So, I up till now I have assumed that you buy +1 size piston rings when your bores are slightly worn, the pistons are ok, so you get the +1 rings, fit them and away you go. However I now see you can buy +1 pistons as well…so does this mean you have to buy the +1 piston as well as the +1 rings??
Wait, what? No , oversize rings are (only) for oversize pistons. The first rebore is usually +0.5 (mm 20 thou is real money). Sometimes you can get 10 thou oversizes, though a worn bore may not clean up at +10 thou. But you can't fit oversize rings to a standrd piston and bore. So if your rings are worn, replace them with new ones of standard size. If the bore is seriously worn, you'll need new oversize pistons, new oversize rings, and a rebore.
Cmoore, what exactly are you referring to when you describe a +1 piston or ring? Are you referring to a 1mm overbore? Usually if you are replacing rings, you check the piston-to-bore clearance and cylinder wear and make sure that the clearance is within the manufacturer's specs. Everything else hinges on this, because if there's too much wear or the piston clearance is too great, you'll be performing a rebore and getting oversize pistons. If the clearance is OK, then generally you'll be replacing the rings with a set which is appropriate for the bore size and with ring widths matching the piston grooves. Measuring the cylinder or piston with accurate measuring gear will tell you whether the bores are standard, +0.25mm, +0.50mm, +0.75mm or +1.00mm and when you've established that, you can then purchase rings and/or pistons as required.
geezzz...thanks......i have had the head honed and measured.....everything is within the limits of the book....but there is wear in the bores, so i was going to get a set of oversized (+1, 0.25) rings..... Bores 1 2 3 4 Top 57.06 57.05 57.05 57.05 Middle 57.05 57.05 57.05 57.05 Bottom 57.03 57.03 57.025 57.03 Taper 0.03 0.02 0.025 0.02
those numbers suggest you need the oversized pistons and matching rings. +0.25 should be enough. but as DD pointed out to me (at least for zooks) you can get aftermarket big bore and higher compression pistons custom made for not much more money than the factory prices for oversized kit (again, at least for zooks). that's the way i'll be going now.
cmoore, be careful fitting oversize rings to a standard bore. You'll need to check the ring end-gap with the rings in the bores, and make sure you're taking those measurements with the rings at the bottom of their travel. The ring-gap can be increased if there's insufficient gap but ideally you'll need a piston ring file, which holds the ring at the correct angle without risking any damage. At a pinch you can do it with a hand file but it's not easy to get a tidy finish. If you don't have enough piston ring end-gap, the rings will expand when heated and cause a lot of damage to the ringlands and bores. Incidently, what do you mean by getting "the head honed and measured"?
thanks max, taylor automotive do a hone and measure, which means they hone/deglaze and then measure the bores to then let you decide what to do...
Why not measure first? If it's out of spec, you've just wasted your money on the honing job!
Personally I would go minimum rebore as possible, big bore kits rob you of oversize options if anything goes wrong.. or wear and tear. Find out the price of the piston and rings and the specs of the rings and ask Taylors if they can source the oversize rings because they may be cheaper They are good guys at Taylors and will hold your hand through the whole process as much as you need them to really. All parts must come through their hands first for machining. You will need to give them ring gap specs anyway, make sure there is no difference between your oversize piston gap and the std gap listed in the manual as they may differ. What's the crank like? Have they given it a mic up yet? Max- I will have to show you the wonders of the Dremmel wafer grinding disc, takes minimal off the ring edge nice and clean and quick Building engines rules! BLUEPRINTING LIGHTENING BALANCING MO' POWER
Max- I will have to show you the wonders of the Dremmel wafer grinding disc, takes minimal off the ring edge nice and clean and quick Dodgy, I have a Dremel with all the attachments. Ya still can't beat a "proper" ring filing gadget . . .
Yes, but an investment like that never seems to happen before you recon your first engine, and after that you continue to make do, saying your not going to do another one... I'm fine without one, made do so long now I would probably stuff it up with the fancypants tool
Originally Posted by cmoore thanks max, taylor automotive do a hone and measure, which means they hone/deglaze and then measure the bores to then let you decide what to do... I'm very familiar with what Taylor Automotive do as I worked for Tom for three years, back in the early '80s. The reason I asked what you meant by getting "the head honed and measured" was to avoid confusion and assumptions. Cylinder heads as a rule don't get honed. Again, you'll need to make sure that the piston-to-bore clearance is within spec for your model. Once you've established that measurement, you can determine whether you'll require just rings, or rings and pistons, or rings and pistons and a rebore.
cmoore, Can you weigh your original pistons for unkie Dodgy please? I'm curious... Guzzi were lousy for it, BMW not a lot better at getting them the same weight per piston. Dr Bob sorts that out quick smart though
Its only 2 thou bore wear, not alot at all. Should be ok for rings, Is there any wear in the pistons? Did they measure them
all good questions guys, the reason i had the bores honed and measured is because i don't have the ability to accurately measure them myself...this was taylors suggestion...they have also looked at my crank and main bearings...all good to go.....as far as the wear amounts etc. they seemed to be telling me not to worry about it...a few thousandths won't be an issue...looking at it from a layman’s point of view i would just needed to know if I should/could reuse the existing pistons and get a new set of standard rings or if I should get a new set of larger pistons and rings….so I shall check my pistons again….and check the wear limits…if within tolerances, I will be going for just a set of standard piston rings….
