1960 Matchless 350 piston replacement and engine inspection

[SPRIDDLER]

Why strip down a complete motor for the sake of a knackered piston.

I'm half in agreement with that, but at this time of year I would probably do a complete strip, especially as I tended to travel quite a lot to distant foreign parts.

Try competing some two strokes and see how many pistons you get through. If you did a strip down every time a piston was knackered there would be no track time only work bench time.

My Greeves Hawkstone didn't have an oil pump, oil pipes and galleries in the crankcase but I suppose one could always keep an eye on the oil return flow of a four stroke to check for any blockages.

[Triumph-Legend]

Hi Dave.
Just curious, (nosey). Have you got your motor sorted out yet? If yes what was needed to fix it. Apart from a bit of filing and a big hammer.

[AFSMatchie61]

Hi Dave.
Just curious, (nosey). Have you got your motor sorted out yet? If yes what was needed to fix it. Apart from a bit of filing and a big hammer.

Hi
Thanks for the interest, been working shifts so not done anything until this afternoon. Drained the oil by taking the lines off the timing side of the cases, and letting it run into a nice new white washing up bowl, by the light of a torch many tiny shiny aluminium pieces (But no gold coloured ones). I took the sump plug out, the expected bits of piston ring on the magnet snd some alloy piston fragments. Then took a vacuum cleaner with some garden hose o it and sucked the big bits of piston skirt out of the sump from above into a fresh vacuum bag so I could cut it open and have a look!
I'm concerned at the oil contamination but that said there's no movement in big or litte end or the main bearings supporting the crank that I can feel. Still undecided on next steps

Building up to using my finest Ebay bore gauge, did a quick and dirty to try out the kit and it seems uniform diameter top to bottom...now ned to do it properly There are a few deep vertical, quite short scores, maybe they'll hone out, maybe need a rebore...
Cheers
Dave

[Triumph-Legend]

Dave, as previously stated. Clean it out time and time again with petrol and cloth. Blow out all the little nooks and crannies with an air line then clean again.
give a good squirting of oil to all the bearing areas and if it all looks OK go ahead and rebuild. Clean oil tank and lines and use a new oil filter.
Have you managed to get a decent piston? What is the bore looking liike? If it's not scored just go with a hone unless you want to rebore or can only find an NOS O/Size piston. If using a new piston be sure to check the fit of the gudgeon pin into the small end bush. If it won't slide in of if it's tight you will need resize the small end bush. (Not a bigger hammer). Hence my preference for a NOS piston.

[AFSMatchie61]

Thanks, am erring that way with an oil change after initial running to get any more bits that might be floating about. Only a brief look at the bore as above, not found a standard wire wound yet of the right vintage but not looked that hard. Not stripped the head yet, need a special tool for those springs I believe?
Cheers

[Triumph-Legend]

Er, that is I hope more fresh oil after the rebuild clean and oil and filter.

Remeber the small end bush. The new pistons can be a flipping nuisance because of the pin fit. Why did not just stay with the standard size and save us all the messing about?

[SPRIDDLER]

Thanks, am erring that way with an oil change after initial running to get any more bits that might be floating about. Only a brief look at the bore as above, not found a standard wire wound yet of the right vintage but not looked that hard. Not stripped the head yet, need a special tool for those springs I believe?
Cheers

If you do go for a non wire wound piston you'll need more clearance than has been allowed for the (scarce) wirewound one. (I think the wirewound have about 1.0 or 1.5 thou clearance and your non w/w will need approx 1.5 thou per inch of cylinder bore diameter, but a new piston should have clearance info included with it). If the scoring in the bore is too deep then a rebore is probably the way to go. The bore of your 350 is 2.72" x 1.5 = 4 thou clearance (but check with the instructions accompanying the piston).
The hair springs can be easily removed with a finger inside the spring and pulling up. They can be refitted without a tool by hooking the closed end under the collet plate first and then 'levering' the lower legs up into place. See page 30 of the Owners Manual for spring removal and how to use the tool here:

http://archives.jampot.dk/book/Owners_m ... models.pdf

The spares shop sells the tool.

http://www.amoc-parts.com/store/comersu ... duct=21316

[AFSMatchie61]

Thank you both for the advice and information, be another week before I can do any more but will update and share some pics then.
Cheers
Dave

[AFSMatchie61]

Couple of photos of the bore don't think my drill mounted honing tool will take out the deeper scoring so will rebore.

E6989BC0-137E-4046-94F6-E85CC4FA2EC0.jpeg

8B953001-F3AB-4F55-BE8C-A5D00E416984.jpeg

[AFSMatchie61]

How would the oil pump etc get cleaned up if I flushed the cases?