ask greeves Posted January 2, 2017 Report Share Posted January 2, 2017 Hi Guy's, This might explain the problem with the Fantic piston, the "Tangs" on the skirt arn't really strong enough to suprt the piston square in the bore. Quote Link to comment Share on other sites More sharing options...
turbo Posted January 2, 2017 Report Share Posted January 2, 2017 I have heard that a piston from a later 309 can be fitted to the 305 motor to help the noise issue , is this true ? (ask greeves ) Thanks. Quote Link to comment Share on other sites More sharing options...
fantic240motor Posted January 2, 2017 Report Share Posted January 2, 2017 33 minutes ago, dadof2 said: The piston in the photo is not necessarily scrap. It has just had a light nip up, there is hardly any wear on the skirt. Clean the nip up marks off with fine (800 to 1200) wet and dry, scraped out the ring grooves if the rings do not move freely and it should be OK. Unfortunately my piston is way past saving I'm afraid. The picture doesn't do it justice. Those are scores, some pretty deep and the other side is worse. It'd be the shape of a 50p by the time it was cleaned up! Shame as it probably hadn't seen a lot of use before the yobs got hold of it. The lack of air filter and the amount of dirt in the air box killed it. Your tip for cleaning up a piston after a nip up is sound, I used to have that method down to a tee back in my scooter riding days! Quote Link to comment Share on other sites More sharing options...
ask greeves Posted January 2, 2017 Report Share Posted January 2, 2017 Hi Turbo, My understanding, any 250cc Reed valve piston, wether it be air cooled or water cooled will fit, and I would have thought that 309 and later would fit, and are supposedly stronger, There is a proviso, which is, are the water cooled pistons a tighter fit in the bore and would the grading letter on the piston barrel, be at the same tolerance for both air cooled and water cooled. This wouldn't matter, if the bore was replated, as the replate would be sized to the piston. Quote Link to comment Share on other sites More sharing options...
turbo Posted January 2, 2017 Report Share Posted January 2, 2017 Thanks for the response ,I ask because i am just about to do a full rebuild on my 305 including a re plate and piston so at this stage could fit whats best . Quote Link to comment Share on other sites More sharing options...
fantic240motor Posted January 2, 2017 Report Share Posted January 2, 2017 17 minutes ago, ask greeves said: Hi Turbo, My understanding, any 250cc Reed valve piston, wether it be air cooled or water cooled will fit, and I would have thought that 309 and later would fit, and are supposedly stronger, There is a proviso, which is, are the water cooled pistons a tighter fit in the bore and would the grading letter on the piston barrel, be at the same tolerance for both air cooled and water cooled. This wouldn't matter, if the bore was replated, as the replate would be sized to the piston. Wish I'd had a closer look to compare the piston on my 309 when I had it apart. Is it thought that Fantic fitted a stronger piston for the 309? Perhaps from a K-Roo? Quote Link to comment Share on other sites More sharing options...
ask greeves Posted January 2, 2017 Report Share Posted January 2, 2017 Hi Guys, Fantic reed valve pistons, both 245 and 305 can come with different configurations for the piston inlet ports, the middle port is a puffer port, directly opposite the exhaust port, doesn't really matter (in my opinion) wether piston has or hasn't got this hole, or can be machined if you really think it's necessary. In my experience, some pistons have no holes whatsoever, but can quite easily drilled/ machined to original spec. Quote Link to comment Share on other sites More sharing options...
pschrauber Posted January 3, 2017 Report Share Posted January 3, 2017 Most important plated cylinder and piston has to match. Some air cooled Monos are known for their bad running behavior. The 250TY and sometimes -not all- batches of Fantics and also Beta TR's with just super noisy engines. If you need both a new cylinder coating and a new piston with rings, pin bearings and circlip, even decide to spend some money in a new con rod and lower pin with bearings. You might ask Woessnerkolben in Germany they do al three things at once, custom build a piston that will fit your cylinder after the old one and plating the cylinder too, then all parts you need too surplus a con-rod with all parts if you are in need. Maybe some extra money spend by a non brainer to me as you get every bit from one supplier and with I the guarantee that it works now and in future. All other combination will be of separated guarantee (if any) a lot of time will pass until everyone knows to which diameter the piston or the cylinder has to be made and so one ... As spread mentioned in my personal experience I can highly recommend their work and craftsmanship. Quote Link to comment Share on other sites More sharing options...
fantic tom Posted January 3, 2017 Author Report Share Posted January 3, 2017 I have taken the head off and was greeted by this when I removed it...... http://s1066.photobucket.com/user/tomburras/media/Mobile Uploads/2017-01/20170103_121622_zpsnjddmukw.mp4.html The bore looks good this is it after removal before wiping... There is tiny black lines but I can't feel a single thing anywhere in there and there's abserlutely no lip at the top of the bore either....... Piston.... Looks a bit dull and worn at the bottom and measures 73.65 - 73.75 with a micrometer. Do you recon a clean up and new piston kit will quieten it down? Cheers for replies so far much appriciated!!! Quote Link to comment Share on other sites More sharing options...
fantic tom Posted January 3, 2017 Author Report Share Posted January 3, 2017 I have taken the head off and was greeted by this when I removed it...... http://s1066.photobucket.com/user/tomburras/media/Mobile Uploads/2017-01/20170103_121622_zpsnjddmukw.mp4.html The bore looks good this is it after removal before wiping... There is tiny black lines but I can't feel a single thing anywhere in there and there's abserlutely no lip at the top of the bore either....... Piston.... Looks a bit dull and worn at the bottom and measures 73.65 - 73.75 with a micrometer. Do you recon a clean up and new piston kit will quieten it down? Cheers for replies so far much appriciated!!! Quote Link to comment Share on other sites More sharing options...
pschrauber Posted January 3, 2017 Report Share Posted January 3, 2017 Well it looks used but still not too bad not to ne used again. The plating looks OK with little wear. The piston is used. To the measurements You made a piston is different in size depending where You measure. The piston should ne a but wider at the bottom compared to the top and also in comparison between the axis in drive direction towards the axis of the piston pin, because the exhaust side is often hotter then the port /intake side. I personal would clean everything up very well polish the piston top and the head Inside, then rebuild all again and ride the bike until you get the feeling the engine has lost power or statt rattling more. Then I would so a complete rebuild including con-rod and crank pin. 1 Quote Link to comment Share on other sites More sharing options...
alberto Posted January 3, 2017 Report Share Posted January 3, 2017 23 hours ago, ask greeves said: Hi Guys, Fantic reed valve pistons, both 245 and 305 can come with different configurations for the piston inlet ports, the middle port is a puffer port, directly opposite the exhaust port, doesn't really matter (in my opinion) wether piston has or hasn't got this hole, or can be machined if you really think it's necessary. In my experience, some pistons have no holes whatsoever, but can quite easily drilled/ machined to original spec. So i can fit the Section piston in my 305 without problem ? And same power ? Quote Link to comment Share on other sites More sharing options...
ask greeves Posted January 4, 2017 Report Share Posted January 4, 2017 Fantic Tom, Would have been nice to have seen the markings (letters) on top of the barrel and the markings on top of the piston (in your photos), these should correspond (be the same). Next, if the barrel looks OK (but it's hard to tell definitely without really seeing the barrel in real life) If for instance both barrel and piston are (say) B, then you would need to aquire a B piston kit (piston, wrist pin, rings and circlips) also (hopefully) would include a wrist pin bearing, but I would fit a new wrist pin bearing also. My experience has been, that to refit a noisey piston, will (at some time) damage the chrome bore, Of course while head and barrel is removed...to check the big end for excessive play, it's pointless to fit a new piston to a suspect bottom end. 2 Quote Link to comment Share on other sites More sharing options...
fantic tom Posted January 4, 2017 Author Report Share Posted January 4, 2017 Hi I had to go to work just after removing the head so I'll get the piston top cleaned up in the morning so I can see the letters and update. If the piston is worn will the rattling about cause much damage to the liner? It's tempt to follow as pschrauber suggests and clean it up, polish and put back together. It runs very nice but the rattle is pretty easy to hear. Quote Link to comment Share on other sites More sharing options...
dadof2 Posted January 4, 2017 Report Share Posted January 4, 2017 Fantic used to match piston to bore using low pressure blowby air flow measurement so you probably can never repeat original engine quietness although is someone like Lancourt replates your bore and matches it to your piston with clearance on the tight side you should get very near. The best way to get a quiet (and long lasting piston) piston to bore fit is to get the bore honed about 0.0005 inch too tight, then run the engine fairly very gently for 1/2 hour, let it cool then run it a bit harder (no more than 1/2 throttle) for another 1/2 hour then strip it and wet and dry the high spots from the piston. Then run in as normal http://www.opieoils.co.uk/p-69390-silkolene-classic-2t-premix-sae-40-synthetic-ester-2-stroke-and-rotary-engine-oil.aspx is far better for air cooled engines than modern 2t oils which tend to be thinner (SAE 20 to 30) for watercooled engines. Quote Link to comment Share on other sites More sharing options...
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