Emgo pistons

Status
Not open for further replies.
3 of them said:
after reading this post i have a sinking feeling .I fitted a pair of jcc pistons about 7000 miles ago with the supplied seger type circlips and have had no problems at all (so far) . Do you consider it wise or essential to strip the top end to replace the clips with those of alternative manufacture ? thank you in advance of your replies
Click to expand...

If you noticed the snap ring was a loose fit then I would definitely pull it down and replace them. A couple gaskets and an evenings work is cheap. If it's a 750 you can just raise the barrels and do it without removing the head.

I am going to estimate about 50% of the snap rings supplied with the pistons are loose enough I wouldn't use them. They all appear to be the correct size but very inconsistent in the amount that they expand when released. If you take a ring that is a loose fit and stretch it just a bit it will lay perfectly on top of a ring that does fit tight.

Just very poor quality control on the snap rings.
 
See related thread "Emgo Pistons Mismatched" at:

https://www.accessnorton.com/NortonCommando/emgo-pistons-mismatched.21840/

The weights can vary per piston per batch - sometimes only 2-4 grams, sometimes 10 to 15 grams.

What's not taken into account here is all the Norton owners who buy JCC pistons in good faith but are not wise to the bad circlips and end up with damaged cylinders. Elmzy was fortunate enough to weigh his pistons and discover that they were mismatched by 14 grams. Hopefully he changed the clips. Others are not so fortunate - they suffer the consequences and never even know the reason.
 
comnoz said:
I keep a supply of heavy duty snap rings here to supply with the pistons I fit.
Part number HO-68SS
Click to expand...

I looked for those at McMaster-Carr and couldn't find them. Does anybody have a part number there?
 
Ok now I'm confused as a newbie and ask for advice. Ms Peel's old barrels are .20 over bore still good to go with just a brief hone clean but need new pistons for factory Trixie Combat, so what should i buy?
 
JCC/Emgo pistons checked for correct markings
Hastings or Total Seal rings
"Seeger" "square section" clips (supplied with pistons) that fit tightly, or if loose, the ones from McMaster-Carr : 91580A175
 
hobot said:
Ok now I'm confused as a newbie and ask for advice. Ms Peel's old barrels are .20 over bore still good to go with just a brief hone clean but need new pistons for factory Trixie Combat, so what should i buy?
Click to expand...


GPM.
 
L.A.B. said:
Emgo/JCC/Hepolite Norton piston kits seem to come supplied with seeger circlips (the original Norton spec.) and the circlip grooves are presumably machined for seeger clips, however, other Emgo/JCC/Hepolite piston kits (for BSA, Triumph, etc.) appear to come supplied with wire circlips (the original BSA/Tri. spec.) therefore those pistons should be machined for wire clips.

Triumph JCC/Hepolite example
Emgo pistons

BSA JCC/Hepolite
Emgo pistons


As comnoz pointed out, the problem can occur if the wrong circlips are fitted.
Click to expand...


Pistons supplied by AN are they hepolite /JCC??
 
stripped my 850 today to change the piston circlips on the Jcc pistons . old clips were as soft as butter . New clips from our friends at Andover Norton snapped in in a lovely positive way .Deep joy so far ........ on reassembly tightening the T/S exhaust rose pulled the welded insert SOD IT better find a kind (and skilled soul ) who can TIG it . ho hum
 
3 of them said:
stripped my 850 today to change the piston circlips on the Jcc pistons . old clips were as soft as butter . New clips from our friends at Andover Norton snapped in in a lovely positive way .Deep joy so far ........ on reassembly tightening the T/S exhaust rose pulled the welded insert SOD IT better find a kind (and skilled soul ) who can TIG it . ho hum
Click to expand...

Could be wrong but surely Andover Norton do not supply seger type circlips ?
 
3 of them said:
stripped my 850 today to change the piston circlips on the Jcc pistons . old clips were as soft as butter . New clips from our friends at Andover Norton snapped in in a lovely positive way .Deep joy so far ........ on reassembly tightening the T/S exhaust rose pulled the welded insert SOD IT better find a kind (and skilled soul ) who can TIG it . ho hum
Click to expand...


Don't weld your poor head, get someone to machine an insert! Ship it to Colorado maybe.
 
yes AN do supply seger clips . The port problem is a durumilium insert wich was done years ago and TIGed in place it has started to move the old weld has fractured and the insert has just started to pull out . the old but very neat weld will be carefully ground off , and re-done by a welding wizard namely pete at black dragon motorcycles here in Somerset England . So rvich dont fret we know what we are up to
 
Ah, all well and good then, since the head is already buggered there is no reason to do a proper repair. Carry on!

Emgo pistons
 
Ron L said:
Seeger clips for Hepolite
Wire clips for GPM
Click to expand...
I realise this is a "Commando" thread but this info may be relevant to here...
My '64 650ss had GPM pistons in it when I disassembled it, complete with Seeger style clips.
I have checked and the clips are a very good, snug fit in the pistons.
My point is that at some stage GPM (at least for 650ss) made pistons for Seeger style clips - at what time did they change to wire clips? I think it odd you select one style of clip for 650 and another for Commandos - so maybe there are some GPM Commando pistons out there that suit Seeger style clips?
It may have been mentioned earlier in this thread (couldn't find it) but it is my belief that the "sharp edge" of the Seeger style clip should face outwards to minimise risk of coming out.
The ones I've seen appear to have been punched so have a "round" edge and a "sharp" one,
Cheers
Rob
Emgo pistons
 
Last edited:
Appreciate the through thinking for me. FanFan's pointing at GPM helps narrow my shopping inquiries. One would expect respected factory replacement piston vendors would know which clips match. Rebuilds by expedient prior owners who knows.
 
Status
Not open for further replies.
Back
Top