The 660 strip down.

nsman · Nov 21, 2016

The 3TB model code on the connecting rod is from a Yamaha XT600 later model 93.

canolman · Nov 21, 2016

Wow! Didn't expect it to be a Yam rod, substantially beefier than the standard one if it is!

canolman · Nov 25, 2016

So! Further talks on a replacement piston, been told it would work, valve cut outs, gudgeon pin, compression height ok but the squish wouldn't be ideal, workable but less than ideal. And then the price!! **** me sideways the pound isn't worth the paper it's printed on! Add our import duty.....and I still need a liner!
Btw, I emailed the technical departments regarding 102mm pistons to Wiseco, Vertex, Wossner, Elko, CP. How many replied? None, zilch, dim, Nada, zero.....:spin:

canolman · Nov 25, 2016

Lancourts do not nikasil iron liners despite their web site stating they do. They do not recommend it and their suggestions was to have Westwood make a liner to fit the pistons I have. Westwood had a liner on the shelf and sold it yesterday! They have the spec on file and will make one in ductile cast to any bore size I want. So I need to pick a piston, 101.810mm or 101.866mm and add suitable clearance? 0.07mm?
Would clearance be any different for cast, plated?

nsman · Nov 25, 2016

give CVTech-AAB a try.

Damo W · Nov 25, 2016

If your looking to get a new liner made, if it were me, I'd be thinking more about getting an old alloy liner and boring that to get the right clearance then replating it. The iron might be the only option when going to say a 105mm piston? Do you still have it anywhere? And it may be a little more expensive initially but should last longer as the Nikasil (or equivalent) is harder than iron.

I think the issue with iron liners in alloy cases having different expansion rates sits a little uncomfortably with me. From what I can read, it's paramount to get a really nice interference fit between the two to aid in heat transfer otherwise the bore may not stay 'round'.

Alloy/alloy appear to be able to run a slightly smaller piston/bore clearance and it stays more uniform up to NOT.

Only my opinion of course.

Decisions decisions.....

Damo

Damo W · Nov 25, 2016

canolman said:
So! Further talks on a replacement piston, been told it would work, valve cut outs, gudgeon pin, compression height ok but the squish wouldn't be ideal, workable but less than ideal. And then the price!! **** me sideways the pound isn't worth the paper it's printed on! Add our import duty.....and I still need a liner!
Btw, I emailed the technical departments regarding 102mm pistons to Wiseco, Vertex, Wossner, Elko, CP. How many replied? None, zilch, dim, Nada, zero.....:spin:

It's hard these days getting anyone to get back to you. Then they complain that business is struggling or slow.... Go figure! :scratch:

Damo

spanner · Nov 25, 2016

I think JBS tried Yamaha raptor rods, 37mm Ø BE pin and I think 22mm Ø little end pin?

canolman · Nov 26, 2016

I don't think the original liner would have enough meat left on it if I tried to bore it? There can't be a lot of metal under those o-rings, surely someone would of tried it? Big torquey motor with a thin Ali liner, it would distort I think. Probably why they went for cast.

canolman · Nov 26, 2016

spanner said:
I think JBS tried Yamaha raptor rods, 37mm Ø BE pin and I think 22mm Ø little end pin?

I think they tried all sorts spanner, no two motors the same perhaps! This one's got a standard 20mm gudgeon pin, generic Hus, KTM

canolman · Nov 28, 2016

Ok, looking through the old JBS website and I see this 102mm piston for original liner.

canolman · Nov 28, 2016

Now this piston here is almost certainly what I have two of, measuring 101.810mm and 101.866mm. Do you think this piston was as big as they could go on a standard liner?:unsure:
The iron liner I have at 102.12mm at the top of the bore is too big for this piston, was it too big before wear? Spoke again with Westwood and they said the only 102mm JBS liner they made was 102.08mm!

Damo W · Nov 28, 2016

canolman said:
Ok, looking through the old JBS website and I see this 102mm piston for original liner.

That's positive then. :thumbup: when I was looking at mine, I thought approx 1mm was doable. But I don't think there'd be much more left to go with the o ring recesses on the back!

I suppose as long as it's making really good contact with the cases, particularly higher up the liner, it's effectively thicker.

Would be good to hear from someone who run one of those JBS kits. Surely someone reading this thread would've had experience.....

Damo

Damo W · Nov 28, 2016

canolman said:
Now this piston here is almost certainly what I have two of, measuring 101.810mm and 101.866mm. Do you think this piston was as big as they could go on a standard liner?:unsure:
The iron liner I have at 102.12mm at the top of the bore is too big for this piston, was it too big before wear? Spoke again with Westwood and they said the only 102mm JBS liner they made was 102.08mm!

Wouldn't worry about it. If you decide in the end to go alloy, just fit one to your cases and have it bored to suit your piston size, the smallest piston. I'm sure you could find a scored or lightly damaged original liner around somewhere maybe?

Damo

canolman · Nov 28, 2016

Damo W said:
I'm sure you could find a scored or lightly damaged original liner around somewhere maybe?

Damo

Oh, I've got a few of them Damo mate!:spin:

canolman · Dec 14, 2016

So, new liner on order with Westwood, long wait though. Will make an exact copy but to a bore size to suit piston.
Plenty of things to get on with.
When I stripped the engine I noticed that the collar nuts had no washers under them, odd I thought as there were four thick washers in the spares box? Three nuts removed but I was struggling with the rear left nut, I couldn't find a socket to fit finally tapping on a 15mm to get it out....oh boy!:spin:
They'd fitted a standard head and the washers wouldn't seat because JBS machined their heads, no problem, fit a custom nut.

canolman · Dec 14, 2016

To fit the RTS head machining of the seats had to be done to except the washers, 4mm x 23.5mm, my mate didn't have a cutter to do the job so he took the head into his work to see if he could borrow a suitable tool overnight. His firm do a lot of prototypes for the military, no phones allowed on the shop floor etc. But his gaffer is a biker and wants to know all about the bike, the engine mods etc. Next thing the head is bolted onto the miller and the seats are cut, job done!
And the fee? Two tubs of Haribos £9.50!:spin:

Damo W · Dec 14, 2016

Maybe they figured because it was a flanged nut that they didn't need the washers?

the flanges aren't really big enough and if they were, I'd personally rather they be partially independent of the nut.

The bigger washers help distribute the load and if I recall correctly would also help stop the Brinelling effect thus keeping correct tension.

I use the ARP studs, hardened washers and multi point nuts on mine (thanks Bushie). With the standard supplied washers I didn't get the bottoming out of the threads reported in a previous post though which was great. They accept a 12mm multi hex socket too which is handy for clearance inside the head.

Carry on Canolman, I always look forward to the updates! :thumbup:

Damo

canolman · Dec 15, 2016

The 'custom' nut didn't appear that tight to me, that and forgetting to fit the small bolt by the coolant outlet I'm not surprised the head gasket was leaking!
What are you torquing your head down too?

Dr_C · Dec 15, 2016

Cheerio Canolman!
FWIW I used to buy custom pistons from JE. When ordering 2 pieces you can choose to have one "oversize" from the same forging. Otherwise they charged extra for another size. That was handy when the steel liner got a little worn, I could just hone it to make the next piston fit!

On the compression height question. Aim for 1,0-1,1mm squish! 1,3-2,0mm can give you problems with knocking (depending on combustion pressure, fuel and combustion chamber design).

Carry on!

The 660 strip down.

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