Resurrecting the 750!

I've been attempting to reinstall my newly cleaned carbs and so far have gotten 2 of the four air hoses back on. What I did according to one of the members here, worked by pushing the air hoses back into the box in order to remove the carbs out the left side. No Problem. Getting them back in is a real test of patience. Anyone out there have a technique? I managed to pull hoses forward but having a hard time coaxing them over the carbs. Is there some kind of "persuader" tool or will I need to remove battery & air box too? I'm so close to getting them on my 85 XJMAXIMX700, I love this bike! Had it for 6+ years (33K) Anyone? Help?


On my XJ650 there is a bolt on top of the airbox. I loosened the bolt and pushed the airbox as far back as it would go and re-tightened the bolt. This gave me another 3/4 inch to work with. I put the airbox to carb boots in place and then slid the carbs into the boots. Then I loosened the airbox again, left it loose and worried the carbs into the intake boots. Once I got the carbs into the intake boots I used a hammer to press the carbs into the intake boots while pushing the airbox toward the front of the bike. I tightened the little collars and voila! Tight seals all around with minimal effort.

 

They are called boots.
try a little bit of liquid dish soap on the inside lips of them. That's what i did.
Also, i'm sure you were smart enough to mark the boot orientation with a sharpy, both on the carb throat and boot, so you could make sure you lined them up exactly the same to go back on, right?
Reaching in the airbox and pushing from behind helps too, if your hands are small enough to fit.
Even if they pop out of the airbox, it's easier to get them on the carb and clamped, then worry about getting the far end back in the airbox correctly.

 

Picked up the grinder today, but had one blistering monster of a day with the kids and the relatives and the job. We'll see if there's any energy left for grinding on the 750 tomorrow.

Wow. Been a long time since I had time to work on the bikes, and no energy to do it. And it's 60 degrees here!

 

Finally got a chance to take the grinder to the oil filter bolt. Ground the head off and was able to pry off the filter cover.

Turns out that the only thing that was stuck was the head of the bolt, assisted by the very tight seal by that first O-ring. Once the head was ground off, it took a little effort to pry the cover off, and the rest of the bolt spun freely.

Ordered a spin-on filter conversion kit from chacal yesterday. Just waiting for that now and I can button it back up and run my compression test!

Though maybe I should try to get the middle gear drain plug ou...

Just kidding, Rick.

 

Ah, time in the garage again. I had bought a spare battery from a buddy of mine in hopes of using it on the 750. The terminals are reversed, but it makes a perfectly good test battery when used with jumper cables, so stuck that batt on the charger, then got to reassembling the oil filtration system.

Checked that the drain plug was secure, assembled the spin-on oil filter kit, and put just a little oil in her (about a quart) so I could see if the previous leaks it had were resolved and went inside.

Came out later to get some real work done. No leaks, so I filled her up with fresh 10W40. Still no leaks. Looking good.

Replaced the headlight bucket and headlight with one that is all in one piece.

Installed the new instrument cluster.

Pulled the plugs, unplugged the TCI, and hooked up the spare battery. Time for a compression test! Two years in the making! Results:

Cyl 1: 145
Cyl 2: 150
Cyl 3: 150
Cyl 4: 155

I was getting tired, so that last one might be a mis-read. I did have the throttle all the way open and let it crank over 5 or 6 times for each test. Tested each cylinder twice, with pretty consistent results. (I hope I didn't do any damage to the starter motor.) But some searching on this forum suggests that those are some pretty good numbers, so big win there! Glad I sprayed the cylinders with fogging oil a few months ago.

Noted that the guage cluster appears to work, though it's hard to tell for sure until the bike runs.

Then I started running into new challenges. First, I discovered that if you use the right tool - 3/8" drive hex socket set, instead of allen wrenches - you can get a lot further with the pinch bolts on the handlebars. However, even after removing those and the split pin and nut from the underside, I can't pull the clip-ons. What's the trick to getting that center bolt out? Is it supposed to just slip straight out, or does it have to be turned?

Another trick is that I bought a used right mirror, which threads in just fine, but the adjuster nut at the bottom doesn't appear to do anything. That thing IS supposed to move up and down on the mirror's shaft as you turn the nut, isn't it? Maybe I don't know how to mount mirrors.

After a very long and productive day (I didn't include the stuff I did to the 650), I called it quits.

 

FINALLY got the handlebars off. Apparently, banging on the bolts that hang beneath the upper steering clamp doesn't help, since they're not attached. The upper cap bolt is threaded and twists off. *sigh*

And, of course, the hex slot in it is not only far too small for a bolt with a head this big (bad design), but it's nearly rounded out and the sides of the bolt are a bit marred from my vice grips.

Been spending a bit more time on the 650, though, so work on the 750 has been slower than usual. I do have the replacement air filter and filter oil, which will get installed before too long. I really ought to pull apart the carbs before trying to fire the engine, though. They're probably full of gum.

 

Haven't had much time to dink with the 750 for a while, but she's coming up soon. I've put a lot of time and money into the 650 and THAT old girl is ready to go again!

Next for the 750 is to install the new air filter (in my possession), clean the carbs, clean the gas tank, and replace the fuel/vacuum hoses.

Then we'll see if she fires up! If she does, I'll go about restoring the rest of the bike. If not... well, it depends on why not. ;p

 

So I finally got some more time to play with this bike and have a couple of bits of good news.

First, I've mostly disassembled the carbs (aside from breaking apart the rack) and haven't found anything too horrible. They were a bit dirty, of course, but nothing some carb cleaner wouldn't get out. I'm a little worried about the enrichment wells, but a couple shots of compressed air seem to at least get fluid flowing through them. Not sure how (or even if) to clean the little nozzle that feeds the well, though.

Found one pilot fuel jet that was a 50, where the others are all 40s (stock). Also damaged one of the other pilot fuel jets getting them out, so that's two pilot fuel jets I'll have to get, plus four float bowl gaskets (just seems wise), and at least one diaphragm.

One of the 16 bolts that hold on the carb hats sheared off, and I did enough damage trying to drill it out that I think it's in there permanently. I don't think it's bad enough that things won't seal with a new diaphragm, but it's still annoying.

The other bit of good news is that with the carbs off, I put in new plugs, hooked everything up, sprayed a shot of starting fluid into each cylinder, and pushed the Start button.

Started. Right. Up.

For only one or two revolutions, of course. Did this test three times, and it ran perfectly three times. ^_^

It's looking like getting the carbs put back together and cleaning up the gas tank are the only major hurdles to getting this old girl running again!

I'm tempted to leave the rack in one piece, replace the funny fuel jets, and just put it back together and see what happens. The anti-tamper caps on the mixture screws are still in place, so with everything else stock and a decent bench sync, I ought to at least get it to fire up.

...in theory. I'm open to suggestions, though. Do I really need to break the carb rack apart and/or replace float needles and all that, or should I at least try it once as-is before going for the full-bore carb rebuild?

 

Well that's tuff to say.
To replace throttle shaft seals you need to break the rack.
It would suck to have cleaned them sterile only to have to pull them back off to replace the shaft seals.
The enrichment ciurcit hole in the bottom of the bowls should be so clean that carb cleaner shots across the room when sprayed through them.
If not they need to be cleaner.
People have boiled them in lemon juice and used guitar strings to clean them out proper.
Same for the "the little nozzle that feeds the well".

Don't take chances that it "might" be clean enough, Taking them on and off is a real pain in the #ss.

 

Well, against previous advice - mainly due to lack of funds and parts at the time that I had help - a friend of mine and I put the carbs back together without breaking the rack and stuck them on the bike. Amazingly, the bike starts!

Not surprisingly, she runs like crap. I have to keep the throttle open to keep her running and she puts out clouds of white smoke (running far too rich).

The important thing, though, is that she *runs*. I've had this bike for 4+ years now and I've never had the engine running. This... is awesome.

Getting the carb rack on and off the engine isn't too hard. We won't bother getting the airbox attached to the carbs until they're cleaned up a bit more. Need a new main fuel jet, repaired or replaced diaphragm, possibly four new floats, and possibly a gasket kit, plus a washer that we lost putting it all together. Everything else should be carb tuning issues.

And, of course, she'll probably need a valve job. Need to do this on the 650 as well, so it won't hurt to get familiar with this. Brakes need a total overhaul, need new tires and mirrors...

...and holy crap! That's about it! She'll be roadworthy!

(Engine and gear oil changes probably wouldn't hurt...)

 

You mean valve ADJUSTMENT. A "valve job" is something totally different involving pulling the head and refurbishing the valve seats, etc.

You need to do a valve ADJUSTMENT before you can effectively sync the carbs.

 

You are correct. "Valve adjustment" on the 750 and the 650 is indeed what I meant. Big difference.

I do need a "valve job" on a different bike that already has the head (and cylinders) removed. Everything pretty crusty in there.

One of these days, it would be nice to have a bike that is more or less in "everything works" condition. It would also be nice to have several scantily clad servant girls running about my garage fetching things for me. They're probably both about as likely to occur. But I digress...

 

Just for grins, a buddy of mine and I put together the carb rack, complete with perforated diaphragm, missing spacer washer, and oversized pilot fuel jet all on #4. Wasn't all that clean, either, but a lot cleaner than when it came off.

Who knows what things were in the cylinders, including fogging oil, starting fluid, etc., not to mention the WD-40 and carb cleaner that was in the carbs when they were assembled. We put it all together and stuck them on the 750 without the airbox boots attached. Attached the fuel tank from the 650 (halfway decent gas and hoses) and attached a spare battery via jumper cables (safety first!) and...

It started. It ran like crap and made big clouds of white smoke and would die without the throttle held open, but...

It started. Boo ya! This thing will run yet! Took the carbs back off later for a better rebuild. Having rebuilt a couple of other carb racks a couple of times, I can now tell that the needles that attach to the vacuum pistons are badly pitted. (The big shiny needles, not the float needles.) That's in addition to all of the other weirdness with odd jets and whatever.

Also been learning how - and WHY! - to do valve adjustments, so this 750 and the 650 are going to benefit from that. Have the shim bucket holder tool thingy already and a good set of feeler gauges on order. We'll see if we can't get these machines to not just run, but run RIGHT! A buddy of mine loaned me his YICS tool and ColorTune plugs. We'll see if I can figure out how to use those correctly as well.

Who knows? Might have a couple of real runners soon! Only taken, what? Four years?

 

Put some Kenda tires that I got from another project bike (an XS 850 that will get reborn later) onto the 750 yesterday. Mirrors both left and right acquired. Carbs have been cleaned (again), perforated diaphragm replaced, jets made consistent, spacer washer replaced. Also did a valve adjustment, which was made a bit easier by swapping shims back and forth among a number of bikes. Getting the airbox boots back on is going to be fun, but that and the brakes are the last things before it can ride! It has been a long trip.

Then begins the *tuning*. I have an electronic carb sync tool and numerous posts to read through regarding that on here. But at that point, the rebuild of the machine is basically complete.

Regarding the brakes (I may start another thread on this), this Maxim has "normal" two-caliper front brakes (no anti-dive connection) and I feel pretty comfortable working on that system. The drum brakes are another story. Getting the shoes on is not complicated. Lubricating the pivot point is not complicated. Evaluating the health of the drum and getting the rear brake adjusted properly is still black magic to me. Any sage advice from the XJ Wizards?

 

With the brake applied, make sure that the cam lever at the drum is at a right angle (90 degrees) to the linkage for maximum brake shoe force. This gives the most leverage at the point of shoe contact!

 

Ah, excellent! Excellent! Thanks!

 

Rear brakes reassembled and working well (at least, on the center stand). Drum was quite rusted and had to drive the cam out to clean and lube it. But after banging and sanding on stuff for about an hour, we finally got it all set up, cleaned, working, and adjusted.

Connected the front right blinker. Works better that way.

Re-mounted the front calipers and dumped some DOT3 into the master cylinder just to see if we could get any pressure. Nada. Junk comes back into the reservoir when the handle is pumped. Even with a brake bleeder pulling -20 psi at the caliper, can't get fluid to flow. Time to rebuild the MC.

Used the heat gun to warm up the airbox boots and got the airbox re-attached to the carbs. Sloshed some fresh gas around in the tank, drained some of the crap out of the tank and installed an in-line fuel filter for good measure.

Discovered that the battery that I just bought has the terminals reversed. Curses! Stole the battery from another 750 and stuck it in.

Started the engine. Won't idle without the throttle cracked open a bit and has a hard time starting. Carbs haven't been synced well. When it's turning over and "wants" to start with the throttle cracked a bit, carbs 3 and 4 read synced. When I close the throttle, carb 3 is pulling harder than 4. (I just threw the sync tool on 3 and 4 before I had to call it quits on Sunday). Definitely need to to a proper sync.

Caps are still installed over the idle mixture screws. May have to remove those. Though doing that means taking the carbs back off. That'll be fun.

Tachometer reads low and moves very slowly upward as the engine is revved. Headlights/highbeams don't work (though the auxiliary light works). Noticed that the high-beams indicator pulses along with the RPMs. Definitely have some electrical tracing to do here. Some aftermarket lights were installed on this thing at one point, and I think at least one of the safety relays has been bypassed. Stuff to decipher.

Oil seals on the forks are shot. Will have to deal with that at some point.

 

Okay, did some major stuff to the 750 last night.

First, cut away the air box. We're going to get pod filters for this thing. It's just too much work dealing with that thing every time I need to work on the carbs. With some effort, a carb sync tool, and a Colortune, I ought to be able to get things working right. (Valves are already adjusted to within spec.)

So the air box is out. Anybody want a set of used airbox boots?

Rebuilt the brake master cylinder after cleaning out a ton of gunk. Used a brass brush for a 12 guage to clean out the bore, and the smallest circular file I have for cleaning welding torches pokes through the tiny port. (The smooth end fits, but not the serrated body, so I don't have to worry about widening or damaging the port.

I'm not totally happy with how clean the reservoir is, but the old seals were shot and the piston covered in gunk. The rebuild kit made the MC work like a champ.

However, the calipers are still a mess. One of them has a stuck brake pad retaining bolt. Still in the process of drilling that one out to the point that the extracter will grab properly. After a brief attempt to use the existing brake system to expel the piston in the other one, we just cut the old brake hoses and disassembled everything. Had to use the brass brush for a 9mm pistol to clean the distribution block, but that's clear now and have brand new stainless lines from chacal. Once we get that retaining bolt out, we'll put it all back together and get those pistons out.

The muddy, murky, slimy stuff that spilled out of a calipers when we took it all down was just... scary. If the current plan to push the pistons out doesn't work, I may just spray brake cleaner in there until the seals dissolve and the pistons fall out.

Also found that we have some electrical gremlins from somewhere. When you turn the key, the high beams light is always on, regardless of the switch position. When we started the engine last, the high beams light would pulse at a rate propotional to the RPMs, and the tach was... wrong. It would rise with the RPMs, but it's almost as though it was more of a voltmeter than a tach. It never indicated more than 2k, though I had it revved far higher than that.

Finally getting somewhere with the old girl, though.

 

i would love to have them

 

PM me your address and I'll mail them to you.