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This is how the piston surface should look / feel like:
right hand side is a stock piston (78mm), left hand side is a big bore piston (86mm).If it has a “burn-in”-hole, it should still move up and down, but may end up like the poor one.
All the best !
Cheers, Michael
My original plan was to just run the purple bike while I rebuilt the other one.
Then the plan goes astray and the engine has to come out.
And now you’re teasing me with photos of a shiny big bore piston.
Are the pistons easy to get hold of and what capacity does it take it up to. Is it just a case of a re-bore and new pistons. Are the cylinders still strong enough and can you get gaskets. Thanks.Hi Kenny,
the big bore set was offered to me after I have asked a lot of engine reworkers to do that for me, but it was close to impossible !The needed parts are not easy to get and the closest pistons (Ducati) still need some rework.
Find a report with some details of another modified Twin:
http://www.z750twin.de/Manfreds_LTD.htmThis shown piston has 86mm bore and gives 906 ccm. The stock sleeves needs removal, the aluminium cylinder a bigger bore and finally new sleeves. Basic information is that the wall of a sleeve must have a minimum of 2.0mm thickness.
I know two other Twins with 865 ccm, one is Martin’s from Germany and the other is ChrisLWGs from the UK 😉
Well, I can provide some more information and pics, but my engine will be completed this winter eventually, incl. new camshafts 😉
If you are looking for standard sized pistons and rings you may find it here:
http://www.scheuerlein-motorentechnik.de/motorrad/Kawasaki/700-799-ccm-k7/Z750-Modelle/Z750-Twin/PS: Gasket at cylinder bottom is paper and can be cut out with a rounded nail-scissors. Cylinder head gasket I will use is made from copper and I have an AutoCAD file for that, so it can be made by a maschine.
Cheers, Michael
Hi,
I’ve got the engine out, wasn’t as bad as I thought.
Started to take the cams out, number 5 bearing cap was on the wrong way round, arrow pointing backwards, alarm bells.
The head came off quite easily, which was more than could be said for the barrels. They came up reasonably easily until the threaded part of the stud, then it was brute force.
The left hand barrel has 2 lumps out of the skirt, one quite large.
The left hand piston then just lifted out. The con rod was still attached but the bottom bearing was missing and the rod is bent.
I tried to upload some photos but can’t seem to do it.
Oh well, nobody said life was easy.Ouch, Like people said use paraffin only don’t leave it in to soak, Drop a match in!!!!
Usually a few engines on ebay but pricy.Hi Kenny,
that’s to bad !
I am still wondering that the engine turns with that damage.
Heavy bending of the con rod and the destructed “foot” of the lower eye looks like there is the issue with seizing.
That bearing is oil-pressurised and the oil pressure can go away especially at this bearing if the large starter clutch wheel, that sits on the crankshaft, is either missing, manipulated or heavily worn.
I have stripped engines here and would give them away for a little fee.
Condition ?
I have to check, but to ensure proper operation a full rebuild seems to be inevitable. Probably with the same old components, but they need to be checked.A hurdle is the shipping method and the price for it from Germany to the UK.
No idea what the cost will be.Good luck !
Cheers, MichaelWow that’s devastation right there !
On a positive note, you’re half way there to a big bore conversion as at least one sleeve needs to be replaced !
Can’t tell from the pic – is the big end journal blued as well as scored ? That would point to oil supply issue.
Considering the damage to the rod, I think you got off light !
Amazed it was still turning over !
That is indeed a sorry engine Kennys but all is not lost. I can help with getting her running again.
If I remember the ebay auction correctly you also got a lot of engine stuff with the bike but if you don’t have what you need I have most engine parts available and also a complete B engine. Let me know if your interested.
Also BTW DO NOT preview a post when it contains pics. It is a glitch in the websites program which I cannot resolve.
Thanks for the offers guys, I did get quite a lot of engine parts with the bikes, but it looks like I’ll have to see what parts will fit. I have barrels and pistons but whether they match or not. The engine has been rebuilt before, although built might not be the right word. I’m surprised it isn’t worse.
I took the good piston off and am amazed at Kawasaki’s engineering brilliance. The second ring is apparently a solid ring, it’s seized into the groove but I’ve gone round it with a torch and can’t find the ends anywhere, not a trace. The hunt continues.
I’ve also attached a photo of the points cam. The nut behind the bolt head has 2 grooves and the cam has 2 marks where I imagine there should have been 2 lugs, one of you guys might know.
I’m getting ahead of myself, but where do I get a VESRAH gasket set, I can only find the other type.Hi Kenny,
the fixing of the points cam holder uses a special “washer” with two grooves and a hex-head.
http://www.cmsnl.com/kawasaki-kz750b2-1977-usa-canadamph-kph_model15507/partslist/57923.html#results
Number 18The points cam holder has two “noses” that match with the grooves.
It may be, that the “noses” are broken off. Not nice, but not a catastrophy.
It is recommended to turn the crankshaft using the larger sized washer head (17mm wrench) and not to use the smaller sized (12 or 14mm?) screw head itself.
Rotation direction of the crankshaft is backwards. Counter-clockwise, looking from the ignition side. As the screw is a normal “right hand” screw, there is a chance of loosen the screw instead of turning the crankshaft.
One of the “gimmicks” in that engine.
Good luck !
Cheers, MichaelPS: I had a damaged piston once and can’t remove the piston rings. There is an undescribable “melting mixture” present, that “glued” piston and rings together.
IF there are no obvious signs of oil starvation, and IF the engine has been “rebuilt” the cynical amongst us might suspect incorrectly torqued / tightened big end nuts ?
If you go own the route of replacement, don’t bin the engine ! I need a mule to mock up the supercharger for the embryonic Glemseck project.
Pulled a bit more off the engine, more problems. When I took the oil filter cover off, the centre tube was damaged. When I took the filter out it was crushed on one side and there was a hole in the housing that shouldn’t be there.
On a brighter note, I made a little frame to support the engine and swivel it over to remove the sump, so that comes off next.
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