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Post by jon on Jun 3, 2022 7:13:57 GMT 1
Kinda, but not really. There had already been 350 and 400 versions of the AC 2T parallel twin so making a 350 of the water cooled unit was always something marketing would want. Many countries had concessions for 250s and one was Japan hence most things RD started as a 250. Ie. In uk it was about learner laws and in Aus it was about 'road tax' etc. The USA and Canada wanted bigger engines and had no concessions, hence only had the bigger engines in almost all models. The loss of the learner law in the uk meant no ypvs sold there, whereas in Japan and Aus they sold way more 250s of those models than 350. The old twin was designed as a small engine from the start, everything is balanced for a 250 and that is why the rev so well. The lineage of the engine goes back to the 60s etc. The Lc was just another in the line of RDs (well it is really an RZ as Z means watercooling) so got the same treatment. The tie bars was something i guess the AC models (I know nothing about AC bikes) didnt have and didnt need, perhaps cos they didnt make the power of a watercooled machine? Jon, I don’t think it has anything to do with the ‘power of a water cooled machine’. As mentioned earlier the engine vibrates with harmonics around idle speed. I suspect, although can’t remember if a 350 is worse than a 250? Also mentioned is the fact it’s dimensions are better suited to the 250 being a square bore and stroke @54 which is what I’ve read is ideal. The 350 pistons must upset this balance to an extent. Interesting you say the Z means water cooled. This can’t be the case in all applications around the same time. What about the TDR 250? I knew usually R denotes a 2 stroke and F a 4 stroke, but don’t know if it’s actually an abbreviation? Jon |
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Post by steve63 on Jun 4, 2022 20:08:52 GMT 1
My experience is that 350LC's rev much quicker than 250's.
I have a YPVS/4L0 that's not had the tie bars fitted ever since I built it in 1987 until about 1996. It was fitted with F2/N2 pipes. I never noticed any excessive engine movement and had no exhaust problems.
My view is that after a few reports of problems with exhaust sealing and cracking Yamaha went belt and braces with the mods to make 100% sure they fixed the issue.
They also changed the gasket in the exhaust port to a wider one after the 4L0-00 cylinders.
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Post by JonW on Jun 5, 2022 0:28:40 GMT 1
Kinda, but not really. There had already been 350 and 400 versions of the AC 2T parallel twin so making a 350 of the water cooled unit was always something marketing would want. Many countries had concessions for 250s and one was Japan hence most things RD started as a 250. Ie. In uk it was about learner laws and in Aus it was about 'road tax' etc. The USA and Canada wanted bigger engines and had no concessions, hence only had the bigger engines in almost all models. The loss of the learner law in the uk meant no ypvs sold there, whereas in Japan and Aus they sold way more 250s of those models than 350. The old twin was designed as a small engine from the start, everything is balanced for a 250 and that is why the rev so well. The lineage of the engine goes back to the 60s etc. The Lc was just another in the line of RDs (well it is really an RZ as Z means watercooling) so got the same treatment. The tie bars was something i guess the AC models (I know nothing about AC bikes) didnt have and didnt need, perhaps cos they didnt make the power of a watercooled machine? Jon, I don’t think it has anything to do with the ‘power of a water cooled machine’. As mentioned earlier the engine vibrates with harmonics around idle speed. I suspect, although can’t remember if a 350 is worse than a 250? Also mentioned is the fact it’s dimensions are better suited to the 250 being a square bore and stroke @54 which is what I’ve read is ideal. The 350 pistons must upset this balance to an extent. Interesting you say the Z means water cooled. This can’t be the case in all applications around the same time. What about the TDR 250? I knew usually R denotes a 2 stroke and F a 4 stroke, but don’t know if it’s actually an abbreviation? Jon Yes the pistons are too heavy for the crank in the 350 as it was designed for a 250. Haha, no idea what or why the TDR is a TDR. Im not saying its a fool proof system, not least as marketing kept the RD name alive in some markets (like the UK) way beyond when it should have become the RZ really. RZ starts in Japan with the LC RZ starts in Aus and Canada with the YPVS RZ starts in the USA with the YPVS but they didnt have the LC etc. |
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Post by JonW on Jun 5, 2022 0:29:47 GMT 1
My experience is that 350LC's rev much quicker than 250's. I have a YPVS/4L0 that's not had the tie bars fitted ever since I built it in 1987 until about 1996. It was fitted with F2/N2 pipes. I never noticed any excessive engine movement and had no exhaust problems. My view is that after a few reports of problems with exhaust sealing and cracking Yamaha went belt and braces with the mods to make 100% sure they fixed the issue. They also changed the gasket in the exhaust port to a wider one after the 4L0-00 cylinders. Ive know guys to break the welds on the frame where the tie bars bolt on. Perhaps you have just been lucky or have a nicely balanced engine and a very true crank? |
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Post by midlifecrisisrd on Jun 5, 2022 10:34:29 GMT 1
My experience is that 350LC's rev much quicker than 250's. I have a YPVS/4L0 that's not had the tie bars fitted ever since I built it in 1987 until about 1996. It was fitted with F2/N2 pipes. I never noticed any excessive engine movement and had no exhaust problems. My view is that after a few reports of problems with exhaust sealing and cracking Yamaha went belt and braces with the mods to make 100% sure they fixed the issue. They also changed the gasket in the exhaust port to a wider one after the 4L0-00 cylinders. Ive know guys to break the welds on the frame where the tie bars bolt on. Perhaps you have just been lucky or have a nicely balanced engine and a very true crank? Not personally seen the weld break but I've had 2 bikes that the actual bracket had split Also had a crack in the frame rail at the engine mount Steve |
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Post by JonW on Jun 5, 2022 14:38:55 GMT 1
Ive know guys to break the welds on the frame where the tie bars bolt on. Perhaps you have just been lucky or have a nicely balanced engine and a very true crank? Not personally seen the weld break but I've had 2 bikes that the actual bracket had split Also had a crack in the frame rail at the engine mount Steve Yep. seen the split from the bolt hole thru to edge of bracket too. Frame rail crack is a new one, but i hear you... These frames are old and can rust from the inside out now etc |
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