February 20, 20197 yr Hi guys back again for some more advice on my TY175 I am rebuilding the engine and wondering whether I should fit an oversized piston. The original problem was a very noisy Rattalee engine coupled with loss of power. The writing on the piston is clear in the picture any advice would be most welcome?
February 20, 20197 yr If I'm not mistaken your piston looks to be 2nd oversize over stock. The correct procedure to do would be to measure (or have it measured) the cylinder bore at different spots to see how much taper or out of round it is. A shop manual will give the correct specs for measuring.That would tell you for sure where you need to go as far as a rebore and oversize. If the engine runs very rattly also check the main bearing play by trying to wiggle the crankshaft flywheel.If you detect any movement you will probably need main bearings... and while you have the crank out might as well have a new rod pressed in for good measure. You don't want to do any work you don't have to obviously but don't short cut it either.. Sam
February 20, 20197 yr The piston numbers say that the piston is 0.5mm oversize (0.5mm bigger than standard). From what you have said, you should have the cylinder rebored to a larger oversize. Which oversize to use can be determined by measurement of the cylinder by someone experienced at the job (usually the person who would be doing the rebore work) Some brands of pistons are available in size steps of 0.25mm and some brands are available in steps of 0.5mm. The biggest piston kit available is 2.00mm oversize. Unless your cylinder is extremely worn, you are likely to only need to increase the piston size to 1.00mm oversize. Don't buy a piston kit until you have had the cylinder measured.
February 21, 20197 yr They are correct. Measure. That being said, I have a 175. With a fresh piston and fresh bore, they rattle a little. Don't know why. To save my cylinder from future wear, I had the cylinder nikasil plated. The piston will wear out before the cylinder. I am using Wiesco Pistons. I think they a for the DT series as some original TY 175 pistons are hard to find. B & J racing in Tennessee is the leading go to for vintage trials in the USA.
February 21, 20197 yr a picture of the bore and side of the piston would be helpful, worn little end & big end bearings can make an engine rattle. and worn rings.
February 22, 20197 yr Author Thanks for your advice one and all. I’m taking it to my local machine shop for measurement before I go any further. Many thanks.
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.