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Leaks and stuck RPM (high) even with clutch in. 83' xs650 Heritage Special

Discussion in 'The Garage' started by MarieKaramazov, Sep 17, 2020.

  1. Raymond

    Raymond XS650 rider, fettler, setting out on a journey XS650.com Supporter Top Contributor

    Agree with 5T - those intake rubbers, carb to cylinder head, don't look too happy. The trick is to spray carb cleaner directly onto the cracked area while the bike is running and see if the revs go up. I think I got that right but if not somebody will correct.

    An air leak in the intakes will cause an erratic idle but will not necessarily show up in the plug condition because the fueling might be much better when you open the throttle to ride round the block

    If you need to replace cracked intake rubbers then tank, air filter boxes and carbs will need to come off. Access varies with model and carb type but it is always very tight in there. I loosen and remove one of the intake rubbers - the right one - to get a bit more space. Other people remove the nut on the cam chain adjuster to make more space. I also wrap a piece of rag around the frame behind the carbs, then they can be pulled off and wiggled free.

    When fitting new intake rubbers, you also need to check the gasket between the intake and the head and make sure this area is clean. Reinstall with a smear of grease or some non-setting gasket goo such as Hylomar.

    I'm slightly confused by all the hoses in your photos - bear of small brain! The one with your thumb in the first photo does not appear to be the petrol feed from the petcock. Cylinder head breather? Looks as if your bike has a vacuum operated fuel tap - the hose below that from the inlet rubber to the fuel tap. I can't see anything to worry about rubbing on the cylinder head.
    MarieKaramazov and gggGary like this.
  2. Jan_P

    Jan_P XS650 Addict

    I was wrong about the Hose Clamp I can now see that it is there

    Cleaning Looks like some yellow dust A regular wash would be my first :Water garden hose
    Spraying it over and a Brush as on an automobile / Sponge + soft Dish washer brush + perhaps old toothbrush. Water can give starting problems but i have done so many years . And then after that with chemicals.

    Filters I would give those a pass for now see 5 Twins above try too se that they slot in right .With gaskets not popping out.

    Intake Manifold .I can see cracks .. ..but in my opinion those manifolds are rather thick so a Crack on the outside might not mean it will go trough.
    I replaced this year and the new ones did not make any difference. I believe the overspray will give that answer.

    Tires High speed for Carburetor cleaning does not mean High speed relative ground as I see it .. it means flow trough the intake and carburetor
    which can be the same for lower speeds and high rev.

    Please check that the wire on the throttle is not sticking. You can do that without the engine on. Twist the throttle and let go .Inspect that the small arm
    Goes all the way back against the small idle Screw. Every time.
    And as mentioned before adjust the idle screw.
    Never mind for now what idle rev is .Turn it counter clockwise until the bike dies .And then back a little. So it runs again.
    If the Intake air valves close at throttle off -- it cant stick ( bike ) on 3000 rpm
    Regardless if it is clogged / dirty -- or not.
    Without getting air somewhere else Downstream of the now closed air valves. aka a Leak

    I dont know carburetors that good but I suppose that if Synchronization is off .The closing of throttle does not close the Carburetor that is off sync.
    It is then still open -- And the rev dont go down.
    Thinking out loud here -- better men correct it if I am wrong again.
    Can't you check that by removing one spark plug at a time. Bike is running and let go of the throttle now at 3000 rpm
    or preferably lower
    Pull off the left sparkplug .. bike dies .. one conclusion can be drawn
    Do the same over again but pull the right spark plug. Still running ?
    Difference ?

    So all in all . I still believe we are in upstarting procedures. Idle adjusting ...Tightening ....Cleaning ...Lubricating ....Leak finding .. Running through carburetor cleaner. perhaps .
    Greyandridin and gggGary like this.
  3. MarieKaramazov

    MarieKaramazov XS650 Enthusiast

    Gonna try a leak test today with carb cleaner and I'll check that wire @Jan_P Put my finger on the carb sliders the other day too (though the air cleaner), and when I pushed them up the both seemed to come all the way back down on their own accord pretty easily, obviously not fully flush to bottom though as carb is rounded. Thought maybe those were getting stuck...
    I get what you're saying about turning down the idle and then inching back up to run, but are you saying after that to see if it inches up to 3000 itself with throttle off? (The idea being that it's running at it's lowest possible idle--so less air from intake--so if it's still shooting up in RPM it's doing so because air is coming from somewhere else as well?) It hasn't shot up in revs just at idle before...it's only after using throttle; occasionally the idle speed will increase the longer it idles, but that's more like 1.5 compared to 1. So to test this I'd have to get the idle down, let it idle, rev it a few times in neutral till it starts getting angry and see if it sticks...but then I'm increasing airflow with throttle, right, so doesn't seem like it'd provide a clear answer whether air is also coming from somewhere else...or am I missing something?
  4. Jan_P

    Jan_P XS650 Addict

    Hi the way I see it
    Is that the carburetor is getting two fluids --- Air and Petrol.
    If one of these are cut off the bike don't run at all ( disregarding for now spark of course )
    So if you were able to put a Cork on the cylinder intake it would not run.
    The carburetor has a circular brass flap at the intake that open and close the Air flow.
    So if that flap would serve as a cork at throttle off the bike would die.
    That small screw ( Idle adjuster ) keeps a little opening so the bike don't die at throttle off.
    It affect the same axle that the throttle activates.
    Clockwise ..the opening gets a little larger and idle rev increases.
    Counter clockwise it gets lower and at some point not large enough air opening so the bike dies
    ( The cork is in so to speak )
    So with a low idle barely running ..Gives gas the throttle opens and the rev increases.
    I you let go of the gas it is supposed to go back to the adjusted position low idle
    Or even die if to low.
    If the flaps goes back and restrict the airflow. I should do that every time.

    So if i get it right here ---you let go of the throttle and assuming the flap closes
    but the rev don't go down. ( The cork is in so to speak )
    But the rev dont go down .. Then if the air don't comes via the intake
    It ( the air ) must come from somewhere else. Which would be impossible without a leak

    Not sure if this is a good explanation ..but the throttle handle with a low idle setting At throttle off. Should stop the bike.
    It runs with every other position the handle is in -- but just not if you let go off the handle.
    The air flow is off and the bike stops. Either it is not closing ( the flaps ) ..wire perhaps needs a lubrication
    or a leak somewhere
    at # 2


    Is a picture of the brass flaps -- you have a different carburetor but it should be about the same.
    To the right is where the throttle wire connects.
    So since there are 2 carburetors .one can close but one is still open if synchronization is off that can be adjusted
    via the screw in the middle between the carburetors .DON'T TOUCH IT FOR NOW.
    My guess is that the wire is sticking and perhaps the idle is not adjusted
    if it differs between 1000 and 1500 it is nothing it can happen and I have never had under 1500 as I can remember

    rev it a few times in neutral till it starts getting angry and see if it sticks...but then I'm increasing airflow with throttle, right, so doesn't seem like it'd provide a clear answer whether air is also coming from somewhere else...or am I missing something?

    You should be able to regulate the aiflow with the throttle handle as you regulate the water in a garden hose with the water tap -- faucet
  5. MarieKaramazov

    MarieKaramazov XS650 Enthusiast

    Yeah I understand all that about airflow/gas and carbs and why a leak would make sense as an option, I just didn't think the sliders would actually go completely flush to the carb bottom letting 0 air in because, from what I could see, the carb bowl is rounded and the sliders are flat at the bottom. (At least mine don't go low enough to wear there's 0 gap at all--theres a small one but not completely gone, and that's with idle screw turned all the way counter.) So even at 0 throttle and low idle there'd still be a gap letting some air in; but I get it, it's such little air it'd die so if it wasn't dying with the screw all the way down there was a significant leak.
    Anyway, I tried that, bike died at the lowest idle screw position. So judging from that one, no air leak. What was interesting, however, was that judging by the fact that it ran fine at a way lower idle--and also judging by the fact that it can't even take full choke on a cold start otherwise the RPM go through the roof--I think the setting should be turned down in general.
    Tried spraying carb cleaner on the carb to cylinder boot (both sides) joint and watched RPM--no increase.
    Side question: do I need to wipe/rinse off the carb cleaner from the boots? Didn't see any thing about that on the bottle, but this was not used in normal context so want to be sure I'm not damaging stuff leaving it.

    The arm connected to carb and throttle/throttle cable snaps closed each time, as does the associated spring between the carbs. S

    The hose with the arrow pointing loops back and leads to the back of the petcock. And it leans against that cylinder head cover which gets real hot, i'v even marks on the hose/head cover
    Raymond likes this.
  6. 5twins

    5twins XS650 Guru Top Contributor

    That hose is the vacuum feed line for your vacuum powered petcock, and it's been changed. The original was a smaller diameter vacuum line. Yours looks like big fat fuel line. It's pretty common for it to touch the valve cover and it usually does it no harm. I've changed the vacuum hoses on mine but use something similar in size to the original stuff. On my '78, I'm using orange silicone hose. It touches the valve covers slightly but that's never hurt it .....

    Raymond and MarieKaramazov like this.
  7. MarieKaramazov

    MarieKaramazov XS650 Enthusiast

    looks much slimmer. I'll def invest in that later
  8. 5twins

    5twins XS650 Guru Top Contributor

    I also see your hose has been secured to the vacuum nipple using a cable tie. There are special little reusable wire clips used there .....

    MarieKaramazov likes this.
  9. Jan_P

    Jan_P XS650 Addict

    It sounds as if this is getting better
    Perhaps you should look from the other end of the carburetor to see the Brass Valve flaps ( perhaps called butterfly valves in English ) the slide is on the other end

    at the beginning at 00.8 you se the slides then he turns it 0.15 you see the brass valves

    Choke it is not so that it is always needed .. I does not matter if the bikes rev up at full choke just don't use it if it starts and runs well .
    ( Spark plugs OK )
    Last summer i saw an old Military bike that did not start at all if choke was on
    At times I myself had a bike that would start best with no choke and no throttle. When kick starting
    So if the bike revs up with full choke I would regard that as a normal situation more or less.
    Don't use the choke if it affects the rev. To much And the bike starts . As long as you can regulate the rev with the right handle bar twist. It should be OK
    MarieKaramazov likes this.
  10. MarieKaramazov

    MarieKaramazov XS650 Enthusiast

    Well, stuck on getting LH Cover off to find leak source—one bolt stuck. Tried WD40 and willpower, no luck. Looked like there was some kind of whitish sediment in hole with it but I got that out, still nothing. Looks like it’s leaning a bit to left of hope too, maybe threaded in wrong.

    Attached Files:

    Last edited: Oct 6, 2020
  11. MarieKaramazov

    MarieKaramazov XS650 Enthusiast

    Muahaha willpower attempt 10 worked
    Raymond and gggGary like this.
  12. 5twins

    5twins XS650 Guru Top Contributor

    If you don't have any, get yourself some anti-seize compound. Apply it to the threads of all the nuts and bolts on the bike eventually, as you get around to pulling them out for some reason or another. Many of the steel fasteners, like these side cover screws, are threaded into aluminum alloy. The dissimilar metals can corrode together. Steel on steel ones will too, getting rusty. This anti-seize compound will prevent that from happening in the future.
    Raymond and MarieKaramazov like this.
  13. Raymond

    Raymond XS650 rider, fettler, setting out on a journey XS650.com Supporter Top Contributor

    Glad your willpower aka persistence worked on this occasion.

    Agree an impact driver is a good investment. Reluctant fasteners require patience and ingenuity. And sometimes the careful & judicious use of extreme force. Sometimes just putting a hex bit into the head of the screw and giving it a sharp tap - okay, a clout - with a hammer will free the threads. Or sometimes, just a bit of extra leverage, like a pipe or box spanner over the Allen key will do the trick. But you have to exert considerable force inwards on the head of the screw to reduce the risk of rounding it out.

    A further level of escalation is to drill down the centre of the screw and tap an 'easy out' in there. Or use a reverse-threaded bolt remover.

    A wise man who introduced me to the ladder of increasing force also advised going and making a cup of tea - how British! - before raising the odds again.
    MarieKaramazov, Jim and GLJ like this.
  14. fredintoon

    fredintoon Fred Hill, S'toon. Top Contributor

    Raymond and MarieKaramazov like this.
  15. bosco659

    bosco659 XS650 Addict XS650.com Supporter

    Raymond likes this.
  16. Raymond

    Raymond XS650 rider, fettler, setting out on a journey XS650.com Supporter Top Contributor

    Careful! Those are probably JIS screws. Worth buying some JIS screwdrivers. This is the one I bought on MaxPete's suggestion:


    It's not the fancy, turn-as-you-hit type of impact driver, but you can give it a clout as you hold and twist and it's the correct profile for the screws on our bikes.
  17. MarieKaramazov

    MarieKaramazov XS650 Enthusiast

    Thanks everyone for the tips! It was dark by the time I finally got the screws off the other day and then the cover still didn’t want to break free. Gonna try to go at it again tomorrow
  18. bosco659

    bosco659 XS650 Addict XS650.com Supporter

    Well worth the investment. Great screwdrivers and grab the screws really well. I tried to buy these through Snap On and they said they never heard of them before! Lol. Anyway, bought a couple for the tool boxes.
    Raymond and Greyandridin like this.
  19. lakeview

    lakeview XS650 Guru XS650.com Supporter Top Contributor

    Dribble penetrating fluid along the seam to help loosen the joint, also there are locating collars front and bottom that are probably a bit corroded. A gentle hammer tap may help.

    Attached Files:

    MarieKaramazov and Raymond like this.

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