This is unfamiliar territory for me. It is looking likely that I'll probably have to get my cylinder bored out on the bike (2 stroke 70cc single cylinder engine). I'll not bullsht here - I'm not 100% clear on what needs done now. I was kind of hoping to buy new standard sized bits but that may not happen so I need to rethink my plan. What I know: Standard bore is 46.0 - 46.015mm Serviceable limit is 46.065mm I have a .5mm oversized piston sitting in the garage, which I'll use If I'm going to get my cylinder rebored what do I need to tell the engineers? Just tell them to move it out to 46.065mm? Should I give them the new piston too? When I get the cylinder bored I assume it's automatically honed/faced for the new piston or is that something I need to specify? Can you recommend somewhere to do it local to Bangor? And ballbag question of the thread (which I think I know the answer to already but will ask regardless)... I assume I need to find bigger rings (+.05) too? Anything else I need to know? Put the engine down and walk away?
OD cars in Belfast, thats who honed my engine. If they bore it it will be honed aswell to give the correct finish. If you take them the piston/rings they'll be able to make everything right (yes you need oversize rings to suit the piston)
you can hone it yourself. Rings are piss easy as well. You'll likely have a set of rings that came with the piston? Sometimes with those kits the rings aren't even file to fit anyway, but best to gap them just in case.
Aye I'd wanted to buy a new barrel and standard piston but couldn't find the barrel. Might just have one sorted though so will hold fire until I know for sure. Honing is probably fine Mark but the cylinder needs bored too and I don't think I could do that, not well anyway
Ideally you need to find out the bore tolerances from the piston supplier/maker. Give these and the piston to the machine shop and they can bore to suit. Rings must be to suit the bore size. Although if it is only 0.05mm difference, good chance std size rings would work ok. 0.05mm is only 2 thou. OD Cars is probably the most local place to you, and will be able to advise.
as somebody has said.what type of bike is it as a lot of bike bores need replated not rebored. check if its nikasil or steel bore.if its coated itl have to go to england to get coated.as far as i know nobody in this country has managed to work out how to do that yet lol..
Suzuki FR70 Suzuki sell a +.5 and +1 piston for it so should be able to bore it alright? Looks like there's a good thick liner on the cylinder but for all I know that means nothing lol. Sorted that stutter for ye troll
http://www.langcourt.com/ are the boys for nikasil. Its very easy to tell if it is, will look smooth and shiny, and likely also be on a liner. something like that is hardly going to be nikasil'd though!!!
OK so the saga continues. Been away for a while so this week I thought I'd tackle this and bought a micro meter to do some measuring. The over sized piston I had in the garage is absolutely miles off. It's 49.5mm OD and although supposedly for a FR70 I suspect it's for a different model because it ain't fitting!! I measured the old cylinder and replacement cylinder ID to see what's going on. The old cylinder measures 45.95mm ID and the old worn piston is 45.85mm OD (these measurements were difficult considering the state of both cylinder & piston - both are a mess). The new cylinder (the one I'm looking the piston for) ID is 46.6mm and by the look of it hasn't been used before - so at some stage it's been rebored before I got it. So... will an 0.5 oversized piston will work OK or will I now have to get it rebored again to 46.95mm and get a +1 O/S piston? Is there some other way I can be measuring this to understand what I need to do? It's got a steel liner BTW.
I would take both the cylinder and piston you have to somebody who is used to doing these things and they can then measure up and advise. If you then need to go to +1 they can rebore and build if you supply them with the piston?
This may be a stupid question, but whats wrong with the piston that came out of it? Can you not just put new rings on it an reuse it?