My Tri-shed piston pics

[ssskipeee]

heres a few pics of the piston in my z, i think you`ll agree its more than fooked and its a miracle it ran at all.[IMG]

[ssskipeee]

the piston onmmy z has a 0 on it does this mean its standard size?

[tecat-z]

This is what happens when air filters are neglected or omitted in some cases for years. The piston to wall clearance becomes so excessive that the skirts become fatigued over time from slamming into cylinder when piston changes direction. I hear a lot of people say ( just re-ring it) I've never been one to do that since it does nothing to correct fitment of piston and reduce the rocking motion. In fact, new rings with correct outward tension gives the excessivly worn piston a better pivot point to rock on. Understand cases like this are relatively rare, but does illustrate the importance of maintenance and that all things in time require replacement.

[ATC-Eric]

ssskipeee, I would suggest you at least hone it (I remember you stating that the jug still looks good). I had a friend bring me his top end, and his piston was worse then yours! I couldnt believe what it looked like! Well the jug looked to be alright suprisingly, when turns out that the glaze had just covered up the real damage. Hone on it for a bit, and see if there is any scoring lurking below!

[ssskipeee]

this is the first time i have taken an engine apart in a bike so its a learning curve so on the risk of sounding stupid what is honing?

also is the 0 on the piston stating a std size?

[tecat-z]

Honing removes the surface in the cylinder slightly, thus removing more metal which creates more clearance. This in not good. You will crack the skirt again, due to severe rocking. These are high performance engines and should be treated as such. If maximum performance is desired along with durability, clearances and tolerances are to be obeyed. Being cheap, just to just get by doesn't pay. It only creates more serious problems and possible catastrofic failure which leads to the discust of the machine. Don't fall prey.

[ATC-Eric]

You dont sound stupid, everyone has to learn at one point or another.

This is a flex hone, its what you would need to hone it:

http://cgi.ebay.com/ebaymotors/2-3-4...77847960QQrdZ1

Very effective, and perfect for a good cross hatch. Cross hatching is done to put "grooves" into the cylinder wall to allow lubrication of the piston. You dont want a perfectly smooth cylinder. The way your piston looks, you might not be able to get a part number off the top. It should be in the middle, take some sand paper to it to see if its under the carbon build up. I dont know what the 0 means, there should be a longer number.

What I did was took a digital micrometer to measure my jug. That way I knew exactly what it was. Then I ordered the piston accordingly.


With the flex hone, you want to put it in a cordless drill on the top speed. Then you turn it on before putting it in the clyinder, making steady level strokes in and out about a dozen times. Dont go to slow, but not to fast. Its all a lot of fun for me, rebuilding my Z engine was an enjoyable experience.

If I was in your shoes, I would end up just boring the thing out.

[tecat-z]

Cylinders wear front to back and take on an oval shape that can only be detacted through accurate measurement. Honing does nothing to correct this problem regardless of weather you have oil retaining crosshatch hone marks. Part of learning is also taking good advice form others who have been there before. If i or anyone else can give advise to a person who is clearely asking for help. We need to help that person to it right the first time so they dont get discouraged. Don't get me wrong, honing is fine if you keep up with maintenance and replace pistons on a yearly basis. And breaking the glaze is desired. Its just that sometimes honing can't help certain situations.

[ssskipeee]

well everyone is giving me great help but i`m afraid this is going to be a slow process as money is tight at the mo as i`m out of work.

i will keep you updated on as i carry on.

the misses is going to flip, she thinks i`m getting rid of it soon but it all takes me back to my 1st 3 wheeler a nice little honda 110 therefore its getting rebuilt to a proper z with a nice lick of paint and a load of new parts!

[rustyhondas]

Be carefull man. That bike and engine are filthy. You are building a engine! This is serious work. You cant be working on a motor when the frame and engine is caked with mud and sandy grime. You got the jug off and dirt is all in and over everything.And the work area looks like hell to.

SLOW DOWN! Take your time do it rite, build it when money is not such a problem. Get your self about 500 bucks saved up or a creditd card you can pay for and get your jug bored and a new piston and whatever other little things you need, ? wheel bearings, brake parts ,and what have you off Ebay.

Dont let that 3 wheeler go to the dogs because you are tearing it apart while it is filthy ,Sand getting in the crank case in a dirty shed while you aint got no job,Come on man.

[InPiEcEs]

Either way you look at it, you need to buy a piston, and a gasket set, so............
spend the extra $40-70, and bring it in to a good cycle shop, let them measure it, and bore it for a new piston. By skipping a bore job, you're saving less than $100, and risking roughly that much money if you lunch a piston, not to mention possibly a crank, and cranks aren't cheap.

[ssskipeee]

Dont let that 3 wheeler go to the dogs because you are tearing it apart while it is filthy ,Sand getting in the crank case in a dirty shed while you aint got no job,Come on man.[/QUOTE]


first off there aint no sand where i live actually you`d be lucky to find sand in scotland and second my lock up aint dirty its just cluttered so dont worry about it it`ll all get sorted with care, i only took the head off to see the damage so like i said this will be a restoration project but will take time not only because i have no money coming in but because i`m off to tunisia in june and have to fork out over £2000 for that.

i`ll get the jug done at a good machine shop where i take my car engines, i know they do bikes aswell they`re the biggest and best place in scotland, all the bike shops send there stuff there too then add there price on top of it.

[03 ORANGE SHEE]

hi, i would pull the motor out of the frame , looks like there are some pieces of pitson shirt broke off that disappeared into the cases. this would damage the crank and lower bearing

[ssskipeee]

that is the plan then i can get the frame cleaned up rubbed down and ready for painting.

i was thinking of going with a 69mm piston & rebore as its cheaper for me to buy the piston from the states and get it shipped for less than what i`d pay over here.

i also need swingarm bearings, chain & sprockets, axle & bearings, tyres, brake pads, hubs and rear wheels along with a few other parts but hey thats part of the fun in doing a rebuild.

[Dirtcrasher]

It's impossible to even guess what size piston to buy before it gets measured up. Som cylinders are so bad it takes 3 or more oversizes toclean up the cylinder to wear it is round again.

As posted above, hones don't salvage cylinders very often - they are a cheap fix that does nothing. Hones are great for crosshatching a freshly bored cylinders. Or for a new set of rings after some hours are logged on. But after that, it's almost always time for a bore job.