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[dave p]

[dave p]

As can be seen in the photo above, there are variations in wire thickness between the different clips available. The clip on the left came with the second-hand piston from our hosts and is much heavier than the other two. The middle one is the survivor from the original piston and the wear/damage inflicted by the gudgeon pin is clearly visible.It appears that the "ears" were the only part of the clip retaining the pin. The third clip is a new one selected from the online parts book,and therefore the correct one ? I shall carefully check that the new one does not sit so deep in the groove as to negate its purpose in restraining the gudgeon pin. Remember that the previous clip was still in its groove, minus the "ears" when the pin passed through it and caused the damage to the bore.

I considered the 535cc option but cost was a consideration. Keeping in mind that the structure of the piston did not fail, only the clips were at fault. I am now agonising over the wear evident on the oil pump spindle !!!

MERRY CHRISTMAS. Dave.

[ric]

That clarifies things a bit - I wrongly thought you had internal circlips fitted when you described having clips with ears.
Do you have four candles

[Leon Novello]

I think a flat circlip would be better suited to resist pressure from a gudgeon pin than a round wire one.

[dave p]

I agree absolutely.I recently spent some time on the line at Cummins Deisel Engines. Their engines all employ conventional flat circlips which are very easy to fit. The only reason that I can think of for wire circlips would be weight saving.....perhaps??

[Bullet Whisperer]

As I already said in my reply on the MBR site, make sure your circlip grooves and circlips are compatible. for wire circlips, the cut will have a radius for that type to fit snugly into and if you fit the flat type as above, they may not locate fully in the circlip grooves. Make sure you fit the right type !!

[Norm]

Circlip should be carrying very little load, can't anybody see that circlip has been pounded out the side, crank not true, crank twists the rod, rod grabs the gudgeon and pounds it out through the circlip.

[papasmurf]

As someone who has in the past machined more circlip grooves than most people have had hot dinners I would NEVER use a wire circlip inside an engine.

Flat circlips only.

[Bullet Whisperer]

In that case, papasmurf, why has every single piston we have ever used in our race engines, be they Accralite, Omega, Wiseco, or the ones we are using currently which are specially made, come with [very strong] wire circlips - which incidentally have never failed, or caused any trouble in 15 years of racing and with an RE 350 which will see 9,500 RPM? The right fit for the right groove is of paramount importance, no way would I try to use flat circlips in our pistons, which are meant to use the wire type.Sorry to contradict, but I just wouldn't do it, any more than I would fit wire circlips where flat ones should go. Regards, Paul.

[dave p]

guns in the dark knight rises


Sorry to harp on about this but I want to get it right.I don't want the same thing happening again.

The photo shows a clip taken from the low mileage second-hand piston. As you can see, the same wear pattern that destroyed the original piston is evident here. No witness marks are evident on the clip apart from at the "ears" This indicates that the "ears" are the only thing holding the gudgeon pin in place. Therefore it seems to me that these clips are not a good idea and I shall be using the plain clips.

Norm, do you think that if there is some misalignment in the crank or rod that the original clips would have lasted 30,000 miles before failing?


With regard to flat circlips, of course I wouldn't use those in a piston designed for wire clips. All of the engines I've rebuilt over the years be they Triumph, Ariel, Laverda, Moto Guzzi, BSA etc have used wire circlips.Though I'd rather they had been flat clips.


Thanks for all the interest.