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Runaway throttle...

Discussion in 'XJ Technical Chat' started by cascott, May 29, 2017.

  1. cascott

    cascott New Member

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    Hello All,
    First thanks so much for all the wonderful information I have read in these posts over the years. I have been lurking all this time, so this is my first post with a problem. I have a 1982 XJ650J Maxim. Sat in my garage for a couple of years.. (uh..1998?) ... I started in 2013 with what I thought was a straight forward carb rebuild, and of course put the jets in wrong per Haynes.. found this website.... and gee.. here we are 2017 and just finishing... I have followed the church of clean, (cleaned, rebuilt, and replaced all the parts inside the carbs that I was supposed to, ( yes... that is an old O ring on the throttle shaft outside of carb one, inside seals are new.. I missed that one.) and rebuilt some other parts (petcock assembly, oil filter swap out, adjusted the tappets..er...valve clearances, exhaust gaskets, ? other odds and ends )... Now I would really like to actually ride this summer, so I am finally getting it back together.

    Did that a month ago, starts, runs up floods out and dies. Let it rest, does the same thing. Thought originally I had not set floats right, so off they came, and set them right this time.. took my time.. . Back on the bike, same thing again. Now thinking I have manifold leak. ( I will take other suggestions to check).

    Cyl-4-Manifold-intake-05292017-smaller.jpg This is intake manifold four, which does look a little cracked around the manifold gauge port.
    Are these hairlines enough of a crack to cause the runaway throttle problem?
    ( looking at these pics, I am wondering how some stems got in the choke assembly ?.. checked and removed them). It's pretty dark in the garage.


    Cyl-1-2--Manifold-intake-05292017.jpg

    I can order 1 and 4 with gaskets, ( ? ) from XJ4ever. It would be great to hear some opinions before I plunk down the cash. ... which I am figuring I will do now...

    2 and 3 do not look as weathered. These cracks don't seem like they go through the whole boot, but I would need to remove them to be sure. Suggestions?

    Thanks again everyone, and I will try to answer questions, although it may take a couple of days. I have been trying to follow the threads for runaway throttle. I am ready to tackle some other problems (brakes? tires? clutch? ) on the bike...(and actually ride it... I don't have another bike right now).. I will take the carbs off again next weekend, but I work a lot, so it takes a while.. ... obviously.
     

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  2. Killerkhezu

    Killerkhezu New Member

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    I had this problem recently on my 82 xj650. Try taking the throttle cable out of the boot it rests in and see what it does. If it idles fine and doesn't run away the butterfly sync is off. I used some paper to sync mine and it runs perfectly .

    Also for the weathered boots I have been told that black RTV works wonders on sealing cracks. You could also try that.
     
  3. BigT

    BigT Active Member

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    I see no mention of a bench sync, if you have not done one then I would pull the carbs and do that first. If you have then I would do as previously suggested and check your throttle cable for slack and double check that you do not have the throttle and choke cables mixed up. Simple things first!

    I noticed you have black plugs over your pilot mixture screws, were they removed and cleaned along with replacing the o-rings?
     
  4. Stumplifter

    Stumplifter Well-Known Member

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    Those look like the ones XJ4EVER sells.

    What is the orange piece in the first picture?
     
  5. cascott

    cascott New Member

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    The orange piece is the original (?) vacuum port plug that was on bike. I fabricated the port 2 plug from new vacuum line and a screw. Looking at my own pictures, I see I don't have the plug clamps on 1 and 2 port plugs, I will do that tonight.. simple things first. I will check the throttle cable.. it's quite loose now, but I will take it out of the holder and try starting. I bench synced using paper clip method, thought perhaps trying a business card method instead. I cleaned the pilot mixture screw ports and screws, and thought plugs looked like good idea. I am pretty sure that I backed them out 1.5 turns from stop when I reassembled, that was a while ago. Black RTV silicone gasket material sounds like alternative solution to the cracks.. thanks for that suggestion. Will look into that this weekend. I don't think the cracks go through.
     
  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    paper clip is ok to do benc sync have you tried backing off on the idle knob to drop idle
     
  7. Stumplifter

    Stumplifter Well-Known Member

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    A bench synch works great on the bench. That plus 2.5 turns out from a soft bottom on the mixture screws will get you to where the bike should run - THEN you need to fine tune. Running synch and colortune are the norm (and one more running synch for that purrr.

    Valve clearances should be verified prior to putting the effort into tuning the carbs.
     
  8. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    No it's not. The originals are the black ones. Someone cobbled that together with vacuum line, and it may very well be the source of your vacuum leak.

    I see that several of the vacuum caps have no clamps on them. I would reccomend getting new caps, and the proper clamps for them. That is likely where the vacuum leaks are.

    While the cracked boots are of concern, I would deal with them after replacing the vacuum caps.
    If you find that there is still a vacuum leak, then thoroughly clean and degrease the intake boots with the carbs removed (you have to get good access for the repair to work). Cover the boots with oil-resistant, black RTV (working it into the cracks) and finish up by smoothing the RTV over with a wet finger.
     
  9. cascott

    cascott New Member

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    Thank you. I will get the vacuum caps and clamps. I will let everyone know how it goes.
     
  10. cascott

    cascott New Member

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    So So cool. Started. As it went to 5000 and holds... reved it a bit.. ... burned off stuff (on new exhaust gaskets and around new oil filter install). So cool. Now using vacuum gauge ( that went fast) and colortune (next) that I bought before I knew about xjbikes.com many years ago now. Thank you everyone for your help, it was vacuum leak fixed with new port seals from xj4ever and Len. Brake shoes and front caliper hose next on list... I will have more questions I'm sure. Thank you for your help. cascott
     
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  11. fiveofakind

    fiveofakind Well-Known Member

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    Those 420 stems in #4 need to come out immediately...Seriously impeding your bike's performance.......& your personal judgment.....lol
     
  12. cascott

    cascott New Member

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    Don't know how those made it thru the ultrasonic cleaner.?? (I didn't think anyone got my joke..:) as a side note, I have been clean and sober 10 yrs now on this June 14..so I seem to want to make these jokes now...) But on this thread... I forgot to mention that I backed the idle adjustment all the way off the stop, and I think that helped... it also took a little starter fluid to get it off the ground the first time..( uh... like it took a couple of days to get it to start... I was getting concerned but kept at it... ) Now it starts right up... no choke,.. nothing .. just a touch of gas... still a little fast on idle, but I have some adjustments to make...this is it cooling.. photos tell so much.. I see my rat's nest wiring under the seat that has to be re-done.. so much work.. but I hope to ride it around the block soon. Work on it and ride it... as opposed to just work on it. WP_20170626_006.jpg
     
  13. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    The idle adjustment knob should not be set so far out that the throttle linkage isn't resting on it. That leaves the throttle plates resting against the carb bores under spring tension, and that will cause wear and binding.
     
  14. cascott

    cascott New Member

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    I should be able to bring that back in tomorrow. I also forgot to use the YICS stick that I bought to use with the vacuum gauges. I not quite there yet. Thank you. Your expertise is very appreciated. :)
     
  15. fiveofakind

    fiveofakind Well-Known Member

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    A proper Bench sync will have the throttle linkage resting against the idle adjustment screw producing a silver of light in the carb bodies when looking at the butter flies when held up to a strong light
     
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  16. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

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    No need for the YICS blocking tool.
     
  17. cascott

    cascott New Member

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    I remember seeing a pinch of light thru the bores when I set them the last time. Interesting about the YICS tool. Totally forgot to use it, as I was so excited it was running.
     
  18. cascott

    cascott New Member

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    Hi. I wanted to update this post. I am at about 100 miles now, and bike runs like a top. I had the idle set too high at first. It really was a simple solution to the run away throttle. I think that there may have been a leak in that one vacuum port as well, thank you K-Moe for that sharp observation. Both may have contributed to the very high idle. I am so pleased with the way the bike runs now and will post again. It was worth the time and effort to do the carbs right. It starts like Hogfiddles said it would. It starts right away all the time, and once it's warmed, it turns over in an instant. So COOL when it does that. :) Planning to ride a bit and fine tune.. Thank you everyone.
     
  19. cascott

    cascott New Member

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    1982 xj650j carbs cleaned and rebuilt 2017.... Bike ran fine last year. Drained carbs in fall. This spring fueled up, bike started, went around block. Next day bike would not start. Pulled plug, no spark. Strange.. so tank off, wiggled wires and plugged and unplugged starter circuit and kickstand relays. Now starter did not turn over. Shorted starter solenoid and it did turn over so I suspected I have loosened something somewhere. Been battling this for a while, and had some personal issues, and now back at it. I bought a decent multi meter with continuity, checked relays although I am still suspicious of them both. The check didn't go to 100 like it said it should in the Hayes manual. Also bought a new diode block, but didn't make any difference, just thought I would eliminate it as cause. Re cleaned starter button and kill switch again today, and checked it from the headlight housing multi plug and they both good for continuity. Feel that I am not checking something somewhere and that it's in the starter wiring or relays...or I am completely off base and think I should get some advice here. It will take a while for me to run all of your suggestions, but could someone point me to the beginning and I just start over with the checks and be more systematic about it. I have read Arron Bergs FAQ a couple of times and it's starting to sink in... I never much good at electrical stuff....Time to learn it now... once I can get it to turn over, I can start trying to figure out the original no spark / starting issue....
     
  20. XJ550H

    XJ550H Well-Known Member Premium Member

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    xj650rj starter circuit.PNG follow the voltage from red/white wire.
    if you disconnect the small connector to the solenoid test for 12 volts there at harness connector.

    then hook meter to both wires and press your starter button you should get 12 volts as starter button works as ground.

    when you press starter button does oil light come on? this confirms ground to.


    if you take 2 jumper wires from battery and attach to solenoid small connector it will activate solenoid and turn over starter
     

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