Standard 916 pistons needed.

Mr.R

Hi,
Maybe not such a long shot but...

Has anyone out there got a pair of 916 pistons in excellent condition that they would sell me CHEAP!!
I'm sooo hard up that the local church mice have been throwing their spare change at me.
I only need the pistons I have the rings, pins etc.

I want/need these so that I can open out the valve pockets to accept 35/30 valves, I could then 'Drop On' my pair of 916SP heads onto my 851/916cc motor.
The pistons already in this motor have been ceramic coated so they won't machine easily...BUGGER!
It seemed like a good idea at the time and they came at a good price.

I'm trying to cobble together the motor after it dropped a valve and killed a camshaft, using mostly kit I've got laying around (spending the least amount of cash as I haven't got any) and it would be nice to have a bit more power at the end of it*
I reckon that with these heads (bigger valves/ports/higher comp' ratio) it'll make over 120 rwbhp under 10,000rpm and kick an SP(4)S,SP5's arse 😎
Not bad for a bike put together in a backyard workshop (read here BIG shed) using mostly 2nd hand parts.

*This just might help me get over the fact that the motor went tits up 4 days before this years TT, also get the bike back on the road whilst we've still got some summer left.
I could cobble it together with parts I've already got but...
It wouldn't be as powerfull as it already was and I've got this problem with taking backward steps when playing with my bikes.

Steve R

guy851

Cheap n Quick rebuild

Steve,

A step backwards but perhaps a quick and cheap way to ride before the sun goes out.

I have a pair of 851 pots and pistons on the shelf, fly cut for G cams already with pins, rings etc.

You can then sort the motor in the dark of winter

Any use?

Guy851

brad black

check the piston to valve clearance, you might not need to machine them at all.

marvin

I've got a pair of 888 pistons that I would sell really cheap (like postage) but they probably won't help much!

Mr.R

Thanks lads,

Guy,
I've got a few spare 851 topends, so I'm stoked up with those spares.

Brad,
It's not the depth of the cutouts I'm worried about, it's the width as my spare 916SP heads have 35/30 valves in them and my pistons are ment for 33/29's.
I think that they'd be pretty close and I could probably ease them out using a Dremmel to gain any clearance needed, (I'm not worried about altering of the balance factor, as a couple of grams less would make cock all difference IME) but I'm a bit concerned about leaving edges where the ceramic finishes, I don't want bits of that stuff flaking off and floating around the combustion chambers/down the bores.
Hence my search for some cheap standard 916 pistons in good condition to play with.

Steve R

Mr.R

marvin wroteI've got a pair of 888 pistons that I would sell really cheap (like postage) but they probably won't help much!

Thanks Marvin,
But the deck height would be all wrong for my motor with it's 916 crank, the 888 pistons also weigh a lot more than 916 items and the bottom ends been balanced for standard 916 pistons.

Steve R

griff851

Steve, check out item 300374087111 on ebay. There is something wrong there as the pistons have way too big inlet fly cuts. They may just be 916 pistons. Might pay to ask some questions

Griff

Mr.R

Hi Griff,
If they did come out of a 748 they're either Hi comp' 748R or bigbore 853 items.
Funnily enough I've got a pair of 748 barrels/pistons* sat here in front of me now and they look nothing like the ones on e-bay.

I was going to get Nessie to put them on e-bay tonight, so I gave the pistons a quick decoke and it turns out that one is an A and the other is a B, they were taken from the same motor, neither of the barrels are marked either A or B.
How very Ducati/Italian...😏

Steve R

brad black

steve

my point was that you might not need the cut outs to be any bigger width wise. i'd test fit them and check the piston to valve clearance.

Mr.R

brad black wrotesteve my point was that you might not need the cut outs to be any bigger width wise. i'd test fit them and check the piston to valve clearance.

Cheers Brad,
I was trying to avoid the whole dry build process again, get on the road a bit sooner.
If I could have found a pair of pistons, I could have machined them whilst waiting for the new cams to arrive.
I have a full time job and a young family that takes up a lot of my time these days, especially now that Mrs R/Nessie is wheelchair bound or on crutches most of the time.

But you're right, I'll build the new cams (996SPS exhausts) and the V Two 604 inlets into the 35/30 916SP heads, dial them in and see what clearence's I've got.
At least I'll get a hotter motor after setting it up on the dyno when I've finished.

Does anyone want to open a book on wether I crack the 120 rwbhp mark at under 10,000 rpm from a 916cc motor?
I've already hit 116 at 9,500 rpm with 33/29 valves and completely standard 916 heads.
I won't be skimming them as I'll be fitting them to the 984 in the future.

I'm just off out to my workshop to get the 916SP heads, fit the inlet cams and then shim them up, while I'm at it I might as well fit the 3 piece carbon Corse airbox and JHP lozenge filter.
That's my weekend sorted, although I'll be at work at 7.30 am on Saturday morning for 4 hours, fetching home the fresh pasties for the families lunch.

Steve R