125-200cc Look what I found

Ok, nothing is wrong with my cylinder or piston, I took it right down and the piston only has a little bit of wear like one line, found this one for the sms so smaller powervalves so will fit mine, but seller said it will run but maybe need a replate. From the pics it doesnt look too bad, I will try a scotchbrite pad on it at first, if it still isn't smooth shall I just get my garage to hone it a bit? I've got a 53.96 mm piston ready, that's size c, standard is a or 53.94mm, say garage hones it then measures the bore, if cylinder is too tight for that piston can the barrel be bored out enough that the ''c'' piston will work in it? It's nikasil coated. I am stupid I know I bought the piston before measuring as I recalled the piston I took out originally was a size C so I assumed the current one would be, and it's a B 53.95mm [but that's the one on the bike atm]

with nikasil, you really cant "hone a bit" theres not much there. if the scotchbrite doesnt work, it will probably need plated.
especially since you are on the road, wouldnt it be better to use wr or cr 125 parts? bump it to a 144?

Yup cant enlarge nikasil buut you can bore it out and get it replated if your doing this expect to pay about£140 i highly recommend poeton http://www.poetonaptec.co.uk these are the only guys i trust in the uk.
If your going to drop a steel liner in then s.e.p in kegworth are worth a shot, my last experience wasn't so good but that was Christmas rush so your gunna have to google that one if your still keen.

get a 165

I am rather poorly funded to increase the bore size, but the guy who does my mot's honed it, checked piston ring end gap and told me I had the ring on upside down, all he wanted was 2 quid so I gave him a tenner, there are still some small scratches but seems to go up and down smoothly enough, it's either gona be my spare top end should the current one ever implode or if I get past 10,000 miles, bearing in mind it's gone either 5000 or 6000 miles/ 200 plus hours that's pretty damn amazing for a cast piston! Still starts 2nd/ third kick too, thanks for the responses

Looks fresh! Run it thats as near as damnit perfect!

I do really want to trust me, heard some bad reviews about these mitaka pistons but stan stephens wrote somewhere they were good for the price, but atm it's still running so well I don't think I need to, on the road I can normally hit 60 in 7 seconds ish without slipping the clutch

and juicy, i've used this with zero issues, cheaper than putoline and similar brands but meets same specs http://www.ebay.co.uk/itm/290679968363?_trksid=p2055119.m1438.l2649&ssPageName=STRK:MEBIDX:IT

Mitaka are fine on small bores i had one in my kmx for 3 years zero issues, even ran a 200 mitaka piston and swiched cylinders nowt wrong with them, funnyly enough ive had more issues with wossner than mitaka! Both huskys 250 and 360 seized with wossners dont know if the stated 00.6mm clearance is enough. But not buying another anytime soon.

thanks for that, it's encouraging, I can only guess because wossners are forged they need a bigger clearance gap? the mitaka is 53.96 m or a 'c' but the barrel has a 'b' stamped on it, guy said it wouldn't matter as it was worn anyway. How many miles did you do on the kmx in that time?

Was used as daily commuter would guestimate over 9000, and she looked perfect when i did the barrel swap too 200cc.

even more encouraging! I've got a new plan, it;s staying as it isu ntil the powervalve starts getting sticky again, I left them in the cylinder last time I took it off and sprayed it with gt85 rather than getting the grime off with oven cleaner or the like so shouldn't be too long, will do a first start vid too

Sounds like your jettings a bit rich or your oils not burning off.
Would suggest trying different two stroke oil but honestly questioning my choice of putoline at moment did use ipone semi synth in kmx.

ok, it took me five hours but I took top end off, piston out, put the mitaka one in, my barrel is stamped as a 'c'' as is the piston size so hopefully it'll be allright! Couldn't get the powervalve or arm out so had to use same barrel instead of the one in pics above, it looks just as good. I HATE circlips, there needs to be some better way of holding these bits together, allright getting the first one in when it was off the bike but soon as it was on the rod, argh!! Finally got it in, checked their gaps were both pointing down at 6 o clock and in the grooves, put it back together, now it's together enough for a start but it has no panels or coolant atm, here are some photos, I really hope I got it all right! Did I put the base gasket on the right way round? Seems to have orange bit on one side f or some reason

old pro x

Your base gasket will only go on one way, its got larger holes for dowels on one side then its got a cut out on front so yup looks good.. 5 hours!?! Not to bad for a first go, you will get quicker.
Just rotate the engine by hand with out spark plug in for a few turns make sure you cant hear any bad sounds.
And a drop of oil down the bore to help those poor dry rings before kicking it to death will be good too.

I lubed up the little end bearing gudgeon pin piston and the ring and the cylinder bore before putting it back together, did a vid, cranked it slowly with my foot three times, then one kick, two kick, three kicks, braaaa! runs fine, let it idle and a few throttle blips for 10 mins ish, will take plug out to listen for noises a bit later

Dw about noises now lol if there was any issues it would of shown up by now, was refering to piston squish clearance abd pv hitting ring. Sweet run the baby hope shes good for many miles to come.