7 replies to this topic

[stevecarter1000]

I have a fantic 156cc engine (with a 125cc bottom end) in an 80cc frame....

It needs a new piston ring - I've heard the term 'Dykes' Piston Ring and wondered what this is? Also, is there an obvious way to tell whether the piston is std or oversize? I've also heard of a suzuki piston being fitted - what is the difference and benefit compared to a Fantic piston please?

All help gratefully received - cheers.

Steve

[stevecarter1000]

Also, the con-rod has a slight amount of play side to side on the big end bearing. There is no discernible twisting play, just side to side. Is this ok?
Ta

[Stork955]

Gday, I cant help with the ring, but a rule of thumb is that if the rod side clearance is getting over 20 thou, its time to rebuild the crank. You may be able to find an accurate specification somewhere on the net. To measure it just slip larger and larger feeler gauges in between the rod and the crank until you can no longer get one in. The largest one that fits is the side clearance.


Cheers,


Stork.

[copemech]

stevecarter1000, on May 23 2010, 07:41 AM, said:

I have a fantic 156cc engine (with a 125cc bottom end) in an 80cc frame....

It needs a new piston ring - I've heard the term 'Dykes' Piston Ring and wondered what this is? Also, is there an obvious way to tell whether the piston is std or oversize? I've also heard of a suzuki piston being fitted - what is the difference and benefit compared to a Fantic piston please?

All help gratefully received - cheers.

Steve

Dykes rings are "L" shaped rather than a "--" shape in the slot, quickly spotted, usually on top groove! Just need to look at things and measure the piston accurately with a micrometer to see the exact size to compare specs and hopefully figure out what you have.

[stevecarter1000]

Guys, many thanks! I'll measure the play as you suggest Stork...

Ref the Dykes ring, is it a choosable alternative fitting for that engine, or does it HAVE to be the Dykes ring? If it's either/or, what difference does it make?

Thanks again,

Steve

[Stork955]

Gday, the Dykes ring is a special fitment - if it had one before it can only use that ring because of the shape. They are the same type as in TY yamaha's. They do work well.

Cheers,


Stork

[jimbo349]

The Fantic 125cc engine was modified by a guy in Wales years ago and fitted with a TS185 piston and I think a cast liner in the barrel. Fantics generally had chrome bores at the time.

I had one of these bikes and the engine was very flat and had none of the zip the Fantic 200 had.

Thats all I can say about the bike I had great for anything that didnt involve a big climb.

[Pat]

Borrowing this thread..

Will kindly ask if any of you know, if any one back in the days did rebore/replate 156cc up to 63.0, 63.5 or 64.0?

BR,

Edited by Pat, 20 February 2011 - 09:04 PM.