ART Pistons

[Seamus]

Hi All,
I have been cleaning things up and noticed that my pistons are not flat, but domed with cut outs for the valves. The pistons are marked ART by the gudgen pin. A quick measure gave me around 63.5mm
This is above the 1mm Honda info.
Could this be part of an aftermarket kit? Any info appreciated.
I guess someone has been playing with my internals.

Cheers

Seamus

[Bryanj]

ART actually made most of Hondas pistons but also at 63.5 its an overbore kit, could be cb350 pistons

[Seamus]

Thanks Bryan. These pistons do not have any other marking except the ART initials by the gudgen pin. I thought that all Honda pistons were marked with "ex" or similar on the crown. There are no markings on the crown (that I have found so far).

Appreciate the thoughts though. A search seems to suggest that all sorts of pistons get used in threse engines.

Cheers

Seamus

[Bryanj]

Only pistons that have to be fitted one way round have any markings like you describe and if you go to our sister site, sohc4.us you will find all sorts of attempts to fit different pistons to get more cc, which is the easiest way of getting, as Tim Taylor would say, More Power!!!

[SteveD CB500K0]

You'll need to go to sohc4.net as the .us site has been closed for a while.

There are a bunch of guys on there who are seriously into upgrading these engines.

For that sort of money, I'd go buy a FireBlade! (trust me, I've ridden a few and they are awesome!)

[Seamus]

Thanks folks. Remeasured the bore at 74mm (makes 810 volume)

As for fireblades, I had a 929 and a 1000RR, followed by an SP2. so hopping up a CB 750 is not on the radar.

I like restoring bikes of my youth (Did a Commando and a Bonneville so far) and really liked the CB750 first time round, hence this one. I seem to recall that someone did an 810 conversion in the 70's. but I could be mistaken.

Thanks again for the info

Seamus

[Bryanj]

Are you sure its 74 not 64, as you say many people did upgrades most sought after being the Pops Yoshimura ones

[Seamus]

Sorry Bryan, it is 64mm. Been reading on the other site and there is lots on 70 odd piston sizes. Stayed in my brain.

Cheers

Seamus

[Bryanj]

Thought so, the 70+ require bigger sleeves with block and case boring and one i did the block went porous so we had it stove enammelled black to stop oil seepage

[Seamus]

Sound like an interesting beast. I guess it was a shade quicker than standard

[the-chauffeur]

Sorry to hijack, but Bryan mentioned stove enamelling the outer barrel case and I was wondering . . .

 . . . Bryan - what's your experience of how well stoving holds up as an engine finish?  I've had a hell of a time with getting conventional VHT paint to adhere to my 750 engine cases - the head and barrels are fine, 'cos it cures fairly well with the heat they generate, but the crankcases don't get anywhere near hot enough (and a fuel leak from one of the carbs has lifted layers right off).

The engine is gonna come out in the autumn/winter so that I can replace the cylinder rods (I think they've stretched) and so I'll have the opportunity to get the engine re-finished properly.  Question is, do I get the cases/head/barrels stoved, or give them to a specialist who'll etch prime, then spray VHT?

Thanks in advance for any advice . . .

Neil 

[Bryanj]

Never done VHT so cant answer definitively but have heard that the finish needs "Baking" to be durable

The one i did was back in 77(ish) and the block was bored to take big liners and when rebuilt leaked oil from somewhere in the fins so we pulled it, had the cylinders blasted and stove enamelled black, Powder may have worked but wasnt about then.

All it did was put a continuous hard coat of paint over the porous alloy and that was enough to keep oil in as it wasnt a pressure leak