G3 500cc conversion after piston death

[AFSMatchie61]

Thank you All. The next decision is if I rebuild it myself or pay someone. Ive done most things on bikes but been lucky and never had to split the cases: I hear its a good one to start on as its pretty simple but reckon the devils in the detail! Still mulling that one over...

[SPRIDDLER]

It's pretty straightforward and you'll have plenty of help.
Have a read of this excellent strip/rebuild article by one-time Jampot member Ken Bryant (Forum name 'ITMA')

http://archives.jampot.dk/technical/Spe ... hanics.pdf

If you aren't aware of it you can Enlarge, Rotate, and Full screen the page to save getting a squint or a crick in your neck by using the buttons indicated below:

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[Mick D]

Hi

You're correct, AMC singles are very easy to understand and work on. If the bike was running fine before the piston let go I'd be tempted to just strip it right down for a good clean and inspection. Don't get too hung up on wear, unless it's very noticeable, the bike will go back together easier the less you replace.

Plan on a new piston / re-bore and work from there. A de-coke, re-grind the valve seats, new set of seals and gaskets, confirm the mains, big and small ends are acceptable, back on the road.

Whereabouts in Scotland are you?

Regards Mick

[AFSMatchie61]

Thank you both for the encouragement, Have had a read and I think Ill give it a go. Ah Mick, you make it sound so easy Im in the same county as you, west of ABZ, who would you reccomend for a rebore locally?
Cheers
Dave

[Mick D]

Sorry Dave

I've not had a re-bore for over 45 years so I'm not really up to speed on local services. There are several other forum members in this area so maybe one of them can chip in with a recommendation, failing that I can ask my local, (very good), garage who they would recommend.

Regards Mick

[AFSMatchie61]

Sorry Dave

I've not had a re-bore for over 45 years so I'm not really up to speed on local services. There are several other forum members in this area so maybe one of them can chip in with a recommendation, failing that I can ask my local, (very good), garage who they would recommend.

Regards Mick

No problem at all Mick, I can ask around, just thought you might have recent experience. Ill start a new thread for the rebuild, plenty of gory photos to kick off with!
All the Best
Dave

[AFSMatchie61]

On a point of interest I am surprised there has been no hands up horror at the piston failing. Does this indicate you Guys have heard of it happening before? Is it A fairly well known failing of old wire wound pistons? I know of one other 350 Matchie that suffered the same fate, again with a wire wound piston. Are there others?
Cheers
Dave

[SPRIDDLER]

I can't say exactly how common it is but I've heard about it several times and recall reading an article about it, probably in this site's Techy articles or maybe in Christians Archive.
I don't remember what the cause was reckoned to be (not that it would be any consolation to you now).

Ref doing a rebuild yourself and if there aren't any bits of the piston or rings missing and with the cylinder off you can confirm that the mains and big end bearings are O.K. I wouldn't split the crankcase but rather than the faff of removing the engine I'd just give the crankcase a thorough flush out with paraffin.

(However, I'm not sure if Mick meant to split the crankcase or not when he wrote: 'strip it right down..............'. He may have done as he is far more conscientious than I am and there's always the risk of bits blocking oilways )

Later.........

I will have to split the cases as some of the Low part of the skirt is missing, presumed in the cases. Shame but There you go.
Thanks
Dave

Yes, in that case I would.

[AFSMatchie61]

Thanks, that's interesting, there is a lot of technical info Icoukd easily have missed an article and have only just Sampled the tip of the iceberg with Jampot back issues! The view among some I know is metal fatigue with age.
I will have to split the cases as some of the Low part of the skirt is missing, presumed in the cases. Shame but There you go.
Thanks
Dave