cylinders honed

[DiverRay]

And what everyone has missed the the possible PISTON SLAP! Usually if you go slightly over on the bore, you knurl the skirts on the piston to keep the fit correct. This is old school, but it worked! You need to check the gap/fit between the piston and the bore.

[petejw]

Isn't there a problem with polishing the sides of the pistons? IIRC, pistons have a specific machined finish on them designed to hold oil for lubrication. Not enought oil, you get scuffed bores/pistons....

hi steve,
not that im aware of, there are oil holes in around the piston's oil ring groove,
as well as oil holes just underneath the oil ring for oil disapation(sp).

hi diverray,
yep, for sure, also the top piston groove/side ring clearance on alloy pistons have a tendancy to wear, this motor has well over 140,000k's and im doing this one on the cheap, (its been less than $100) there are some things i dont wanna know. lol

ive gota big bore kit that i want to put into my original siezed engine,
that one ill be doing properly.

hey nate,
only the thickness between the top and bottom compression rings
are different, the thick one wont fit into the smaller ring land.

[petejw]

honing,
if you were to do it properly
theres a proper tool to remove only the top ridge groove
you could use that prior to honing which would be a better/proper
way of doing it, but again im doing this on the cheap and dont have
the tool.

[Rickrod3]

Pardon me for asking but;

And what everyone has missed the the possible PISTON SLAP! Usually if you go slightly over on the bore, you knurl the skirts on the piston to keep the fit correct. This is old school, but it worked! You need to check the gap/fit between the piston and the bore.

What is knurling a piston skirt?
Knowing this may come in handy.

Rick

[crazy steve]

What is knurling a piston skirt?
Knowing this may come in handy.

'Knurling' is pressing a cross-hatch pattern into the metal (just like a ratchet handle) which 'raises' the metal. Doing pistons used to be pretty common 'back in the day'; the process is still used to bring back valve guides if they're not worn too badly. The one big disadvantage is it's not a good idea in a high-rpm motor as this tends to make the piston more prone to cracking. I wonder if you can even find anybody to still do pistons?

[natemoen]

One other question Pete. Did you use the 1st over wavy part of the oil ring or just reuse the old one?

[petejw]

ask away nate,
i reused the old oil rail, but used the new oil rings,
i cleaned that with oven cleaner,
letting it sit for a good 15 - 20 min then got a
tooth brush into it, i had to do that a few times too
there was a fair bit of carbon build up on it.
if theres anything u want pics of let me know hey.

these rings also dont have an up or down theyll go
in either way, some rings have an inside champher(sp)
and need to be fitted a particular side up.


i measured the bores with callipers and there
still just in spec, not the most accurate way but
good enough to get a rough idea.

a machine shop might knurl the piston skirts but
if your going to that extreme ur better off getting
new pistons and a rebore, all depends on how much
money u want to spend.

[natemoen]

Your saying none of the rings have an up or down side?

[Rickrod3]

'Knurling' is pressing a cross-hatch pattern into the metal (just like a ratchet handle) which 'raises' the metal. Doing pistons used to be pretty common 'back in the day'; the process is still used to bring back valve guides if they're not worn too badly. The one big disadvantage is it's not a good idea in a high-rpm motor as this tends to make the piston more prone to cracking. I wonder if you can even find anybody to still do pistons?

Wow! Pretty interesting the ideas and ways people got around problems.
Seems like many mechanical skills are being lost.
It seems to me that the younger techs are more versed in electronic skills.
Thanks for the info Steve.
Rick

[petejw]

Your saying none of the rings have an up or down side?

yep, thats right.

[TomB]

I ask cause the 1st over rings are only .25mm larger correct, so shouldnt be much material to remove.

The diameter goes up 0.25mm yes but the rings increase in circumference by 0.25mm x 3.142 so the ends of the rings need taking back by 0.7855mm.

I've recently done the same job as Pete, when honing my bores I took off an absolute minimum just to take off the glazing so the rings could bed in easy.

I've done a couple hundred miles on the motor and its not burning oil so I'm well pleased

Seems like many mechanical skills are being lost.

Theres still some of us doing all the old dodges, when I was Toolmaking we'd have a queue of folk wanting this sort of work done, I had a line on knurling old Triumph valve guides and pressing them back into the heads, I still have a 1/4" reamer with 2 thou ground off (to account for worn valve stems) for reaming the valve guides out once fitted to make sure the guide/valve stem clearance hadn't closed up with the new interference fit in the head.

[natemoen]

The diameter goes up 0.25mm yes but the rings increase in circumference by 0.25mm x 3.142 so the ends of the rings need taking back by 0.7855mm.

So from 1 hair to 3 hairs

Yeah I need to just get to doing those rings so I can get the engine put back together....u hate rings!

[TomB]

So from 1 hair to 3 hairs

maybe a little more



Heres the pics and write up I did, hope it helps for when you do yours (ignore the date on the pics, bleedin thing resets every time I turn the camera on )


I ground the end gaps of the 0.25mm oversize rings to fit the standard bores today. End gap sizes should be 0.2 - 0.4mm and max wear 1.0mm, As my bores are worn I did them 0.2mm with the new ring sat in the unworn part of the bore at the top, when slid down to the worn part of the bore the gap went out to 0.3mm so nicely in tolerance


I used an angle grinder thin cutting disc but held in an electric drill


Marked a rough guide with marker pen so I knew how much I was grinding off


Pistons cleaned up nice after I had to chisel the old rings out

[Jarion]

First time I've seen the cylinders of these bikes.
Looks like there's "PLENTY" of room for boring - bigger pistons?

[DGXSER]

The biggest bore kit I have heard of on here is the 1179 kit from Wiseco. I think some time ago Dan Hodges wrote up some stuff on how big you could go and it seems this is pretty close to the limit.