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Thanks for all the feedback. I am curious that out of a 4 cylinder 500 there is only 60hp at the wheel. We run a 500 twin (500T) at the moment and get reliably get 60 bhp at the rear wheel from that. By 'The Laws of Honda' the mutlicylinder should be capable of producing more; what is the limiting factor with the 500/4? i.e. is weak spot.
hei freak,You shouldnt be surprised about the 500t beating the fours, Todd Henning beat even MV's with his crazy 500 twins. But you cant get that kind of horsepower witout plenty of $$$, heavy mods and switching to coil valve springs. getting 60-65 from a four is 'relatively' easy and cheap, managed to do that in my small and not very well equiped garage. 75 rwhp from a 500c.c. CB500 four ? Would love to see the dyno print or just send us a link to the data you saw. Some very smart people here are not getting that kind of number even with 600cc+ motors, so dont believe the all hype you hear / read. Weak spot in the 500-4 is like some said, the small IN valves, motor can safely rev to 13K but stops breathing well at 10K or so. Solving that would involve fitting new seats at a different included angle, not a cheap excersize in a four pot motor, but it has been done by big Honda in their little known CB500R (a 650 actually). Got the time and money to go into that? The 650 head looks like a interesting option even if not quite vintage legal. It will need special high dome pistons too if you wan to stay 500cc'sCant see why you would want to redo the CC in the 500 head. Its very compact as it is and you can get 13:1 with a pretty low piston.Regarding useful threads, too many to list, check some of mine under "racer developement" and "10 degrees downdraft" "small block pride", + posts by howell, TTR, bwaller, benton, mrieck, CB500fourC'mmon, dont be lazy..... TG
Plus Manx Nortons.
I didn't know John was still riding, he must be about 110 now fast Goldie though if you can call it one. Sam.
Quote from: SamCB750A on February 08, 2010, 10:53:22 AMI didn't know John was still riding, he must be about 110 now fast Goldie though if you can call it one. Sam. Sam, you are worse than me, that was 1999....That said, John came to Italy last years and got spanked too (so he still rides)Lea Gourlay on the other hand, gave everybody a 2 sec a lap lesson on the 500 paton... some riderMy own memory must be playing tricks, thought I rembered todd beating an MV once or twice, but I am old and senile by now (and i wanst even there.).Back to the subject, I am tempted to give the 500-4 the title of "easiest vintage 4stroke to get 65 hp from" Freak, nice idea about the bathtub thing, but I dont think its very relevant to a 57mm bore. with a thin 7mm sqush ring spark timing can be already very late' like 30 degs or less. I tend to think that a Bathtub approack is much more relevant to 400cc + pots, with bores more than 80-90mm where fast burning is critical. my 0.02A few things to cover here... First Patton used today are not even close to their original design as they made them up now with 4 valves per cylinder and they never raced in the day... that way. I am not sure why the British, and Europeans have to change history in that way. They still are mad that Honda came over and kicked their arsses!...I suppose.Secondly...bathtub chambers work on any size chambers..we had great success with "tub-ing"our M3 CB500 based racer from 1997-2000 in AHRMA but we could not beat the Yamy RD350 derived two strokes on the big tracks. Just too much port area and a lot lighter, but occasional they would do "the two stroke thing" and blowup sometimes moving us up two places to get on the box at Daytona!Also, Robert Yates of Yates Racing Engines, the developers of the latest NASCAR Ford two valve V8's has lead most builders down the road of almost flat pistons tops, small bathtub chambers, smaller than normal valves and not that large of ports to be the HP king in that group of BIG engines. He gets very early late ignition timing numbers, as there is NO dome to have to climb over with your intake charge.Note: probably the WORST bore stroke multi valve combination ever made? Yamaha 5 valve. That engine need almost 47 degrees of spark lead just to get it lit off in time to make any power. Have you noticed they never used 5 valve tech in Moto GP, new YZ450 motocross bike and even Ferrari quit trying to make it work. When Mr Gotto came over from Honda GP car team and joined Ferrari, after Honda quit at end of V12 & V10 era...the first thing he did was to s**t can that idea.KOS