|
|
Post by jon on Jul 24, 2022 10:16:57 GMT 1
|
|
|
|
Post by jessy03 on Jul 24, 2022 15:27:51 GMT 1
I’ve looked on a couple wiseco boxes I have and 68mm is 0.051 and 73.5mm 0.102mm.
I normally have my LC pistons done 0.06mm, perhaps email the manufacturer??
Jess
|
|
|
|
Post by Tobyjugs on Jul 24, 2022 17:20:00 GMT 1
Hi Jon they look wossener Pistons try looking for info on their site.
To be honest Martin should be able to advise you as he is selling them.
|
|
|
|
Post by Tobyjugs on Jul 24, 2022 17:22:41 GMT 1
Hi Jon they look wossener Pistons try looking for info on their site. To be honest Martin should be able to advise you as he is selling them. Off the top of my head I will say 0.06 mm clearance between piston and liner. The piston should be measured at the bottom of the skirt as it will be tapered. You probably know this do sorry if I'm teaching you to suck eggs |
|
|
|
Post by bare on Jul 24, 2022 17:49:20 GMT 1
Best (only??) reason IMO to use Forged (Wisecos in My experiences) are their Thin Rings.
There are No other worth the trouble reasons TBH.
G'luck
|
|
|
|
Post by jessy03 on Jul 24, 2022 19:00:56 GMT 1
|
|
|
|
Post by jon on Jul 25, 2022 7:09:09 GMT 1
Best (only??) reason IMO to use Forged (Wisecos in My experiences) are their Thin Rings. There are No other worth the trouble reasons TBH. G'luck No bare, not the only reason. These have 5mm less crown height for use with long rods to help alleviate side thrust on the bore. Jon |
|
|
|
Post by tsa on Jul 25, 2022 10:13:51 GMT 1
Id do 0.065mm-0.07mm if none-light porting and 0.07mm-0.075mm if fast road-race porting If its going to be used hard. If not used hard then 0.06mm-0.065mm should be ok this will not make so much noise when cold. But like anything else it's what I use and it may not work for your purpose.
|
|
|
|
Post by jon on Jul 25, 2022 13:54:33 GMT 1
Id do 0.065mm-0.07mm if none-light porting and 0.07mm-0.075mm if fast road-race porting If its going to be used hard. If not used hard then 0.06mm-0.065mm should be ok this will not make so much noise when cold. But like anything else it's what I use and it may not work for your purpose. It’s a Mick Abbey tuned 385 YPVS tuned for bottom end power. I guess from all the useful replies above I should be 0.065-0.07. Jon |
|
|
|
Post by jon on Jul 25, 2022 13:57:18 GMT 1
Hi Jon they look wossener Pistons try looking for info on their site. To be honest Martin should be able to advise you as he is selling them. Hi Tobyjugs, I thought I’d asked him at the time but could be wrong? Anyway they are made by Wossner so I would think 0.06mm is recommended? I’m going to get them checked for clearance and opened up if need be. Jon |
|
|
|
Post by 4l04ever on Jul 25, 2022 14:16:43 GMT 1
Usually the piston is undersize by the amount of clearance it needs to match a certain bore. i.e. Piston = 64.94mm for bore of 65.00mm if 0.06mm clearance is required.
|
|
|
|
Post by jon on Jul 29, 2022 19:21:49 GMT 1
I’ve gone with TSA’s advice and plumbed bang in the middle @ 0.07mm clearance as it’s a Mick Abbey tuned for bottom end to mid range 385cc.
They were on 0.06mm as Wossner suggest.
I feel a bit more relaxed about it.
Jon
|
|
|
|
Post by JonW on Aug 12, 2022 1:56:24 GMT 1
Usually the piston is undersize by the amount of clearance it needs to match a certain bore. i.e. Piston = 64.94mm for bore of 65.00mm if 0.06mm clearance is required. This. Thanks Rob for posting this. Ive said before that ive had 2 reborers tell me that this is a misnomer post the 90s and certainly 2000. So much talk on forums about clearances but pistons are deigned to fit a bore size, not have the bore sized to fit. Modern pistons are made almost perfectly and do not vary like the old stuff so should fit the size they say on the box. If you bore to a piston then you can only use that piston in that bore, what if you need to swap out a piston after some miles and its minimally larger etc. What you will also see is that the difference between left and right is really minimal anyway. In the old days you'd buy an aftermarket set of pistons and bang em in to refresh your engine over the weekend, then ride it like you stole it. Never had an issue in single or twin 2Ts, even used old pistons from my mates when times were hard. It all worked. I think today we overthink this stuff, like we do with oils. |
|
|
|
Post by jon on Aug 13, 2022 8:49:50 GMT 1
I had a set of cylinders rebored for 0.5mm Mitaka pistons a year or so back. I subsequently got a pair of 0.5mm genuine banshee pistons. They were extremely tight in the bores, and the skirt wouldn’t fit at all, so I suspect the actual piston diameters were 65.5mm.
Jon
|
|
|
|
Post by arrow on Aug 13, 2022 10:26:19 GMT 1
I had a set of cylinders rebored for 0.5mm Mitaka pistons a year or so back. I subsequently got a pair of 0.5mm genuine banshee pistons. They were extremely tight in the bores, and the skirt wouldn’t fit at all, so I suspect the actual piston diameters were 65.5mm. Jon I had this 11 years ago with my 250E. New Mitaka pistons were 2 thou smaller than the old ART pistons that had done 28000 miles. |
|
|
|
Post by 4l04ever on Aug 13, 2022 10:47:43 GMT 1
I had a set of cylinders rebored for 0.5mm Mitaka pistons a year or so back. I subsequently got a pair of 0.5mm genuine banshee pistons. They were extremely tight in the bores, and the skirt wouldn’t fit at all, so I suspect the actual piston diameters were 65.5mm. Jon I had this 11 years ago with my 250E. New Mitaka pistons were 2 thou smaller than the old ART pistons that had done 28000 miles. Some manufacturers make accurate parts, but some do not... My engineering man found this with certain car pistons. He found some that were good quality material, but you needed to measure each one and match the bore to suit. |
|
|
|
Post by jon on Aug 13, 2022 13:34:00 GMT 1
I would have thought Japanese Mitaka pistons and ART Yamaha OEM we’re both good.
I think some manufacturers do it one way and others another way with clearances.
Jon
|
|
|
|
Post by dougw on Aug 25, 2022 10:58:58 GMT 1
Two years ago PJME re-lined my barrels and the mitaka pistons supplied where clearly labelled by PJME as left and right, so presumably they think the bore should be matched to the piston. 2000 miles in it is a lovely quiet engine. I tried measuring the bore clearance for the first time using a micrometer and a bore gauge and by my reckoning the clearance was 0.04mm (many years ago I was an instrument technician and had to check the calibration of dial gauges and micrometers , so have some experience of accurate measurement). Back in the 80`s the "Fully race prepared" 250LC I got to replace my stolen LC had holed ANOTHER piston the day before me and a mate where due to be racing at Donington, not many opportunities for the great unwashed to ride Donington back then. I was ready to give up in disgust, but my mate turned up with his collection of spare barrels and pistons. Using two different height barrels adjusted by base gaskets , and hacksawing the cracked portion out of the skirt of a piston we cobbled together an engine that just about ran with a good push start. It survived two practice sessions and three races at Donington the next day, with a distinctively clanking engine once you had managed to push it fast enough to start. Mate beat me in first two races and there was a bet between our respective partners that he was going to make it 3 out of 3. That spurred me on in the last race, didn`t actually make the last corner onto the start finish straight, the two I was planning to pass and put between me and matey both fell, I took to the grass to avoid them and re-joined just pipping my mate. He claimed foul play and that I had deliberately dragged mud onto the track to slow him down  |
|
