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Project The Second Fizzer

Discussion in 'Your 250cc Projects' started by Joker, Sep 28, 2016.

  1. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Those bores look to have been badly scratched with too course hone.
    If you have better then hone them correctly and put your new rings in them.
     
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  2. Joker

    Joker CLUB250 Staff Member Premium Member Ride and Events Crew Contributing Member

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    Hmmmmm..... having a look at this cylinder head it's definitely been in the hands of a "backyard" job.

    I have to get it skimmed, the surface is all scratched up...

    21768299_10159360985695716_812703964506444476_n.jpg
    The second and more concerning part is that all the cam journals seem to be scored similar to the below. Neither of my other cylinder heads has this, it suggests someone might have put in different cams without checking clearances. Funnily enough the cams look OK.

    21687646_10159360985405716_6952067933772042098_n.jpg

    I mean either way it will probably run, but it's not ideal.
     
  3. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club

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    Nothing is ideal on these old bikes, have to make it work with what you have or pay bigtime
     
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  4. Murdo

    Murdo The Good Doctor Staff Member Premium Member Ride and Events Crew Contributing Member

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    Don't worry too much about the bottoms of the journals, it's the top caps that take the load against the spring pressure. So long as they are good and you are getting plenty of oil through it should not be a problem.
     
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  5. Joker

    Joker CLUB250 Staff Member Premium Member Ride and Events Crew Contributing Member

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    Cool well I've taken all the valves out now, won't bore you all with photos (plus I'm feeling lazy) but they all seem to be OK. The intakes in particular are good, but on all these 3LN heads I am finding the exhaust valves have worn significantly more.

    I ran out of lapping paste so I'm going to have to get some more before I can continue. The rest of the motor looks OK so new rings, steam seals, oil and filter and I'm expecting she'll go OK after mucking around with valve clearances again.

    I still can't find my damn baggie of shim spares... really annoying because I'm going to need it very soon.
     
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  6. beano

    beano Well-Known Member Premium Member

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    if you have those pics and you dont mind throwing them up some day when you have the time?? i have a spare 3ln engine in the garage with low compression and i want to tear it down some day to learn how it all goes. So i love these threads with all the engine pics, they're really really nice to just sit down with a coffee and read through.
     
  7. Joker

    Joker CLUB250 Staff Member Premium Member Ride and Events Crew Contributing Member

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    It's one of those things where you're all motivated at the start and then once you coat your phone in oil and grease because of your dirty hands it gets old pretty quickly and the motivation goes lol
     
  8. Joker

    Joker CLUB250 Staff Member Premium Member Ride and Events Crew Contributing Member

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    Finished rebuilding the head today, seems to be OK. Valves lapped, new stem seals... lubed up etc. Hopefully valve clearances won't be too far out when I reassemble.

    22089318_10159382871615716_3335031878292770282_n.jpg 22050001_10159382871655716_350086297354702956_n.jpg 22089465_10159382871715716_1848052398377794872_n.jpg
     
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  9. Joker

    Joker CLUB250 Staff Member Premium Member Ride and Events Crew Contributing Member

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    New rings, a "better" bore and cylinder head back on. I am still buying these chinese AHL rings from ali express as this is the 3rd time I've used them in a motor and I haven't had any issues related to the rings. No binding so looking good, still to torque the head down then play with valve clearances which I most certainly am NOT looking foward to - especially since I still can't find my spare shim baggie. Damn thing...

    So you know if you are buying AHL rings:

    Chrome ring is 2nd ring
    Black ring is top ring
    AHL markings on both rings face UP.

    Yes I had that clarified with AHL directly :)

    20170929_163103.jpg
     
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  10. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club

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    Interesting that they say the chrome ring should be used as the 2nd compression ring. I was told to use the chrome ring on top when assembling my 3LN3.
     
  11. Joker

    Joker CLUB250 Staff Member Premium Member Ride and Events Crew Contributing Member

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    No idea... this lot had a chrome ring and a black ring, the previous lot was 2 black rings (but one with a chrome border)? Which did you get?

    Also, what torque did you use on the cylinder head bolts? I can't recall what I did before but looking through the info - for the 2KR it is 1.8kgm, but the 400 has 2.5 kgm and 3.7 kgm depending on which manual you refer to. No real similarities...
     
  12. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club

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    3LN's are 2.5kgm / 25nm on the head bolts, inner to outer in a diagonal pattern, from memory.

    I believe the AHL rings I received had a full chrome top ring. Given the RPM's these things do, and the iron cylinder sleeves, chrome ring on top would be a good choice (but what would I know?)
     
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  13. Joker

    Joker CLUB250 Staff Member Premium Member Ride and Events Crew Contributing Member

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    Hmm... well sometimes you can get different stories from these chinese people I suppose. I'm not sure I understand what you mean by references to the RPM, iron cylinder sleeves etc and the relationship to the chrome ring needing to be on top? Can you explain please?

    I never really thought about which would go on top in terms of the make up of the ring itself, I always just assumed it didn't matter if it was black or chrome and it was more about ring gap or something...?
     
  14. Linkin

    Linkin The Apprentice Premium Member Dirty Wheel Club

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    Better wear resistance with the chrome ring on top
     
  15. risky

    risky Megelli King Premium Member Contributing Member

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    and more able to withstand the combustion heat.
     
  16. Joker

    Joker CLUB250 Staff Member Premium Member Ride and Events Crew Contributing Member

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    I hear what you're saying, but can you please help me understand the background behind what you're saying? Is it about a different ring material composition? the outer ring coating? Something else?
     
  17. Andych

    Andych Well-Known Member Premium Member Contributing Member

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  18. Joker

    Joker CLUB250 Staff Member Premium Member Ride and Events Crew Contributing Member

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    Cool good link thanks. Answer is here:

    "In order for a steel ring to be compatible with cast iron cylinder bores, it must be coated with moly, chrome, PVD (Particle Vapor Deposition), or gas nitriding. Moly coatings are applied to the face of the ring. Moly offers a high resistance to scuffing, but also is porous which provides some oil retention.

    Chrome is a very hard coating used in high load applications and is found often in dirt racing engines. The chrome coating can resist dirt impregnation and send the debris out the exhaust port. If you were to use moly coated rings in these applications, the dirt ingestion would be caught in the face of the ring because of porosity, and damage to the bore would result."

    I'm on engine rebuild no 3 with AHL rings, so far so good. Remains to be seen if they can withstand the test of time though.
     
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  19. risky

    risky Megelli King Premium Member Contributing Member

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    the other thing to do is how you set the rings up. they should have the top face marked.could be a dimple. could say up?if you have 3 piece oil ringd set the end gap opposed over the gudgeon pin.top ring needs to have compresion gas behind it.
     
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  20. Andych

    Andych Well-Known Member Premium Member Contributing Member

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    The manuals will generally give you the ring end position offsets which are important... even more important is to ensure the end gap on the rings is in tolerance.. again... refer to the manual... measure half way down the bore using a piston to set the ring so it is straight... none of it is hard... you just need to follow the instructions and you cant go wrong...
     
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