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Hello from Oregon!

Discussion in 'XJ Technical Chat' started by StarGeneral, Jul 2, 2020.

  1. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    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
     
  2. StarGeneral

    StarGeneral Active Member

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    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!
     
  3. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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    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
     
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  4. StarGeneral

    StarGeneral Active Member

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    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.
     
  5. StarGeneral

    StarGeneral Active Member

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    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 :eek:. 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.
     
  6. StarGeneral

    StarGeneral Active Member

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    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.
     
  7. StarGeneral

    StarGeneral Active Member

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    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 :D
     
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  8. StarGeneral

    StarGeneral Active Member

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    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.
     
  9. Polock

    Polock Well-Known Member

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    open the gas cap and see if it helps
     
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  10. StarGeneral

    StarGeneral Active Member

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    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.
     
  11. Minimutly

    Minimutly Well-Known Member

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    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.
     
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  12. hogfiddles

    hogfiddles XJ-Wizard, Host-Central NY Carb Clinic Moderator Premium Member

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

    StarGeneral Active Member

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    Anybody want to test out my TCI? :D 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....
     
    Last edited: Aug 2, 2021
  14. Huntchuks

    Huntchuks Active Member

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

    Minimutly Well-Known Member

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    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.
     
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  16. StarGeneral

    StarGeneral Active Member

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    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.
     
  17. Toyobaru866

    Toyobaru866 Active Member

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

    StarGeneral Active Member

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    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 :confused:
     
  19. Toyobaru866

    Toyobaru866 Active Member

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    Interesting...
     
  20. lostboy

    lostboy Well-Known Member

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

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