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Project 1994 ZXR250

Discussion in 'Your 250cc Projects' started by Adamn, Nov 6, 2021.

  1. Adamn

    Adamn Member Premium Member

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    End of year update ..... I'm going to try use less words and more pictures

    Carbs are back together and bench sync'd using a round feeler gauge. Diaphragms seating issue resolved by cleaning any trace of INOX around the rim and trying numerous times to get a consistent 'woosh' across the 4.

    20211219_171602.jpg

    Carbs bagged up and stored while I move on to other things ... I wanted to check the valve clearance and leak test the motor and, i also wanted to clean the rest of the motor before I went ahead and found these adjustable feet which served as a carb intake plug, also found 16mm chair tips to block the crankcase breather hose.

    20211217_212746.jpg


    after yet another wash (I've fast forwarded a few steps here in stripping the rad and cam cover):

    20211230_143809.jpg

    Dropped the oil which looked pretty good - appears like good quality red stuff and no real particles to speak of. Coolant wasn't too bad either. 20211228_164705.jpg

    Picked up one of these to do a leakdown test, I figure I can use the adaptors and buy a higher PSI gauge with a check valve if I want a compression tester also.

    20211229_141807.jpg

    CR8E plugs were found to be installed instead of CR9E's
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    Today was clearance measuring day, below are the results - I will check again to make sure I measured correctly.

    20211230_152624.jpg

    One thing i'm not sure is the cam timing marks - I believe this should be #1 TDC on the compression stroke, however I'm not convinced the cams are lined up correctly.... I also noticed that depending on the crank position, the chain is noticeably tighter and looser - apart from a tensioner or chain issue, I don't see what else could explain that.

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    Last pic shows where the chain has given the cam cover a little kiss.

    20211230_152636.jpg
     

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  2. Linkin

    Linkin The Mechanic Premium Member Contributing Member Dirty Wheel Club

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    That's all pretty standard fare for a bike of this era.

    The ZXR's are known for their cam chain/tensioner issues. I would suggest replacing them. You can get a chain, either endless or unjoined from ebay for about $100, the tensioner bits are the same as a GPX250 - when I did mine I ordered the individual parts and assembled it. Lubricate with oil and perhaps moly grease additive. The plunger, bearing and body take most of the brunt.

    There is a mod you can do to the crankcase to change the chain, using an endless type, without having to split the engine in half, but I'd leave that for later.

    All your clearances are at or below minimum specification so they need attention - this will greatly affect compression and leakdown readings. Set them to the upper end of the clearance range for maximum time between adjustments. A little bit over spec is OK (talking 0.01mm) but may be noisy. Loose (within spec) valves are happy valves. No valvetrain noise indicates tight clearances generally.
     
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  3. Adamn

    Adamn Member Premium Member

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    Happy new year everyone!

    Thanks @Linkin for the advice. Chain ordered (un-jointed).

    I'll check the tensioner for wear, I wasn't able to locate the specs in the service manual though. If the body does wear i might be best to replace it as a unit - anyone know if a ZR250 (Balius), OEM part 12048-5002 is compatible?
     
  4. Adamn

    Adamn Member Premium Member

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    2022 update 1:

    I ended up measuring all valve clearances a second time and quickly became very confused as all the valves had seemingly tightened up ! As it turned out, in reality they hadn't moved at all - the feeler gauges I recently bought have imperial and metric values printed on them and I was reading the imperial values by mistake ... turns out I fell into the same trap during round 1 on a pair of valves also. The old saying "measure twice, cut once" is still valid !

    A quick spreadsheet to minimise mathematical errors was definitely a good move. Keeping track of what came from where and placing the new shim in the allocated tray was my best friend during the process also.

    20220115_171247.jpg

    I leak down tested the engine while the cams were out, interesting process and my take-away trick is a nitrile glove on the exhaust is a good indicator for exhaust valve leakage. I also had to McGyver a thread adaptor as the one supplied with the kit did not want to thread in to the spark plug holes after it's first use. I ended up dismantling a spark plug and using JB weld to join the original M10 x 1.0mm adaptor to it.
    There was some air leakage across all cylinders but the majority of the noise seemed to be coming from the crankcase (rings). I'm not too concerned with the leakage from the valves at this stage in that the engine hasn't run for numerous years and none of the valve clearances were 0.0 mm, or should I be concerned ?

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  5. Adamn

    Adamn Member Premium Member

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    Missed a couple of pics.

    Mr Glove

    20220104_165732.jpg

    Shims going in (I installed spark plugs immediately after taking this photo!)

    20220115_170850.jpg
     
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  6. 2valve

    2valve Well-Known Member

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    The top end look's super clean with no sludge that i can spot. Must have been well looked after at one stage.

    Look's like your work area is set up well and spotless too , we must be related down the line.

    Is Mr Glove stuck in the muffler trying to get out , he may have drank to much soft drink shown in the top picture.
     
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  7. Adamn

    Adamn Member Premium Member

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    Before I undo the cam holder (I like how the tightening sequence is stamped in it BTW) ... is it 28 or 29 pins between the inlet and exhaust timing marks? It appears i have mistaken the 9 for an 8 in the service manual.

    I'm pretty sure i need to rotate the inlet cam CCW 1 tooth....

    Cheers

    20220121_115609.jpg
     
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  8. Adamn

    Adamn Member Premium Member

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    Cam timing sorted. Valve cover soda blasted and painted the little discs that hold the oil seal against the cover.
    Coil On Plug wiring done, I made some small lacing bars out of 10mm square aluminium to mount where the original coils sat so the wiring is secured:

    20220208_183812.jpg
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    Rad fan shroud is being 'relieved' as the coils foul on them - think 25mm hole saw...


    All cables lubed:
    20220205_121222.jpg

    I also discovered the RHS clip on bar is bent - NOS bar on the way:

    20220205_113554.jpg 20220205_113422.jpg
     
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  9. Adamn

    Adamn Member Premium Member

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    I decided to dig into the cooling system a bit more as I wanted to paint the pump cover to match the freshly painted stator cover. Impeller has some errosion on it but I think it's still usable. @GreyImport - I noticed you have a shiny new metal pipe that connects the hose from the water pump to the hose going to the cylinder. Is that a home made job ? I might have to do the same as the one I have is starting to fall apart. Is it just mild steel ?

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  10. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    Yes it was a 1 off ..... @maelstrom will know exactly what its made of as he had it done for me
     
  11. Adamn

    Adamn Member Premium Member

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    Thanks mate. I actually bought a welder I didn't need a while ago - sounds like a learning opportunity !
     
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  12. maelstrom

    maelstrom LiteTek Staff Member Premium Member 250cc Vendor Contributing Member

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    It is stainless and has the original steel bracket.
     
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  13. GreyImport

    GreyImport Administrator Staff Member The Chief Contributing Member

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    coolant joint.JPG
     
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  14. Adamn

    Adamn Member Premium Member

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    Been a while so here is a status update:

    • Flywheel cover and water pump housing(s) blasted and painted

    20220220_134711.jpg

    Freshly baked ...

    20220312_155805.jpg

    • Homemade gaskets as I was hoping to not wait for parts to come from Japan, as it happened I needed to wait for a new mechanical seal and a couple of other bits anyway. Also, I haven't tried making them since high school.
    20220312_160043.jpg

    • The exhaust headers ... I was going to paint them but there is a local guy that does cerakote so I took the easy option and splurged on that instead.

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    • I needed a way to prop the front end up so I could take the forks and triple clamps off, I bought a bit of square tube and solid round bar, drilled some holes in the right places and inserted them into some axle stands. Works Ok, stable enough
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    • Forks are currently apart, waiting on new seals to come in. I also used my TIG welder in anger for the very first time (it's actually the first time i've TIG welded anything - the quality of the job shows). I made a fork cylinder holder out of a bit of 25mm tube and some nyloc nuts. Fork oil is nice and dirty
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    • And lastly, I'm giving the brakes a full overhaul - definitely something you want to have some faith in
    20220416_112107.jpg
     
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