Modifying FE450 101mm piston

WArdogG · May 18, 2015

I have a 100.94mm Wooooossner piston Part#8593D100 which I bought on a whim because it was ridiculously cheap. I'm thinking of applying some home butchering/hammering/lawnmowering to the thing to make it work on my 650.
I'm thinking of mounting my lawnmower wheels on micrometers and get the right height to mow the dome and 1.3mm off the deck height to get to 23mm deck height. Alas, my swiss army knife does not include the milling machine blade...:furious:

Will this then be an acceptable piston for my beloved sixfive-oh? (2008)
And is there some form of anodizing or surface plating on the piston, in which case I could have it ceramicoated? Or should I rather just get me a 450 to match my piston...? (We seem to have developed a bad habit of spending all our hard earned cashhh on buying any old BerG we can get our hands on, precioussss)

Any thoughts?

bushmechanic · May 18, 2015

all sounds good, though ive not looked up the dimensional specs on that piston

most pistons up to 12.5:1 are 4.3-4.5mm thick in the middle of the crown as long as that is achievable with 1-1.2mm squish I think its a great idea

FWIW Dr_C mentioned a trick of leaving the piston top rough so it can attract a carbon coat acting similar to a coating

ned37 · May 19, 2015

Any thoughts?

ya, quite a few

Taffy · May 19, 2015

the 2014 manual gave only a 0.5mm oversize?

I suppose if the nikasil is all ripped and chipped and that the alloy underneath has a deep groove etc then this would be a must!

I have quite a few old liners here that I've been hoarding and it might even resurect one or two!

I know that Langcourt here in the UK will bore out the alloy liner so it could be a goer.

the compression on the standard FE is- IMHO - too high so this makes it worse. see if the dome is exactly the same. squish will be OK>

regards

Taffy

WArdogG · May 19, 2015

The specs as per the Wossner catalogue:

450 (57.2 stroke)
comp 13.1:1
dome +9cc
comp ht 24.3mm

From the top of the pin hole to the top of the dome is +-18mm, the dome is +-3.4mm above the deck, from the top of the pin hole to the underside of the deck is +-12mm, where they have machined out about 3mm in the middle of the under-deck(I assume for clearance for the smallend). That would leave me with about 2.6 odd mm deck thickness in the smallend area with the dome chopped off... Not looking too good there..

WArdogG · May 19, 2015

Taffy, I suppose taking 1mm or so off the dome would be OK to reduce the compression a tad, and leave enough thickness in the crown area. Though reducing the whole deck so that this piston would work for a 650 seems like a no-go. Seeing as I don't have a 450, I may sell the piston to an interested individual, unless I can find me a 450 somewhere...

Taffy · May 20, 2015

we would run at best a flat piston in a 650. but we don't get ANY feedback from customers. they buy, they fit, they say nothing.

I would take about 1.0mm dish out the top. make a nice piston that!

you will have a 641cc bike and it will be a claimed 13.3 to 1 compression. real will be more like 12.8 to 1.

regards

Taffy

WArdogG · Oct 22, 2015

bushmechanic said:
8551 is listed for a 650 but its not right

specs 23mm in height, -2.1cc volume

which is a copy of some of the early 644 pistons and the later 550 piston

your squish with that piston on the 80mm crank is approx 2.7mm and the cr is also a bit lower than the oem piston.

while this obviously works there is a better way to do it.

the OEM ELKO piston for the 80mm crank has a height of 24.5mm and a volume of -10.5cc (approx) this gives squish equal to the compressed head gasket thickness (1.2mm) and a CR of approx 11.8:1

if you want a wossner with these dimensions you have the 2 options i mentioned above or if i understand his post correctly you could consider the wossner as an oem part as mentioned by johhnyberg, im not familiar with this piston though.

**** I've been using the Wossner cat to get the piston specs. I didnt know their piston spec for the 628 was the wrong piston.

In that case the 628 piston nearly the same as the 450 piston. Except of course the 450 has a +9cc dome...

450 (57.2 stroke)
comp 13.1:1
dome +9cc
comp ht 24.3mm

I thought I would have to machine the deck down to 23mm, but it seems I can lop off the dome for a flat top piston for the 628. Well, the deck will be 0,2mm lower than standard 628 piston,then...
How high can I run the comp ratio in a 628 on 95 pump fuel?

BTW this is a 101mm Piston

Taffy · Oct 22, 2015

perhaps in the post beforehand I was talking in my sleep? LOL!!!

regards

Taffy

WArdogG · Oct 22, 2015

But at that little machined out area the piston is about 6mm thick to the top of the dome. And if I machine the +-3.4mm dome off it will leave me with 2.6mm piston thickness there. Not good.

Could I possibly reduce the comp somehow so that I can leave a bit more on the dome, like increasing the head volume. Though that means I will always have to use the 450 piston for my 628.

WArdogG · Oct 22, 2015

Or what type of fuel can I use to counteract the detonation with the piston just like that? 102, metahnol, ethanol, rohypnol, or plutonium?

laughing at my own stupid joke. haha. I'm going to look for a 450 to put my shiny new 101mm piston in...

bergbro · Oct 22, 2015

I love it wardodg......
you bought a cheap piston for your sixfifty but it wont fit so now your looking for a 450 to fit the piston.
Brilliant....!
your supposed to find a piston to fit the hole not find a hole to fit the piston....

Sorry mate.... couldn't resist on lovely Friday morn such as this.

but what about the poor old sixfiddy?

WArdogG · Oct 22, 2015

Hey Bergbro, I guess I'll just have to buy the right piston, which at this point will be the oem elko, which costs twice what the Wossner is, and since Wossner can't supply the right piston I guess I have my answer. I would buy a Piston from Taffmeisters, but the exchange rate is so bad now that importing anything is just plain stupid.

WArdogG · Oct 22, 2015

Taffy, no, its just that the piston I have I don't think its safe to modify, otherwise I would have done like you mentioned in the post.

I was just wondering what the comp ratio would be if I used the domed 450 piston in the 650(I can work it out, I was just toot lazy), and what the maximum comp ratio is that I could safely run in the 628, without the use of 102 race fuel.

Taffy · Oct 23, 2015

i wouldn't go any higher than a real measured 13.5 to 1. we only have generic ignition systems so you'll just knock out your big end and mains and also they aren't actually any quicker anyway. they spend as much time trying to run backwards as forwards so just over 13 is nice.

so you reckon, with a 1mm dish you would only have 2.6mm is that right?

a piston here without VAT is 134gbp for a std wossner to you. OEM will be about 250gbp but the extra money is just about worth it I reckon, the mahle is a better piston than any aftermarket piston.

regards

Taffy

WArdogG · Oct 23, 2015

Thats not even a dish, that is flat top.

I think I had some nasty knocking going on in there anyways, the top of the bigend pin and the the top of the bigend inside was banged to bits. All the hardening had come off, and those lil bits of hardening flakes completely destroyed my piston. Was at 140hr, almost 12,000km. But looking at the piston(standard elko), underneath all the scoremarks and flakes, I can still see the machining grooves clearly on the piston. I reckon that piston would have been good for another 100+ hrs if the bigend hadn't ruined the piston.
The main bearings were still OK, they hadn't started coming apart yet.

I was contemplating all this destruction and my only guess is that it may have been in part caused by TPS advancing the ignition timing(load sensing, I believe is what yamaha called it), and since I am running very long sprocket ratios, I believe this made it even worse, as I was probably running too much on advanced ign timing. This is all speculation though. I cannot believe that it was an oil related issue, as the pump is working fine, crank tip seal still fine and the crank oil port open. And I changed my oil 3 times a week. (long distance riding everyday)

Modifying FE450 101mm piston

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