Yamaha Ypvs/Athena Conversion

[dusty350]

Scan_20231211 (23) by dusty miller, on Flickr

Scan_20231211 (24) by dusty miller, on Flickr

Scan_20231211 (25) by dusty miller, on Flickr

[jon]

I’m not sure I agree with the costing here? A rebore, pistons and a tune is less than £800 nowadays. Bearing in mind most would add £200+ or so for a set of pistons with the Athena, as the standard ones get a bad rep compared to others. Then there is the exhaust question. Bodge a set of adapters on or spend another £800 on exhausts.

When I get my 385 done I’d love to get Mutts to dyno it and compare the torque curves of it against an Athena. I quite expect less HP but more torque? To me the area under the power curve is far more important that peak HP.

Jon

[JonW]

Its always funny to read Stan's articles, hes not a stupid man.

In his column he's advertising his services and his products and I bet each time the mag went out that his sales jumped for the products/services he'd talked about.

His rep (built from back in the day) and the interest in our bikes during the era of this article meant blokes with money were itching to talk to Stan on his 40p/min (or something like that) phone line.

Fair play to Stan, he wasnt in business to lose money and he knew he'd only have a few years to ride this wave to retirement...

Anyway, the point is that he says the pistons are ok... and they are 'ok', nothing more. He says they are Japanese... I doubt that, but they could be. Most people didnt use em tho cos they went 421 and the supplied 68mm units were only good for 392. At a time when people dissed the supplied pistons its interesting he was the lone voice saying they were ok... go figure.

Athena (and other big bores, especially the non PV variety) have their place. Lots of people in the 'shee world just want more power and this is a simple upgrade and is easily 50+% as a bolt on. This is cos the Banshee makes very lower power, its worse than an LC really.

Of course the value/power equation is not as simple with our bikes as the YPVS already made almost that power of course, hence 421 being more worth the effort as you'd need a new crank and pipes anyway.

Amusingly 10 years or so back Roger from Wicked did a post on the RZRD500 forum doing as budget Athena install as he could. He used OEM YPVS pipes I think with an adaptor, but defo used OEM carbs. No programmable ignition either, tho maybe an adjustable banshee stator plate. ie it was all the cheapest bits n bobs.

He still got a decent upgrade over a ypvs on the actual dyno and the 'bum dyno'... and of course if you fit better pipes, intakes, carbs, programmable ignition etc etc you add bhp with every bolt on.

Roger isnt silly either, he also sold a bunch of kits on the back of that article i bet. He was one of the first to cross pollinate the banshee parts into the RD/RZ world as he was a fan of the road bikes but came up from the banshee world. He came at the bikes as for testing his porting work and didnt live near the dunes, so finding a road bike with the same engine meant he could test on the lane out front of his shop; no brainer.

Ride ability is always interesting with upgrades like this. Most are designed for USA off road quad riding, so there is a lot of 'all or nothing' as most are upgraded to race their mates or as cheaper alternative to buying new/used OEM cyls. There isnt as much pottering about in the dunes... ie the use is different to how others used em; like a uk green lane or 30(20!)mph zone round town. Its one of the reasons the banshee quads are huge in parts of the USA, but not other places.

The Athena was designed as a simple base platform to build upon. It works with no extra mods and standard parts right up to very exy porting and pipes/intakes etc. There is a lot you can do with the simple and relatively cheap kit, plus there is lots of knowledge out there about it as lots have used it in many different ways.

Sure the Athena is a bit base and there are better things out there for going fast or bragging about bhp numbers, but none with more experience and knowledge and none with the value proposition of the Athena.

I still have a lot of love for the Athena product. Its not perfect, but it made it possible for many of us to cross over into some of the banshee scene a bit and pick up some great parts and improve bike performance, although not always as rideable as you might like.

I say that as a 421 can be a bit of an animal, when the power bites the bike really takes off. I think Dave (Mutts) summed it up really well ages back when he said that the Athena was one of the fastest bikes to rev up, ie build revs once in the Power Band. It tends to do @6-10k like a light switch and you need to be aware of that on road. That is fun, but it can also bite you of course.

As for the price... hmm... The cyls/pistons/gaskets kit used to be well under US$800 on ebay... when I did the big bore primer I figured that if you were sourcing 350 cyls as an upgrade from a 250 (not something sold in the UK I know, but in Aus this is super relevant) or over bored 350 cyls on their last size that you would be better off with Athena, but if you just needed pistons and a rebore it'd always be cheaper to redo a ypvs 350.

All said tho, For those that have done it the thrill of riding a 'mega LC rush' on a big piped, programmed ignition, big carbed 421... its a bit addictive... and, well, if thats what you want from your bike then youre planning on spending a lot of money beyond a rebore anyway. But, you will get Thrills, Chills, Skills and Spills, which is what an RD/RZ is all about lol