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Wossner pistons.. Seizes list

juicypips

juicypips

Husqvarna
Pro Class
Right i personally have had 2 wossner pistons one in my wr250 lasted 40 mins before cold seize this was on fresh nicasil lining from poeton and sized to wossner tolerance.. So that toasted the piston and the liner survived. Parted bike out.

Second was on my 360 with a chromemoly liner done by kustom kraft in us of a this seized after 17 hours hard riding time on it and yes it probably was my fault but 5 mins warm up 4 mins riding i thought it was good to let er breathe ... Nope seized on 4 spots cold seize but im confused why the wossners recomend such tight tolerance when i know its not just me thats had issues.

Anyone else had a bad experiance with any pistons wossner or otherwise? Shall i just smash an extra .1 thou on clearance from now on? Should i boycot wossner? They look supurb but at £160+ vat for a piston for 360 in gunna hold out for better.
 
have installed 4 now to wossner spec, all with 40:1 oil...
1 in 84 wr250
1 in 87 xc430 for friend
1 in 83 xc500 for friend, wore his out from dirty/torn filter and being hammered hard, but no seize ever.
1 in 95 wxc360
all were broken in for an hour then hammered. all were cast iron except the 360 which was nikasil, had machine shop check jug for tolerance as per book spec and ordered appropriate piston. the 360 gets run, has about 45 hours on it now. still looks fairly new through the ports and compression hasnt changed since rebuild.

not trying to argue or saying youre wrong, just my experience. havent seen anything to discourage me yet. :excuseme: i tend to jet on the edge of being too rich (four stroking) but i have no spooge or smoke issues. all my bikes have run castor based oil for years now and the 360 is lectron'd
 
For me wossner is the choice when there is no other, If something is available I usually take it over the Wossner. I do appreciate that they make stuff that no one else does, but I have seen a few problems with them.
 
I personally have had wonderful success with their custom piston that I use. The only time I have had even a suggestion of a issue is when using it with their Moly coating. The coating thickness can be inconsistent at times. Since I have gone away from the coating the pistons have been completely bullet proof and very long lived and tough. They were good with the coating but if the coating was too thick then there were issues.
 
What type of issues wallybean? And are we talking the blackish coating below the rings all over the skirt?
Do you use their tolerances too?

Im not slating the workmanship of wossner afterall theyre huge and still going so they cant make crap, im just saying this is my experiance and whilest ive rebuilt only a handfull of motorcycle engines im confident in my workmanship and skills enough to think that its not me... I run putoline now at 40:1 but used to be 33:1 wich is a tiny amount like a few more percent in fuel so im sure its not that ive ran putoline for years in everything no issues.
My 360 is also lectroned no issues with the carb. No airleaks and i send piston and cylinder out to be matched as i dont have the facilitys to do it myself, i have internal bore measures and i relieve the exhaust bridge a few hundreths of a thou for clearances sake.
Like i also mentioned it could be my warm up with cast liners but ive not had issues with smaller bores 125's
I cant source a gillardoni piston and ive orderd a set of rings and filed out the damage on the piston it will be used again im getting my monies worth from it lol
 
Yes it is the black coating. I use the recommended tolerance for my kits. There spec for my pistons is consistent with other manufacturers for this bore size. I had a batch of pistons with too thick a coating and it would create tight areas.
 
Probably but s.e.p. Kegworth did the matching bored out cylinder too suit so if wossner suggests 00.6 mm thats what it got.
Im more than willing to give it ago again, what extra tolerance with a chrome moly cylinder should i of got? .1 .6 thou?
 
You must mean .06mm? That is still too tight for a 78mm bore in my opinion. I would set it up at least .07mm and would lean towards .08mm. Its not like a big piston like that is going to experience piston slap with an extra .01mm which is ~.0004" that's in ten thousands for us backward US types. I think you could set it up at .1mm and suffer no real issues considering the 360 powerband. When I seized my 360...no coolant for about 10 miles of WOT idiocy....Don't ask, I believe George set the new cylinder up at .003" and it ran and I am sure is still running perfect. Seems like a lifetime ago. .003" = ~.075mm
 
Wow yes sorry i did mean 0.06 wrong decimal point. I will get the cylinder honed out a touch more and keep running, so there is no real need to stray away from wossners recomendarion for cast liners then?
Sorry to come across thick but once ive been informed i retain the information quite well.
And thank you wallybean for the responce and help so far.
 
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