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ZL600 Engine Options:

Trojan441 Jul 27, 2018

  1. Trojan441

    Trojan441 Active Member

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    Hi,
    I will have to completely strip down the engine to clean and oil and repair, what options are there out there seeing it will need the barrels re-bored, can the ZL600 barrels and pistons be taken out further I wouldn't mind taking the engine out a little towards 650cc, b'cos I love that old fashioned 40 cubic inch capacity, is this possible and what pistons would I need or barrels, what will the head allow me in extra capacity?

    Can a different crank b put in what are the options here?
     
  2. ZLrider

    ZLrider Well-Known Member

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    I'd think rebuilding the engine could well exceed the value of the bike. If it were me I'd start looking for another 600 for parts or a 600 engine. If you have no luck, your only choice could well be a rebuild, but might as well explore your options. I've never had mine apart, but back when I used to blow up snowmobiles on a regular basis, the costs to repair were sobering. Especially if the 600 has pressed in sleeves.
     
  3. Trojan441

    Trojan441 Active Member

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    Thanks for your input, not sure apart from the slightly marked bore in the barrels what exactly is wrong with it, counting from the left surprise, surprise, it is cylinder 3! Cylinder 3 seems to be the one that plays up on these engines!
    We still re-bore here, for instance I have a British OHC 4 cylinder engine all aluminium, small car engine based on the Coventry Climax race engine @ 930cc, that can be taken out safely to about 965-970cc, if I could get pistons to fit! Incidentally for this Rootes engine, Kawasaki 8 valve engine, motorcycle pistons are often substituted in race guise.

    Everything has gone up here in respect to motorcycles and now Japanese motorcycles are spiraling up in value, a second hand ZL engine is more expensive than the commoner GPZ and GPX engines, expect to pay £350-£450! All the breakers are raising their prices in conjunction with one another, just like Estate agents do that sell houses! Whereas a few years ago £50 may have got you an engine, now they want 6 times that figure unless you buy from an guy who just has some bits!
     
  4. Trojan441

    Trojan441 Active Member

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    I have the ZL 600cc engine, 60mm x 52.4mm stood next to the 930cc engine, bore and stroke 70mm x 60.37mm and it looks dinky in comparison, and the ZL 400 must look dinkier still, but power wise little cylinder are more efficient a 1980s ZL 400 manages an average of 2.2 bhp a cubic inch, a ZL600 cc 2 bhp a cubic inch, the ZL 900 will be a even lower output if you do the figures, thermodynamics 4 U, to do with cylinder volume and surface area available to conduct away the heat produced. Yet Ibelieve research has shown that Longer stroke engines through better more flexible torque production are better on fuel. Now watch longer strokes/narrower bores creep into the new engines.

    Imagine how dinky a 4 cylinder 250cc is, but they are mighty efficient, at producing power for their size of displacement!
     
  5. Trojan441

    Trojan441 Active Member

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    Looks like there may be 61mm pistons available for the ZL600 adding round about 19/20cc to the displacement! 592cc to say 611 cc! Still researching at the moment!
     
  6. 87kawzl

    87kawzl Well-Known Member

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    Maybe 636 pistons and rods could work for ya. Just a thought, no research done on my part.
     
  7. MikeC

    MikeC Senior Member

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    Question: when you bore a cylinder oversized, does anything else change as far as intake valves or anything or does it produce more power with the same fuel mix/ volume?
     
  8. 87kawzl

    87kawzl Well-Known Member

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    It's all parts to fit into an equation. You would need fuel and exhaust change to get max benefit from over bore.
     
  9. MikeC

    MikeC Senior Member

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    I see. Thanks
     
  10. Trojan441

    Trojan441 Active Member

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    An Old boy, Geoff Monty who built his own engines 1950s'1960s, based round either sleeved down or short stroke BSA pre -unit singless, depending on whether he was in the 250cc or 350cc class. Or sometimes, even changing the dimensions of the standard 500cc BSA Gold Star unit, confounded the cognoscenti of the day, by using the same bore carburettors and exhausts for the various capacities of the modified racing BSA Gold Star single engines from 250cc to the 500cc class! But these were fully kitted out racing engines, with enhanced oil pimps e.t.c.

    He was so good at building these racing specials, they used to regularly come in behind the works MVs in 4th place!

    If using a slight over-bored barrel and piston,sometimes you have to have a modified cylinder head gasket, a slightly larger main jet in the carburettor and if you have a good free flowing exhaust system all should be well! You just benefit slightly from the small increase in capacity, so a slight increase in power. Often better stronger lightweight pistons, (Slipper design), can be fitted at a cost, this can give you a higher rpm if the bottom end (Crank and connecting rods), are strong enough to take it!

    However, the crucial factor is how much the cylinder barrels can be over-bored, without weakening them +10,+20, +30, +40, +50 1000/Inch, looks like on data I have seen that some Kawasaki barrels can be over-bored by 3mm, that's a massive 120/1000" overbore a pretty big increase giving around a 62 cc increase in capacity on a 4 cylinder machine, each barrel facilitating 15 + plus cc, (cubic centimetres), almost a Cubic Inch, (16.39cc), increase, probably adding 1-1.5 + bhp per cylinder!

    Another way of increasing capacity is to have the crank stroked and that is more complicated and more expensive than a re-bore, but increases torque if not absolute power / bhp figures, which increases an engines response through the rpm range in terms of flexibility.

    You can have cylinder heads gas flowed and larger valves put in , but if you overdo it the engine can turn into a gutless wonder unless you rpm is over 7,000 and then it would go like a rocket, but that is not very practical for road use!
     
  11. Trojan441

    Trojan441 Active Member

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    Of the 3 small 4s, the ZL500A, approx 4 x 125cc cylinders comes out the most efficient as far as producing power is concerned, producing 71 bhp @11,500 rpm, it has the stroke of the 600 and just smaller pistons @ 55 mm. Incidentally the 52.4 stroke is in the long-stroke 33 bhp SOHC 2 valve, GPZ 250 of 1983-1985, which has the same bore pistons as the ZL500 @ 55 mm. The ZL 600 has the same stroke too of 52.4 mm!

    The ZL400 has a slightly shorter stroke than the short-stroke engine of the short-stroke 45 bhp , DOHC GPZ 250R parallel twin introduced in 1986, 62 x 41.2 mm (Bore & Stroke), incidentally, this stoke is still being used in the Ninja 250cc bikes. In both of the 80s 250cc bikes had SOHC 17 litre/ DOHC 18 litre petrol tanks! Just shows you how much was put into Learner Legal motorcycles at that time! Air cooled GPZ550 has the same 52.4 mm stoke! KLE 4 valve 250 cc pistons are 62mm.

    In short there must be a cross-over in utility of engine components for piston, crankshaft. connecting rod, perhaps even cylinder heads if needed, options and possible upgrades for the ZL engines! As used copiously in "Princess Bride" film, it is inconceivable that Kawasaki didn't use the same components in multiple uses across the range of motorcycle engine options marketed! The small fours may be more generously served that the bigger engined machines!
     
  12. Trojan441

    Trojan441 Active Member

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    636 pistons are a massive 67mm bore when I checked them out!
     
  13. Trojan441

    Trojan441 Active Member

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    ZX-R 400R pistons @ 57mm are 1 mm bigge in sizer than the ZL400 bore!
     
  14. Trojan441

    Trojan441 Active Member

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    Has nobody who uses the site experimented with the 3 small 4 engines?
    Never seen a ZL500, no idea where they were marketed!

    Just if I am having the barrels re-bored taking them out slightly may make sense, or do later model barrels bolt straight on?

    To recast engine bottom- end casings, costs a lot of money, so there may be compatibility here!
     
  15. ZLrider

    ZLrider Well-Known Member

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    Just one guy's opinion, but when you want to go faster it seems smarter to get a bigger bike. Once you reach the top of the food chain and still want more, by all means modify what you got. I'm a bit of a traditionalist. I hate to see original stock vehicles made into Frankenstein jobs which only appeal to the owners or a limited pool of like-minded individuals.

    Generally you'll be money ahead and avoid all the labor by selling what you have when you get tired of it and moving up to a larger displacement bike. This may explain why few bother to swap engines, bore them out, etcetera, on the mid sized engines. It just really doesn't seem to make a lot of sense.
     
  16. Trojan441

    Trojan441 Active Member

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    Good point and I can see what you are saying, but I like sometimes a "Wolf in Sheep's clothing, rather than a Sheep in Wolf's clothing"!

    The mod's wouldn't really show, even 2 an experienced eye, bigger bikes can be slow and ponderous too, we get taxed on "Cubes" having 30-60cc more than on the panel amuses me, cos I am not being taxed on it see, strange I know!
     

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