Piston "Buttons" .........?
Turbo Mini Forums

Having seen Wil h's how to on making them and hearing some stories,

is it worth making some up at work, or only really nessasary on a very high powered engine,

as for fitment, i from what i gather its a case of placing the piston (flattop 998 +80) onto the rod, gudion pin though and and press fit the button.... ??

is it worth ensureing a tight fit into the pin or can there be some movement,

ie push them in by thumb or having to use a flypress

thanks

gaz

Nothing to do with engine power purely to do with the risk of the circlips falling off.

Mine are just pushed on by hand, can't see any benefit making them an interference fit.

normaly a series rods are heated, and the pin and piston fited before the pin cools, onece fitted they arn't going anywhere,

Instead of this some (earlier) small bores engines have the pins "floating" and a clip at either end, these clips can come loos at high rpm, so people started fitting ptfe buttons.

some people like to ream the rod in big bores so the pistons can be taken of the rods easily and fit the buttons.

Bah, beat me to it, with a pic too!

Edited by Joe C on 1st Sep, 2008.

so its deffo worth me taking the time to make them, i'll crack on with them then

cheers

I'm making a set at the moment,

after a couple of calcs, on a 73.5mm bore if you taper the outer face 4 deg it should fit against the bore wall fairly well,

for small bores i'd guess 5 deg would be pretty close.

so are there buttons fitted instead of the circlip then?
Id imagen they act as buffers to stop a floating pin from taking the cylinder wall with it.
And as also said the circlips come adrift at high rpm

always wonderd what they are for lol

Yes i moved to the darkside

Instagram @jdm_brett

no the circlip is still inplace the buttons just stop them coming off and letting the pin drift out......i think.

if not ive made myself look like a foooooool!!

probably the fool option TBH!

both ways have been used,

:( but still :)

If you want to keep the circlip you can, but it makes making the buttons VERY difficult and has no advantage over binning them.

Mine are finger tight in the pins.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

I still have to fit mine. BUT do i need to make sure that there is no button overhanging the edge of the piston

I fit them by fitting them to the gudgen pin then making them a nice snug fit in the bore (0.5mm play). Then fit the piston to the rod.

it's not too important where they are relative to the piston.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

Anyone fancy making me a set for a 998 +0.120"?!?!?

I can do a set for £20, but you can't be in a rush for them.

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

yep thats good with me, we dont have the block bored yet its still one piece so you have plenty of time. PM me when they are done and Ill send you some spondoolies :)