XJ650 Starting issues

Well that's the thing, I was tightening it by hand on one of them with the hex, until it was snug, but it was still leaking, and I remember tightening it more until I started hearing a slight creaking, and then I stopped. It was still leaking (slightly). As this was happening the fuel in the tube was lowering (because it was coming out of the drain screw, cause I had turned off the aux tank at this point, which shouldn't have mattered because there's still fluid in the line and gravity should refill it.)

I went back to using the brass screws and I did this enough times to feel comfortable that I didn't drastically overtighten the drain screws, it was just seemingly a function of physics? Or something. It doesn't happen unless there is gas on a hose attached to the nipple causing some sort of static pressure

 

With these dissimilar metals (stainless doesn't like alloy castings or aluminum), I'd put either grease or anti-seize on the threads to prevent fuel from wicking out the threads. Of course, those lubricated threads now need less torque, so use the usual caution against overtightening....

 

That's what I was thinking, but I was worried about getting anti-seize into the fuel and clogging the carbs

Also no local location sells nickel anti-seize, it's all copper. I'd have to yet again send Len money

 

I erroneuosly said to leave the drain screws open, of they should be closed. Are you sure gas is coming out through the threads of the screws and not from the tube nipples and migrating along the bottom of the bowls to the drains? Your setup has static hoses attached and not easy to manipulate. If closing a drain screw raises the level in a tube, you just need to lower the tubing so that more fuel will flow into it and level off at the same level as inside the bowl. I do one bowl at a time with one, longer piece of tubing which I hand hold vertically. I can lower it to check the level as more fuel is entering the bowl. Just never raise it because the fuel in the tube will not be accurate.

 

Why not?

 

This is the setup that I had to do in order to get the carburetors level. I had bought a k&l carb rack on eBay but I had so many problems with it. I just clamped it, but then I had to stick wooden shims under it in order to make it level because the thing that the carb would attach to didn't actually fit even though it said that it would. And also didn't have any instructions that came with it.

It's not stupid if it works

I also attached what the carbs look like attached back on the bike

 

Trying to make sure that I don't over tighten this, what is the torque spec of this?

I set it to 2 lb, that seems like enough.

The most frustrating thing about all of this is when the shim doesn't perfectly go into the bucket, and you have to like make sure to lube it up and to stick like a hard feeler gauge in there and try to make sure it's as level as possible

 

Doesn’t need to be a whole lot. Just enough to hold the bucket down. About 1/4~1/2 of an ugga-dugga

 

Being inside of the engine always makes me really worried. Anyways, I've replaced three of the shims on the left side that needed replacing and now I just have to do all of the ones on the right side

Annnnnnd of course the intake 2 shim is off by .01mm, which means the spec was .11 not .1.

I'll have to put the shim back because technically that one was within clearance

 

Alright, I finally finished with the valve clearance and adjustment, here are the results:

Left to right:

E
.2 .2 .16 .16

I
.11 .11 .14 .13

I think it would probably be good to check these clearances again in like say, 500 miles, since intake 1&2 and exhaust 3&4 are right on the wire of being in-spec, and then rotate back to a 5000 mile valve check. Only really because I don't have any frame of reference to how long these valve shims last for! (Yes, I understand it's not the shim's fault, it's the valve's fault for seating further into the head, but you know what I mean)

Once I replaced the shim, I would rotate the engine and then check the measurement again, to make sure the shim I put in actually ended up being okay. I forgot today was voting day, so I went and did that and headed over to the bike. I thought this would take 2 hours, since I only had to replace 6 more shims. Instead it took four. Part of what took so long was once I replaced Intake #2 shim, I realized my measurement was slightly off, and by going down 5 it actually put me out of spec. (in effect, I only needed to replace 6 shims, not 7 of 8). I noted this and left the wrong size shim in there while I moved onto the others, and would put the original shim back in later. (I thought I had measured .10mm, but it was .11mm, so when I went down a shim size now the gap was .16mm not .15mm. Oops.)

The other wrinkle was when I went to put some of these shims in, looking at you exhaust #3, it would just bounce around on top of the bucket and I spent a bunch of time fudging with the damn shim trying to get it to fit back into the bucket. Since I had cleaned up a little bit of the oil that was collected in the top there, it was a little dry, and when I had measured this the first time around to know what shims to buy, I didn't really oil the shims after wiping them off with a rag to look and see what I was working with. When I installed the new ones however, I made sure to let them soak for a few minutes in some T4 Rotella oil before installing. Most of these were fine but some of these were a right pain in the ass. I also had some assembly lube on hand which was rather handy to just put like an 1/8 of a teaspoon on the bucket and tried to see if that would help, along with a minuscule (less than a cap) of oil to try and help with the install. I got it eventually but some of these would not want to seat easily and I struggled with that for a while.

Then, when I measured intake #4, which had a 305 shim in there, and all I could get in was a .03mm feeler before, I decided to go down to a 295 shim. Measured .03mm with the feeler gauge, so to get it in spec, you must add .1mm right? WRONG
Intake #4 had negative clearance. I didn't need to go down .10mm, I needed to go down .15mm to put myself in spec. uh oh. Three shim sizes from a 305 to a 290? WTF

Thankfully, the shim I had planned to install into intake #2 instead would work for intake #4.

Again, after every time I installed one, I went back and double checked, mixing feeler gauges to make sure. Was I sure this was .16mm? Could it be .17mm? What about .15mm?

So, of course, this took forever. People are like, yeah stick a screwdriver in there and pop it up, I tried that and I struggled with that. What worked was using my ex's air compressor, though. Blast some air at the notch and unseat that stubborn wafer. This worked pretty easily, except for when it blew back oil into my face and hair, thankfully I was wearing my glasses but ugh.

So with the adjustments installed and double checked, I took out the hi-tack (god this stuff STINKS) and a crappy little brush and tried to get it in the valve cover crevasses, though it loves to leave little streamers everywhere, and then installed the gasket. I didn't think I needed it, because previously the gasket was doing a decent job being held in by tension, but I bought it, may as well try it out.

I then got the black sealant gasket and tried to put a little bit on the half moon circles, but of course the tube had other ideas and it all came out in a blurp. I wiped as much as I could off the rubber with a towel and finger and just gave it a decent coating on the half-moons, not "i really love cream cheese and want a half inch on my bagel" amount of gasket, but a reasonable amount of "coat the toast with butter" amount of gasket.

I then put the valve cover on. I had got new rubber grommets installed on the valve cover screws, and put the center ones in first, tightening them by hand until they were...snug? (imagine me shrugging my shoulders) because there wasn't enough height between the valve cover and the frame to get my torque wrench in there with the hex head.

I did tighten all the 8 outside screws which I could get to, to about 60 inch pounds, which based on trying to gently turn them with the hex key, are probably tighter than the center screws, to be fair. I heard "no more than 7.2 ft pounds" so I made sure I went under because, with doing all this, my smartwatch thought I was going jogging, when I certainly wasn't.

Anyways, valve clearance is done

 

Also, one of my friends locally 3D printed me the STL files from the forum, to block off the petcock and the sending unit and the gas cap cover.

And I just got in my paint and stencils, for the new tank. I'm really excited. I probably won't have time to do anything with the xj750 tank this week, it might be next week or the week after.

 

I would recommend trying to get all of the cover bolts (inners and outers) to the same tightness, as much as is possible even w/o a torque wrench, otherwise.....as uneven force on the cover is how valvecover warpage occurs over time.....and you really don't want that.

If you have a scale (i.e. a bathroom scale or the like) you can "calibrate" your hand pressure by trying to mimic the "feel" of the pressure you're exerting. So go tighten the (or "feel" how much pressure your hand is feeling) on the outer bolts, and try to duplicate that amount of pressure by pushing down on a scale. Then try to imitate that feeling-of-pressure on the other bolts. Without using a torque wrench, that's about the closest you can come to "accuracy".

Of course, if you have a bolt that is known (via use of torque wrench) to be a 7.2 ft-lbs, then you can do the whole scale-feelie-thingy at a known torque, and you can duplicate that on a scale and maybe it ends up being around 10 lbs of downward force on a scale (which you now know = about 7.2 ft-lbs on a fastener).....recall that "foot-pounds" is how much pressure is being applied on/at the center of a fastener when you are applying "x" amount of force (downwards or sideways, doesn't matter) at a point exactly 1-foot (12 inches) away from the center of the fastener.............hence "amount of force applied 12" away from the fastener = FOOT POUNDS.

So if you apply the same amount of force (let's say 10 pounds of force) at only a distance of 6" away from the fastener (using a short wrench), you're only applying 5 foot-pounds or torque (since you're applying the 10 pounds of force at a distance of only half-a-foot away (6") from the fastener....10 x 1/2 = 5 ft-lbs.

And always remember....the use of anti-seize on threads reduces the amount of torque that a fastener should be torqued to.....unless the service manual already specifies that a fastener should have anti-seize applied to it (in which case the specified torque value in the manual is correct). On any fastener where anti-seize is not specifically specified, the use of anti-seize will reduce the torque needed by up to 10-15% in steel, or up to 25% in aluminum or other "soft" metals.

 

I'm not going to be back over there until Friday, but I can tighten the center four bolts down then a bit more.

They certainly could be tightened more, but, reading that it's really easy to crack the head, that leads me to not tightening it as much as I would initially be keen on doing.

 

"Less is more" when it comes to valvecover bolts........

 

One thing that really irritated me about the valve shim tool was the fact that I'd have it seemingly perfectly aligned, and I'd tighten it down (even to 2 ft lbs) and as I'd rotate the engine to raise the bucket, the pressure of the bucket would push against the tool, causing it to shift slightly away from the engine.

My fix? as the bucket would start to apply pressure to the tool, I would put downward pressure on the tool and hold it in place, and just holding my hand against it with decent pressure would be enough to keep it from shifting. Made me wish that there was another bolt or something in there instead of 1. Also, this would make it awkward because you'd almost have to have 3 hands as you're leaning over the bike.

also things that made my heart rate skyrocket, I would rotate the engine (sparks in) CCW towards the front, and it would go from being very easy to turn, to needing some tension. I would go very slowly, flipping the wrench I got from len (since it was thicker on one side than the other, so it would change how much distance your rotation would travel) while making absolutely sure to not touch the pick ups on the ignition timing plate. This would be the case in CW and CCW, but especially slow with CW (reverse) motion. The engine being easy to turn at certain points in the rotation and harder certainly made me nervous, if only because I just assume that's normal but my anxiety goes "yeah but what if it isn't and what if you, even though you've spent hours of research reading and watching videos and reading manuals, even though you think you've been excruciatingly careful, what if you broke something?"

Couple this in with not having a good working space, and tools are just kind of...everywhere, trying to have a system, and then going like "where the **** did I put that, I was just holding it!!" only to find it is literally right in front of me

Anyways, compression test on friday afternoon, if the engine does the compression test and doesn't make any expensive noises then I know I didn't. I don't think I did, I certainly feel like I was careful, but there's that little voice...

 

Lol yes. To everything you said.
Sounds like it's going well!

 

Cross your fingers for me or something cause all I need to do is:
1. put battery back and screw airbox back in and such
2. do compression test. if it doesn't make expensive sounds, continue on
3. hook up aux tank and hook up carb tune pro, and hope and pray I don't make things worse somehow, because setting these butterfly valves to be close was a fiddly pain in the ass
4. turn bike on and pray it doesn't explode (more likely that it just won't turn on and I will need to use starting fluid or something)
5. once bike is tuned, then change the oil. IDK if the last tech did so and i want to be SURE. I know what I did to this bike, and I'm making myself a "service history" excel sheet where I cover what I did, on what date, and what mileage it was at when I did it.
6. replace the front inner fork tube, I have an extra oil seal on hand in case I need to replace it, but I really think the steps are just going to be; take the fork off, take cap off, take spring and spacers out, drain fluid out of container, unscrew bottom hex bolt, pull inner fork tube out, put brand new fork tube in (god it looks so damn nice), and reverse order of install.

after that she should be good to go...barring any other new things happen...as working on an old bike is wont to be.

My next project for this bike?

With how hot the summers have been, I think I have two priorities:
1. install bigger 750 maxim tank I bought so I don't have to refuel as quickly, and strip the existing paint and clean out it's insides, and get ready to paint it glittery pink. I got stencils to go, and a vision and everything!
2. install an oil cooler, the Maxims deserve it, and I want this bike to last as long as possible.

 

I got a friend to 3D print these for me!

 

You can use carb cleaner in the YICS port right?

I got a wire brush from harbor freight that I'm going to use, and then I suppose I'll try to wipe down the port with a rag after, and then use that little pokey tool that I got from Len.

 

I bottomed out all the idle screws (I think) by gently tightening them until they stopped. I'll look up what I back them out to before syncing. 2.5?

I used a stainless wire brush to scrub the yics port, but it wasn't that dirty. I used the pokey tool and nothing seemed to be blocked.

I re-ran compression tests on #1 & #4, they went from 131.3 to 152.7 and 128 to 140.3 respectively. 16.3% increase and 9.61%! #4 was less than anticipated but that, so far puts it within psi range... barely.

Now I'm waiting for the battery to charge up a little bit before I re-test 2&3

 

All right, I did the compression tests on 2&3, 3 went up slightly, and I think 2 stayed the same, which would make sense because I didn't end up changing any shims on 2.

We plugged in the aux tank, and I waited for it to stop filling the float bowls, and it seemed good, it stopped emptying. So we went to try to turn the bike on, and it sounded like it was running on one cylinder. My ex said that exhaust #1 was hot, though I didn't measure it.

We kept trying and eventually it sounded like it was running on two cylinders, and I used a temperature gun to confirm that #3 & #4, exhaust headers were like 50° warmer than #1 & #2.

The idle screws were all set to 2 and 1/2 turns out, but the tachometer was saying it was idling around 3,000. I don't think I had tightened the idle speed screw at all.

Am I missing something?

 

On the drive back home I had a few thoughts, I have brand new ignition coils from len, I'm pretty sure I have the left one going to 1&4 and right to 2&3, but I'll double check I didn't make the coils 1&2 and 3&4 tomorrow after work.

Then I'll dial down (tighten) the idle screws half a turn, then make sure the idle speed screw isn't engaged and try again. If it still isn't working great, I'll pull the carbs, and re-check the fuel levels, I think maybe 1-3 might be a smidge too low, and maybe that has something to do with it, because I think #4 was perfect, it was maybe 2mm from the bottom of the carb body, which is supposedly good, and 1-3 was about 4mm, which still should be fine.

I didn't get the chance to touch the sync screws today, but I'm pretty sure I had bench synced adequately

Past that, I'm not sure what it can be. I can try to put the old ignition coils back?

As an aside, I noticed the enrichment cable kept coming loose, at the handle, I'd put it back and make sure the enrichment wasn't engaged.

 

Sync and cv carbs ouch.
You have bench synced which is a good starting point.
Next you need to sync across the cylinders if compression is different between them.
Blocking the Yics helps when doing that.
Good times. Not so much if it can't idle mind you.

Not sure that the float levels have much to do with the idle circuit, except for flooding that is.

Not helpful but you'll get there!

 

1. I have bench sync'd. I am 98% certain the bench sync is correct. I used 30gauge guitar wire and it was golden, I opened them to full throttle, and eyeballed the levels of the butterfly valves when open and they looked visually the same at full throttle, and when everything was released, all the butterfly valves were open at the bottom a fraction, enough for a little bit to shine through with the speed screw not touching the backplate thing of the throttle plate.
2. I already did compression and they are all within 12 psi of each other, which the catalog says they need to be within 14psi of each other. Cylinder 1 is now the highest at 152 and Cylinder 4 is the lowest at 140. These tests were cold tests.
3. I already did a valve adjustment, and I am 99%-100% sure that every shim is now within spec, as I spent a lot of time on it, and double and triple checked, and the fact that compression went up substantially on the cylinders that were affected.
4. it was running (though poorly at warm idle intersections, running seemingly great at mid-high range) before all this, so I am not convinced it is currently an engine issue.
5. I did set fuel levels, but I am 100% certain that the fuel levels were not set too high. All measurements of fluid did not go above the bottom of the carb body. I have not had the time to pull the sparks to see what they look like. I did clean the dry soot that was on them before doing all this (rich or uncombusted), so I can check when I get out of work this afternoon.
6. Completely pulled apart carbs, cleaned all carbs in ultrasonic w/ dawn dish soap, replaced all rubber components, and shone light through every hole I could find, but didn't technically spray carb cleaner through every hole (didn't have carb cleaner yet). Verified that each carb was not missing shims, seals, etc. Made sure that enrichment circuit was clear visually, all springs were replaced with brand new ones, new washer, new orings, in the correct order. Triple checked that air mixture screws were in correct location, the piston clunk test worked, diaphragms seemed pliable and good. No scoring on needle, or extra holes, or extra shims (y-10). fuel jets were #40 & #112 (previous owner settings), swapped out with #41 and brand new #112, which should be fine since these were jetted lean at factory, and this has a 4-1 exhaust (previous owner)
7. before reinstalling carbs, I pulled all intake boots, and they were pretty pliable and not cracked, that I could tell. I also shone a bright light into the intake manifolds and did not see a single crack anywhere, but they were hard as a rock.

Based on all this, here's what I think could be the issue:
1. Ignition coils could be set up wrong? The new ones from @chacal looked good, visually, and according to the information I have, it doesn't matter which of the wires is hooked up to which cylinder, they are interchangeable, as long as one of the coils goes to 1&4 and the other goes to 2&3. I suppose it's possible that I have the left one plugged into the right and vice versa, but I am not sure!
2. Fuel levels on 1-3 which were known to be slightly lower than 4, could be the issue. First time we started and it fired on one cylinder, I was told that only cylinder #1 header was hot. Second time we started it up, now #3 and #4 were running, which may make sense if the bike wasn't level (it's on the center stand, but no idea if it's actually perfectly level horizontally) and the fluid was filling up #4, then "filled up" and since the fuel was "full" in bowl #4, its neighbor got more fuel, and then started.
3. it's certainly possible that carbs 1&2 are clogged via the process of ultrasonic, but keep in mind, the bike was running before, just poorly (My guess was less because of the carbs, but because the valve clearance and thus subsequent compression on two cylinders was bad.) But I'm less inclined to think that if it was running on one cylinder on cylinder 1, that 1&2 are clogged, otherwise it wouldn't have run at all on cylinder 1.

I'm leaning more towards ignition coils, and wet fuel levels need to be increased slightly on 1-3. If it's not that, then I am unsure what to check next. I certainly can break the rack and take all the rubber components out of carbs 1&2 and blast the heck out of every hole with carb cleaner, but I am not convinced that's needed. Today should have been syncing the carbs, not fiddling with float levels and chasing ignition issues...especially since the bike has an appointment with a pro so I can get a sticker, and tomorrow is the day it needs to be over at the shop, so I am running out of time.

if you have any other suggestions halp! If I can't figure it out by sunday afternoon I will have to throw in the towel and just tow it to the shop, which I really didn't want to have to do...

 

Ouch.
But yes.
If the leads aren't right then no joy.
Check spark on each plug after.
Check if the plugs are wet after being sure.

2 things make it fire. Fuel and spark.

Before you bench synced the rack could have been a lot different.
One open more than another to compensate.

Use the enrichment circuit to see if it's lack of fuel to start with. It will soot the plugs up because it's super rich but you'll get an idea.

You need more time to fiddle. Not good doing this on a time limit.

 

I did fully open enrichment to get it to start, and I'm fairly certain I had bottomed out each idle screw, then backed it out 2.5 turns. I did not touch the sync screws at all yet from bench sync.

First thing I will check around 430pm EST is the ignition coils, swapping cables and making sure the coils are 1&4 and 2&3, and not on the wrong side.

I'll also look at spark plugs.

If problem persists, I'll pull carbs and recheck fuel levels and test.

Unfortunately I can only work on this on the weekends.

 

I agree no sense questioning anything until a running sync is done

 

Enrichment makes it run on all four. (This is key to the rest of what I say)

Then you can exclude electrical.

Bowl must have fuel so that is good.

Idle is complex and the ideal. But...

If you increase the throttle do the rest start firing.

If so... Then you can start wrestling with the idle screws first as the throttle will be lifting the needles and using the main jet.

Dial the screw out on one that isn't firing until it fires. Colourtune plug works well at this point.

Keep going.

I wouldn't give my bike to a technician unless they worked in a Yamaha dealership today or were motorcycle mechanics in the 80s. Otherwise they are in the same predicament as you are. Floppy discs to USB drives/streaming issue.

 

These guys tend to work on cafe racer conversion projects, specialize in japanese and european bikes only, and when I brought up the YICS (yiks) port he seemed to take on a bitter tone as he said "Oh we're very familiar with the yikes port". They're the only folks who work on vintage yamahas in the area. One of their projects was a "1981 Yamaha XS650H", and seem to primarily work on late 70's and 80's motorcycles.

Unfortunately, I have a deadline, and needed to bring it to a shop before a bike show that is extremely important to me.

You're saying I should do a sync anyways, given the previous information? It would seem like unless I double check the parts I mentioned, syncing would be a waste of time to start with. I would struggle with syncing only to find it was because something was off. I certainly can do a sync anyways, it just seems backwards.

Right, so when I started this, the enrichment was fully engaged, and all the plungers were raised on the carb rack (the enrichment cable is being a bit weird, falling out of the handlebar section, but it is engaged on the carb side, and I'm able to push the enrichment back down, after popping the cable back into the handlebar slot.)

The bowl very very likely has fuel, I can test this afternoon, but I am more worried that the fuel level needs to be raised a smidge.

I can also check the oil for smells of gas, just in case it's overflowing to the crank case, but I can't imagine it is flooding when I'm 100% sure I set the fuel levels to lower than the bottom of the carb body.

all screws 2.5 turns out (pretty sure, I was tightening the idle screws with 2 fingers very gently until it stopped rotating, making sure not to overtighten). It sounds like you're suggesting I unscrew the idle screws more?

the RPM at default was holding at around 3000 rpms already (on #3 & #4), though I didn't have the chance to check the idle speed screw. I believe I already had it fully backed out before this, but I'm not sure.

 

It's a funky problem.
That's why the bench sync is ideal.

If you have one cylinder with more compression or more fuel then it will drag the engine speed up naturally.

Inversely if you have 3 perfectly tuned and synced carbs and one off that single carb will throw everything out of whack.

Sounds like you have everything to spec. And this ought to make it run fine/roughly at least without fine tuning.

It's a hard one. The basics are fuel/air and spark.
Full tuning is after that for the main jet.

Again, not very helpful but I have no magic answer as you are the one at the forge.

 

Ignition coil on the left is going into 1&4
Ignition coil on the right is going into 2&3

That looks right.

 

This is what would be 3.5mm from quote the manual "below from the carburetor mixing chamber body edge"

 

I tried, again, to check the fuel levels with a hose, and opening the drain screw.

While they are on the bike, and the bike is level, horizontally, I marked off on the hose where this should be.

It did not reach the level I had measured with the carbs off the bike. Again, while the hose was connected to the drain nipple, even if I fully closed the drain screw, fluid would leak out of the drain screw.

Once I removed the drain hose from the nipple, the leaking stopped.

So, I'm leaning towards that the float levels are too low, and I was too conservative about the levels.

So now I have to make a choice of what I want to do.

 

I was so sure that these thick gloves would act as an interim gasket, but they're still really slow leak of the vinegar water. I think I needed to wrap some Teflon tape around the threads of the screws, because I'm thinking that the leak is coming from the screws themselves.

Or maybe I can just put some Teflon tape over the hole directly?

 

You don't want to use teflon tape with gasoline, it will breakdown into a gooey mess (at first) and then dissolve.

For fittings exposed to gasoline, you need Gasoila E-Seal, east to find and somewhat inexpensive on eBay, Amazon, etc. Smells horrible and toxic though......

 

The only thing that I'm doing right now is trying to get the rust out of this "new" tank