meat Posted April 6, 2009 Share Posted April 6, 2009 I picked up a little 100cc Yam yesterday at a yard sale for the boy. It seemed to be in decent shape but I don't know much about these bikes at all. The guy said that he was having some electrical issues with it and couldn't get it started but when I cranked it over the cylinder sounded dry..... I figured what the heck, it's 50 bux. I got it home and started messing with it a little to see if I could at least figure out some of the problems right away. I have been trying to do some research on the net to see where I can get parts for this bike and what exactly it is. According to the manufacture sticker and engine it is a LT2 that was made sometime in '71. Probably sold in '72, since it seems LT2s where only sold in '72. I am starting to become interested in this little bike and the fact that it was classified as an enduro. I would love to find the lights for it again and put it back together, possibly even restore it. Let me know what you guys think. If you know anywhere I can get parts for this little guy I would appreciate a point in the right direction. Thanks The sticker is a little worse for wear but I can make out a 71 on date of manufacture and the VIN for the bike. Here are some of the problems I found on day 1. He gave me the original ignition switch, which seems to be fine.... other than some really bad soldering work. Hearing the dry sound in the cylinder when I cranked it made me think I would find rust. Well the broken piston looks rust free to me. Link to comment Share on other sites More sharing options...
JimR Posted April 6, 2009 Share Posted April 6, 2009 I picked up a little 100cc Yam yesterday at a yard sale for the boy. It seemed to be in decent shape but I don't know much about these bikes at all. The guy said that he was having some electrical issues with it and couldn't get it started but when I cranked it over the cylinder sounded dry..... I figured what the heck, it's 50 bux. I got it home and started messing with it a little to see if I could at least figure out some of the problems right away. I have been trying to do some research on the net to see where I can get parts for this bike and what exactly it is. According to the manufacture sticker and engine it is a LT2 that was made sometime in '71. Probably sold in '72, since it seems LT2s where only sold in '72. I am starting to become interested in this little bike and the fact that it was classified as an enduro. I would love to find the lights for it again and put it back together, possibly even restore it. Let me know what you guys think. If you know anywhere I can get parts for this little guy I would appreciate a point in the right direction. Thanks Hearing the dry sound in the cylinder when I cranked it made me think I would find rust. Well the broken piston looks rust free to me. Hi There Meat (beef, lamb or pork ?) looks like a 'metal mouse' has been gnawing at your piston while the bike was laid up but from the pics I would guess you could make a nice little bike from it as long as you can find a piston kit for it which is the next oversize up so the cylinder is bored just to clean it up. If the bike has been laid up for some time you may want to strip it down and fit new main bearings & seals (new motor nearly) and if the big end is noisey fit one of them too (total motor rebuild) . I would guess you could have a good little bike there as long as you can find the parts to restore it. In the UK we had DT100 and from the Pics some parts may fit ! Regards Jim Link to comment Share on other sites More sharing options...
meat Posted April 6, 2009 Author Share Posted April 6, 2009 Hi There Meat (beef, lamb or pork ?) looks like a 'metal mouse' has been gnawing at your piston while the bike was laid up but from the pics I would guess you could make a nice little bike from it as long as you can find a piston kit for it which is the next oversize up so the cylinder is bored just to clean it up. If the bike has been laid up for some time you may want to strip it down and fit new main bearings & seals (new motor nearly) and if the big end is noisey fit one of them too (total motor rebuild) . I would guess you could have a good little bike there as long as you can find the parts to restore it. In the UK we had DT100 and from the Pics some parts may fit ! Regards Jim Thanks Jim. I looked up DT100 and was able to find some pistons. Parts seem hard to find for these little guys though. I have decided that I am going to rebuild the engine/gearbox and try to get the lights for it again. If you or anyone else knows a place I can source the lights, bearings for the engine/gearbox or any other parts I may need, please let me know. Again from what I can tell it is a 71 LT2 100cc two stroke with oil injection. Cheers Link to comment Share on other sites More sharing options...
Twin Shock Posted April 6, 2009 Share Posted April 6, 2009 Thanks Jim. I looked up DT100 and was able to find some pistons. Parts seem hard to find for these little guys though. I have decided that I am going to rebuild the engine/gearbox and try to get the lights for it again. If you or anyone else knows a place I can source the lights, bearings for the engine/gearbox or any other parts I may need, please let me know. Again from what I can tell it is a 71 LT2 100cc two stroke with oil injection. Cheers The DT and the LT are totally different engines, Lights, watch E Bay, engine bearings, your local Yamaha dealer. Link to comment Share on other sites More sharing options...
JimR Posted April 7, 2009 Share Posted April 7, 2009 The DT and the LT are totally different engines, Lights, watch E Bay, engine bearings, your local Yamaha dealer. Hi TS, If the bore & piston height are the same for the 2 motors the pistons will interchange (piston height = distance between the piston pin & crown), if the piston skirt is lower on the DT this could be adjusted to suit the LT motor if the skirt is higher I would be inclined to fit the piston and make other adjustments to the inlet tract, ign timming and exhaust. I would guess parts for the LT motor are just about exhausted so parts from a 'cousin' engine may very well keep this motor running. Regards Jim Link to comment Share on other sites More sharing options...
Twin Shock Posted April 7, 2009 Share Posted April 7, 2009 Hi TS, If the bore & piston height are the same for the 2 motors the pistons will interchange (piston height = distance between the piston pin & crown), if the piston skirt is lower on the DT this could be adjusted to suit the LT motor if the skirt is higher I would be inclined to fit the piston and make other adjustments to the inlet tract, ign timming and exhaust. I would guess parts for the LT motor are just about exhausted so parts from a 'cousin' engine may very well keep this motor running. Regards Jim Jim,yes the bore and stroke are the same 52x45.6 the LT2 is a piston port and the DT is a reed valve engine. The piston's are still avaliable here in the USA for the LT2, However I don't use cast pistons. You are correct however the Dt piston can be modified to work. Link to comment Share on other sites More sharing options...
JimR Posted April 9, 2009 Share Posted April 9, 2009 Jim,yes the bore and stroke are the same 52x45.6 the LT2 is a piston port and the DT is a reed valve engine. The piston's are still avaliable here in the USA for the LT2, However I don't use cast pistons. You are correct however the Dt piston can be modified to work. Hi TS, I am playing with FS1's may be FB5 in your country, this motor shares the same bore & stroke with, in the UK, the RD50. The FS1 is a disk valve motor (piston ported), the RD is a reed valved motor. To date I have fitted an RD50 piston, which I must admit, has a slightly higher crown (by about a mm) and the reed valve windows at the rear of the piston skirt which now allows the motor to rev some what more. The windows appear to allow extra fuel into the transfer ports but to date I'm having problems with the disk valve ... how much do I cut it back ? Rgards Jim Link to comment Share on other sites More sharing options...
Twin Shock Posted April 9, 2009 Share Posted April 9, 2009 Hi TS, I am playing with FS1's may be FB5 in your country, this motor shares the same bore & stroke with, in the UK, the RD50. The FS1 is a disk valve motor (piston ported), the RD is a reed valved motor. To date I have fitted an RD50 piston, which I must admit, has a slightly higher crown (by about a mm) and the reed valve windows at the rear of the piston skirt which now allows the motor to rev some what more. The windows appear to allow extra fuel into the transfer ports but to date I'm having problems with the disk valve ... how much do I cut it back ? Rgards Jim Jim we don't have those bikes here, actually the 2 stroke motorcycle is nearly gone from the show room floor except for 2 motocross versions. Are you saying the piston top suface is 1 MM too tall for the cylinder? If so you can raise the cylinder which will also help exaust port timing. A friend of mine is building a land speed bike from a 1976 RD 60 in which he has sleeved down to a 50. Link to comment Share on other sites More sharing options...
JimR Posted April 10, 2009 Share Posted April 10, 2009 Jim we don't have those bikes here, actually the 2 stroke motorcycle is nearly gone from the show room floor except for 2 motocross versions. Are you saying the piston top suface is 1 MM too tall for the cylinder? If so you can raise the cylinder which will also help exaust port timing. A friend of mine is building a land speed bike from a 1976 RD 60 in which he has sleeved down to a 50. Hi TS, The FS1 motor in the UK is a sort of cult bike if you are between 45 & 55 years of age as they were all we could ride back in those days! The RD50 came to the UK in 78 and was slowed to 30mph/45kph (government legislation). The RD 50 piston is a mm taller than the std FS1 piston but the FS1 cylinder head allows for this no problem. My question/comment was how much do I need to cut back the FS1 disk valve to accomodate the extra ports in the piston, I guess I already know the answer as on modaling the FS1 cylinder, today, with the RD piston there will be very little it could do without a lot of work to the rear transfer port on the FS1 barrel. Regards Jim Link to comment Share on other sites More sharing options...
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