My XJ650 project

Hello all, Marcus from Washington. I picked up an 82 XJ650J last year (unknown miles and needing lots of work.) I've been doing little things as I can afford them. I've replaced the airbox boots and clamps, super cleaned the carbs and replaced the bowl gasket, needle valve and seats and the o-rings on the fuel lines between the carbs. New fuel hose, petcock valve, valve cover gasket, air filter and of course new oil filter and oil (several times. Regreased the rear end and changed the "differential" oil. Just put on new brakes pads both front and back (even though they didn't really need it) and one of the first things I did was new tires and a new battery and spark plugs.

The seat was very clean and though the tank has some rust inside, the rest of the bike is very clean and it came with a 4-into-1 exhaust.

I've had a variety of minor issues that I've managed to solve such as a couple shorts that caused the head light and tail light to randomly turn off. I've cleaned out the carbs several times, each time going a little deeper as I learn more. I spend a tone of time reading on the interwebs to figure stuff out. And every time I get into working on the bike, I learn of a new issue to fix.

I developed a problem not too long ago where the bike would just up and stall, as if starving for fuel. So I decided to completely tear the carbs down and replace anything made of rubber or gasket and even pull the pilot screws (though I didn't replace the o-rings in there as they seemed to be in good shape, may have to do them too.) Anyway I got the carbs cleaned up thoroughly, replaced the airbox boots with new clamps too and spent a couple days trying to tune the bike. I also went through the valves and replaced the shims to make sure the clearance was within spec and in doing that I replaced all the bolt gaskets and the valve cover gasket.

The exhaust smelled off, like it was fuel rich. So I leaned the pilot screws to 2 full turns out from the 2.5. But now my issue is with popping and backfire. Which from reading means too lean. Now the vacuum plugs for the intake boots are old and need to be replaced, so that will probably be part of my next purchase along with new intake boots. One of them has fine cracks in it and when I squeeze it I can get a small amount of old fuel to come out. So it's very possible I have some air leaks around the boots and the vacuum lines.

Now, having read about it, I want to get one of those colortune deals, but they come in different sizes and I'm going to have to figure out what size to get. I think it's the 12mm, but I'll look at the manual and see. Standard XJ650.

Anyway, basically I just wanted to let folks know where I'm at as I will likely come in from time to time and whine about something wrong. I really like the bike and had hoped it would make for a good commuter bike as my truck just uses too much gas. So if I'm wrong in my thinking, just let me know.

Oh, and in this adventure I've had to replace all the exhaust studs with bolts as the nuts were uber rusty. Two of the studs broke off. One of those broke twice and I had to drill it out and chase the threads. Fun fun fun.

Oh yeah, And I had to replace the speedometer.

 

So, questions I have.

Since exhaust is 4 into 1, what jets do I need to replace and what size should I go to? I believe they are all at factory sizes.

What size spark plug is standard so I can get the right Colortune tool?

 

Double-check the current jet sizes to see what you are working with and how much to increase, if needed. 14mm colortune plug.

 

Welcome sirpuma. You'll find a wealth of knowledge on here. I have used it periodically to assist me with my project. Best of luck.

 

There are days when I want to take this old horse out to a remote pasture and lovingly shoot the hell out of it.

I got the valve shims set as close to spec per the book as I can, went through the carbs again. Got the Colortune deal and gave it my best effort to get this thing running right. I adjusted the mixtures till the colortune had the right color then synched the carbs. Ran one good test run. The next day it ran like crap. No power at all at low RPM, missing on 2-4 enough that those exhaust pipes were half the temp of #1. Sounds like a bad lawn mower.

Only thing I can think of is the engine and valves don't like the tighter tolerances. I think I'm going to go through the shims again and put the originals back in place and readjust the carbs. See if I can't get it back to where it was.

 

NO, put the valve clearances IN SPEC. Not "close." There is only one size shim that will put any given clearance IN spec.

Plus ensure your floats are accurately WET-SET to SPEC.

You did your carb tuning in reverse.

Set all the mixture screws at 2.5 ~ 3 turns out, then do your running vacuum sync (with YICS blocked.)

Once it's in sync, THEN do the ColorTuning.

Then you'll probably need to touch up the sync again.

 

I ordered a mess of shims in a kit and went through all the valves and put in shims. All are currently in the spec range, though one or two are on the edge of the range. I could have got them a little better if I had more money to buy shims but no one sells just one or two shims, you have to buy them in batches.

I had went through the carbs and adjusted the floats and then did a sync with the pilot screws at 2.5 turns out but it was popping a LOT so I used the color tune on one cylinder and played with it to see if I could get any color change and didn't see any real change till 4 turns out. I set all of them to that and ran a test ride that was fine. But the next day it ran like crap and wasn't running on all four.

I looked at my plugs and while they didn't look fouled, they were dark. So I cleaned the plugs, turned the pilot screws back to 3 and the bike seemed to run fine again. But after it warmed up it ran like ultra crap again. If I try to slowly rev up the RPMs it sounds like a rough running lawn mower and when they hit 3k the engine suddenly loses all power and dies.

I may just be without a bike for a year before I can afford to take it into a shop and pay someone else to get it running. I just don't have the $600-800 they estimated to get it working.

And what do you mean by "YICS blocked"? I'm not sure how the whole YICS thing works.

 

YICS is essentially a part of the engine that allows the cylinders to equalize pressure between them. That section has to be blocked for proper adjustments as you won't know which cylinder needs to be adjusted.

http://www.xjbikes.com/Forums/viewtopic/t=14757.html

 

Ah, so that's what the YICS tool is for. I was wondering. Anyway to blank that out without the tool?

 

Sure. And XJ4Ever sells individual shims; plus member HogFiddles runs a shim pool.

Being on the edge of spec is fine; there is only one shim that will put any valve in spec. They're either in or they're out; "close" if in, is in, and if not, is out. If they are IN SPEC you couldn't have gotten them any better.

Tight valves is a primary cause of "starts fine cold, won't start warm."

You can do a DIY YICS blockoff using an old t-shirt or other COTTON rag soaked in motor oil and twisted into a rope and pulled into the YICS passage with a hunk of wire. Be sure the rag is 100% cotton, a polyester blend will melt in the passage.

Float levels wet-set to spec?

Quite honestly, from your description, you've still got plugged passages in the carbs or your float levels are off.

 

Yeah, float levels are to spec. That took me a couple days to get right. Had to replace the drain screws.

So the YICS fuel ports aren't isolated but "plugged"? If so then I have a cool solution. I have a brass rod and some vacuum line that I can pull over it that will make for a snug fit through the passage. The rubber hose should hold up to the temps long enough to make some adjustments.

I used a .410 brass cleaning brush and my shotgun cleaning kit with acetone to scrub out the chamber. Man was it nasty.

 

The Yamaha YICS tool isolates the passages from each other; blocking the ports with an oil-soaked rag "rope" effectively accomplishes the same thing. If they're blocked they can't affect each other while tuning.

The vacuum line WILL NOT hold up to the temp inside the YICS passage, and you'll just gave another mess to clean out.

 

Going though everything again, including the valve shims it would just figure that I did something wrong. I made the mistake of going by the Haynes manual. After reading in here and then looking in the left side panel of the bike I see I had all my intake valves out of adjustment and One of my exhaust valves was out. Once I have those replaced, in a week or three, then I'll go back through the adjustment bit. I'll have to figure out a good way to block off the YICS ports though. I'll have to do a temperature test on the vacuum line I have. If that doesn't work out then I'll look at some rope method, though I don't know what I would use.

 

For the "rope method" you use an old COTTON T-shirt (polyester/blends will melt.) Soaked in motor oil and twisted into a tight rope, then pulled into the passage with a hook of coat-hanger wire. Get it twisted real tight so that when it untwists and blocks the passage it's still wound pretty darn tight. "Jersey" (T-shirt material) is perfect for this purpose because it's "springy" to begin with, and cotton won't melt.

 

Ok, so thanks to XJ4ever I have all the right shims and the YICS tool. I made sure all the valves were in the proper spec this time and got the carbs all synched. So far so good. Even sounded good. Unfortunately it wanted to idle at 4500. GHAAAAAAAAA

Ok, so, now I need to figure out why it wants to idle at such a high RPM. Time to start searching the forums.

*note - If I press hard on the throttle circuit rod, idle will drop. If I press hard on the enrichment circuit, idle will drop. But they are both at their lowest point already. I tightened the bolts in the YICS chamber (they were a little loose ) but my RPMs stayed at between 3500-4000 as an idle.

I even turned my mixture screws down to 2 full turns from 2.5 full turns to see if that would help. Nope.

I really need to be able to drive something much cheaper than my truck and I don't have a grand to sink into a $500 bike at a shop. Hell, I've already put about a grand into it all told.

 

So, to recap the carb work.

New parts:
Bowl gasket
Drain plug
Needle valve assy with washer
Boot to airbox
Boot to intake
Airbox boot clamps
Gasket for boot to intake
O-Rings to all the ends of the main fuel line
Vacuum hose
Vacuum caps
Vacuum line/cap clamps
Fuel hose w/clamps

Adjusted floats

Scrubbed several times all other parts including the mixture screws though I didn't replace the o-rings in them (probably should) but don't see that as contributing to high idle.

With everything set for idle, the throttle cable has a tad bit of slack in it.

*note - Well. I dare say I think it might be in the enrichment circuit (partly). Looking carefully at each carb as I pressed on the lever where the cable hooked up cyl 1,2,& 4 plungers didn't move, but 3 did.

I got it down to 2000 but then while sitting here editing this the idle jumped on its own to about 3 grand as the engine got hot. I have a hanging tank with fresh gas in it. I actually shut the fuel valve off and let it run itself out in the bowls. It sure is taking a while.

Anywho, as I pressed on just the plunger for #3 it went in a bit and my idle dropped to about 1200. I should be able to get it down to 900 though.

 

Throttle shaft seals? Common source of an air leak and the result is a high idle. Use the propane method around each individual carb to see if your carbs are sucking air from somewhere they shouldn't be...

Also, check out the forum for "bench sync" of carbs.....may help you with the idle...

 

I'm thinking I can pull the plungers out, clean them (again) and replace the springs. I have lots of spring stock of various sizes and strengths.

I looked at the throttle shaft seals when I had the carbs apart and they seemed fine, though old. They did seem to fit a little lose and one of the plastic washers crumbled. I would like to just replace them but not sure how much I can afford. I'll get with XJ4ever and get quotes for some more parts.

I love riding it, but she's turning into a farging money pit.

 

Well, I went through the fuel enrichment circuit and the mixture screws, again. Cleaned out some stuff. Took a super smooth stone to the plungers to clean their surfaces up and make them smoother. Took a ball stone (adjusted the shape a little) and cleaned up the plunger ports. Did a quick bench synch. Got them on the bike and after a bit of fuel control trouble (using an external feed tank with a ball valve) I got things running. Used the YICS tool and my synch tool and got things adjusted. Managed to get the bike running smooth and idling around 1200-1500. I was able to get the idle, with some playing around to settle around 900, but I discovered where I need some more work.

I need to replace the springs in the plungers, replace one plunger, and replace a plunger lever with set screw. And I'll probably replace the seals on the ends of the throttle shaft too. Just need to save up a little more money.

But for now she's running well enough to ride again. WOOOT! Now I can ride to school on non icy days and save on gas.