Resurrecting the 750!

"pilot" jets essentially determine the idle mixture and the "main" jets determine WOT mixture. Jets are the "coarse" adjustment and the mixture screws are the "fine" adjustment.
50% credit for that one, WOT is all on the main jet size on these carbs
overall 80%, could have got 95% but you left out midrange (needle position)
next semester you'll do needle taper and slide cut-away
keep up the good work

 

I'm not going to stop you if you want to go the pods route but if you are not that well versed with carbs, I'd stick with stock until you get some experience on something a little cheaper in terms of parts.

 

Well, I tend to switch between long-term and short-term planning without warning, and given that I'd have to either drop the engine or destroy the air box to get it out, it's likely to stay for the near future.

Also, I have a spare carb rack for the 650, so my plan was to familiarize myself using those, then work on the 750 (since I can't break what doesn't run). Also, the Ninja and CBR not mentioned in my .sig are carbureted, so at the risk of breaking working bikes, I can always pull those off for additional reference material.

I figure that as long as I don't bend, break, shear, twist, or tear anything, the worst I can do is foul plugs and waste gas. Besides, getting the 750 to run AT ALL will be a huge win. Tuning it will be be bonus of this decade!

 

While I'm thinking about testing things (see "CDI" thread), what parts of the electrical system to I actually *need* to get the engine to run?

Will need a good fuse panel with main and ignition fuses intact. Start button, kill switch, starter relay, reg/rect, TCI, coils, plugs, alternator (need to check brushes), starter motor (need to inspect and lube), battery (of course)...

...that's it, right? I may have to hot-wire some things to bypass the missing computer, but that's about it, right? Also don't need various sensors (oil, neutral, clutch, side stand) I don't think, though I'll want to change the oil, put it in neutral, and listen for valves clacking (if the oil pressure doesn't rise)!

Just trying to think of how I can quickly get to just running an ignition test on the engine without spending all summer waiting on guages. If I can get to testing the engine, I can work the engine/carbs and electrical system (and brakes, and suspension) all in parallel. But if the engine is toast, there isn't much point in working on the rest.

 

Not much, but not nothing. Took the TCI from the 750 and put it on the 650. It did, indeed, run kinda rough, but it ran. Took the 650 for a little spin for maybe 30 minutes or so. Nearly got run over twice by idiots in cages.

 

You will need the Main and Ignition and that is it. You don't need lights or anything else. Just make sure the Ignition system (this includes the TCI and voltage regulator) gets the voltage it needs to keep alive and you should be just fine without anything else.

 

Pulled the coils, flasher relay, and cancelling unit from the 750 to test on the 650 tomorrow. About to go peruse the Haynes manual to familiarize myself with the other three relays (one is obviously the starter relay) so I know what they do and can test them on the 650 as well.

Hopefully some real progress on Saturday.

 

Tested the flasher relay and the self-cancelling unit. Also tested the starter cut-out relay. All good. Will test the coils tomorrow.

At least, I *think* I tested the starter cut-out relay. I have come to find out that none of the relays (other than the main starter relay) on the 650 are where they are supposed to be (see other thread), which is making things a little more complicated. I may need to re-run some relay tests.

But for now, it looks like most of the electrical system is a go. I need to remember to run continuity tests on all of the control switches on the clip-ons tomorrow.

Oh yeah. The side stand switch is toast, I think. I'll double-check tomorrow, but if I was testing the right leads, it read 20 Ohms in both positions. I could bypass it, but it should really be fixed at some point.

 

The Relay that controls the Safety Related is a "Special" Relay. It is, in fact, the Safety Relay and NOT configured like a generic power relay.

The Load and Trigger terminals are different from a Power Relay ... so, dont get confused.

Side by side they look like twins.
Power signal in and out ... totally different.

Generic Relay:

+__+
#__#

Safety Relay:

+__#
+__#

If you hook-up a generic Relay where a Safety Relay belongs ... the Safety Circuit becomes a nightmare.

The Bike will not start unless the Shifter is actually in Neutral.
Worse:
The Starter Button will engage the Starter Motor with the Bike IN Gear and the Clutch Lever >> Released!

This is an extremely hazardous condition.
The Bike will lurch forward as the Starter is engaged.

Look at a wiring diagram to see the difference.
This Post is so you know they are diffferent!

 

Sorry, my post wasn't very clear.

The relays are the correct relays and do what they're supposed to do. They're just in the wrong places. Someone has fiddled with the wiring.

For example, the relay mounted below the TCI is supposed to be the side stand relay, right? But if you start the bike and pull that relay, the headlight goes out. This makes sense only because the relay is marked blue. If you then go to where the headlight relay is supposed to be (by the self-cancelling unit), you find an all-black relay (the safety one). Sure enough, if you pull that relay, you have all kinds of problems starting the bike.

The right relays are attached to the right circuits... just mounted in all the wrong places. It's really strange.

I could verify it all completely, except the side stand switch has its leads cut, which makes it more difficult to test the side stand relay (and I have other things to work on yet).

Coil swapping today!

 

Removed the highway pegs. That was tricky, since the lower front engine mount bolts held them on, and the engine dropped about 1/8" when I pulled the bolt on the right side. Took some work to get that back in there.

Removed the right side engine cover. What is supposed to be in there? I found a black seal (looks fine) and a LOT of white powder that looks like corrosion. Only one bolt was *really* stuck, but it came loose with WD-40 and vice grips on the head. Only a few degrees turn with the grips and it came free. Yay! No drilling! I'll replace these bolts anyway...

Tested the coils by putting them on the 650. Turns out that both bikes had the coils on backwards. It doesn't *really* matter, since 1-2-3-4 and 4-3-2-1 ignition is compatible on these bikes, but as a purist, I'll set them up correctly when I swap them back. Coils work like a champ. Kept on firing steadily through 9k RPM.

Tested all of the controls and switches on both handlebars for continuity. All passed. Woo!

Got the remaining fuse connectors replaced and the heat-shrink covering bent so the new fuse panel could be mounted. Looks fantastic! I'll have to get another one of these when the 750 is back in action. The 650 might get envious.

Got a fair amount done today. Need to send some people some money for parts on Monday.

 

Hi There,
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?

 

Do the two Middle ones first. Reach-in the airbox and push-out the Boot and get the two middle carbs done, first.
Greasing the locating channel on the Boot helps to rotate the Boots as they capture the airbox lip and need to be rotated.

Once you have the Middle two done, the outsides are next.
There isn't a lot of room so you have to be ready to put-on the Clamp when the Boot fits over the Carbs.

I make a little "Shoe horn" out of a piece of steel rod. Heat the end and flatten it out to be able to slip the end in between the Boot and the Carb.
You need a short right angle and a flattened-out tip that has been sanded down dull so it wont cut or tear the Rubber Boot.

Wrapping the Boots in a Moist towel and microwaving them for 45-seconds will make them soft and pliable to arrange in the confines of the limited space.

 

Only two things happened with the 750 today... sorta. Got my thread hijacked by a newbie (see above) and found out that my 750 is actually a Maxim, not a Seca.

Ah, well. All knowledge is learning and therefore good. At least I won't be buying parts for the wrong bike!

 

Still a 750 though ... right?

That means you can tune-it into a screamer.
Think of all the fun you'll be having inthe upcoming months.

Dusting a few HOG's off-the-line.
Showing-of your Brake Light to cagers trying to out-gun you.
Not having to spend 50-Bucks to fill-it-up!

Have some fun.
Maxim. Seca.
It's all good!

 

yet

 

Definitely still a 750. 15R means 750 Maxim! This helps explain a lot about why the electrical component diagrams were "all wrong". When I re-check against the right diagrams, I'll bet things match right up!

I need to buy a filter and some oil for it and I think I'm ready for a compression test (though not a running test). Any words of advice before trying it?

It has oil in the crankcase, so it hasn't been completely dry, but that oil has been leaking, and I don't think the engine has actually been turned over since about 2000. My intention is to pull the plugs and spray fogging oil in each of the cylinders and let that sit overnight. Then spray in a little more, remove the timing plate cover, grab hold of that center bolt and turn it counterclockwise a few times to lube the cylinders a bit.

Change the oil, make sure the covers are secure, make sure the starter is secure (it's currently loose), hook up a battery and let 'er rip!

Coils are removed and I don't care about these plugs. I'll connect the tester to each cylinder and let the engine crank until it reads max pressure, then on to the next cylinder. As long as I prep the engine and change the oil (and there isn't anything else horribly wrong with it) it ought to be a proper test, yah?

Wish me luck!

P.S. Rick: "It's all good." You bet it is! The idea of having another running XJ just fires me up!

 

Sounds like you got it all under control.

Rather than Fogging Oil ... I'd use Marvel Mystery Oil.

I'm betting on that bike running.
The Cycle Press said it best in several articles about the legendary XJ Engine.

They actually gave the Engine high praises! They're exact words were:

"Hard to Kill"

 

Finally got back to work on Yamahas today. Removed the fuse box from the 750 so I could put it on the 650, so I'll need to get another of those at some point. (Main fuse on the 750 is a bigger fuse anyway.)

Removed the rear wheel to have a look. The splined hub and inner parts seem to have been sealed well, still greasy, no visible damage. However, the rear axle pinch bolt was so rusty that I want to replace it, and I'll tap out the holes for it just to be sure. Clouds of dust when that was pulled.

When I removed the cover plate for the rear brakes, the brake material on the shoes FELL OUT. Yeah. Those have been sitting for a while. I had intended to replace them on both bikes anyway, so now I have a good reason to learn how!

Pulled the starter moter for examination. I'd like to clean the power terminal - pretty corroded - but the gears are in good shape and it runs fine when power is applied. I was going to take it apart, but since it seems to be fine, I'll leave it as it unless it has problems under load. Remounted.

Pulled the plugs and sprayed some fogging oil in the cylinders. (I should get some Marvel at some point, but I already have the fogging oil.) I decided that since this bike seems to be in decent shape other than the neglect, that I would go ahead and try to turn the engine. Pulled the timing cover and turned the engine over a few times by hand (counter-clockwise). Turns smooth, no grinding or scraping sounds from within. Didn't feel at all like I had to break something loose to make it move. That's a good sign.

It *does* sort of settle into a "notch" at some interval, though. Is that normal, or does that indicate some sort of wear in bearings/shafts/gears? It seems to be about every 2/3 of a turn at the timing plate, though I'm sure the exact amount is different. I know for sure that it isn't exactly every turn or 1/2 turn or 1/x turn at the timing plate, since it doesn't "notch" at the same place on each rotation.

Unless someone warns me differently, based on this post, I think this engine is about ready for a test! Plugs looked pretty black, number 1 and 4 plugs were a little wet, and I still need to at least CLEAN the air box first (no filter yet either), but I can test the compression and see if she'll fire pretty soon! Yay!

 

That hitch in jacking-over the engine is normal. You probably feel the point where all the Cylinders have an open valve.

If its spinning free ... like you say; you might as well see if it's going to go!
It either will ... or, ...
It won't ... or, ...
Try to start but needing Fuel Jets and Passages Cleaned first.

It's fun for me to read these threads about someone bringing a bike back from oblivion.
I know its a time consuming and labor intensive adventure.

But,, it sounds like you got a handle on it and are making good headway.
Keep-up the good work and supplement your Posts with a photo or two so we can see how things look and are shaping up.