varadero Posted April 7, 2011 Report Share Posted April 7, 2011 (edited) Will a B piston fit in a A barrel, I am ordering my parts today and I will have a chat to sandifords about this Edited April 7, 2011 by varadero Quote Link to comment Share on other sites More sharing options...
copemech Posted April 7, 2011 Report Share Posted April 7, 2011 (edited) Will a B piston fit in a A barrel, I am ordering my parts today and I will have a chat to sandifords about this PLEASE excuse my spelling mistake and I dont know how to fix it Should with a proper light hone job properly done. Fitment is critical and the piston sizes are normally +- .005mm different i think. Edited April 8, 2011 by copemech Quote Link to comment Share on other sites More sharing options...
varadero Posted April 7, 2011 Author Report Share Posted April 7, 2011 Should with a proper light hoe job properly done. Fitment is critical and the piston sizes are normally .005mm different i think. thanks for the reply, I was talking to sandifords this evening and will be again tomorrow morning and I will ask them aswell. Quote Link to comment Share on other sites More sharing options...
sherco29 Posted April 8, 2011 Report Share Posted April 8, 2011 Post up your findings please! I will be doing the same thing soon. Quote Link to comment Share on other sites More sharing options...
varadero Posted April 8, 2011 Author Report Share Posted April 8, 2011 Post up your findings please! I will be doing the same thing soon. Yes I spoke with Martin Sandiford this morning and after our chat I have ordered a B piston for my A barrel. The difference between them is minute and would suit a barrel that has worn over time. Also I might add that they were very helpfull and good prices Quote Link to comment Share on other sites More sharing options...
sherco29 Posted April 9, 2011 Report Share Posted April 9, 2011 Thanks! Quote Link to comment Share on other sites More sharing options...
varadero Posted April 18, 2011 Author Report Share Posted April 18, 2011 My parts arrived this morning and I couldnt wait to get started on my bike. The B piston was a lovely fit and I had the engine back in the bike in short time with new rings , small end, gudgeon pin , clips and gaskets. It started on the 3rd kick and I now have a nice quiet engine, no more piston slap. I thought I had good compression before , Its got some compression now. I can understand how (dakota) thought he had done something wrong during his rebuild. I have changed the wheel bearings front and rear aswell and replaced some spokes front and rear, washed the muck out of the airbox . Here is a little tip for those of you with very loose front discs. While I had the front wheel off I removed 2 opposite studs holding on the disc and stretched a very small O ring over each spacer and it fitted back inside the hole in the disc , taking up the play that was there. Roll on tomorrow for some garden practice Quote Link to comment Share on other sites More sharing options...
bikepilot Posted April 21, 2011 Report Share Posted April 21, 2011 Nice work. Does the 315R use a steel sleeve or a plated cylinder? Quote Link to comment Share on other sites More sharing options...
varadero Posted April 22, 2011 Author Report Share Posted April 22, 2011 (edited) Nice work. Does the 315R use a steel sleeve or a plated cylinder? THANKS, To the best of my knowledge its a plated cylinder Edited April 22, 2011 by varadero Quote Link to comment Share on other sites More sharing options...
bikepilot Posted April 22, 2011 Report Share Posted April 22, 2011 Thanks for that. If its any use to anyone, you definitely cannot hone a plated cylinder to fit an oversized piston (and really shouldn't hone them at all imho). I'm new to Montys, but have almost two decades doing 2-stroke MX engines. The difference between A, B, C etc is very small though. Wiesco for example just uses one piston for all letter sized cylinders for the CR250R and it works out just fine. The main thing if you run the piston on the tight side is to take a bit of extra care to warm it up slowly - doubly true if using a forged piston. Quote Link to comment Share on other sites More sharing options...
varadero Posted April 23, 2011 Author Report Share Posted April 23, 2011 Thanks for that. If its any use to anyone, you definitely cannot hone a plated cylinder to fit an oversized piston (and really shouldn't hone them at all imho). I'm new to Montys, but have almost two decades doing 2-stroke MX engines. The difference between A, B, C etc is very small though. Wiesco for example just uses one piston for all letter sized cylinders for the CR250R and it works out just fine. The main thing if you run the piston on the tight side is to take a bit of extra care to warm it up slowly - doubly true if using a forged piston. I didnt do anything with my cylinder, mainly because I didnt have tools to hone it and it was in good condition anyway. What was noticable in mine was a fair amount of play or looseness around the lower skirt area of the old piston, When I trial fitted the new B piston in the cylinder it was a nice fit and wasnt tight or loose either , if you know what i mean. Just when I have my 315 nearly sorted I bought a 03gas gas 280txt pro today, another seriously neglected bike Quote Link to comment Share on other sites More sharing options...
sherco29 Posted May 3, 2012 Report Share Posted May 3, 2012 (edited) bump for confirmation! I just ordered a B size piston for my A size cylinder. This was recomended by Lewisport. Now (little late) I check the specs in the manual and its showing A is the largest piston, C the smallest!?!?!? Typo in the manual or is it backwards from every other bike I know of????? Stuff should be here tomorrow...trials this weekend. So its going in no matter what...but I am going to be upset if I actually got a smaller piston and my bike still rattles...$200 bucks for a piston!!!!! EDIT: new B piston is in...no more rattle at idle! Still curious if the manual is messed up and A is the smallest???? Edited May 4, 2012 by sherco29 Quote Link to comment Share on other sites More sharing options...
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