1981 Yamaha XJ650 Maxim Valve clearance/ carb issues

something like this...

http://www.youtube.com/watch?v=2PiQBr20kM8

I like this design. the large volume of air in the bottles dampens the intake pulses that make a normal tube style manometer jump.

CN

 

Hahaha I know what you mean MiCarl, if the compression sucks it's not worth spending time on anything else . So now on to the carb synch? Sorry polock I meant to put up the link that cyclenoob did: www.youtube.com/watch?v=2PiQBr20kM8 I guess I wasn't paying attention haha. so I synch the first and second carb, then sync the third and fourth carb then the second and third? and the only problems is I CAN NOT get my bike to idle at 1000 +-50 I don't know if that has to do with the carb synch. maybe they're so far out of adjustment that it won't even idle? I don't know.. also I did have to remove the pilot screws so the mixtured it off for sure, I've thought about getting a color tune. how would you guys suggest I proceed?

 

Double check your bench sync, if you can do it re check your float level, and double check all the jets have made it back to the correct places. Double check that your pilot screws are all set to 2 3\4 out and that the washers and springs are stacked in the right order, make sure your idle adjust screw is adjusted to about half way out before you bench sysnc ( if you don't realize something out of order the spell doesn't work). Check that you have a good steady fuel flow. Check that your plug boots are all solidly connected and that each individual plug is gapped and making a good spark. Double check your carb boots aren't folded over and once you are idling at all check for leaks again with some propane. If all that's in order you should be able to set the idle anywhere you want as soon as it warms up as long as your carbs are clean and the enrichment circuit is clear.

 

The only thing that I haven't done in your list is to check the float levels, I don't know if my idle screw was halfway out or not when I did the bench sync... I'll double check that. I know I probably have an intake leak where the boots on the carbs meet with the airbox, but I have no idea how to fix that.. they seem to have shrunk a little, just enough for them to not seat properly.

 

If all your carbs are not having the same amount of resistance to pulling in air they are going to try to run differently from each other. You should ask Fitz how big a difference it will make but I think that while you will be able to get a smooth idle you will never be able to get them synced or balanced properly and its going to throw off your air fuel mix every time the joint is flexed changing the amount of the leak. If you can't afford or don't want to wait for new boots, you can make some new ones from flexible rubber plumbing joints. They are about $1.50 each, on my bike the end that mates to the airbox just has a retaining ring that has been carved into it to seal. A little time with a sharp knife to carve one of the same size into the plumbing connectors and changeo presto new flexible and sturdy boots. That won't leak and that has a nice wide brand new clamp to seal to the carbs thrown in for free

 

I was thinking about something like that.. I also thought that maybe I could cut the old boots in half and use a piece of rubber tubing to connect them again. that way I get the seal at the airbox and the carburetor and just have a piece of tube in the middle.

 

Its hillbilly, ugly, cheap, and will work. I like it. A lot of rtv or liquid electrical tape and maybe a sleeve made from a inner tube just for extra peace of mind and overlap on the seal. Yup cheap and workable. How do you come up with this in Utah where you can't get a beer to drink while you stare at the bike and think?

 

Or was it Oregon that wouldn't sell me beer and said I had to go to Utah?

 

go ahead and put some kind of sync tool on it if you have a reliable or not.
you have to start somewhere, turn the mixture screws 2 3/4 out, use the sync tool to get it closer than it is now, you might surprise yourself.

 

It was Utah that wouldn't sell you the beer, though that isn't the case anymore. The Microbrew revolution began in Califiornia and Oregon.

 

Haha well I have no idea why you wouldn't be able to get a beer in Utah! But I'm still pretty young so I can drink legally. And I don't think I ever really will haha that's just me though. I'll try putting a sync tool on it and see what kinds of results I get with it. Then I'll decide about modifying the boots. I have to say though I'm pretty sure those leaks are all pretty even across all the carbs. The boots all have the same problem. Still though I'll probably end up modifying them . Question though, how would you guys suggest I measure the float height accurately. I know they say you shouldn't measure them on your bike because they're a little slanted. how did you guys do it? Also could this be the reason my bike won't start even with the choke on all the way? I am almost 100% sure that the enrichment circuit is CLEAN! I cleaned the crap out of it haha. Thanks for the help!

 

First the important part. It was sometime in the mid maybe early nineties I think when I was working my way around the country that I was told no beer for a thirsty man.

To set your float levels you really need a rack. Whether it is just bolting them to a board and setting that in a vice, buying a $600 specialty rack, or just plumbing some pvc together to make a support.

I used pvc so I could shim and get everything perfectly level every time I touched and knocked it out of true, it also let me add an arm to hold my tank and have the carbs at shoulder hight for me so I could work on them without having to bend over.

The really important thing is that you have the carbs level on both axis everytime you are measuring them. Not just eye level, actually level.

This actually took me longer than cleaning them and checking my valve clearances together. But I used a rebuild kit with slightly longer float needles so I had to reset each one and I insisted that they be exactly what was called for no + or -.

there are a lot of guides on here on how to do it but its simple. All you are doing is measuring the amount of gas inside the float bowl by running a line from the drain spigot up next to the carb body. leave the gas flowing and the spigot open and the gas outside will fill the line to the same level as whats in the bowl. Just measure how far above or below it is and make MINUTE adjustments to the tang on your float. then repeat and repeat.

 

http://www.xj4ever.com/setting%20fuel%20levels.pdf

Pull the carbs take your time and do it right.

 

Ok, I'll be taking the carbs off again and trying to get those floats right. I just found another youtube video for a manometer and it looks like it would be quite a bit easier to make and cheaper as well what do you guys think? http://www.youtube.com/watch?v=nEE508WzNC8

 

That should work, though if you do it like that you will be only able to do two at a time. Adding two t joints and two more uprights will let you get all four at once.

 

So I finally had time today to set the float heights! I went and bought some PVC and made a stand like it shows on the XJ4ever website. all the levels were actually pretty low, so I bent the tangs so the level was closer to the top of the bowl. Tomorrow if I have time I'm going to start trying to sync my carbs, wish me luck!!

 

Good luck. I had a stuck float on mine that I noticed today, had to rebuild my stand, reset where I had bent one float tang out of spec. And clean everything all over again since I went through the trouble of pulling them again anyway.

Syncing them really isn't hard at all once you have them benched well enough to start.
It will take you about fifteen minutes once you have the tank off and your manometer hooked up. Then off you go enjoying the ride.

 

Make sure the bike is warmed up before the sync. Like completely warm. You'll probably need to go for a little ride to get it really warmed up.

 

Wow kcleft those compression values are really low. Mine are #4 is 150 psi and the rest are 145. Test with a MAC Tools tester. As for the lean condition the carbs are junk, YICS, too much ethanol in the gas.

 

Altlandf, this is the second post of yours I have run across tonight saying how bad these carbs and the bikes in general are. For someone who is really down on them you spend a lot of time following and posting on an enthusiast's forum.

 

did you do your compression test after you had ridden the bike? I'm not sure about the carbs yet, I know they are completely out of adjustment, so I can't say they are crap. and my motor isn't a YICS, it's a Pre-YICS also from what I understand 120psi is the sign of a decent engine, I was getting within 15psi cold, I think after it's warmed up I could be seeing over 120.

 

Your compression numbers are good. Even a 70-80 on a cold test means the engine is viable. Might need rings or a valve job but its one that would work. Yours is definitely good.

 

So last night while I had the carbs off I decided to take a look at the enrichment circuit, and I realized that I had never cleaned the passages in the bowl! I removed all the float bowls and put pressurized carb cleaner in to the passages and cleared up at least 2 of them! hopefully that will help when trying to start it cold haha. Anyways today I had time to take a look at the boots that connect the carbs to the airbox and decided to cut them in half and I used radiator hose that was just a little bit smaller than the middle of the boots so they would fit snugly. I didn't use RTV because I wanted to make sure it worked. Anyways that eliminates the intake leak! I got the carbs on and modified boots on, and reconnected everything to get it ready to start. Gave it a quick spray of starter fluid (habit, sorry..) and she started right up! what's even better is that the revs jumped to about 2.5 and dropped a little to about 2k and they were steady revs, no jumping around at all haha. I turned the idle screw down and easily reached 1k and she didn't sound bad at all! the idle was extremely smooth and she easily revved then dropped right down to 1k as soon as I let off the throttle. IT WAS AMAZING!!!! I seems like modifying those boots was the right thing to do. no more hanging idle baby!

After letting it idle for a little bit I took it for a little ride and once again there was absolutely no hesitation at all. no problem with the idle no nothing. Even after she was warmed up I didn't notice any problems. I built the manometer and hooked it up the 2 carbs at a time. I did 1 & 2 then 3 & 4 then 2 & 3. they were all extremely close and only required very minor adjustments now they all have roughly the same vacuum now!

I'm not kidding when I say this bike is completely different now compared to when I had first bought it. it's like a brand new bike really . Anyways I just wanted to say thank you to everyone who helped me get her running so amazingly! So THANK YOU!!!!!!

 

Sounds like you are good to go then. Just a quick question so I don't look back through this thread. Have you gone over your brake system and at least flushed your fluid? And if you have a drum brake replaced the shoes? Otherwise run it hard and enjoy it.

 

Um, no, and no... lol who ever tried to open the master cylinder before I did did a fantastic job at striping the screws.. that will most likely be my next project. I need to take a closer look at my front pads, but is looks like they might be worn down. as for the back brakes I haven't really checked them out yet. I do hear a wonderful squeal from them though, so they most likely need to be changed too. Looks like I'm in for another fun time!

 

Nah all that is easy.

 

Just did a quick check on eBay and found a couple of new master cylinders and a few rebuilds for less than $40.

 

really? sweet! haha that makes life a little easier haha. I still might try to get it open though, I don't give up that easily good to know there's a relatively cheap alternative though just in case!

 

a steady hand and a sharp drill bit can take the heads of the screws and leave enough to grab with pliers

 

Polock, couldnhe dismount it and use an impact driver without damaging it? I am at work soi I can't look to see if you could properly support it at the right places to avoid damage.

 

I used an extractor set on one of mine, and the reverse drill bit got them out without ever having to use the extractor bit.

And plan on rebuilding any master cylinder you buy off eBay unless it's brand new. Anything over 4 years old will need to be rebuilt; and don't trust the seller who claims to have already done it.

 

that brake fluid stuff gets soft with heat, maybe a soldering gun on the screw head might work

 

Drill the screw heads.

Don't worry about the remnants.

There's enough stock to drill new holes and tap them.

All you need to do is drill the Caps screw holes to match the oversize fasteners.
The Diaphragm Gasket holes need to be enlarged too.
Use a single-hole paper punch.

Stainless Cap Screws will add a custom look.

 

Ok, I'll take a look at the screws today to see if there's any way to get them out without drilling them all the way out. An extractor may do the trick for me. I'll let you know how it goes! Thanks again guys!

 

Alright guys, so I'm still working on getting everything I need for the brakes. However today I took her for a small ride (about 7 or 8 miles) at the beginning of the ride it was running great! I had to make a few adjustments with the idle screw and choke, but everything was working good. about 7 miles into the ride after it had properly warmed up, it started hesitating like it was out of gas... I would start it and turn the choke up to see if it wasn't getting the right amount of fuel and with the choke all the way on it would rev to 6k or so. I dropped the choke so it was on just a little (around 2k) and I started driving it. After I had let the clutch all the way out she hesitated and died. no matter how I messed with the throttle she would die. I ended up pushing her home (luckily it was only 2 blocks.. but that was still more than I wanted to haha). I've got the mixture screws out about.. 3 1/2 turns. and that's where I've been keeping them until I can get a color tune plug. Sorry for bugging you guys so much, but I really want her running soon!!! thanks!

 

Normally you set the idle after it is warmed up. If I set mine so that it idles at a thousand as soon as I can turn off the choke by the time I have gone 20 minutes down the road and it is actually at temp it will be trying to idle at 4000 at a stop. To start on this I would begin by checking for air leaks where you patched your boots, then throttle motion, the easiest first. Then clutch adjustment. Then the more difficult. Double check you didn't swap your jets around. I can't remember did you check your valve clearances? If its not the fuel mix then I would be worried about your valves. Try backing your mixture screws in to 2 3\4 - 3, 3 1\2 sounds like it should be a little rich, I believe factory is at 2 1\2 and is a little lean. Check your plugs for color. Since it sounds like a lean issue it is probably to much air but lack of throttle response is odd. Your sure you were in first and not stuck in second or third and not able to downshift when it was dying when you were trying to take off? That would be your clutch adjustment. Let us know.

 

An easy thing you can try - turn your Pilot screws all the way in, lightly seated, then re-set to where your bike ran good.

Crud can move around in carbs and partly block the Pilot Needle. Fresh gas and engine vibes dislodge and move sediments.

You could remove the Pilots and spray a shot of carb cleaner, but you need to keep track of the "O" rings and washers.

You also need to finish your tune-up, with a ColorTune, or plug reading, and all the Pilots will be set to it's own level, number of turns.

 

kc,

As you know our bikes are not FI. The use of the enrichment circuit (choke)is the equivalent of using starter fluid. Ambient temperature determines how long your bike will need the choke to warm the engine (around 3mins max at temps below 32*F). Full choke should only be necessary to START your bike when it's stone cold. Once she fires you should be able to go to half choke. As your bike warms you should start closing the choke to bring the idle down until it is able to idle at spec without the aid of the choke. The first block or so of your ride should be in 2d to allow your bike to pick up the fuel supply off idle, burn condensation, and reach full operating temperature. If you are using the choke after 7 miles of riding something is not right. Remember, your bike is not charging the battery at idle and you will need to do plug chops and or use a colortune plug to get a more accurate read on those spark plugs. Hot plugs burn remaining fuel left in the chambers and will give you false readings should you try to read them after a ride. Hope this helps.

Roc

 

It might help to point out that the "choke" ISN'T; it's just an enriching circuit and it has no "blocking" effect on the intake tract the way a "real" choke does.

 

I agree ^.

 

Sorry for the late reply guys, but thank you for all the input! I think I figured it out. I had the screws set out way too far I moved them to about 3ish turns out and now she runs beautifully, I also had bad low end power when I was running rich, but not anymore! I got a new battery because the one I had on it before was dead. Now she starts with the push of a button. she might actually start if I have the enrichment circuit closed and give it just a little bit of throttle. I'll try it tomorrow. I should make note that I tested my battery when it was running at 3000rpm and I was getting about 14.11v I know that it should be 14.5v +- .3. so I might be having some problems with my alternator, but it's technically charging the battery... any thing to worry about there? Also I'm still working on doing the front brakes, but I got the rear pads and I want to switch them out since they're probably the original pads (they're worn all the way down and I hear squeaking when I push them). I was reading the manual and it says I need to remove the rear wheel which is all good and all, I just wasn't sure if i needed to drain the oil from where the drive shaft connects to the wheel. and if I do do i put 80w-90 back in it? also if there's a forum on how to change the rear brakes, could one of you guys send me a link to it? Thanks a ton!!!

 

You don't have to change the final drive to do the bakes but you should anyway. 80 gear oil from auto zone is what you want. There is a link somewhere but its pretty easy to do. Remove your license plate if it hangs off the fender. I forgot and creased it badly. Remove cotter pin and break free crown but on axle. Up on the center stand. Detach sway bar from right side. Detach the brake actuator lever, put the but back on to hold the spring in. Loosen the clamp on the axle and put a screwdriver through the hole there. Remove the crown but, the screwdriver is there to keep the axle from spinning with the but. Work the axle out through the right side, be gentle, use the screwdriver to pull, spin, gently pry. Put the bike in neutral and spin the rear tire and kick the bottom of the tire a few times and the wheel will work itself free. Work the wheel out, the shoe side of your brakes will slide out if the hub. Ckean with brake cleaner not air. Replace the shoes. Check your bearings and splines and replace your grease while its off. Reassemble and gently work your wheel back into place. Lift it up and slide back into the final drive, a bit of rotation makes mating every thing up easier. Slide the axle back through and get your spacers into place and loosely tighten your but. While you can rotate the hub reattach your actuator rod with the nut just barely on. Re attach the swing arm and put in a new cotter pin. Tighten your crown but, I keep the wheelk spinning to make sure every thing is mated and smooth as I tighten it down. Torque is 94lbs . new cotter pin. Tighten up the action on your brakes make sure they are not rubbing and you have a bit of play but not a lot of slop. Spin the wheel again and listen for anything rubbing and to make sure everything is is in true. Try it again. With the motor running working it up into fith with the throttle closed just to check for wobble under higher speeds, throw it in neutral and check your brakes out by how quick they kill the rotation. Put your license plate on and go for a genkte ride around the neighborhood and work them out adjust as needed and make sure your drum isn't heating from drag when your not applying the brakes. Remove the screwdriver you have been driving around with stuck through your axle.

 

Spelling mangeled by spell check. But was nut. Had to type that three times to get it to stop changing it for one sentence.

 

Alright! swapped out the rear brakes and got the new ones on! Not sure if the old ones were the original.. but that doesn't matter now haha. So I've got another question about fuel mixture again.. I didn't really think about it at the time, but it's recommended that you start the mixture screws out at 2 1/2 to 3 turns out, but that's with the stock exhaust.. the current exhaust on there is a lot more free flowing than stock, and usually with a more free flowing exhaust the mixture tends to be leaner right? if that's the case should I put my screws at 3 1/4 turns out? it has a hard time idling, even if I adjust my idle screw. it will idle at 1500rpm without any problems, but if I try to drop it any further, it will still run for a few seconds, but eventually if I don't give it any gas, it will die. I know when I was running it rich it would Idle at 1k just fine, that's what makes me think it needs to be a little richer.. what do you guys think?

 

I'll assume (without reading back through 10 pages of posts) that somewhere along the line, you got your valves in spec.

The next step, before trying to do any real mixture tuning, is a running vacuum sync; THEN start tweaking the idle mixtures.

 

You might want to go look through some of the modification threads to see what problems and solutions people have had with the lowered back pressure. I would check your plugs for your mixture reading though. Its been pretty cold here, with my idle set right for when its at temp it will not idle properly without the choke and occasionally bumping the throttle when it is first started. Every thing is in sync and properly adjusted, after five minutes of riding to the gas staion and its perfect.

 

I did do the valves and I've also done the vacuum sync. I think I'm where I need to be for the mixture now. I'll check my plugs, I've been riding around for a little while, so it should show me how it's running hopefully! I have to bump it a little bit with the choke all the way off after 2-3 minutes idling with the choke on followed by a 5-10 minute ride. if it's running lean the plugs should be white right? and if it's rich it will show them nearly black, so somewhere in between is what they should look like right?

 

So the very ends or my plugs (on the arm that goes over it) are extremely white.. around the base where it screws in it is relatively sooty.. I think that's a lean mixture.. not entirely sure though. I might try to clean them up a little bit, then take it on another good ride and double check them.

 

You want t look at the ceramic portion of your plug for color. Medium toast or light chocolate is good. Your right about lighter being leaner and darker richer.