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Little pulling power and slight backfire?

Discussion in 'XJ Technical Chat' started by Eric Hughes, Mar 9, 2021.

  1. Eric Hughes

    Eric Hughes Member

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    Since we have some decent weather here in North Carolina (no rain) I've had the 82 650 Maxim XJ650J out for a few rides around. The other day it was good no issues. Stopped got a beverage and headed back out, but now it gave a slight backfire when shifting and had very little top end. Had to run full throttle most of the way home just to stay at a decent speed, 50 mph. Once home and was able to take a slightly better look and listen, everything seemed fine revs good, shifts fine (hard but fine). Took it out today to see how it goes and same thing, low on the pulling power and slight backfire shifting. I have not checked the valves or cleaned the carbs but since this was a drastic change I'm not sure what to think. Other than valves and carbs any ideas what might have changed?
     
  2. k-moe

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

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    History is important. Do you have an existing thread for the bike?
     
  3. Eric Hughes

    Eric Hughes Member

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    There are a few threads around from me but nothing about actually work being done other than a petcock rebuild. I got this bike a little less than a year ago and have done very little to it since it has been running good and haven't had any real issues. I know I need to check the valves and go through the carbs. Since this change happened essentially in the middle of the ride, seemingly not related to those two items. Possibly it picked up some junk in the fuel from sitting for a few months.
     
  4. cds1984

    cds1984 Active Member

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    Sounds like, maybe, something has blocked your airbox intake maybe? Not enough air? so too much fuel?
    If you have black plugs, this could be something.
     
  5. Eric Hughes

    Eric Hughes Member

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    I'm going to have some time this weekend to do a bit more troubleshooting. Just odd that it changed from one start to the next.
     
  6. Franz

    Franz Well-Known Member

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    Have you got an in line fuel filter that could have become clogged, sounds like fuel starvation to me? Next time it does it open the gas cap in case you have a partial vaccum above the fuel. It's probably not that but worth eliminating it as a potential cause. I think there are offset holes in the gas cap to let air in.

    Do all of your cylinders have a spark at the plugs? My Honda CB 750 had two sets of points and once on my way home one set locked up so I was running on two cylinders instead of four. Our XJ's don't have points but mabe you have a loose electrical connection affecting the sparks?
     
    Last edited: Mar 11, 2021
  7. Eric Hughes

    Eric Hughes Member

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    Agreed that is sounds like starvation. Air box and filter seem good. Pulled the plugs and they don’t look bad but I’ll replace those this weekend. Looks a little lean (gray tips on plugs) which is somewhat expected if it’s starving. Will continue down the path and see what comes up. Planning on checking valves as part of this since it does need to get done. Nervous about that but with what I’ve read here and watched on the tubes it’s not as bad as it seems at first glance.
     
  8. Franz

    Franz Well-Known Member

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    Check your line from the third inlet stub from the left of the bike for splits as it opens the fuel flow to the carburettors l believe.
     
  9. Eric Hughes

    Eric Hughes Member

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    Pulled the carbs today to take a closer look and I may have found at least part of the issue.... gave everything a blast of carb cleaner took the hat and bowl off #4 and it looks ok other than the missing screw. Cleaned and re gapped the plugs as well since the tank was off. Doesn’t look like anything is down in there so I’m thinking that hasn’t been gone too long. Pulled a screw spring and o ring from the other bike, 81 midnight maxim, (currently in the completely apart stage). It goes in but only goes about 3 turns and seems to hit bottom and is quite loose when I back it out a turn or so.
     

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  10. Eric Hughes

    Eric Hughes Member

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    It actually idles better than it did but still not right under power.
     
  11. k-moe

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

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    There were two different thread pitches used in idle mixture needles for the early Hitachi carbs for the XJ. Make sure that your needles have the correct pitch when swapping between carbs.
     
  12. Eric Hughes

    Eric Hughes Member

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    I’ll swap between the rack to test, then get the appropriate one. Along with rebuild kits, since that needs to happen too. Len will be hearing from me again soon.
     
  13. Eric Hughes

    Eric Hughes Member

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    Hopefully this will do the trick. Since its sunny and 75 here I really hope so because it is going to be a great week to ride. Len at xj4ever, as always, had what I needed and got it here right on time.
     

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  14. Eric Hughes

    Eric Hughes Member

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    Same same. New screw in, o ring on the bottom. Set the screw to basically the same as the others. What I am thinking is 2.5 full turns of the screw from soft bottom. I don’t have a vacuum sync tool as of yet to test it for real. Checked for air leaks with staring fluid sparingly around the intake boots, throttle shaft o rings, and air seals on the tops on the intakes. No changes. Runs fine and revs up nicely sitting still. Just nothing on the top end while moving. Lucky to hit 70 wide open down hill. Occasionally it gives a little hesitation like it wants to go but never does. Slight backfires on shifts about half the time. Somewhat frustrating since it was good one start and then not good every start after. Back to the drawing board. Valves, plugs, tank vent, church clean and a prayer.
     
  15. tabaka45

    tabaka45 Well-Known Member

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    I'm wondering if there is a electrical problem. I don't know much about electrical issues, but could it be a bad coil or something that isn't firing under load?
     
  16. Eric Hughes

    Eric Hughes Member

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    There could also be a electrical problem I’ll get into checking that too. However today I decided to pull the carbs apart to check everything out sync the butterflies, check the linkage etc. found several issues in that process. Two of the slides had the needles off and one of those has a major crack in the plastic ring on top of the diaphragm. Only the one mixture screw that just got replaced was 100% correct two others had no washer and one had some melted looking o-ring. Truly now I’m surprised that it ran as good as it did before this issue popped up. Would wager a guess that the jets are wrong but at least they are the same 50 and 205, 40 and 110. I don’t know what each one is called at the moment. Once I figure out the standard jetting I’ll know what needs to get ordered. Also cleaned the filler cap vent, dumped gas and checked the petcock. It’s a lovely Sunday for a ride too....oh well soon hopefully.
     

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  17. tabaka45

    tabaka45 Well-Known Member

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    I am amazed it ran at all, much less 50 mph!!
     
  18. Eric Hughes

    Eric Hughes Member

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    Yeah exactly. It ran great until it didn’t. I’ve never seen the needles off a slide so I’m gonna guess that not supposed to be like that. And I’ll have to get new slide diaphragms needles and all. Also funny that the only mixture screw that was correct was the one that just got replaced.
     
  19. tabaka45

    tabaka45 Well-Known Member

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    Might be a good idea to look for a good set of used carbs. There are several sets on eBay for $200-$300.
     
    Last edited: Apr 11, 2021
  20. Eric Hughes

    Eric Hughes Member

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    That is looking more likely. Got the full rebuild kit from Len and began the take apart and photo note taking and discovered #4 has a broken and kinda fixed float post. Looks like JB Weld. Wiggles just a little like the beginnings of a loose tooth. Also the plunger needles, main jet needles, whatever they are called are marked Y-262. Unless I’m looking at the wrong thing they should be. Y-10.
     

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  21. Eric Hughes

    Eric Hughes Member

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    Finished the carb rebuild and got them back on the bike. 2.5 turns out on the mixtures and float levels 17.5 +/- .5, synced the butterflies. Got a little nervous doing the butterflies as the throttle shaft was much tighter after getting the carbs back on the rack and didn’t want to snap shut like I thought they should. Loosed all the rack screws up and gave everything a little wiggle and then back tight while holding flat with a chunk of angle iron and a granite counter top scrap. Seemed good after that. Took forever to get it started the first time. Once it was running it took some fiddling with the idle screw to get it close. Short ride for gas and the idle was not right after warming up fiddled that a bit more and it was much better. Longer ride and it has good power and the hesitation from before is gone. Took long enough to get everything clean and rebuilt but since this was my first big project on this bike I’m happy with it. Will need some fine tuning but no need for that until I do a proper valve check. Many thanks @chacal for answering questions and the rest of you for helping as well. Next up for this bike will be fork seals, since there is some leakage down onto the front caliper which is not good. And while they are off might as well to the head bearings and front brake system too. Happy to be in the wind again.
     
    Huntchuks, chacal and Simmy like this.
  22. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Y-262 are the markings on the aftermarket versions of the Y-10 original needles.
     
  23. Eric Hughes

    Eric Hughes Member

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    Pulled the plugs today to see how they looked since cylinder 4 doesn’t seem to fire until warm or high rpm. Looks a bit lean all around. Swapped 3 and 4 and no change. Since valve check is up next I’m not going to mess with the mixtures yet.
     

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  24. Eric Hughes

    Eric Hughes Member

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    Back again with a different issue but staying on the same thread for bike consistency. Been running good with the slight hesitation when cold and at low RPM, but overall good.

    Current issue is what sounds like a engine rattle. I tried to "clean" the engine to see if it would resolve the starter clutch issue on a warm start that seems to be the norm. Using some possible fixes from the site here I put some Seafoam in the oil, like 4 ounces-ish, ran it a bit, probably about 30 minutes total, on the center stand and a short trip or two up the road. Changed the oil and filter with some generic Fram 20w50, didn't have the Rotela T4 where I went to get oil. What I read around about the Fram was no additives and it would be ok for the wet clutch even though it isn't specifically JASO rated. Didn't see any bits of metal or plastic in the dirty oil which I was happy about. After a few rides it now has what to me sounds like a vibration rattle when RPMs are fairly high. Checked exaughts for tightness and other bits as well while on the stand and taching it up a bit listening for and holding things to try and narrow it down. Clutch isn't slipping or I would blame it on the oil.

    What kind of symptoms might be expected from non conforming oil? Hate to dump it again if its not the issue. Oil isn't that expensive but its not free either. Tried to make a video to show the noise but it wasn't really detectable in the audio over other engine/exhaust noise, may try a different method to capture the audio.
     
  25. Polock

    Polock Well-Known Member

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    mobil delvac 1300 works good in these, diesel oil. but your oil is ok
    cam chains can make noise, easy to adjust
    3 feet of old garden hose, one end on your ear the other moves around till you find the noise
    plugs are a little lean
    adjust your valves
     
  26. Eric Hughes

    Eric Hughes Member

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    Don't think my 650J has adjustable cam chain tension? But yeah need to check the valves and work on the carbs a bit for better sync. I've seen people use a wooden dowel to find noise, old garden hose seems obvious but never though of it, thanks for the tip. Was. bit worried since this noise started after the oil change, and don't want to ruin it with non-conforming oil.
     
  27. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    If strange noises started after an oil change, maybe the filter got installed incorrectly? That might lead to less oil pressure, less oil in the valvetrain and more noise??? Just an idea.
     
  28. Eric Hughes

    Eric Hughes Member

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    Very possible that I put the filter in backwards, I can never remember which way it goes. The filter I got had the O rings with it but they were not the correct thickness so I reused the old ones that were still in good shape https://www.amazon.com/dp/B000CNLIFQ?psc=1&ref=ppx_yo2_dt_b_product_details. Plan to check the valves this weekend and will check that too. Need to check the clutch too while I'm doing things. (because I haven't since I got the bike) so I might as well go ahead and get some new gaskets for the clutch cover. The list grows on...
     
  29. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    If you did happen to install the filter incorrectly, you wouldn't be the first one to do so. Don't ask how I know. No shame here.

    There are several reports of those o-rings included with the filters are trash, so it's not surprising.

    I don't think they need to be changed that often anyway. Seems like they should last for several years without an issue. Also, they are not price prohibitive to get the "good" ones. @chacal at xj4ever.com can hook you up with OEM or an aftermarket option for those o-rings. In fact, those o-rings are are common enough that they are still in the Yamaha parts book, so if you get an itchy trigger finger you could check to see if your friendly neighborhood Yamaha dealer has them in stock. Still probably a lot easier and safer to get them from xj4ever and save yourself a trip to the dealer and possibly end up with the wrong thing.

    For reference on xj4ever: http://xj4ever.com/catalog/e-1-gaskets-top-650.html

    Since I know there have been some people out there - cough - who have installed the oil filter incorrectly, let me just post this for reference:
    filter.png

    Parts #2 and #3 usually come with the filter. The flat side of the filter goes against the engine block, then the washer (#7) goes against that, then the spring (#8) pushes against the cover (#1).

    In reverse order, as usually done when re-installing:
    - Start with cover (#1) with bolt and relief valve assembly (#4) installed, the little o-ring (#5) provides the seal between the bolt and the cover.
    - Then put on spring (#8)
    - then the washer (#7)
    - then the filter (#2,#3), with the concave side of the filter facing the washer/spring
    - then the big o-ring (#6) goes around outside of oil cover (#1), to seal between cover and block
    - install, should have the flat side of the filter being pushed against the block by the spring.
     
  30. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    Or the easy way: Install the spin-on filter conversion kit.
     
  31. Polock

    Polock Well-Known Member

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    you can hold on that for awhile, the best way to check the clutch is to ride it
     
  32. Eric Hughes

    Eric Hughes Member

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    Thanks for the image. I “think” that is the way it is but….. I’ll check. Chacal has had more than one order from me so that is where I get anything that I want to be right.

    As for the clutch it probably needs adjustment more than anything. Shifts fine but clunks a bit maybe more since the oil change as well which made me question the oil. Sometimes when sitting at a light I think it’s in first but it’s actually in neutral but the neutral indicator doesn’t light till I let the clutch lever out and then crap I’m revving and no go, clunk it down again and go for real.

    Since I’m gonna check the filter orientation I’ll probably go back to known good oil and see if anything changes.
     
  33. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    The "concave" depression in the filter is where the spring goes. Most of the filters have a finely stamped "engine side" wording on them (some of the aftermarket ones do not).
     
  34. Eric Hughes

    Eric Hughes Member

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    Pulled the filter off and discovered that it was on backwards, concave to the engine. Also discovered after flipping it over and putting it back on....while typing this and looking at the diagram, there is no washer #7 in the diagram above. I changed the oil last year and figure there has not been one there for a while since it isn't now, probably wasn't then either.
     
  35. Dan Gardner

    Dan Gardner Well-Known Member Premium Member

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    OK, that's progress I suppose.

    That washer is kind of a flimsy little thing - I think it is just there to prevent the spring from tearing up the rubber seal in the middle of the filter.

    I did a quick look on xj4ever and couldn't find that specific washer in the catalog. Maybe @chacal could point us in the right direction. On the Yamaha parts fiche it is part # 90201-21608. It is used on a jillion bikes.

    If I were you, I would order a new one. In the mean time just install it without the washer (so spring pushing on filter directly) or I would go up to my local hardware store and see if I can find a washer that is close enough. Disclaimer: you should never listen to my advice.
     
  36. chacal

    chacal Moderator Moderator Supporting Vendor Premium Member

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    Correct!

    HCP1493 OEM oil filter element compression spring SEAT PLATE WASHER, fits all XJ550, 1984-85 FJ600, 1986-88 FZ600, 1986-90 YX600 Radian, XJ650, XJ700, XJ750, and all XJ900RK, RL, N/FN, and F models, and XJ1100 models, each:
     

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