Gonna have to call your bluf! I'm guessing either you have a TX500 or you are assuming you have 8 valves in that motor!
Hey Sean....what are the XS classes right now, v-3 and bump to v-4? Where are the KWC?....lurking in the shadows with their fingers crossed? I'm betting a stocker XS goes down hard in V-3.....maybe consider some good limits and let a stocker run V-2 ??? That puts it on the track with 500GP anyway. Where is Oldalowski?....how about Chapman or Padgett?
Bike bandit show it as two valves per cylinder. And, the only mention I could find online at 4 valves per cylinder was on the TX500 1974 Yamaha TX750A Parts 1974 Yamaha TX750A OEM Parts http://www.bikebandit.com/houseofmotorcycles/1974-yamaha-tx750a/o/m7789#sch219117
No clue what the current classes are. Just relaying a question as it was asked, didn't do a lot of research yet, figured I'd use you guys first
And, thanks for the consult opportunity. Between more horsepower, a fifth gear, overhead cam, and a significant increase in reliability, having an XS650 in the GP500 heard will be a major game changer. The addition of the Honda 350 twins was a major game changer too. It saved the GP350 class. But, adding the Hona 350 twins already saved the GP500 class with half the displacement!
However... The XS650, like the CB/CL/SL350s are the most popular model in their class. They were produced from 1968 to 1985. They are among the most supported (aftermarket and OEM) vintage motorcycles out there. As time goes on, that will make a big difference in what is reasonably available to racers. I believe that the XS650 should have a class where it is successful. I believe the same for the RD350.
I'll be 60 this year and unfortunately have no bike for the SR classes.I think the classes I run primarily are more competitive and fun at my age anyway: V5, Clubman, V5lw, and DSB. Even got some regional championships. Just like a fine wine... So point is if you're getting too old to compete w/ the young whipper-snappers in 40plus, come on down to the modern small bikes and vintage. Even the 2-fiddy class is way cool for the mature crowd.
Just to add a little more confusion, the XS-1, which Sean first asked about, is the first version of the Yamaha OHC 650. It had a longer stroke than the later XS-2, which was renamed the XS650, which was renamed the TX650 which was re-renamed the XS650, again. The XS-1 also had drum brakes and was only produced for a year or 2. If it was allowed in 500GP, it would not be a bad fit, but as soon as people started sticking XS650 motors in and all that then it would be opening up a whole can of worms. I don't think it is worth the bother since it has other classes it can run in. Ken
I'm restricted to 30mm carbs, 4 spd. trans. and 34 mm forks. My Bonneville is a 1972. the 5 speeds were already out by this time, but mine was shipped to dealers like it was a left over 71. 500 gp calls for pre 72 models, production based. Over bore size has always been a question for me ( i never asked cause it's not an issue yet) the rules don't say ss spec. Just production based. I aslo wonder about boring carbs, as long as they start as 30mm production based.
Speaking of 250GP, are Yamaha CS3 and CS5 eligible since they are essentially the same are the YCS-1 the meets the pre-'68 requirement? It seems like that question has been asked before...
My Opinion... When I raced Triumphs in V3 & V4 the XS650 (punched out to 750) was also in the class. An XS, with enough money spent on it, might ultimately make more power, but in general they are an equal match. The 70'-72' R5 350 street bike is a lesser equal to the RD350. There is no reason they should not run in the same class, from an engine performance perspective. Compared to an RD350, they had a similar chassis, drum brakes, 5-speed instead of 6, and no reed valves. I've owned both (many) and the RD is a superior bike to the R5.
No they're not, the YCS-1 was initially a 180 from 1968, the CS3 and CS5 were 200's from the early 70's which makes them not legal. And they are faster that's why AHRMA won't allow them in the their 200GP class, however they do run in 250GP.
