Pistons and Barrels

[Mick D]

Hi

Glad things seem to be working out nicely.

It would be good if you could post some 'after' pictures to show folks what can be achieved with patience and gentle elbow grease.

Regards Mick

[Simon.Gardiner]

As these machines are new to you it's probably a good idea for someone to mention main bearing seals, needed to maintain crankcase compression - not only do they not age well but only modern ones use ethanol-resistant materials....

SG

[Bernie Blundell]

Have the piston ring grooves been modified to suit Dykes rings ?

[Ggriffin236]

It would be good if you could post some 'after' pictures to show folks what can be achieved with patience and gentle elbow grease.

Hi Mick. Absolutely i will. I do not have any of the cylinders unfortunately at this time. My work has me out of the country until christmas unfortunately but will definitely get those and put them in.

As these machines are new to you it's probably a good idea for someone to mention main bearing seals, needed to maintain crankcase compression - not only do they not age well but only modern ones use ethanol-resistant materials....

Hi Simon. Absolutely. I have done some research and read this before. I have already got the replacement seals and the cranks are split and old seals removed. They were very hard already but i imagine alot of that is due to this bike being sat around and not running since ~1980s. Once i get back home i will look to clean up the crankcase and start to rebuild it from the ground up replacing any broken or wearing parts like bearings and these seals.

Thanks for the enthusiasm guys. Really appreciate it.

[nadab_sardar]

Good to hear it's all come up so well, and no pitting is a great result on a bike that's been standing since '73.

The Dykes ring is nothing to worry about. It's a perfectly normal piston ring setup for that era, and plenty of people have run them successfully. Just make sure the ring is a good fit in its groove and the gap is checked in the bore before you refit. A Dykes ring is an L-section ring, so make sure it goes back the right way up with the expander (if fitted) seated correctly.

Since the pistons are marked +20, I'd measure the bores properly with a micrometer or bore gauge before you rebuild. That'll tell you whether they really are sitting at +20 now, and what piston-to-bore clearance you've got. If you're unsure, ask someone with a decent set of mics to double check.

Nice work getting it this far. Keep us posted with how the rebuild goes.

[Simon.Gardiner]

There's a reference in one of the tuning articles to Hepolite making Dykes-ringed pistons for the Arrow.
Hepolite numbers:
18550 YKR (described as a high-silicon racing piston)
16388Y
15721Y

The last one also appears in the 1963 Hepolite catalogue, along with 14154 which looks identical apart from having what I assume are 'standard' rings and being made of a different material (Heplex as opposed to 'Al' - Heplex is the most commonly given material in the piston listing).
The '63 catalogue (or sections of it) can be found on the web (also in the AOMCC online library).

Be interesting to know what the numbers are on your pistons, GG!

SG