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Post by gcrank1 on Nov 9, 2023 8:09:55 GMT -5
For those who do not know, high performance piston skirts are not 'round'; ie, cylindrical. The shape is such that the thicker/thinner parts expand to become more cylindrical when completely warmed up. The piston skirt to cyl. wall clearance on those pistons should be checked at those now obvious contact points (I dont know if that is/was in their specs; never had one).
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Post by andy on Nov 9, 2023 14:33:26 GMT -5
All understood and this is where I'm going with it :- the piston on the area's where there were no scuffing/pick up's where in original condition as it left the manufacturer and you could still see the turning marks. I was extremely careful to remove the scuffing to the absolute minimum. After talking with a mate who has far more experience than me when refurbing bores/pistons he looked at it and recommended a minimum hone/glaze bust of the bore and new rings,I'm happy with that and recently ordered all the neccessary from Kedo and a few items from Rex's Speedshop [both excellent service and not too severe on the prices]. With a fair bit of enthusiasm I should have it already for a shakedown in a couple of weeks. Just throw this in, before the tear down I did a stone cold compression test,wide open throttle and 3-4 good kicks through, 100 psi was the best result..so a bit of a pointer when its all bedded in. I'm still scratching my head over the oil consumption and although I may never know,my money is on the incorrect fitting of the oil control ring i,e over lapped join instead of end to end.  |
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Post by gcrank1 on Nov 10, 2023 0:21:26 GMT -5
Mind you keep the end gaps in the 'right places'. Wish I could be more specific, but, you know, 'old-timers'.
Fwiw, what I seem to recall was no gap on the major or minor thrust axis'.
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Post by andy on Nov 14, 2023 14:39:03 GMT -5
I'm still scratching my head over the oil consumption and although I may never know,my money is on the incorrect fitting of the oil control ring i,e over lapped join instead of end to end. Maybe my theory was perhaps right.  |
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Post by stevep on Nov 16, 2023 12:53:00 GMT -5
Be great if you get away with just a hone and reassembly! Or are you still planning on a rebore and a Yam piston?
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Post by andy on Nov 16, 2023 15:26:01 GMT -5
After much deliberating,measuring ,inspecting I've cleaned the piston up and bought a new set of wiseco rings and though I say it myself  made a thorough job of gapping,positioning and properly fitting them.The bore was perfect [condition and size] so a light scratch with wet and dry,washdown and on we go. Measuring the wear on the old rings [end gaps] showed significant wear,how much of that was down to the balls up with the fitting of the original oil scraper expansion ring who knows,read my last bit with the info sheet from wiseco  . If the refurb dissapoints me I'll tear it down and go for a new piston/possible rebore to suit. Bottom line is I don't do a huge mileage these days and 2. I've quite enjoyed doing the job at my leisure. Those wossner pistons look the dogs wotsits with the skirt coated with teflon or something slippery,so thats plan B if neccesary. Just waiting on the kickstarter stop plates from Kedo to finish the engine and then back into the frame. New oil pump seals fitted,new kickstart spring arrived o.k, grubscrew mod done on rocker shafts. Keep the advice/comments coming lads and thanks,very useful indeed. |
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Post by gcrank1 on Nov 16, 2023 23:17:30 GMT -5
Wasnt there something about refurbing the check-valve to avoid the potential wet-sumping issue?
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Post by andy on Nov 17, 2023 3:41:17 GMT -5
Correct Blake,and I've bought that as well.I'll fit that last job before buttoning the cover back up...if that ba**ard leaks again I'll scream  |
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Post by gotsron on Nov 17, 2023 20:06:41 GMT -5
Great going Andy ! I was pretty sure that overlapping the expander for the oil control rings was the source of your original issue (but I was too polite to say so  ) It looks like you are down to reassembly. Are you going to spend any left over monies on non-essential goodies? I always wanted a metal cover for the cam chain adjuster. or braided steel oil lines  |
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Post by andy on Nov 19, 2023 4:24:48 GMT -5
This will make you smile lads I'm sure.After sleeping on it I've not been convinced about using the original piston even though it looks fine and I've spent a few quid on replacement rings,so its scrapping that idea and going for a new piston [wossner I reckon].   . Yeah,done a 360 deg turn, £180 to not have to tear it all down again seems the way. Paul, I bought one of those smart aliminium camchain adjuster covers a while back and theres a bloke on e-bay sell ing braided oil lines for around £65...i've bought one cutletcustoms check it out. Conclusion :- Andy,change your religion from orthodox tightarse and as you enter the twilight years....get your hand in your pocket.  |
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Post by andy on Nov 28, 2023 18:22:08 GMT -5
Starting to gather pace👍. New piston turned up and fitted after honing /glaze busting the cylinder bore. Fingers crossed should be about all back together and ready for firing up by the weekend.
Neal, if your reading this you will see my 4 corner piston ‘nip up’ pics , it’s cost a few quid to replace the piston but hopefully it all turns out okay. What clearance you running on your Wiseco piston ? I’ve aimed for 4 thou and won’t risk going flat out again and messing it up 😥
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Post by andy on Dec 9, 2023 15:07:24 GMT -5
Okay you boys,its took a fair while but all back together and ready for the first fire up. After a few kicks it kicked into life and sounded sweet. Next part of this project..a shakedown ride. Yeah ! happy at the minute . |
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Post by gcrank1 on Dec 9, 2023 22:24:23 GMT -5
Oh, the trepidation leading to fire-up after a deep refurb! Hope the shake goes well, but if you are like me it will take a fair bit to get comfortable with it |
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Post by stevep on Dec 10, 2023 8:32:12 GMT -5
Okay you boys,its took a fair while but all back together and ready for the first fire up. After a few kicks it kicked into life and sounded sweet. Next part of this project..a shakedown ride. Yeah ! happy at the minute . Did the Wiseco piston have a spec or data sheet giving recommended clearance? Fingers crossed it all goes well on the test ride. |
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Post by andy on Dec 10, 2023 13:18:06 GMT -5
[/quote]Did the Wiseco piston have a spec or data sheet giving recommended clearance? Fingers crossed it all goes well on the test ride. [/quote] Good point Steve,the only sheet I got was for the ring gaps which I obviously followed. My bore measured 88:00 which I gave a light hone to bust the glaze and clean up. The clearance is on the piston and as gcrank mentions previously in this post is not dead round owing to the differing thicknesses of the piston material around the skirt BUT on placing the new piston in the bore without rings I was just getting a 4 thou [.1 mm] feeler in between. I'm happy with this clearance after the previous [same size piston picked up]. Experts say that you can run tighter clearances on Wiseco pistons but I'm comfortable with the above figures after cleaning the cylinder up. What I'll never know is how long into the 12000 miles on the old piston nipped up and was it caused by over revving the bike on a hot day OR did the obvious incorrect fitting of the oil expander ring contribute ?? I've been ultra careful in rebuilding the motor and will be the same when running it in.After that 5000-5,500 rpm will be max. Early days but I think the oil level is holding up Onwards and upwards |
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made a thorough job of gapping,positioning and properly fitting them.The bore was perfect [condition and size] so a light scratch with wet and dry,washdown and on we go. Measuring the wear on the old rings [end gaps] showed significant wear,how much of that was down to the balls up with the fitting of the original oil scraper expansion ring who knows,read my last bit with the info sheet from wiseco 
.
) It looks like you are down to reassembly. Are you going to spend any left over monies on non-essential goodies? I always wanted a metal cover for the cam chain adjuster. or braided steel oil lines 
. Yeah,done a 360 deg turn, £180 to not have to tear it all down again seems the way.