Hello from Oregon!

Update: Petcock wasn't the issue. I tried the OEM petcock but it was leaking even after I gave it some TLC so I threw the aftermarket one back on. Seems like idle speed wasn't adjusted right, or got slightly out of adjustment. Need to check carb sync to see where I'm at as I feel the idle is set a bit too high. Bike will idle alright around 1300 rpm with choke off once it warms off, but any lower than that and it starts to sound sad. It kinda sounds like it's not running on all cylinders but hard to tell - might have to try the temp gun trick on the headers.

Bike was running better sans-air-filter, and now is running decent with the air filter properly cleaned out and oiled up.

Still need to figure out why it dies in gear but I suspect an issue with the sidestand relay. I'm going to try pulling it and see where that gets me initially.

The brake system still isn't performing as well as I'd like so I see pulling the MC to re-hone the piston bore in my near future.

 

I took her on her first ride today!!! Just a short around the block a few times, etc. Got up to third gear and the longer I rode it the better it started running.

The issue with the spongy brake was the MC not being bench bled when I installed it. I adjusted the lever all the way out for free play and started pumping the brake handle like mad. Gradually, the engagement started to move further and further to the beginning of the lever travel. I kept a close eye on the brake fluid level and kept adjusting the cable until I had a firm handle.

The clutch issue was due to a seemingly bad side stand relay. I pulled the relay and was able to shift the bike into gear, ride around, etc.

I know this is the beginning of the ownership road but today was a huge milestone.

 

I've been out riding a time or two since uploading that last video, and unfortunately my brakes have sprung a leak (several, actually). Despite using new crush washers on my banjo bolts (and tightening them to spec), I had a leak from one of the banjo bolts on the right side, as well as leaks from both brake caliper bleeder screws around the threads (not the nipple). I've tried tightening all, but in general the caliper bleed screws are surely tighter than 7 ft/lbs and are still leaking from around the threads. I've heard that the thread is not the sealing surface, but the seat of the needle, and so it's possible I could either have some corrosion in my seat or a possible the bleeder screw tips themselves(?). Anyway, I'm going to have to pull those bleeders and see what's up, which likely means bleeding the system alllllll over again. *sigh

 

Tear. It would appear that my document have erased every one of the pics. In any case, I'll transfer a video gathering when it's assembled back. A couple of ends of the week to go at this point..... Presently not running the guard grille simply because I hit a thick tree limb that annihilated Safety Vest the grille and broke the guard and I just eliminated it and never tried supplanting it.

 

Uhh, welcome to my thread! Hahaha.

Today I got my brakes wrapped up. I still had leaks after bleeding and suprise surpise, it was the stupid bleeder plugs on the anti-dive units again. The left side one was the offender this time. I took it out and inspected the seat - didn't look good, and no matter how tight I tightened it up with the allen wrench, it wasn't sealing at all. Since I didn't really see a solution to this, but knew the metal of the bleeder plug is harder than the body itself...i only saw 1 way out - had to risk it for the biscuit....

Cleaned it out with some carb cleaner and a rag tip (didn't have q-tips), put my allen-head socket on my ratchet and cranked that sucker down until it more or less cut a new seat. Firm handle now, and no leaks on either side. I figured 50/50 of success. I would NOT recommend going this route to anyone else I just didn't know any other way of fixing the seat for the bleed screw inside since it was already marred....and I had already rebuilt my anti-dive unit on that side anyway so I was kinda all-in on the existing units...

Motorcycle shop says 5 day turnaround for mounting new tires. That's way too slow for me, so I'm learning to do it myself. Zip tie method seems to be the way to go as I don't have tire irons of my own.

 

StarGeneral I see your in Oregon! What part. I'm up in the Portland Area. Be awesome to see your bike and swap bike stories. Rebuilt mine from the ground up. Still working out the kinks on my carburetor though.

 

Hey man! I'm down in Springfield/Eugene area. Let me know if you're ever in the area maybe we can grab a beer. I'm pretty new to motorcycle stuff but also basically rebuilt my bike from the ground up, so that's about the only story I have to tell at the moment

 

Latest update: I got the front tire off the front wheel and OH MY GOD someone went crazy with the Slime. I'm so glad I decided to change that tire because 1) it was definitley older than the rear tire (which still has the tits but is 7 years old now), and 2) it was PACKED with Slime. I spent a large portion of the day removing the front tire and cleaning all that crap off the rim. I then noticed how beat up and scratched the rim is. It probably had problems sealing so they filled it with Slime LOL.

I wet-sanded the inside of the rim with 220, 600, and 1000 grit sandpaper till I got most of the rough spots out, but I suspect it's still going to need some bead sealer with the new tire. I decided to just have a shop mount the new tires because I don't want to go through the trouble of balancing them, and I'd like to have them balanced if I'm putting new tires on.

So here's the FUN part about my tire change. I ordered what I should have ordered, but what should fit, doesn't.
Keen-eyed observers may have spotted a mismatched rear wheel on my bike from prior photos/videos, and you are correct. It's not an XJ750 wheel....so what is it??? The 120/90-18 that the SECA calls for on the rear was way too slim and tall for this rear wheel.

Well...she may be more of a Franken-bike than I thought. This rear wheel is in fact from an 85 or newer XJ700. I have no idea of the usual interchange between these rims, but it takes a 130/90-16 size tire. Quite a bit shorter and fatter than the standard XJ750 tire. Maybe they swapped the final drive gear at some point to make it mate up??? IDK, all I know is it fits and they'd been riding with that wheel for about a decade before the bike came into my hands, so I've got a 130/90-16 tire on the way

 

Bikes gots fresh D404s on the front and rear. Front brake system finally leak-free. The anti-dive bleeder plugs (not bleeder screws) ended up being the biggest contributor to the brake system leaks. I really had to crank those in to get them to stop leaking. Handle is firm now after a re-bleed and keeping the handle tied down.

Unfortunately, one or more of the disc rotors appears to be warped as I'm getting some pretty big pulsing in braking at high speeds (50+mph). I have two used rotors on the way that are thicker than my current ones, so hoping to get those installed before my next ride.

Thinking about installing some crash bars soon as I dropped the bike (somewhat gently) trying to get it up on the center stand the other day when I was pretty tired.

My valve cover is leaking on the front left side...which really sucks because I used a fresh gasket, fresh donuts, not too much torque, etc. From what I can see, the gasket squished slightly out of place when I tightened it down right in the corner. I'll have to see if I can re-clean everything and try sealing it again.

Start clutch is iffy. If the bike gets real hot it tends to skip a lot, which is a problem when the bike doesn't want to idle super well after it warms up. I have to run my hot idle around 1500 to prevent it from stalling when I let out the clutch slowly.

I also have a performance issue where the bike will suddenly start to run on 3 cylinders (seemingly) after it warms up which really sucks.

Oh well, I'm enjoying myself so far. Just waiting for this heat wave to pass so I can spend more time in the garage

 

Cyl cutting out when hot—-
1. I don’t see where you actually do a valve clearance adjustment..... only where it is on your “to do” list and not marked as ‘completed’.

2. TCI can be starting to fail

dfox

 

Fair point! It was on my To-do list but after discussing with PO, he assured me it had been done very recently...however due to the fact that my valve cover is leaking anyway, now would be a good time to go back and check all of those anyway.
Hopefully it is not the TCI, but I'll stick with eliminating the easy stuff first. Thanks for your input!

 

So if it was done recently, he should have had a record of what’s in there now.
If no record, you should automatically assume it’s never been done. That way, YOU do it..... and you establish YOUR baseline. Even if it had been done, you have no way of knowing for sure—— unless every single valve is in-spec, I guess

 

You're right, and after finding all of the neglect while I was rebuilding the bike, I ought to know better by now... my desire to get on the bike got the better of me so I'm not surprised I'm running into issues. This weekend's project is going to be to take care of several of these things at once. I have to re-seal the valve cover anyway and get some new carb boots put on, so I can tackle all of those things at once. The starter clutch will have to wait till Winter probably as I don't plan on splitting the cases or doing any valve lapping this Summer.

 

Got the shims read yesterday and started cleaning up the valve cover gasket to prep for the re-install. 1 of the exhaust valves was well out of spec and THREE of the intake valves were way out of spec, with one reading <.038 . Boy am I glad I checked them!

I decided to tear into a few things while I'm waiting for the shims. My brake master cylinder STILL will not let the plunger return easily to the beginning of its travel and has had plenty of time to "break-in", so I pulled it off the bike to see what the hell is going on inside there.

Installed some other (thicker) used rotors because mine were warped (confirmed on a pane of glass as well).
Got the old carb intake boots off and prepping to put the new ones on.

Throttle cable was questionable so I'm replacing that (plastic bits near the metal tube up by the handlebars were destroyed).
Got some replacement relays coming so I have spares on hard for most everything (right now I needed a sidestand relay and possibly switch as well).

Next weekend hoping to have the engine buttoned up again, with the carb rack and new boots installed. I doubt I'll be able to ride as I still have to tangle with my master cylinder. From what I could see the pressure-relief hole behind the reservoir is not blocked, but its such a tiny hole its impossible to tell. I ran the body of the MC through the ultrasonic hot cycle with simple green like 4 times before the rebuild, but sprayed some brake cleaner through there for good measure.

 

Got the MC off this weekend and inspected. Luckily no damage to the seals inside or anything which was good news. I put it in the vice and started honing it out as I noticed it tends to catch on the last 1/4 end of travel within the piston - at that position I saw some wear marks and other small scratches so I think the seal was getting caught up on those. Honed it out progressively with 600, then 1000 and 1200 grit sandpaper till it was shiny smooth (mainly focusing on the problem area. After about three honings I got to the point where the piston returns rather quickly after being depressed. Some of the "tension" was also coming from my brake cable itself, so I re-lubed the cable as well as the armature attached to the MC only to find that my brake cable had three frayed wires up near the handlebar where it passes through the adjustment knurl. It was rubbing there and making it hard for the piston to push the handle forward. I have a replacement cable on the way.

Also got the replacement throttle cable installed (my old one had a plastic tube but this one is made of steel) and lubed.

This weekend I also started installing my new NGK caps and wires onto my new EMGO CB750 coils. I found one of my stock coils had a big crack in the bottom I somehow missed when I inspected them the first time. Will mount those up next weekend.

Need a few more shims and some other parts so a few things will need to wait till next weekend.

 

Valve shims complete as of yesterday, along with new brake cable and throttle cable installation. Got the new carb boots installed and carb rack installed into them (dang, the new ones were tight!).

Today need to put the airbox boots back onto the carbs, cut some new fuel line for a 90 degree fuel filter I purchased, and put some female spade terminals on the coil connectors. Once we get that set back up, just gotta put the air filter back in and go for a ride

 

Update: bike is still cutting out. On my last outing I rode at 55+ for around 15 miles before I ran into any issues. Running with the petcock on PRI makes no difference if the issue starts to occur.

The issue seems to crop up once the ambient temperature exceeds about 75 degrees. I haven't ridden in the morning enough to confirm this, but I can't think of too many other logical explanations that would explain the bike riding perfectly for 15 miles before I ran into issues...

Once the ambient temp reaches about that high I start running into issues. The "bog" or "stutter" starts once the bike starts to approach 5k rpm. If I back off a bit and keep the throttle only cracked as much as needed, I can get away with it for a bit, but if I try to power through it ( If I need to start going faster than 50mph) then the bike starts to run progressively worse at lower and lower RPM. If I downshift to first without cracking the throttle, the bike will idle itself down to death quickly and stall. If I goose the throttle while it is bogging down I can feel the bum cylinder cut in and out occasionally and I will get a small surge of power.

Once it dies, if I pop on the enricher to about halfway-engaged and let the bike sit for about 1-2 minutes, I can get it going again. Usually Impossible to re-start without the enricher on. I can also adjust the idle screw up a tad to raise the base idle and accomplish the same thing (but it's easier to use the enricher).

I have yet to take these carbs to church, and I'm certain there is a throttle shaft seal leak....however...would that alone cause this strange combination of symptoms? A leak is a leak, and I doubt that it would suddenly make a HUGE difference 15 miles down the road, rather than all the time. That's the part I can't wrap my head around.

Either way, I acknowledge I don't want to be running lean for long periods of time, and church is inevitable now that I've discovered the throttle shaft seal leak on the right side (outermost seal). So I plan on doing that anyway.

 

open the gas cap and see if it helps

 

I'll give that a shot tomorrow - I did take my gas cap apart and checked the vent "ball", cleaned that port out with some carb cleaner, cleaned the ball...didn't look too bad though.

 

Seal leak, whatever - this is not what is causing your bike to die on you. Don't let it sideline your thinking.
Sounds like fuel starvation to me still.

 

The carbs still need to go to church, but it also sounds like the classic TCI symptoms, too

 

Anybody want to test out my TCI? I have hobbyist soldering experience and all the gear... (I've soldered on laptop motherboards before), so I might be able to repair mine... but I'd like to test it before I desolder the pins to check out the other side of the board....the side behind the cover doesn't have any obvious damage or scorched traces.

As far as what Minimutly said, I supposed its possible there could be a fuel starvation issue somehow still. These are the things I've done to check for that:

1. Running an aftermarket vacuum petcock. Tried running on PRI when issue occurs - doesn't seem to make a difference.
2. New fuel line and clips (of proper length and inner diameter. No sections of the line run higher than the petcock.
3. Partially disassembled the gas cap and cleaned the vent ball, and shot through the vent hole with carb cleaner several times.

Anything else I can think to do related to fuel delivery? (besides running with the gas cap open) I don't have any leaking bowls or fuel rail o rings...
The reason I'm not running my factory petcock is because it leaks when set to ON. I suppose if we suspected that the aftermarket petcock somehow wasn't allowing enough fuel to pass through the line, I could pop my OEM one back on, and run a cut-off switch just past it to shut the fuel supply off once the bike has been turned off....

 

Your best bet with petcocks is to rebuild the original and use it.

 

Hmm, tci, maybe. Fuel starvation, still likely I think. Have you managed to crack open the carb drain screws -preferably one of the outside ones? If you have, next time it happens get the drain open and see what comes out. It doesn't eliminate gunged up carbs, or one of the ones you haven't drained, so not a perfect test.

 

I have not yet, I did remove the float bowls and put those through the ultrasonic several times as they had some nasty gunk stuck onto the bottom. That was a while back. I'll see if I can get a screwdriver on the outside ones.

 

If this would be the problem then why would it run good for the first 15 miles.

 

No idea, but take a look at https://xjbikes.com/forums/posts/659447/. Guy had the same symptoms as I did and swapped to an OEM style petcock - problem gone

 

Interesting...

 

Do you have an in line fuel filter? If yes is paper or brass ?

 

I do, it is the recommended sintered brass style. every bit of the fuel line including the filter section runs below the petcock as well (I use the 90-degree style cone filters).

 

Well it's not the filter then. It was worth a shot.

 

Maybe it's a much too simple thought but can't you rule out the petcock and fuel line just by doing a flow test? So measure the amount of fuel that flows every minute. You would say that 1 liter every 3 minutes would be enough? If you want to I can measure the flow of my OEM petcock.

 

The flow could affect fuel starvation issues. When you start out the bowls are full. As you ride, the floats go down and fuel flows in but if the inflow rate is just a tad slow, eventually you would end up with a level that is too low. If you have cool looking colored semi-transparent fuel lines, which have thin walls, it is conceivable that a sharp bend could restrict the flow also. Just ideas and possibilities.

 

Tank was off so did a little test. The OEM petcock with 20 inch fuel line hanging down takes about 40 seconds to pass 1 liter of fuel.

 

More than enough, I would say. Check for sharp bends in the fuel lines next. Other than that, it's something else.

 

Once I get out to the garage this weekend I'll try the drip test with my cheap-o petcock and with the OEM one that I have coming. We'll see how they stack up.

 

Update:

Tried to flow test with the existing aftermarket petcock. On PRI it took over 4 minutes to fill most of a 1 liter bottle, nowhere close to 40 seconds.

In comparing with the OEM-style petcock (Taiyo-Giken) on PRI, that still took about 2-3 minutes to fill a 1 liter bottle.

The old petcock had some rubber bits in it, a much smaller fuel outlet port, and was not working properly in the RES position, so I suspect that it was pretty much trashed anyway, however the issue is still present with the new petcock.

At this point I suspect the TCI, an issue with the Fuel cap not venting (will need to try the drip test with the gas cap open), or contaminants in the tank somehow clogging the screen on the petcock.

I did try running the bike with the fuel cap open, made no difference, so maybe not an issue with the vent.

 

40 seconds for 1 liter of flow sounds incredible. That's a LOT of fuel thru a 1/4" ID hose that is operating at atmospheric pressure.

But, even 2-3 minutes for a flow of 1 liter should be just fine. These engines can't possibly use that much fuel, even at WOT and full load.

If running with the gas cap open still results in the issue, then you are correct, the cap is not the problem.

 

Well it does, mine is an almost new OEM petcock.

 

New (old) TCI came today along with a lot of all the relays and switches that go to my XJ (figured it can't hurt to have spares anyway). Another reason I picked this one is because it seems to have some "legitimate" work done to it. See the photos below. I've never seen this type of sticker on one of these. I also noted that the mounting plate screws on the back have been sharpied over so it is obvious if someone has tampered with the unit...The sticker says "Return Void if removed 1333"

 

Who had money on the TCI being the issue?

Just came back from about two hours of riding. The TCI was the issue. I'm not having any of the misfire/bog or stalling when hot / not starting when hot issues anymore. Runs great! Still be taking the carbs to church this Winter though.

 

Wow, that's good news!

 

Well then I think hogfiddles wins the grand prize!

 

@StarGeneral if the big problem with the carbs is one or two of the outer throttle shaft seals, then those can be replaced with the rack on the bike. Might be a band-aid to get you through until you break and build the whole rack.

Just an idea.

 

That's actually a good point. yes only the outer right one was...questionable! Maybe I'll replace it with the rack on the bike like ya said. Thanks for the idea! Hadn't thought of that.

 

Latest update: after replacing the faulty TCI my friend and I went on a repeat of our earlier ride. We rode for about 3 hours and the bike did not miss a beat! We started about 7:30 and I rode out to meet him. Got to see the sun cresting and coming up over the mountains which was awesome...minimal traffic out in the country that time of day.

After I got home, due to the bugs being out I decided to give the bike a wash. I'm aware that you should only rinse with the necessary amount of water and so I did so using what I perceived was the least amount of water needed to get the job done. After hand-drying I started her up and let her idle for a while to dry things out, turned it off, and parked the bike inside so I could begin the process of syncing the carbs (no, I hadn't had an opportunity to sync till today lol) and then do some colortuning with my new Colortune plug (thanks Len!).

Anyhow, prior to this I decided to hot-shot the carbs with some seafoam. I drained the bowls (after freeing the drain screws for the first time with some penetrating oil), and then filled them back up with seafoam. Let that soak in for about an hour, then started the bike and let it idle for a second or two, shut her down and walked away.

When I came back, the bike was INCREDIBLY difficult to start. I tried and tried to start her up but no amount of fiddling with choke would do it. Eventually had to pull the plugs and crank it over because A) I drained the battery and B) figured by this time I had flooded the engine out with gas. Plugs were wet as expected, cranked over and let her dry out a while.

On the second attempt I got the bike to fire up, however it was idling horribly low and if I tried to crack the throttle past 2k rpm the tach needle would jump and the bike would bog something horrible (sounded like the butterflies were fluttering). No matter what I did the bike would not idle well - I couldn't understand it. Not my first rodeo with Seafoam.

I figured oh well, I'll let it idle where it's happy and see if it burns something off that's stuck in the bowls or other...but no dice. About 4 minutes later I crack the throttle and the bike just cuts out. Power's not out as the display and lights are on. I turn the key off, restart and it idles for about 10 seconds, then dies...At this point I'm thinking oh shit did I fry my new TCI somehow?

At this point I start inspecting the Rectifier/TCI area and notice some water still seeping out. I cut the power and pull the cover of my TCI - nope no water in there (though I did get a good look at the minty board repair that someone else had done! Looked like a professional job for sure). But some was coming out of the area where the rectifier sits. Started it up again and kept bike revved at around 2k rpm. Within 10 seconds bike flat out dies, so at this point I'm like "OK...that's defo not carbs...probably something electrical for sure". Pulled the plug off the rectifier and am seeing the Red wire terminal slot looking slightly melty, not burnt yet but not normal. Also now noticing that the battery is on the charger...it looks like it's bulging a bit and I can see the top edge of the casing is not flush with the body of the battery - could it have been overcharged somehow?

Keep in mind this is not the original rectifier, this is one I swapped onto the bike from my parts bin when I was trying to troubleshoot the TCI.

I start the bike again and wiggle wires near the Rectifier - yes it cuts out. I try again, this time wiggling the wires isn't making a difference, so I give the rectifier a little tap with my wrench and the bike cuts out on queue lol.

Fast forward to today - I swapped in my original Rectifier - all these issues completely gone. Battery didn't boil down and seems to be holding a charge so I'm throwing it back on the bike and will closely monitor for now.

Got my Carb sync done today (my first one ever) and was able to get her dialed in. Got the YICS chamber cleaned out to shiny-clean level, picked the YICS holes clean and made sure they were carbon-free, then installed the YICS tool with some motor oil.

After sync, the bike now idles smooth right about 1100 RPM which it has NEVER done - I've been running it around 1500 RPM to "mask" the bogging issues I'd have off-idle till now. Pre-sync readings showed quite a bit of variance between the cylinders, so no huge surprise it's idling better now.

Tomorrow I'll be doing the Colortune and Re-sync

 

Good job young man!

 

Figured I'd share the video I put together of the restoration footage I shot.

 

UPDATE: Great job young man!