Got it running!

A little time every Sunday and now I've got my 82 maxim xj650 running. (I don't want to say how many Sundays!) Most of the problem was the float level - I was too timid to bend the tang enough to make a difference. After many feeble attempts I finally got brave enough to bend it so that it started to make a difference. It starts nice now but I still have a little tweaking to do. So I'd love just a a little more advice if someone cares to provide it. It idles the way it is, but it bogs a little when I hit the gas.
I think there are two issues that may be factors. First thing is that the screws that face up on the top of each carb, which are usually sealed by the factory, have been unsealed by someone to adjust them. But they only succeeded in unsealing three so they can be turned. The remaining one is kind of partially unsealed but can't be turned. I've got the three turned out about three turns after turning them all the way to their seat.
The second thing that I think I need to pay attention to is that after bench synching I wasn't sure how much to open those butterflies with the knob that controls all of them. A friend who worked on them with me told me to keep opening as it was idling and I obeyed even though in my mind I thought they were going to be open a little bit too much. If I get the first item - those screws that are now unsealed- set to approximately where they should be, am I correct to assume that I should just get it to idle at the right rpms by turning the knob to open/close those butterflies? What should the idle speed by? How many rpms?
Thanks a lot for any advice. I really appreciate all the previous info that helped me get this thing running and learn a little in the process.
Scott

 

T'hose screws you are referring to are pilot screws and you should be able to turn all four. Are you unable to turn it because the part of the cap is still there, or the threads are damaged or the screw head is damaged? You should be able to gently remove any remaining cap. I soaked mine with wd-40 and them blew them out with an air compressor, which removed all the dirt and grime and allowed me to gently turn the screw to seat it and then remove it. 2 1/2 to 3 turns out is a good starting point.

If you have the engine running, then the big knob will lower or increase rpm. I set my XJ700 at about 1100 and start the bench sync, and then adjust as needed. Be sure use a YICS tool to block the YICS ports when syncing. If you don't have one some folks use a knotted piece of cotton t-shirt soaked in oil. I'm sure someone will give you a link to look at. Be darn sure to have a fan blowing on your engine while syncing it.

 

I think we need to clarify a bit further.

The "sealed" screws being discussed are the pilot mixture screws, and have nothing to do with a "bench sync." They should all be set at the same for the sync process (2.5 ~ 3 turns as above) then adjusted accordingly as part of mixture tuning. But synchronization, both on the bench and on the running bike, comes FIRST.

Carb SYNC is obtained via the three screws located on the linkages of carbs #1, #2 and #4. Carb #3 is controlled only by that big knob; and is "home base" for the sync process. Additionally, #1 is "slaved" to #2, so whatever adjustment you make to #2 will likewise affect #1.

The process is this:

-VALVE CLEARANCES IN SPEC. http://xjbikes.com/Forums/viewtopic/t=14827.html Can't synchronize or tune carbs until they are.

-Carbs thoroughly and religiously cleaned, those mixture screws need to come out and have their rubber o-rings replaced and their passages flushed out, etc. You haven't yet fully serviced the carbs and that WILL BE necessary as well.

-Float levels accurately wet-set. http://www.xj4ever.com/setting%20fuel%20levels.pdf

-Bench Sync.

-Return carbs to bike; mixtures all at 2.5 ~ 3 turns out.

-Running vacuum sync (adjusting the same screws you did the bench sync with.)

-THEN and only then do you adjust the mixture screws. Most people prefer to use a ColorTune for this, as most of us don't own an EGA. You can use the "idle drop" method, by ear, but it's something that requires experience to get even close to right.

You're getting ahead of yourself trying to set up carbs that haven't been properly cleaned and serviced. If you haven't even taken all of the pilot screws out then it's nowhere near time to bench sync;

But none of this is going to do you one bit of good if your valve clearances aren't in spec first.

SLOW DOWN and do it right. Shortcuts don't work.

 

Fitz... you have always proved to be extremely helpful. I'm sure I speak for everyone when I say "Thank you!"

 

I'll second that!

 

Thanks for all the help guys. It was two separate problems and after solving them it seems to run great. I still can't get the plug out of that one carb, and didn't want to damage the pilot screw trying to get it out. Furthermore, I decided that that screw must be where the factory put it since it can't be turned so I set the other three to 2 1/2 turns out. Then I acted on a hunch that turned out to be right. I turned the petcock to prime and it runs beautiful. When I put it to the on position it bogs because it's just not getting enough fuel. There must be something amiss with the petcock. I put a rebuild kit in this one, but I don't know if I did something wrong or what. I'll try to find another but in the meantime I can just leave it set on prime when it's running. There's no problem doing that - right?
Anyway, thanks again everyone.
Now there

 

OK, it runs.

Now check your valve clearances.

 

XJ650la - Does your engine run "boggy" or "good" on "RES" ??
You may have a partially plugged filter tower screen, as only half the screen is used on "ON".

I am assuming you didn't pull the Pilot needles out of the carb bodies and inspect the 4 "O" rings - - there's more work to be done, my friend.

Your bike "could" be in a state-of-tune that might hole a piston on a high-speed blast !

 

Okay, so here's my plan. I'm going to get it registered now, so that I can ride it around just a little bit (no high-speed blasts) for more practice. Adjust the valves, pull the carbs back off and replace the pilot needles "O" rings, double check the float levels, bench synch and replace the carbs.
I'll check out the "RES" position and see how it runs, but if the filter tower screen is the one that attaches to the top of the petcock, then that's new. I'm thinking there is just something not right with the petcock itself. Does that sound credible? I rebuilt it, but could I have done something wrong? Or could the kit be defective in some way? It seems to me like the vacuum from the running engine isn't succeeding in opening the diaphragm when it's supposed to be.

 

In regard to the petcock: Did you see this? http://xjbikes.com/Forums/viewtopic/t=25058.html

Make note of the part about the little "one-way" check valve disc in the output flange. See pics 2 and 7 in the article. If it's stuck, the petcock won't work properly.

The other thing about the petcock: it's vacuum operated. If your valves are horribly out of spec, you're not going to be pulling much manifold vacuum so the little bugger won't work either.

The other item is the vacuum signal line. It has to be actual vacuum hose; it can't just be "hose." If it's not real vacuum line, it may collapse in on itself once warm.

QUIT RIDING IT. Did you pull the rear brake apart to physically inspect the shoes? http://xjbikes.com/Forums/viewtopic/t=15874.html

Check the date codes on the front brake lines? http://xjbikes.com/Forums/viewtopic/t=41400.html

How old are the tubeless tires?

Have you even changed the oil and filter yet? You need to use motorcycle oil; not car oil and the commonly available oil filter is the FRAM CH6003, which comes with both o-rings.

You need to attend to these things BEFORE you go and blow it up or get yourself killed trying to ride it. It's NOT A USED CAR. It's an old motorcycle; the game has different rules and much higher stakes.

 

Thanks for all this Fitz. I've actually done pretty good having been poring over these forums kind of obsessively, but I still appreciate all the info. I've replaced the brake shoes, the pads in the front, brake line in the front with braided, and rebuilt the caliper. Changed the oil using motorcycle oil and changed the filter as well. I definitely need tires, and I'm not riding it yet because of that, and because it's not even registered yet. I'm just riding it a little in an ally to make sure I get all kinks taken care of before proceeding. Which brings me to another question: I found an 82 650 Seca parts bike and I'm going tonight to see what I might be able to use even as spares. He just put a new tire and tube on the back before wrecking it. Will that fit on mine without any issues? Its a Bridgestone Spitfire 130 90 18mc 69h. I'm still very confused by motorcycle tire sizes but I know in some cases they can be too wide for the frame or fender.

 

Your '82 Maxim (if it's an '82) has a YICS motor, the Seca 650 had the pre-YICS motor; plus the forks, front brakes, frame and a lot of things are completely different. Electronic tach vs. mechanical, etc. This limits interchangeability.

A good case in point is the rear wheel/tire. Your bike has a 16" rear wheel; the stock tire is a 130/90-16 and you really don't have the room to go any bigger. The Seca has an 18" rear wheel, the owner has fitted a one-size wider rear hence the 130/90-18; while the swap is possible it will drastically change the look of your bike (un-Maxim it a bit.) I'd be suspicious of the whole "tube" thing too; these bikes use tubeless tires. The only reason for running a tube is to "use up" an older or sketchily repaired tire.

The way modern motorcycle tires sizes work is this:

The first number is the width, in MM. The 120, 130, etc.

The second number is the aspect ratio, the percentage of sidewall height compared to treadwidth. Our bikes all use a 90% aspect ratio tire. Hence the "/90."

The third number is the wheel diameter, in inches.

The various letters indicate load ranges and speed ratings.

This is exactly how automobile tires work these days as well; motorcycle tires were "brought into line" with car tires a while back. Some manufacturers of motorcycle tires still offer some models in the old sizing, which was just width (in inches) followed by diameter (for instance, 3.25-19 or 4.00-18.)

You might wanna pass on the Seca.

 

Perfect. Thanks again. Fitz. That explains everything. Now I can tire shop.

 

Don't ignore your valve clearances. They just get tighter.