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Help ZXR250A not starting

Discussion in 'Kawasaki 250cc In-line 4's' started by Why?, Oct 31, 2024.

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  1. Why?

    Why? Well-Known Member Premium Member

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    I have a ZXR250A which has not been used for almost 15 years, I have removed the carburetors and they have been thoroughly cleaned, needles and seats replaced gaskets replaced, jets and emulsion tubes cleaned. I have tried both 2 1/4 and 2 3/4 turns out on the pilot screws ( I found 2 1/4 in a manual and 2 3/4 on this forum) the 2 3/4 seems to a least give me some firing. I have good spark on all 4 and have new plugs, coil packs and leads.

    It did start once when I splashed a small amount of fuel in the in the carburetors but was only running on 3 cylinders, after that I re did the carburetors and replaced the coils and leads.

    Any advice would be most welcome
     
    Why?, Oct 31, 2024
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  2. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    First thing to do would be set the fuel tap to prime setting and let it gravity feed. ZXR fuel taps are a vacuum tap so if it hasn't run in ages and the bowls are dry you will need a lot of cranking to fill the bowls, which is what the prime setting is for.

    Hope you did the needle valve seats and orings otherwise it will flood and hydrolock
     
    Linkin, Oct 31, 2024
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  3. Why?

    Why? Well-Known Member Premium Member

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    Thanks for the reply, I am not using the fuel tank I have a clear fuel container suspended about the bike, when I turn the tap on I can watch the level go down as its filling the bowls, it then stops.

    Needle valves, springs, o rings and washers are new.

    Its got me stumped ATM, I have fuel (pretty sure), I have spark, so it should bloody start. I have also checked the right coils are connected to the right spark plugs.
     
    Why?, Oct 31, 2024
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  4. Murdo

    Murdo The Good Doctor Premium Member Contributing Member

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    How much compression does it have?
    I'm working on a 250DRZ at the moment with same symtoms, been sitting for 10 plus years. Turned out to be the rings stuck in the piston.
     
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    Murdo, Oct 31, 2024
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  5. Why?

    Why? Well-Known Member Premium Member

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    Funny you should say that I was going to get a compression tester and test the compression this weekend. I will now definitely do it.
     
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    Why?, Oct 31, 2024
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  6. Frankster

    Frankster Grey Pride...Adventure before Dementia Premium Member

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    I'd also check the valve clearances while you're at it.
     
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    Frankster, Nov 1, 2024
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  7. Why?

    Why? Well-Known Member Premium Member

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    Compression is all over the place, #4 good, #2 & #3 Average, #1 poor. Looks like the motor is coming out. Hopefully not a hole in a piston. Never dropped a motor on a ZXR, only FZR's and CBR's any tips?
     
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    Why?, Nov 4, 2024
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  8. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    You can pull the head and barrels off with the engine still in the frame, but you will need to remove airbox/carbs and radiator.

    Worth checking valve clearances first

    Leakdown test is handy as well
     
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    Linkin, Nov 4, 2024
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  9. Frankster

    Frankster Grey Pride...Adventure before Dementia Premium Member

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    Drop the engine out and check it properly. Effing around with the engine in the frame is just painful.

    Disconnect everything and drain water. I don't drain the oil, but it might be easier if you do. be careful of the external oil line. I use a lift platform under the engine and undo the front retainer and the higher rear retainer. This makes the engine drop out from the front and pivot around the rear retainer in the frame. Get a mate to hold it steady and remove the rear (lowest) frame bolt and drop her out. Put her back in in the reverse order. I'd give you a hand, but I'm on the boat (to TAS) after Melbourne Cup.
     
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  10. Why?

    Why? Well-Known Member Premium Member

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    I'll drop her out next week, need to get a couple of small jobs done (joys of being semi retired). Have already removed the radiator and carbies, easier to work on on a bench. Thanks Linkin and Frankster for the tips.
     
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    Why?, Nov 4, 2024
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  11. Why?

    Why? Well-Known Member Premium Member

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    OK Engine out valve clearances measured (I can't measure any smaller than 0.04mm) and to closest 0.02mm

    From top left to right intake: 0.00 0.00 0.00 0.10 0.16 0.10 0.10 0.15

    From bottom left to right Exh: 0.16 0.16 0.20 0.20 0.20 0.24 0.20 0.23

    Which hopefully explains my **** compression on 1 IMG_1974.JPG
     
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    Why?, Nov 6, 2024
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  12. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    That'll do it.

    You'll want to set the clearances to the maximum spec, virtually impossible to do first go when you have zero clearance, a good starting point is to go down 0.1mm in shim size (eg 160 to 150) and re-measure

    Cam cap has to be torqued to spec or you will get inaccurate readings.

    You can leave the chain off and install one cam at a time, rotate the engine so the pistons are clear of the valves before you install a cam.

    This way you don't have to set timing every time you remove and reinstall the cams to change shims.

    Be curious to see what your shim sizes are. When I did clearances on my ZXR, after 10,000km they had tightened again, and it needed yet another tensioner.

    If you end up pulling the head, it's worth popping the valves out to check their condition and either cut or lap them so that they seal properly again.
     
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    Linkin, Nov 6, 2024
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  13. Why?

    Why? Well-Known Member Premium Member

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    Thanks for that,

    Need to order in a shim kit. Are the Ebay kits OK with various sizes?
     
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    Why?, Nov 6, 2024
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  14. Frankster

    Frankster Grey Pride...Adventure before Dementia Premium Member

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    Use Chris at Precision Shims (in Melbourne). Make sure you tell him the shim diameter as he often sends out 7.5mm shims (for CBR).
     
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    Frankster, Nov 7, 2024
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  15. Linkin

    Linkin The Mechanic - Moderator Staff Member Premium Member Contributing Member Dirty Wheel Club

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    Measure the shim diameter and check the valve retainers too, some ZXRs have 8mm shims
     
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    Linkin, Nov 7, 2024
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  16. gyro gearloose

    gyro gearloose Well-Known Member

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    just buy the box of shims on fleabay... hot cams or whatever theyre called. that box of 60pcs or so is about the same price as messing around with getting a few shims from most bike shops in my experience... unless theyll do an "exchange"... still adds up if you gotta do a few. factor in travel time, maybe a day off work, etc etc... buy the box.

    with "negative clearances"... slap the smallest shim in... usually a 1.2. gotta do the same thing when any valve work is done, as its rather annoying to have to tighten all them cam caps up, only to find its STILL "negative clearance"... try and reduce the assemble/disassemble as much as possible?

    and once you have them all done? WRITE IT DOWN!!!!

    definitely pays to pop the head and check the valves... those zero measurements suggest its been flogged to death... even maybe interference damage... ouch. fingers crossed?
     
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    gyro gearloose, Nov 7, 2024
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  17. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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  18. Frankster

    Frankster Grey Pride...Adventure before Dementia Premium Member

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    Looking at the image from left to right, Cylinder 1 is the one on the right & it has one intake valve below spec and two other valves at the low end of spec. Cyl 4 is the worst, followed by 3 and then 1 and 2.

    Also, FYI those O-rings being used to seal the spark plug cavities are not the correct piece.

    upload_2024-11-8_10-52-15.png
     
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    Frankster, Nov 8, 2024
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  19. Why?

    Why? Well-Known Member Premium Member

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    Thanks for that I'll order the correct parts

    Parts now ordered from Matt Jones Kawasaki
     
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    Why?, Nov 8, 2024
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  20. Why?

    Why? Well-Known Member Premium Member

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    1st go at re shimming the valves, all except 1 are now well within tolerances, bugger it was one of the valves with zero clearance so it was an educated guess, it is an intake valve now 0.08mm so I'll go 0.12 mm smaller so it comes in at 0.20mm. Practice makes perfect. IMG_1988.jpg
     
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    Why?, Nov 11, 2024
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