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1985 XJ700N not starting.

Discussion in 'XJ Technical Chat' started by ratch, Sep 11, 2020.

  1. ratch

    ratch New Member

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    Little history, bought this bike about a month ago. the guy said he hasn't ridden it in over a year. he had it listed incorrectly but after Identifying numbers on the frame I found the correct year and model. We were unable to verify running on the day of purchase.

    After getting it home, I removed the Carbs so I could Check the Bowls for corrosion. there was nothing obvious. They looked pretty clean, just some brownish dust. a quick squirt down with cleaner and I reassembled it. While the carbs were off I also did a Compression and spark test. all 4 cylinders had right at 95psi compression. All four cylinders also had good spark. fast forward to now, I got some gas yesterday(9/10/2020), after making sure there were no leaks in the tank I put a good gallon plus in the tank. I popped the vacuum line off the Cyl 2 intake boot and sucked on it a couple seconds to prim the carb bowls. I have a chinese replacement petcock that has weird positioning so the knob to turn it to PRI hits the tank way before leaving the ON position. with a battery jumping it I tried starting. it just turns over and doesn't even try Firing. I have noticed the ocaissional sound, that sounds like gear slip, after cranking it for a bit. I suspect that's just the starter and I suspect that's not supposed to happen. I tediously pulled the valve covers of not long ago and have re assembled the bike after not finding anything obvious.

    The only thing left that I can think of is the carb jets are dirty. I pulled the Spark Plugs out of the cylinders and I couldn't smell gas. At least not obviously.

    Any other suggestions would be welcomed. with the weather and My mom's birthday today I'm not messing with it until tomorrow.
     
  2. ratch

    ratch New Member

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    Ok so reading through the Service manual pdf i found on the Net, minimum compression is ~128psi. It's also supposed to be measured with the throttle wide open. Looks like I'm doing another compression test. If I get similar results I might not have adequate Compression to run. I'm also betting the Carbs are an issue as well.

    EDIT: so, did a new Compression test and it looks like all 4 cylinders are around 115psi. which is about where it was when I did the first test. my compression tester goes in increments of 30, so it goes from 90 to 120. and based on my lines I'm putting it around 115psi for the compression. and since they're all even ish, I'm thinking it should be fine for now. I'll probably clean the carbs tomorrow.
     
    Last edited: Sep 11, 2020
  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    check shim clearance first if out of spec it will affect results and change results if you correct them after the test.

    if you got 95 across the board I would not be to concerned

    also some say cold some say warmed up


    wide open throttle airfilter removed or a new filter mmm 700n very expensive filter

    https://www.xjbikes.com/forums/threads/the-information-overload-hour.27544/

    XJ700 non-X (air-cooled) engines:
    Minimum: 128 psi
    Standard: 156 psi
    Maximum: 171 psi
    Max. variance between lowest and highest: 14 psi

    - COMPRESSION TESTING:

    Yamaha recommends that you perform a compression test every 5,000 miles or so, and that you should record the readings, per cylinder, for future comparison and evaluation. The acceptable readings (specified at sea level) are as follows:

    To do a compression test properly, you should first make sure all of your engine valves are properly adjusted to their recommended clearances, as valves that are too "tight" (not enough clearance) will allow the intake or exhaust valve to be open more than is necessary, or at the wrong time within the compression stroke cycle, thus bleeding off compression that would otherwise be developed.

    http://www.xjbikes.com/forums/threads/compression-test-xj650.113151

    Do not use thread adapters or the like on your pressure gauge, as the added volume of air space within the adapter will reduce the indicated pressure readings.

    a) make sure the engine is warm (at operating temperature).

    b) remove all spark plugs, and then stick the plugs back into their caps and make sure the plugs are grounded to the cylinder head (or even better, disconnect your TCI unit).

    c) remove the airbox filter lid and the air filter.

    d) make sure the battery is FULLY charged, and remains so throughout the course of these tests! It is actually recommended that for purposes of compression testing that the TCI be un-plugged and jumper cables to a large capacity battery (i.e. car battery) be used to make sure that the cranking speed remains pretty constant between each reading. Slow or sluggish cranking speeds will reduce the indicated compression pressure. Yamaha specifies their compression pressures at 300 rpms (which is why the battery needs to be in good shape).

    e) open the throttle FULLY and keep it open during testing.

    f) crank the engine over until the needle stops advancing.

    g) Let the starter cool down for a minute or so, then do the next cylinder, etc.).

    h) If the readings are below spec, then shoot about a teaspoon amount of motor oil into each cylinder, crank the engine over a few revolutions with the starter (to spread the oil around), and then re-test each cylinder using the above procedure.

    i) compare the two results and analyze.

    j) keep all of your figures, and note the date and mileage from your odometer, so you can compare the next time you take readings (every 5,000 miles or so).
     
  4. k-moe

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

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  5. ratch

    ratch New Member

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    PO?

    The good news, we dumped a little gas in the cylinders, it fired. after attempting starting it when we pulled the plugs both my brothers confirmed what I suspected. fuel is not making it to the carb. I know there's fuel in the bowls because I manually sucked the Vacuum line to open it and then removed the drain screw from the bowl and fuel came out. But it fired off the fuel in the cylinders, so I just need to do maintenance on the carbs. it sounds like My starter is trying to die so I'll need to probably rebuild it. at least that's the suspicion based on the noise I hear. But I feel less stressed now that I know it will fire. just need to get tio to fire and run xD

    @XJ550H the airbox is only half on and the filter is out. it's one of the K&N ones.
     
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  6. k-moe

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

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    Previous Owner.

    The engine needs a paper filter with stock jetting. The bike was pretty lean to begin with, and any of the foam filters will lean it out a lot more; to the point of not wanting to start when cold. My K&N filter is sitting in a box, and has been for 7 years.

    If you are hearing a lot of noise (a can full of rocks) then you definitely need to start with rebrushing the starter and cleaning all of the electrical contacts in the starter circuit. The starter clutch will slip if the starter can't turn fast enough (load test the battery too. If you see less than 10 volts during startup then you need a new battery). It can also slip if the wrong type of oil is used (or if the rollers and springs are worn).Choosing Oil for a Wet Clutch Motorcycle

    Carb Info:
    IN THE CHURCH OF CLEAN

    Inside your Carbs

    xj-parts-catalog-section-c-fuel-system.44642

    Replacing your Hitachi throttle shaft seals

    Why you should replace butterfly (throttle shaft) seals.

    Setting the fuel levels

    The Hitach carbs are excellent, but do not suffer lazy refreshes. Do it right; do it once.
     
    Last edited: Sep 11, 2020
  7. Timbox

    Timbox Well-Known Member

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    Do yourself a huge favor and take the carbs apart, do them right and take your time doing them. I know that you want to get the bike running as it is a new toy to you, I have been there many times with these bikes. You know she will fire now, the compression will more than likely get better with a little run time. Sometimes the rings stick to the pistons and are not really free to push on the cylinder walls. Getting those carbs right the first time so you can just put them in and leave them in is a great feeling. Best of luck and keep us posted.
     
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  8. ratch

    ratch New Member

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    OK so my carbs are disassembled. well mostly. the enrichment needle and throttle shafts are still in there. I wanted to look those up first. I already watched dissably of the rest of the carbs so I knew what I was doing. I don't have access to a Ultrasonic so Carb cleaner and "elbow grease" will be how I clean them. I might try the electric sander method for a makeshift parts cleaner for these.

    I'm all for being complete and doing it all right. This is less a toy and a planned Daily driver. there's a lot of "nickel and dime" things with it. But it's 35 years old. I'm wanting to do an overhaul on the engine. probably not a full teardown but replacing gaskets and such on it. Gotta do the fork seals as well, they're leaking. in the spring when it gets close to riding weather I can to do the Tank. chemically clean the inside and seal it. I also plan on taking off the paint and giving it a good repaint.

    I'm debating on whether i want to do a custom build with it. I really like the look of Cafe Racers and some bobs. I was leaning Cafe Racer since I can have a longer seat so my daughter can still ride with me. but this is all just very big Maybes. chances are the only thing I'll do is a custom Intake. I really hate this one. it's ugly and a PITA to get in and out. I like the look of Pods but I'm not going to get balls deep in rejetting and tuning the carbs. I don't want to be chasing "rabbit holes" in the tuning. the custom Airbox is pretty sound. in fact there's a thread on this forum with essentially what I was thinking about doing. That thread is half the reason I joined this forum lol.

    Anyways, I'm going to fix me some dinner then look for Carb rebuild kits.
     
  9. k-moe

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

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    I've never bothered with an ultrasonic cleaner. They are fine for most things, but sound has a reaally difficult time going around sharp bends. I'm not convinced that they are the best tool for cleaning old carbs that have sat. Berryman's carb dip (or similar) has always worked perfectly.

    As for rebuild kits, look no further than info@xj4ever.com
    Far too many kits that you'll find aren't really correct. Chacal has the right stuff in stock, and backs up his sales with real customer service.
     
  10. ratch

    ratch New Member

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    I'll message him but money is an Issue. I went into business for myself last year. And well with the global event going on, I might as well be jobless. I have a single client that has work for me, but that's unreliable and inconsistent income since I have no vehicle atm to get to his shop to do work. So money is an issue. if it's going to be over 100 for the rebuild kit then I'll go ebay shopping.
     
  11. k-moe

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

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    I understand. Be very careful though. Money spent on crap is worth a whole lot less than waiting to buy decent stuff.
    You can be more than certain that the fuel and air jets will only need to be cleaned. You will need float bowl gaskets, float needles (these are critical, and most Ebay kits will not have the correct ones), idle mixture o-rings, fuel rail seals, and throttle shaft seals. If you're lucky you can skip the last two items for a while, but that's a rare occurance unless the carbs have been rebuilt before.
     
  12. tabaka45

    tabaka45 Well-Known Member

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    Boil your carbs for 10-15 minutes and then blow them out with carb cleaner. Does a great job of getting all the varnish, etc, out of the small openings.
     
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  13. ratch

    ratch New Member

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    yeah I been scouring the interwebs. Ebay and Amazon, there's a lot of kits that have a Wide array of "compatibility" however knowing what i know from reading the info the guy from xj4ever sent me, none of them have the right jets. I have to get jets, they got mangled on removal. someone else was in those carbs and tightened the crap out of the jets. I know it was someone else because there was a little bit of wear on the jets from where a screwdriver was used.

    One of my future desires is a good cleaning and possible Overhaul of the engine itself. I bet it could use a round of new gaskets and such.
     
  14. k-moe

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

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    That xj4ever guy knows his stuff. He also bought up a ton of NOS parts from Yamaha dealers.
     
  15. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    for starters, don't submerge the carbs in anything unless you plan to do the whole 100% throttle shaft seal replacement rebuild, which could get expensive. DO clean them as per the recommended maintenance procedures, then WET-SET the float levels and do a careful, accurate bench sync before returning them to the bike and trying to start it.

    How many miles are on this bike?
     
  16. ratch

    ratch New Member

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    according to the gauges there's only 7200 miles on the bike. it could be 107200 miles for all I know. it's 35 years old. However, I'm more willing to bet it's 7200. our states don't keep track of milage on the title for Bikes. I live on the border of KS and MO. bout the bike in MO. so It'll have to have an inspection when I get a tag.

    As far as the carb rebuild. the Carbs are all disassembled, down to the point of removing the throttle shafts and enrichment needle. Even though I thought ahead and marked each carb with position, they're all stamped with the info. each carb has it's own little magnetic tin with the internals in it. I'm prepared for seal replacement. However, the kits are a bit pricey from xj4ever. So the carb rebuild is paused while I accumulate money. I don't want to disassemble these carbs again. I've done my research on how to do it. I made the newb mistake of not looking up prices first. So I'm too far down the rabbit hole. I won't remove the Throttle shafts unless I know I'm getting the seals.
     
  17. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    Cool. The 7200 miles is very plausible; and IF TRUE it means that there wasn't a lot of time for wear to occur or lack of maintenance to hurt it too bad. You've already learned the most important lesson: know what you're getting into BEFORE tearing something apart and being faced with a lot more time and expense than you expected. Personally, I wouldn't have "broken the rack" until I was ready to do throttle shaft seals; you are wise to pause.

    Long-term, if the motor only has 7200 miles on it, then it's barely overdue for a valve adjustment even if they were never checked. My point being, the need for an actual "overhaul" probably doesn't exist; don't create the need by ripping into something that didn't need to be. From the sound of things, this bike needs more in the way of catching up on maintenance than it does anything resembling an overhaul.
     
  18. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    while your carb rebuild is on hold, now is an excellent time to check the valve clearances. Then that'll be out of the way before you attempt to tune the carbs when they're ready.
     
  19. ratch

    ratch New Member

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    I only meant overhaul for gaskets that need replaced. the valve cover gasket for instance. it's pretty hard, not rubber anymore xD. I had no intentions of full engine disassembly, but a lot of the gaskets are most likely 35 years old. I suspect this bike was a garage bike with an occasional ride on a weekend. until getting into the hands of idiots.
     
  20. bigfitz52

    bigfitz52 Well-Known Member Premium Member

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    COOL. Valve cover gasket for sure; and any other covers you remove (clutch, ignition, etc). When you replace the valve cover gasket, also replace the metal and rubber "donuts" on the bolts. The bolts have stop collars, they only tighten so far. Those 'donuts' are what actually press the cover against the gasket, and if you don't replace them even a new gasket will leak. They get baked hard in a compressed condition and don't work any more, and you can't tighten up the bolts to compensate.
     

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