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Discussion in 'Thumpers' started by HighFive, Sep 18, 2010.
Thats because we are running to order our own 50% HP and Torque increase
Thanks High Five
I didn't get a look until 2am so I was fairly tired. I am thoroughly impressed. It looks to really give that extra little punch in the low rpms that's missing and makes the top end scream even more. I would say the non corrected numbers are probably a little more accurate of just bolting on the kit in the same conditions since you did get in and do some extra work on it. Still very impressive and something I'd consider once I become a more skilled rider or blow the engine. To think, I have even more to do now than just the exhaust, airbox mod, and programmer.
It's to see the end of the journey though.
Jealous was more what I was thinking.... Now all I need to do is upgrade my XT to a WR.
lol - you were one of those kids that needed/got a lot of attention, weren't ya??
Seriously, very impressive stuff - thanks for your meticulous record-keeping, pics, etc - definitely a great data set to review.
Sorry HighFive, I had been checking so often I finally gave up on you and decided to wait a while, so I didn't see the results until today. 20+% increase from the kit alone is a staggering gain for any performance modification short of a blower, so you should be proud of yourself.
I have to admit I cringed when I saw your head and port modifications. From what I've read, porting and combustion chamber shaping often requires more trial and error than theory. Some of the old gray-haired geniuses like Bob Braverman, Gordon Jennings, and Kevin Cameron have told from bitter experience about discarding cylinder heads after even the most obvious-seeming improvements turned out to be steps backwards. So I was relieved when I saw the big gains. If nothing else, you couldn't have screwed it up too much. And I was especially surprised at the gain in upper rpm horsepower, which is not a typical result of a bore increase. So maybe your porting had something to do with that.
You are to be commended for putting an incredible amount of time and money into sharing your experiment. Many of us have bought magazines for far less information. I don't expect anyone to step up and put the same amount of effort into documenting the stroker kit, but I hope at least you will get a chance to ride a stroked bike side by side with yours and offer some thoughts.
WE are speechless, thats why
The results are just awesome. Thanks for the hard work and money spent to make this happen! Now we know what this bike can do with the right mods.
I fully understand your "cringing". I'd be lying if I said I wasn't a bit nervous about it myself. But, you know how it is when two old friends get together and start pondering What If. One thing leads to another......and then another. It took a stiff shot and a steady hand. Ok, maybe four.
I didn't expect much from the porting, as I'm well aware money spent on 4-stroke head modifications is typically the worst money spent in the "gain per buck" department. But apparently, I'm just not the typical type. We did the work ourselves, so no money was spent.
And, I already had plenty of riding time on the Athena Big Bore to know its performance characteristics fairly well....at least by feel. So, I had a specific target in mind before we messed with it. Not something for the weak knee or faint heart. That's for certain. No one should attempt anything like it just willy nilly. And, I'd say your interpretation of the results is fairly accurate. At the least, we got lucky and didn't screw it up. At the most, I gained some additional mental HP.
I think you did a great job with the porting. There is no way the factory can spend the time cleaning up the ports on every head. They just run with close enough and that "close enough" costs power in the top end. That said, how close is the water jacket to where you were grinding? Did you feel there was enough meat in the casting?
Great thread! I have always been a big fan of big bore kits. Recently did a big bore kit on my GF's Vespa 50cc to 70cc it runs great. My next big bore kit will be a 453 kit installed in my KTM 400. Thanks for the time and effort to post in here.
Unknown.....its rather hard to guess at that one. If antifreeze mix shows up in my oil, then will know the answer was "not enough".
I would also like to thank Highfive, from the bottom of my crankcase, for the effort and attention to detail in documenting these upgrades. Thinking long and hard about stroking my WRX now!
I might ought to mention, there was one other difference in my bike between Dyno 1 & 2 vs. Dyno 3 runs.
My first two runs were made with Krause Racing Ti sprockets and Sidewinder Smart-chain. Just before the Dyno 3 run, I changed to Supersprox combo with RK-xwring chain. Kept the exact same gearing ratio at 13/46, but only had about 300 miles on new chain & sprockets prior to Dyno3.
If anything, I would expect the heavier (new) chain and sprockets to yield more drag. The Sidewinder combo is claimed to add about 1.5 hp. So, I might of had an even better result running the original combo, but it was totally worn out.
Doesn't really matter to me, but I thought you ought to be made aware of these minor changes which could have affected test results (slightly). FWIW
Thank you Highfive for your detailed posts. I know these things come at some expense if dyno costs are anything like they are in Australia.
Have you noticed much of a difference long term now regarding fuel consumption compared to stock?
HighFive, You'll have to make the short drive up to C'ville and give me a test ride
Yes indeed, they are. Think my project costs have exceeded intentions. But, that gnawing quest to know....
Guess I should have charged admission. I'll gladly accept papypal donations and start another project.
I have not measured fuel consumption yet. But, I guess I can do that now. I was averaging about 55 mpg (+/-) previously. Give me some time, and I'll report back later.
Cycle World magazine, June 11 issue.
They added a Athena big bore kit too.
(plus GYTR Slip on muffler,gearing changed to 13/49, EFI box?)
Anyway, H.P. went from 28 stock to 33
Torque went from 17 to 22
Most likely on a different dyno and different weather then HighFive's, but you get the idea of improvements made by the big bore kit!!
Thanks for the heads up. Here's the web link:
I am very impressed with the torque curve. It is FLAT from 4300 - >8500!!!! I like the HP boost also, but so many times the torque suffers due to HP gains. Manufacturers would kill for that kind of flexibility! You,sir, have made a very different machine than Yamaha shipped over the ocean. It should be called the HF 290.
And it runs good too....
Thanks for your kind comments. I'm very pleased with the result. Seems better and better every day I ride it. I'll be hitting some serious trails this weekend.