is a screw between each pair as described that balance that particular pair.


you can just about see the screw in the above picture for the right pair. it's between the inlet rubbers.

now start the bike and let it warm (until it is off choke)

I personaly like to set my carbs at around 2500 rpm.
with the bike warm the carb tuner looks like this


as you can see the carbs are all over the place, so working on the right side, you don't need to worry about the scale on the gauge, what you are trying to achieve is to get all four rods at the same height.



the right side balanced




left side balanced



both together

thats the carb balancing done. time to put the bike back together and take her for a ride. (remember when rebuilding to put the vaccuum balance pipes back on)

After going for a ride, mr bike was silky smooth and pulled like a train all the way up to silly speeds.

Hope this is of a little help to some of you. Might just solve some of your carb troubles!

 

Great Post! Just want to catch one thing though. There are A LOT of threads about intake screws being hard to remove. Mine came out without snapping...but many others have failed on this. A WARNING (and possibly link to other threads) would be good for any newbies who might just dive right in and not know that they could snap a screw off in the head. Also, (again I didn't do this) it's recommended that the screws be replaced with new hardened fasteners. And that you use anti-seize, so they'll come out again when you need to take them off.

 

Kevw,

Fantastic post! This is going on my favorites list.

 

Thanks guys.

I am going to do my head race bearings and fit an automatc chain oiler soon, so I might write these up in the same fashion if it's of any help to anyone.

Kev

 

Like ALL Instructional Articles employing accompanying photographs, ... this is well done.

WARNING
WARNING
WARNING

The Intake Manifolds on XJ-Bikes are secured to the Head with Cheap, Soft-steel, Cap Screws.
These Cap Screws are KNOWN to SEIZE in the Aluminum Threads of the Cylinder.

ATTEMPTED REMOVAL OF THE INTAKE MANIFOLDS WILL CAUSE THESE CHEAP FASTENERS TO BREAK-OFF AND NEED TOP BE EXTRACTED BY A MACHINE SHOP AFTER THE CYLINDER HEAD IS REMOVED!!!

Attempt to remove Intake Manifolds AT YOUR OWN RISK!

 

Thanks Rick. I overlooked putting a warning in.

 

Great post and very informative. For a newbie thats never done it, makes it seem pretty easy. Since i know I need to do this very soon, along with the rest of the carb work i take all the "step-by-steps" I can get. Thanks for the info. Its greatly appreciated.

 

Here is a mechanics trick I know to get these bolts loosen without breaking the heads off... Before even attempting to wrench it loose, take a suitable drift ( like a old socket extension ) and tap the bolt head with many short blows with enough force to break the bond which form between two dissimilar metals. Do this repeatedly for several minutes on each head, then with caution put a little torque on your wrench ( remember "righty-tighty, lefty- loosey) and I suggest that you use a socket driven Allen not a regular one with a cheater. Also, use a breaker bar and tap the wrench with a ball peen hammer as you try turning the wrench. If this method fails to work there is one last thing to try, use a propane torch to heat the head; aluminum expands faster than steel. But don't hold the flame too long as you may damage your boots. Finally, when reassembling the boots, put anti-seize compound on the threads, in fact this should be done on all threads where steel meets aluminum including the spark plugs.

 

Just one little piece to the puzzle left out. Give those bolts a good soaking with Kroil, or PBBlaster before trying to remove. Give it a good chance to soak in. Then use the hammer/drift trick.

Any bolt that takes more than light pressure should be considered siezed, and soaked again. These bolts are only torqued at 11 ft-lbs (15 Nm)

The problem with the dissimailar metals is further aggravated by moisture trapped in the bolt hole of the boot. This is what usually causes the bolts to lock up, and break inside of the boot.

Ghost

 

And a good chance means overnight or longer.

 

With the carbs off this is the perfect time to adjust the cam chain.