My OCC chopper appears to have hung a ring.

Discussion in 'Stretch Cruiser & Chopper Motorized Bicycles' started by kelly dean, Oct 7, 2019.

  1. kelly dean

    kelly dean Active Member

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    My OCC appears to have hung a ring i think. the cylinder is badly scored above the transfer port and scored badly and beginning a crack below the transfer port. the piston is badly scored in various places but mostly starting half way up the piston in the area of the intake port and the lower ring is broken. The engine is a triple 40 ZL40 rod it was running a OZ heavy coil and a gasbike supercharge cdi . speed carb and a stock muffler that i had cut approximately in half for ground clearance the cap was reattached but the inner baffle tube to the cap had been chopped. running 40 to 1, 87 octane and full synthetic oil about 5 weeks before this self destruct i had swapped the stock cylinder for a ported cylinder i used the original piston but replaced the rings .the ring pins were aligned toward the intake port. i ran one lower gasket the port timing at exhaust was fair about 3/16 of the piston peeking through at BDC i slightly filed the piston skirt to have a clear intake port at TDC. the initial start of the bike after the cylinder went well the bike pulled really strong running a 44t sprocket. i checked the plug after the initial start and short run it was lean and i adjusted the needle height raised one notch to richin and it looked good the right toast color. there was no indication that anything was amiss the bike ran really strong through out the entire range. it was running along good and then it just popped and lost abut half the compression and wouldnt start again . Picture 227.jpg Picture 227.jpg Picture 228.jpg Picture 229.jpg Picture 230.jpg Picture 231.jpg
    im expecting a cylinder and piston kit mon 7th i have ordered a G4 cylinder and a G5 piston kit. I had a good quality new crankcase gaskit. this is my second adventure into cracking a case and be certain there is no debris lurking in there to ruin my day again ;)
     
    #1 kelly dean, Oct 7, 2019
    Last edited: Oct 7, 2019
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  2. indian22

    indian22 Well-Known Member

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    Sorry Kelly. Reading your detailed post nothing you did seems out of the ordinary in your engine work, setup, tune or fuel mix all appear quite proper. I'll mention a couple of things that you may be already aware of, but are easy to overlook in engine assembly (our own or factory built) checking ring gap clearance with a feeler gauge and making sure all port work has no sharp edges to "catch" a ring. Pre-lube cylinder with standard mineral oil (four stroke oil is fine for this purpose) before assembly, don't use synthetic lube for this purpose or during the break-in period either. Rotate the piston assembly in the jug slowly by hand and watch for snagging on port edges or extreme tightness through the complete cycle. If it looks and feels right complete the assembly of the top end.

    Use regular 2-cycle oil at 16:1 fuel mix for quicker and proper break-in and then switch to semi or full synthetic at 32:1 after first couple of tanks of break in mix. The regular oil allows parts "burnishing" to tolerance during break-in, the synthetic is too slick for this important purpose. If you like 40:1 performance switch to that when the engine really comes to life...in my experience that's after about 400 miles of mixed riding. Most of all don't push the bike for top end speed or get the engine too hot during long rides until after you switch to 32:1 mix....then, if required, fine tune the carb. Chop the plug occasionally during the process but don't over react to any reading other than lean...and lean needs to be quickly eliminated always.

    Kelly some of the cylinders we're getting shipped are "spawling" chrome liner, plating is coming off, so carefully check the jug when it arrives for any sign of plating imperfections if there are don't use it. Also if you do some port work check for flaking of chrome around the port afterwards, if there is flaking it will eventually get worse. No sharp edges on any port, smooth with emery paper.

    I'm sure you will build a good motor for your beautiful chopper.

    Rick C.
     
  3. kelly dean

    kelly dean Active Member

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    thank you so much for your reply Rick, I'll follow your advice on the fuel mixture. I've got the case reassembled using 2stoke oil on shafts seals etc., locktite blue is my best friend. I've got the new cylinder and the chrome is the best i've ever seen. Its the new design or perhaps a rebirth of old design, its got the open transfers. I'm not planning any serious porting behond chamfering edges the ports are large as is . I havent looked at port timing yet but will see what we see and thank you again

    kelly
     
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  4. indian22

    indian22 Well-Known Member

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    Kelly everything seems golden. Where did you purchase the new jug? I'd like to try one out.

    Rick C.
     
  5. kelly dean

    kelly dean Active Member

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    i bought the jug and the piston kit from bmw " bicyclemotorworks" like everyting some good reviws some not good personally ive always been happy with them. the jug was 23 plus reasonable shipping . it came with an aluminum intake manifold on on it came with exhaust studs installed, and intake/exhaust gaskets. Outside its typical chinese but the chrome is beautiful
     
  6. indian22

    indian22 Well-Known Member

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    Kelly I've bought stuff from them for years and BMW has always been a reliable vendor. I'll check with them as I'm interested in sourcing quality cylinder replacements. Thanks for the quick reply.

    Rick C.
     
  7. kelly dean

    kelly dean Active Member

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  8. kelly dean

    kelly dean Active Member

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    1 lower gasket the exhaust port timeing is perfect..it will
    it will take about 2 mill off the piston skirt to correct the intrake timing
     
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  9. kelly dean

    kelly dean Active Member

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    it could stand a mill to correct the trasfers
     
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  10. indian22

    indian22 Well-Known Member

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    Good fortune on the base gasket now to deal with getting squish perfect and I like using copper gaskets for sealing the combustion chamber and to juggle compression ratios. I usually use the thick copper gasket to get up and running for initial easy starting and then switch to thinner to get compression right for daily running, final gasket selection 'kinda depends on the performance head you're running 4cc, 6cc or 8cc chamber volume etc. but I'm an old guy and really prefer not to have difficulty pedal starting, but still want good performance. Once the engine starts well I go higher on compression. Compression is really good until it's not: detonation and heat kill engines quickly and getting compression too high does both though the dynamics are many.

    Engine work is only as good as the precision put into it, get the port timing right and it will make a difference.

    Back up and running quickly, rapidly as well should be a good outcome.

    Rick C.
     
    #10 indian22, Oct 8, 2019
    Last edited: Oct 8, 2019
  11. kelly dean

    kelly dean Active Member

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    it's back up and i spent lots of careful study time on the motor. I was really pleased at the port timing on this cylinder exhaust was perfect and it took a a very minimal notch of the piston skirt to open the intake. Im using the same HC head i have on it,Its a 6cc chamber it does have compression plenty to pedal on a fixie and i have the standard thick copper head gasket. i added the big banana expansion chamber i dont expect huge gains but i could afford it its gotta back fuel better than stock. Of course it didnt fit but nothing ever does on these OCC stingrays. plenty of frame clearance the motor is offset to compensate for the fat wheel nowhere near pedal clearance, for now i had an old xport exhaust manifold bought it long ago as a power upgrade it was worthless for that lol. I angled off from nil to about 5/16ths, turned the pipe in and it worked well im looking for a wide crank thats just the crank standard stuff doesnt fit the bottom bracket. It started up immediately. But it has a exhaust leak i shut it right down.I only had one gasket and tried to goop it but of course that didnt work lol. I ordered 2 gaskets from Oriley's have them in the morning, the O2 sensor gasket for a 02 toyota highlander fits almost perfect. While it was down it got a fresh coat of paint same scheme but i really detailed it, all the fasteners are contrasted between pink/black it really looks good ill post a couple updated pics. Thank you for your help and advise, regards.
     
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  12. indian22

    indian22 Well-Known Member

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    Well thought out Kelly your head setup is where I start on my new engines and those that aren't highly modified tend to stay that way, I don't chase high compression yet I have found some of the 66cc (regardless of brand) benefit in all around performance from going to the next thinner copper gasket. You'll feel the engine asking for a bit more and the plug chop and maybe head and piston cleanup is a guide as well.

    X-port, lol, I bought two of them and found them useless at first, yet looked nice in a 1950's retro way, I'd say they help cool the exhaust port somewhat, but enough to increase power? That's funny , but I use them them on two bikes because it set the exhaust pipe at the proper angle to clear things, as you found out. but running two gaskets is proper and will seal.

    If you are running JAP tapered pedal shaft, just buying a pair of wide pedals (some vendors sell wide pedals by themselves) some of these are noticeably wider than others. These may give you enough clearance to clear the exhaust, without buying a complete wide shaft and bottom bracket set with wide pedal levers. It just depends on how wide you need to go on that one side. Heat and bend the painted pedal levers works, that's what we used to have to do, so there are options.

    Contrast makes bikes pop visually and adds to nice paint work. I'll enjoy the photos.

    Rick C.
     

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