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Not everyones cup of tea

Discussion in 'Modifications and Projects' at netrider.net.au started by Devery, Sep 28, 2009.

  1. But it is a motorcycle and, for anyone interested, here is how my little CZ is doing.


  2. Good for you. Where are you pulling the bike apart - looks like a living room, not garage!
  3. Well done....70's bikes are so cool. I agree with you about re-birthing it as a cafe racer.
  4. that's nice mate........ love 70's bikes.

    Where abouts did you pick it up from?
  5. I must say, that is a very tidy example.

    As a former owner of a multitude of 250 twins and closely related Jawa 350s, I'd offer the following tips.

    1) Even if you leave all the other electrical components stock, replace every wire on the bike with something heavier and more corrosion resistant with proper insulation. You've only got 6 Volts and (IIRC) 75 Watts total dynamo output. You can't afford to waste any through skinny wires and corroded connections.

    2) If you possibly can, find a later twin leading shoe front brake plate. With a bit of fiddling around, it can be made to equal most Japanese discs on the small bikes of the late 70s.

    3) If the bike ever falls over in the rain (not unusual 'cos the stand's a bit narrow), don't ride it without ensuring that all water is drained out of the brake drums. Finding that it's not is very exciting but not in a good way.

    4) I never saw an auto-oiling bike that hadn't been converted to premix. Not sure why though.

    5) Looks like it's lost its fully enclosed chainguard, which is a pity in one way as chains would last forever, but good in another because of the distressing tendency of the bottom half of the chainguard to drop off and get wrapped up in the rear sprocket.

    6) Keep an eye on the screws securing the float chamber top. They tend to vibrate loose and the engine then runs lean. First warning is the tinkling sound of pre-ignition. Heed it.

    7) Nifty 3-in-1 kickstart/gearshift/clutch lifter is fun and worth practicing with as it will get you home in the event of a snapped clutch lever or cable.

    8) Expect to be tweaking ignition timing regularly to maintain performance. You may find that timing in accordance with Haynes instructions makes the engine run backwards (but the singles book may be different). Finding points and condensers may be difficult. Take samples to Supercrap and see if you can hunt down something similar from the car world.

    Good luck.
  6. looks like fun ;)

    Can't be too much to rebuilding a smoker can there? Keep the updates coming.

  7. Thanks for the replies everyone :)

    "Where are you pulling the bike apart - looks like a living room, not garage!"

    Hehe, its a spare room out back. My brother moved out so my bike moved in! Only the best for my bike.

    "I agree with you about re-birthing it as a cafe racer."

    I'm going to do the cafe racer thing on an SR250 first, then maybe I'll do the same on the second CZ.

    "Where abouts did you pick it up from?"

    Good ol' eBay. The gentleman was in Victoria and he just put it on his mates truck and he drove it round.

    Pat! Great tips. Let me go through them one by one.

    1) I just bought a kit to convert it to 12V. The electronics were driving me insane. Regulator broke, so I replaced that. Just recently I replaced the carbon brushes but still had a charging issue. Rewired everything. No luck. Hopefully this 12V kit is good. Its called VAPE. I hear good things about it.

    2) Sounds like a worthy job some time down the line.

    3) Will do.

    4) Haha, mines going pretty well at the moment I think... Although the gasket on the mixer is a bit mushy I think, leaking a bit.

    5) I have one from another CZ 477 I bought, would you recommend fitting it?

    6) Noted.

    7) I had the front brake cable break on me, not the clutch yet... but still a very handy tool.

    8) I have got it going backwards after doing some timing! Quite a shock. I'll be interested in how timing is done with this new system.

    "Can't be too much to rebuilding a smoker can there? Keep the updates coming."

    Thats the theory!! and will do.
  8. Hmmm....I need to dredge the old long term memory banks for this.

    A 12V conversion, assuming it's a good one, will solve a lot of the electrical gremlins that I remember. If nothing else it will halve the current load on your switchgear, which is beneficial in itself. Stuff like bulb holders will still be the questionable Czech items though. I'd recommend hunting for stuff like headlamps and indicators, with styling in keeping with the bike, from Germany or Japan. Even Lucas gear would be an improvement. 12V will also allow you to fit a decent coil (although I'll admit I never had any trouble with mine).

    The brake light switches on my bikes were rubbish, the internals literally dissolving in the English winter, but not before permanently illuminating the brake light and running the battery flat. Again, even Lucas universal stuff would be better.

    Full chain enclosures might not be cool or sporty, but for a practical, everyday ride, they're the bollox. If you can find an o-ring chain the right size, it'll last practically for ever inside an enclosure. The CZ unit is nice thick metal and fits well, unlike the crappy tin things a lot of Jap commutercycles were burdened with. However, it is carefully designed to kill you when the single bolt that holds it together at the rear vibrates out or the bracket fatigues off and the bottom half gets wrapped up in the rear sprocket. Fit your spare one but make sure it's got some additional means of securing it in place. Even a couple of big cable ties all the way around top and bottom halves would provide some degree of fail-safe. Incidentally, on the premix bikes, drips from the carb tickler are routed into the chain enclosure so your chain gets a shot of two stroke oil every morning. No additional lubrication is necessary.

    Timing was an interesting experience. Bear in mind that all my bikes were twins though, so the singles ight be different. I found that, if the points gaps were set in accordance with Haynes' wisdom, it was impossible to rotate the points plate far enough to get the timing right or, indeed, get close enough to avoid ankle breaking kickbacks and reversed running. The only solution that I could see, using standard CZ points, was to ignore the points gap spec in the book and to set the gap to a figure of somewhere between "bloody huge" and "ridiculous" and then fiddle with the points plate to get a spark at (IIRC) 1.8 mm Before Top Dead Centre as specified in the book. This works because points gap affects the timing.

    As I've noted elswhere, I consider CZ's designs to be basically sound, if somewhat out of date. Once the electrics are sorted, it should be a reasonably reliable bike, although the performance is aeons behind anything from Japan. Apparently they're fairly tuneable, using techniques developed for the likes of BSA Bantams and later Villiers engined stuff (which the Czech bikes closely resemble in many ways), but you can't go too far as you're stuck with a rather clunky, wide ratio gearbox which limits how vicious a powerband can be used. As my 250s could be thrashed along at a steady 70mph and handled well enough in a stiffly sprung sort of way to maintain a highish average speed on backroads, I never bothered.

    Oh yes, use a good oil and give the bike a regular thrash. The auto oiling might help, but my premixers tended to suffer from a build up of unburned oil in the exhausts if used excessively in traffic, resulting in a contrail worthy of a high altitude 747 the next time they were opened up out of town. Like visible for a mile or more behind the bike, I shit you not. Very embarrassing.

    A CZ will make an excellent first project (assuming spares availability). Enjoy it.