kuelmuel Posted May 10, 2009 Report Share Posted May 10, 2009 I think my engine seriously needs rebuilding now, just wondering how much it would cost roughly? Say if it needed new big and little ends, main bearings + seals, new piston and a rebore? It's had a brand new clutch at some point which is in really good nick, I rebuilt it and all the friction plates, smooth plates and springs are actually oversized according to the manual, so it doesn't slip at all! I gearbox is sweet aswell, changes really smoothly. Quote Link to comment Share on other sites More sharing options...
shercoman2k8 Posted May 10, 2009 Report Share Posted May 10, 2009 Id take a guess in the region of Quote Link to comment Share on other sites More sharing options...
alan_nc Posted May 10, 2009 Report Share Posted May 10, 2009 I just did my 74 TY250. Piston, piston pin, rings, top and bottom rod bearing, crank bearings, and seals. Cost about $80 total (about 160 pounds). I did everything my self. It really isn't that hard if you take your time, read all of the instructions and ask questions. You do need the use of a press to take the crank apart and put it back together (I used a 15 ton hydraulic which worked fine). Hint: Crank bearings and seals are just "off the shelf" items. Get the numbers off of them and you can get them from any industrial supplier for under $5.00 each. I found a piston kit on Ebay for a total of $24.00 shipped to my house (piston, pin, clips, rings). Remember you don't need a TY piston, several other Yamaha units work. Oh, and check your bore carefully - unless you have some special problem I'd be surprised if you need a bore job. Now I'm slow but I did have 40 to 60 hours of work in the job (from putting the first wrench on the engine to riding the bike down the drive). Other than the press I don't have any special tools. Good luck.... it's a fun project. Alan Quote Link to comment Share on other sites More sharing options...
kuelmuel Posted May 11, 2009 Author Report Share Posted May 11, 2009 From what I remember from stripping the top end last time, (over a year ago), the piston could twist from side to side slightly in the bore, so I'm guessing there isn't much left of the big and little ends by now. It has been rebored at some point to +0.5mm, so I may well get away with a set of new rings. If I can get the big end bearings, Daddy will be able to split and rejoin the crank. Quick question though, what about the race the bearings run on in the conrod? I assume they're just press-fitted? So just heat it up in the oven for a bit then drift it out? We can get the bearings for free, just have to say they're for Dad's machine at work, but we'd have to buy the mains and seals. Looks like I might be able to do it on the cheap if I can get away without doing a rebore, I'll ring JK Hirst this week and see how much I'm looking at for the big end, little end and a set of rings. Cheers for the help guys! Quote Link to comment Share on other sites More sharing options...
yamahaty250xox Posted May 11, 2009 Report Share Posted May 11, 2009 Muel, From when ive done other engines in the past, DO NOT DRIFT IT OUT! The safest way is to use a press, as the rase is pressed in the first place. It may work by using a drift, but its really not worth it. Find a motobike shop that has a press and they should let you use it for next to nothing. Max Quote Link to comment Share on other sites More sharing options...
kuelmuel Posted May 11, 2009 Author Report Share Posted May 11, 2009 Hey Max, never realised you were yamahaty250xox!! I'm pretty sure that my Dad made a press when he replaced the conrod races in his AJS, so we shouldn't find it very difficult. The plan is to rebuild the bottom end and get it all perfect, try and get away with a set of rings and then look into more torque/power mods in the future. Quote Link to comment Share on other sites More sharing options...
yamahaty250xox Posted May 11, 2009 Report Share Posted May 11, 2009 haha, silly name but it was all i could think of at the time lol. The plan sounds sweet muel. I will be keen to know what the finished product is like! Max Quote Link to comment Share on other sites More sharing options...
majesty320 Posted May 11, 2009 Report Share Posted May 11, 2009 (edited) I agree that there are pistons from other models that will fit and the bike will run, but are the transfer ports and other things the same, as this makes all the difference to the power characteristics of the bike. When I first bought my Ty it was fitted with a non standard piston. When I fitted a genuine Yamaha trials piston it was transformed. A word of caution it my say fits ty/dt/yz or what ever, but dont be fooled. I know its more expensive but I personally wouldnt fit any thing but a genuine TY piston and rings. Edited May 11, 2009 by majesty320 Quote Link to comment Share on other sites More sharing options...
jon v8 Posted May 11, 2009 Report Share Posted May 11, 2009 I agree that there are pistons from other models that will fit and the bike will run, but are the transfer ports and other things the same, as this makes all the difference to the power characteristics of the bike. When I first bought my Ty it was fitted with a non standard piston. When I fitted a genuine Yamaha trials piston it was transformed. A word of caution it my say fits ty/dt/yz or what ever, but dont be fooled. I know its more expensive but I personally wouldnt fit any thing but a genuine TY piston and rings.Am I right in thinking you are from Trail and Trials,did I buy some grey mudguards off you at Telford ? If thats so then do you have any genuine 250 twinshock piston/ring kits,as I searched for them when I did mine a couple of years back - to no avail.Ended up with a pattern one from Hirsts,(Excellent company/service) but never been too happy with the piston.Considering how much trouble I went to in building the motor up with a neat job of port chamfering and attention to bore size etc - it has always rattled.If if could get a Yam piston I'd have one in there,then it might sound as good as my sons TY80.(All genuine bits.) Quote Link to comment Share on other sites More sharing options...
kuelmuel Posted May 11, 2009 Author Report Share Posted May 11, 2009 Thanks for the advice guys. Anyone got a number for Birketts? I can't find one on the net anywhere and I don't get TMX any more. Quote Link to comment Share on other sites More sharing options...
alan_nc Posted May 11, 2009 Report Share Posted May 11, 2009 Jon/Majesty, I think you will find the DT piston ports are exactly the same - at least that's what my caliper said, and crank bearings are just a standard industrial bearing. Piston pin even has the same number. Crank (big end pin) I did buy from Yamaha. If you are looking for original parts try these guys, they have had everything I have ever wanted (and at a discount price). www.boats.net/parts Now Jon: Your comment about a rattle in a rebuilt engine interests me. I have two '74, TY250's, both rebuilt with the same parts (and care). Both seem to be well balanced and don't vibrate bad at all.... but all that said one has a low end rattle at times. Doesn't do it all the time. Sure would like to know what causes it. Alan Quote Link to comment Share on other sites More sharing options...
jon v8 Posted May 11, 2009 Report Share Posted May 11, 2009 Jon/Majesty,I think you will find the DT piston ports are exactly the same - at least that's what my caliper said, and crank bearings are just a standard industrial bearing. Piston pin even has the same number. Crank (big end pin) I did buy from Yamaha. If you are looking for original parts try these guys, they have had everything I have ever wanted (and at a discount price). www.boats.net/parts Now Jon: Your comment about a rattle in a rebuilt engine interests me. I have two '74, TY250's, both rebuilt with the same parts (and care). Both seem to be well balanced and don't vibrate bad at all.... but all that said one has a low end rattle at times. Doesn't do it all the time. Sure would like to know what causes it. Alan Yep,its bugged me since I first started it up.I have built loads of engines over the years and take great care and pride over them.I know people expect aircooled two strokes to rattle,(most of the engines I build now are Rover V8's or 4,5 or 6 cyl diesels ) but I am disappointed,the only consolation is that it goes very well and is reliable - how a Yam should be. Quote Link to comment Share on other sites More sharing options...
majesty320 Posted May 12, 2009 Report Share Posted May 12, 2009 jonv8. I remember speaking to you at Malvern, In answer to your question I just Help John (Trail and Trials) at the shows sometimes, and yes he had genuine TY250 pistons in stock when I spoke to him today. Alan_nc. Sorry my mistake a DT piston will fit a TY250, but only one specific model, and even so I still wouldnt fit a pattern piston as quality control can vary greatly as I found out when rebuilding My Bultaco. Quote Link to comment Share on other sites More sharing options...
andy.t Posted May 12, 2009 Report Share Posted May 12, 2009 Jon/Majesty,I think you will find the DT piston ports are exactly the same - at least that's what my caliper said, and crank bearings are just a standard industrial bearing. Piston pin even has the same number. Crank (big end pin) I did buy from Yamaha. If you are looking for original parts try these guys, they have had everything I have ever wanted (and at a discount price). www.boats.net/parts Now Jon: Your comment about a rattle in a rebuilt engine interests me. I have two '74, TY250's, both rebuilt with the same parts (and care). Both seem to be well balanced and don't vibrate bad at all.... but all that said one has a low end rattle at times. Doesn't do it all the time. Sure would like to know what causes it. Alan With regards to piston rattle in my experience its sometimes due to the slow running mixture being weak, could require a bigger slow running jet, my bike sounds sweet but I could make it rattle if I wanted to by adjusting the mixture. Quote Link to comment Share on other sites More sharing options...
alan_nc Posted May 13, 2009 Report Share Posted May 13, 2009 Andy, Interesting thought. I'll richen up the mixture on that bike and see what happens. Thanks Alan Quote Link to comment Share on other sites More sharing options...
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