mainekz Posted August 26, 2008 Share Posted August 26, 2008 Afternoon Just signed up hoping you guys can help me with some advice about the R5 model. I'm looking at a 72 R5C which looks like a pretty original and straight bike but the owner tells me it's has a reed valve conversion (from the later RD I guess). Now I know my way round old Suzuki oil burners OK, but I'm new to the 70s Yams so I'd like to hear any opinions on this conversion - good thing? bad thing? doesn't matter thing? Also any general comments tips and hints on what to look for with an R5 would be welcome. Cheers - MaineKZ Link to comment Share on other sites More sharing options...
Petey Posted August 30, 2008 Share Posted August 30, 2008 As far as the reed conversion, I have read that it improves performance, especially at the lower revs. From a general point on this two stroke, I've haven't heard/read much in the negative side. It has the oil pump that injects oil into the gas mixture and I read that when just idling, the pump doesn't run. This didn't seem to be a problem but I suppose it could be if it were to sit idling for a long time. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 30, 2008 Moderator Share Posted August 30, 2008 As far as the reed conversion, I have read that it improves performance, especially at the lower revs. From a general point on this two stroke, I've haven't heard/read much in the negative side. It has the oil pump that injects oil into the gas mixture and I read that when just idling, the pump doesn't run. This didn't seem to be a problem but I suppose it could be if it were to sit idling for a long time. Cant see anything wrong with fitting a reed valve so would say 'good thing' The oil pumps work from the rotation of the crank usually so the slower the crank rotation, ie idling, then also the slowest the pump will stroke (frequency). Coupled with this they are also connected to the throttle cable, so the wider the throttle is opened the stroke of the pump gets longer. In summary, At full throttle the engine revs are high and so the pump stroke frequency is high, also the pump stroke length is high, Therefore high frequency and long strokes = maximum oil is pumped...Just what you'd want at full throttle If youve heard about this bike oil pump not working when idling, then Mr Yamaha must have connected it to a gearbox shaft, a bit of a blunder I would say, But I doubt it, Mr Yamaha is cleverer than that Link to comment Share on other sites More sharing options...
Petey Posted August 31, 2008 Share Posted August 31, 2008 If youve heard about this bike oil pump not working when idling, then Mr Yamaha must have connected it to a gearbox shaft, a bit of a blunder I would say, But I doubt it, Mr Yamaha is cleverer than that Connect it to the gearbox is exactly what "Mr Yamaha" did on some models....clever guy that he is. Link to comment Share on other sites More sharing options...
Moderator Airhead Posted August 31, 2008 Moderator Share Posted August 31, 2008 Connect it to the gearbox is exactly what "Mr Yamaha" did on some models....clever guy that he is. Silly man Still it would take a heck of a lot of idling to be a problem I expect Link to comment Share on other sites More sharing options...
Petey Posted August 31, 2008 Share Posted August 31, 2008 Silly man Still it would take a heck of a lot of idling to be a problem I expect I got the info after reading an old review when the '72 first came out....I copped this part out: (When first introduced on some models, the pump was driven from the gearbox. If a rider was to have this particular model with the engine running while at a standstill, clutch lever in with the bike in gear, the oil pump would not be in motion. This never amounted to any problem, but it was a disturbing fact to those who realized what was going on.) I would assume that if you idled in neutral, the pump would be in motion. In reading the article, I took it that he was talking about the 350 R5C, but I'm pretty sure now that he was noting this as being on other Yamaha 2 stroke models and not on the R5C. He was just pointing out one of the improvements on the bike....sooo...never mind. Link to comment Share on other sites More sharing options...
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