Hi All, we had a really good time at the Buckfastleigh weekend, great weather and plenty of road runs, the downside for me was on the run out to Widecombe in the Moor the bike suddenly (for those in the know I was riding Ram-Jam)lost power and stopped, to cut a long story short on removing the head revealed a broken ring and a bit of the piston chipped, now this is where I am out of my depth, stamped on the piston is,435 P5 1V +1MM,
86-1024 Wellworthy.

any suggestion on the best place to get a replacement. should have said the bore is undamaged. cheers

email (option): colin.harmes@virgin.net

Colin, sorry I couldn't be with you this year.
+1mm is the metric equivalent of 40 thou oversize on the bore. It would probably pay you to get the bore miked up by an engineer shop to determine if it's worn enough to warrant a rebore out to O/S 60 thou or at least to see if it could do with a de-glaze hone. Ron

email (option): ronpier@talk21.com

off the track a little bit but obviously when you rebore an engine the CC goes up do you need to inform the insurance company that the CC is bigger that original spec

No, when reboring plus 20, 40 or 60 thou the increase in cc is insignificant and does not require informing the DVLA or insurance companys.

Insurance companies have always accepted this....Each rebore in the case of an M20 adds 6cc (assuming .020" increments)...

So standard to plus .060" will mean the capacity increasing from 496cc to 514cc..

Careful how you go with all that extra power... ...Ian

email (option): ian@wright52.plus.com

Er,
I'd like to be able to help, but I don't know that much about ramjam.
Is ramjam an M20? If people can assume that there are people out there who don't know their bikes have nicknames, they would open their appeals up to a wide audience.

In my garage. I have a Bonnie (obvious), Berk ( the Wife's Triumph), Bemer (not a BMW) and My Ford (a lathe).

email (option): duncanfairley@btinternet.com

Hi Duncan, Ram-Jam is my M20 its nick-m-name was bestowed by Ron Pier when I first got it, its Indian heritage you understand

email (option): colin.harmes@virgin.net

Here is Colin's piston. Ron

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email (option): ronpier@talk21.com

Ouch, it was probably a good thing that the bit of ring found its way onto the valve and closed the spark plug gap before more damage was done.

Rob

email (option): robmiller11(a)yahoo.co.uk

I was lucky really in a few ways, it could have happened on the dual carriage way, or worse when over in France.

email (option): colin.harmes@virgin.net

I was lucky really in a few ways, it could have happened on the dual carriage way, or worse when over in France.

email (option): colin.harmes@virgin.net

Hi Colin

Sorry to see you have had bike problems

With piston picture as evidence, is there any one with an idea as to what happened here ? Apart from the piston breaking up, what is suggested root cause ?

Is this a common failure ?

Also, I found out on Saturday that buckfastleigh was on last weekend & not this coming weekend - I had booked all this week off & after last year did not want to miss the Thursday ride out

Instead I have missed the lot of it

Doh !!

Jo'b

email (option): Jonnyob1@googlemail.com

Have seen similar damage caused initialy by a broken ring which chews the alloy up eventually breaking through at the top. Am now VERY careful fitting pistons not to break rings!

Over enthusastic cleaning of the groove.
Careless handleing of the piston out of the engine.
over stretching of the ring to get it in the slot
Ring expanders are not expensive compared to the damage that can be done
Twisting the ring.
Careless insertion of the piston into the barrel. I have even seen people hitting the barrel with a mallet to drive down the barrels-SHAME on them . Ring clamps are only a few £
Cheap piustons with bad machining of the ring groove ( almost every thing on evilbay )

email (option): wariron@tpg,com,au

None of the above I don't think...

It was a genuine NOS piston when I rebuilt the engine and I've done a few before... ...plus I have all the kit to do the work properly...

I did the job a few years back and it has been running very nicely until now...

Saying all that and despite the fact I am very careful when assembling engines, fussy about tolerances etc. something caused the problem.. ...Ian

email (option): ian@wright52.plus.com

Maybe someones had it apart since you built it, Ian.

P.S. If it was a NOS piston shouldn,t it have been marked +40 instead of +1mm?

In reply for Ian Wright, its been nearly 7 years since Ian rebuilt the engine, its always started first or second kick and this is the first problem that I have had (engine wise) the speedo has not always worked so not sure of the total mileage but I used to use the bike for work and it is well used at shows (convoy & escort work)in short, I have no complaints, its just one of those things

email (option): colin.harmes@virgin.net

Thanks Colin...When you have had the bore checked let me know the situation and I'll see if I have a piston...I still have some NOS ones....

Kieth...Some NOS M20 pistons are marked with a part number to indicate size (frequently but not always so with BSA pistons) and some with a numerical oversize stamp.

Of those some are marked with an Imperial size and some with a Metric size...It really rather depends whether a NOS BSA or NOS aftermarket piston is being used and from which manufacturer/period it originated...

I haven't used a 'modern' pattern piston for years, apart from the 'specials' I have manufactured myself and they are produced to a higher specification than the originals....Ian

email (option): ian@wright52.plus.com

Ian, I will ring you in the few days

email (option): colin.harmes@virgin.net

Hi Colin...E mail me in the first instance..I also have that petrol tank if you still need one....Ian

email (option): ian@wright52.plus.com

After a bit of a delay Ram-Jam now fitted with new piston (thanks to Russell Motors & Ian) done a short road test and all seems well, just got to run it in now

email (option): colin.harmes@virgin.net