Gandini Pistons

News to you it is then Grant...was a few years ago so couldnt say if he still does them...nice slugs though at least to my untrained eye. Have a nice set and barrels hardly used...changed when i got the new RGS head and pistons and barrels from the Slaters show engine a few years ago..Clem and Richard Slater worked on that together.Sweet as now running C4 cams of course, 3 angle valve seats by Nr Nairn and drilled cam sprockets etc etc
 
nick7 said:
News to you it is then Grant...was a few years ago so couldnt say if he still does them...nice slugs though at least to my untrained eye.
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be around 10 years ago now, you are correct that Wolfgang did supply JE Pistons but they became difficult to deal with
they were taken over by one of the larger automotive supply mobs and became OEM suppliers so were not that interested in small orders anymore
and their ring end gaps were woeful, from the packet some would measure 0.70mm, still have a couple of sets of their rings in stock
 
Noted Red! Yes there  was a problem getting info on ring gaps...i dont think a lot of non engineer riders are aware that you cant just assume that all is well out of the box! Recall Paul Le  talking about ring gapping experiences. Rings being brittle i imagine its quite a job actually filing the buggers to size with requisite precision.Not something for the amatuer i think.
 
Filing down rings made for a larger bore size isn't really advisable as you end up losing compression at 90 deg to where the gaps are and probably cause the bores to become scored at the gaps too... I've done it with old mini engines but can't say it was a great success (used more oil too).
 
Have always check piston ring gaps since I was a boy . And if you find filing to hard try a stone but you must always make shore your gaps are correct.
Jap stuff will probaly not need altering
Some even have there rings marked up as A, B or C like Moto Guzzi
Regards Andy
 
When i had pistons made - I used to source and supply the ring sets - i would use a 0.10mm (4 thou)O/S ring set and found that often the two top rings had the gap i wanted and only the lower ring would need a tad taken off it. Eg - I used a 75.4 piston with a 75.5mm ring set. I always used a spiro backed Cast iron oil ring as per original spec. -  Found that the honing was most important - done as it should be I ran my engines flat out with virtually no running in period. -  Regards - Phil
 
nick7 said:
Noted Red! Yes there  was a problem getting info on ring gaps
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the issue with the JE rings is that most of them had too large of a ring gap straight from the packet
if you are looking for 0.35mm and the new rings supplied are already at 0.70mm, one has an issue

is not difficult to file rings, they are not made from particularly hard material
 
AndyW said:
Filing down rings made for a larger bore size isn't really advisable as you end up losing compression at 90 deg to where the gaps are and probably cause the bores to become scored at the gaps too... I've done it with old mini engines but can't say it was a great success (used more oil too).
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i can't imagine a .1mm difference in dia would be detectable as an out-of-round. As Phil points out, he has always used 1st OS ring sets without issue. have done the same many times myself. if you used rings from a 1.00mm OS then sure, you will probably have gaps at the circumference.

So Phil, you always use/d oil rings as found in the std Laverda factory pistons? Are there advantages or disadvantages with these over 'modern' three-piece?
 
So Phil, you always use/d oil rings as found in the std Laverda factory pistons? Are there advantages or disadvantages with these over 'modern' three-piece?
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  Yes Quentin - i have used a chromed spiro backed C.I oil ring though. I've never been massively technical in my approach to almost any sort of work on motors. - the original ring/bore set-up on Laverdas is very trouble free and long lasting - so i stuck with that I don't know if the C.I oil rings are any better or worse than the modern type - but they are easy to grind to the gap i need. It did have another benefit in that as customers filed/ground/bodged their ring sets and often broke them- I made more profit selling them more. >:D  I use a simple hand operated grinder . - Regards - Phil
 

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the issue with the JE rings is that most of them had too large of a ring gap straight from the packet
if you are looking for 0.35mm and the new rings supplied are already at 0.70mm, one has an issue 
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Had same issue Red  - when i used to sell the Je pistons in the UK when Lance Weil originally had them made - this is what made me go for larger ring sets than piston size. - Regards - Phil
 
I'm on a roll now - 3 posts on the trot!! - just found my old instructions for the Accralite pistons i distributed in the nineties. - regards - Phil

TODD LAVERDA PISTON & RING FITTING INFORMATION

PISTON/BORE CLEARANCE IS 0.10mm (0.004?), MEASURED AT BOTTOM OF SKIRT, ON THE THRUST FACES.
PISTON RINGS ARE SUPPLIED WITH SLIGHTLY UNDERSIZE GAPS IN MOST CASES, CAREFULLY & SQUARELEY GRIND OR FILE THE ENDS TO THE FOLLOWING DIMENSIONS :-
75.4, 75.9 & 76.4mm PISTONS ? END GAP = 0.20 ? 0.30mm (0.008-0.012?)
80.4 & 80.9mm PISTONS ? END GAP = 0.25 ? 0.35mm (0.010 ? 0.014?)
MAKE SURE THAT A SUBSTANTIAL CHAMFER IS PUT ON BOTTOM OF LINER AS THE RINGS (ESPECIALLY THE 75.4mm SERIES) ARE EASILY BROKEN IF FORCED INTO INSUFICIENTLY CHAMFERED LINERS.
REMOVE ALL BURRS WHEN FINISHED. DO NOT USE HIGH REVS ON A COLD MOTOR IF USING THE SMALLEST RECOMMENDED CLEARANCES.
 
Piranha Brother 2 said:
i can't imagine a .1mm difference in dia would be detectable as an out-of-round. As Phil points out, he has always used 1st OS ring sets without issue. have done the same many times myself. if you used rings from a 1.00mm OS then sure, you will probably have gaps at the circumference.

So Phil, you always use/d oil rings as found in the std Laverda factory pistons? Are there advantages or disadvantages with these over 'modern' three-piece?
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I too thought as you did until a few years ago whenI took my Hurricane barrels in to my local machine shop in Townsville for a light hone/freshen prior to fitting new rings. I'd bought the next (first) oversize rings with the intention of filing down the gaps to suit the final bore dimension. The machinist advised against this for the reasons I described earlier and demonstrated how, when you fit an oversize ring to the bore, the ring doesn't seal at the 90deg sides of the bore. If held up to the light or a torch shone up the barrel  then light could be seen between ring and bore. In his experience and opinion it was far better to have a slightly larger ring gap than mismatched ring/bore sizes. In the end I opted for new pistons (first oversize) as the old ones were out of clearance tolerance and he bored the barrels to suit the pistons. The machinist specialised only in motorcycle engines and generally works on KTM desert racers and, to date, my Hurricane runs well and doesn't smoke... :D 8)
 
I wonder whether the microgap would seal after bedding in? And if so, whether the bedding in would simply increase the ring gap!! Innaresting case study. personally, I hate big ring gaps and blowby.
 
I hear you: the machinist said that when using filed o/s rings the bore becomes polished at 0 and 180 deg to the gap. Blowby is eliminated by staggering the gap positions. I assume using staggered o/s rings results in faster bore wear :o
 
AndyW said:
I hear you: the machinist said that when using filed o/s rings the bore becomes polished at 0 and 180 deg to the gap. Blowby is eliminated by staggering the gap positions. I assume using staggered o/s rings results in faster bore wear :o
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Huh ??? Seems strange, don't rings rotate during running??
 
i only use a 0.1mm ring oversize - as i said - often the end gap is then correct without any filing - a 0.4or 0.5mm 1st O/S may well give  some gap as Andy suggests  - never tried it. All my motors never smoke or seize and they have a much tougher life than most. - regards - Phil
 
Lots to know! So for those of us entrusting say a rebore to a professional, seems you really need to take your new pistons with so he..or she..can do the whole thing properly.
 
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