2639 Posted February 1, 2013 Report Share Posted February 1, 2013 RZ500's. The front cylinders are fitted with reed valves. The rear cylinders are piston ported. Is this just for packaging reasons, there doesn't appear to be that much space between the cylinders, perhaps frame production reasons or carb shape dictated the above. Or it is intentional. There being different systems makes the cylinder banks compliment different loads or speeds better. eg front pair provide more torque through reed use, the rear pair have faster response time so it makes more power??? Anyone care to comment? Cheers Andy. ps; its cos I've volunteered to do some articles. I wanted to be speaking from some sound grounding, and this little detail interested me. Link to comment Share on other sites More sharing options...
wazrs257 Posted February 1, 2013 Report Share Posted February 1, 2013 I would say it's down to packaging. I think it would be difficult if not impossible to tune the two banks of cylinders to perform better at different speeds, because when one pair is giving better low down power, it's having to drag the other pair round that isn't. And vice versa. It would be a loose, loose situation. Link to comment Share on other sites More sharing options...
rs125plus Posted February 1, 2013 Report Share Posted February 1, 2013 looks like 4 reeds to me... Link to comment Share on other sites More sharing options...
2T Institue Posted February 1, 2013 Report Share Posted February 1, 2013 Puch 250 had a piston port and disc valve Link to comment Share on other sites More sharing options...
wazrs257 Posted February 2, 2013 Report Share Posted February 2, 2013 looks like 4 reeds to me... I knew there was a difference in induction between the two banks of cylinders, but wasn't 100% sure what it was. There you go, 2x cylinder and 2x crank case induction, every day's a school day! I still think it was packaging over design though. Link to comment Share on other sites More sharing options...
wazrs257 Posted February 2, 2013 Report Share Posted February 2, 2013 Puch 250 had a piston port and disc valve Was it any good? AFAIK the RD500 was never really succesfull even in F1 trim. Link to comment Share on other sites More sharing options...
2T Institue Posted February 2, 2013 Report Share Posted February 2, 2013 Good enough for Harry Everts to win the 75 250cc mx world title on Link to comment Share on other sites More sharing options...
rs125plus Posted February 3, 2013 Report Share Posted February 3, 2013 http://www.earlyyearsofmx.com/Puch2501975.html i bet keeping the twin carby in tune with each other was fun..... Link to comment Share on other sites More sharing options...
2T Institue Posted February 3, 2013 Report Share Posted February 3, 2013 Takes 5 mins every twin is the same, 2 X 5mm drills(diameter isn't important) under the slides and adjust at the cable stop. Link to comment Share on other sites More sharing options...
willbloke Posted February 4, 2013 Report Share Posted February 4, 2013 I'm not really sure why Yamaha saw fit to bolt a TZR250 engine to a 250LC engine to get the RD500 , but basically , that's what it is . I would guess case reed (TZR) was more bulky ? Link to comment Share on other sites More sharing options...
CMSMJ1 Posted February 4, 2013 Report Share Posted February 4, 2013 I do get engines... and I like looking at them - but can someone explain the crack with reeds and whatnot - and also the disc stuff..and also is the point of this that the motor up top picture has a pair of crank inlets adn a pair of piston ported ones? Enlightne me please...as, for my sins, I have never had a 2t The only one I have ever had a proper go on was a Parilla (sp) 100cc national class kart around Gutersloh and Bruggen in about 1991 when I was a scrote Link to comment Share on other sites More sharing options...
Kayla Posted February 4, 2013 Report Share Posted February 4, 2013 I think there's a bit of confusion with terminology in the OP Piston ported engines use the piston to open/close the inlet (no reed or disc) Port reed engines (LCs, YPVS) have the reed block on the barrel (ie like a piston ported cylinder but with a reed block attached) Case reed engines (TZRs) have the reed block bolted to the crankcase. I think the RD500LC intakes were more for packaging all the road gubbins rather than any advantage, it's more of a compromise than having 4 case reed intakes. I'm way out of my depth with disc valves, but I know that they allow asymmetric timing which is better for outright power (this is all cribbed from A. Graham Bell's book by the way!). Reed valve engines tend to be a little more forgiving. Link to comment Share on other sites More sharing options...
rs125plus Posted February 4, 2013 Report Share Posted February 4, 2013 the rg500 race bike and rg500 gamma were disc valved suzuki stayed close to the original race engine - they just made it 'productionized' this made a better bike - more tunable - more reliable - a smaller package i had 9 at one point - when you could pick up non runners for under £ 500 in the late 90's i loved that engine - the frame less so ! probably the most powerfull 2 stroke engine (per cc) was a disc valve would be nice if someone would develope a v4 from the rsa..... Link to comment Share on other sites More sharing options...
2T Institue Posted February 4, 2013 Report Share Posted February 4, 2013 Very difficult to make a V4 with rear discs. Reeds have asymetric timing according to engine demand, discs don't need the throttle open for combustion, disc has smoother 'liquid' power in band. Even piston ported engines can be very tractable like the legendary Maico 490 Link to comment Share on other sites More sharing options...
Rich Posted February 6, 2013 Report Share Posted February 6, 2013 RD500 is reed valve front and rear. However front cylinders are crankcase induction and rears are direct into the cylinder. I believe this was purely for space (or lack of it) for the carbs. However they still had to fit 90 degree inlets and mount the carbs on the side. A lot of Suzuki strokers have crankcase and reed induction - X7s and RG250s do and I think the aircooled TS trailies did too. Kawasaki AR125 and KR250 have disc and reed valve induction Link to comment Share on other sites More sharing options...
2639 Posted February 11, 2013 Author Report Share Posted February 11, 2013 I think there's a bit of confusion with terminology in the OP Indeed there was. I had not got my head fully around the differences, combined with a lack of side on photo making it clear, resulted in being a div... RD500 is reed valve front and rear. However front cylinders are crankcase induction and rears are direct into the cylinder. I believe this was purely for space (or lack of it) for the carbs. However they still had to fit 90 degree inlets and mount the carbs on the side. A lot of Suzuki strokers have crankcase and reed induction - X7s and RG250s do and I think the aircooled TS trailies did too. Kawasaki AR125 and KR250 have disc and reed valve induction Many thanks. Oh and the TS250C of about 78 vintage I had was reed into crankcase... I remeber this as the little rivets holding the petals in place came adrift allowing the reeds to do whatever they liked. This resulted in a push of a fecking long way one, New Years Eve 1999. Grrr. Link to comment Share on other sites More sharing options...
Scottydog Posted February 14, 2013 Report Share Posted February 14, 2013 A lot of Suzuki strokers have crankcase and reed induction - X7s and RG250s do and I think the aircooled TS trailies did too. I think to be crankcase induction, it's by default reed induction. There is piston port, piston port with reeds, piston port with reeds and crankcase induction and then purely crankcase induction. Not sure if there are anymore variations? I've converted a few piston port with reed type engines into piston port with reeds and crankcase induction. I found it gave big gains, the engine could breathe much better. It does kinda beg the question why the manufacturer never did the same in the first place? Just requires a little machining. Link to comment Share on other sites More sharing options...
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