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It is if the rest of the engine won't hold up. Even stock they have a shadowed reputation.
Yeah but other than that
Yeah I rode a 426 back in the day. I detect no lie.
That thing damn near kicked my 120 lb ass in 02 over bars trying to start it.
Athena make a 304cc cylinder kit for the yz250f
https://www.athena.eu/en-us/big-bore-cylinder-kit-85-mm-300-cc-to-increase-performance-P179195.htm
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Luxon 4-Post Bar Mounts
$189.95 - $239.95
Frantic makes a 310. It’s a Yamaha.
My suggestion to Yamaha is to stop wasting time “developing” a 350 and produce one already. What the hell is their to “develop” other than a market of buyers?
Japanese seems staunchly against cutting into there 450 sales. I’d bet we never see one from a Japanese OEM.
Do they spec an MX version or just enduro?
Years ago you picked a class and made the bike work. Today folks want you to build a bike stark/350 etc. that does all the work.
Damn it! I was coming in here to post this lol. It was my show he called into and dropped that info. From what I have put together since then, Him at Yamaha confirmed. as far as the 350 goes. I think that will be a 1-3 year thing to see come out. (if we're lucky enough)
And of course it's click bait, I'm trying to grow my show lol.
Hell, I'm giving away a YZ250 just to encourage people to call in and share stories that I can play on my show.... All my shows have been a good listen so far!
Good luck with the show. I will give it a listen. That being said with EFI and all the mapping options available now is displacement really that big of an issue as it used to be anyway? I have only ever ridden 250, 2 and 4 stroke, but can't you mod a 450 with mapping and such to perform more like a 350?
Keffer keeps saying you CAN’T turn a 450 into a 350, but I really don’t get why there isn’t a kit out there for it. To make that happen, you’d need a destroked crank, a resized cylinder and piston, plus a completely redesigned head. The valve sizes would also be a big deal—if they’re too big for a 350 setup, that could really mess with the performance.
I’ve had some in-depth discussions with a friend of mine who’s a head engineer at Yanmar, and we’ve gone over how this could work. It seems like there’s potential here that’s just not being explored!
100% click bait. no one should click it! 😀
The magic in the 350 is less rotating mass. It's the inertia of the motor in a 450 that makes them feel so heavy and wears you out quicker.
I'm not an engineer but I don't think it's possible to make a 450 feel like a 350 really.
its not that easy, crankshaft mass is one of the things that make a 450 feel the way it feels.
All I know is if Yamaha releases a 350, i will have one!
Didn't KR557 race a KTM150 some years ago at the Ironman GNCC after he already won the championship on the 350 in XC1 class? Grant Davis won an overall this year in the XC2 class on a 250. I am not familiar with all the rules but he could maybe just ride a modified YZ250F in the XC1 class. I mean look at Deegan's lap times on that bike, I don't think the added engine size is a huge advantage anymore. I don't know how some of these XC1 guys race a 450 in the woods at that pace for 3 hours! (Stu, Grant, RickyR, Strang, JordanA, etc.)
He will be riding a 250 in the XC1 class. Yes he did ride a KTM 150 at Ironman (I just live up the road). In regard to a big bore 250 it is overrated (I have unfortunately done it to a Kawasaki, Yamaha and Honda), you lose significant "over rev". He will be just as fast to ride a bone stock engine.
Pit Row
350 = Magic!
https://www.merriam-webster.com/dictionary/magic
What you just laid out is basically a whole new motor.
You can’t map a 450 to be like a 350, too much crank weight and reciprocating mass. A 450 tunes to be like a 350 would feel ungodly heavy. 350 is also DOHC and the 450 is SOHC.
I was thinking about a 300 Athena kit on a 250kx for enduro riding.. its not a good idea? You gain power in the mid and bottom and lose it on the top or what?
Yes, its the whole package in that frame on the 350 that makes the ergonomics of the ktm 350 pretty dang good, atleast I enjoy riding it.. but I did beg for a 350f when i got a yam250f 2 years ago, so i hope this is good true news!!!!
I have been at this since 1973. I have had big bore kits on all bikes except a Suzuki. I regretted all of them because I ended up losing "over rev", I acknowledge the new ECU's may help compensate for this fault. I am part of the group they call "church of the 350", I think they are the perfect motor because you can lug it or scream it.....
Not everyone is a complete bad ass like you that needs the full power of a 450.
Has anyone installed one of these and run it? If so can you send us a ride report? Curious.....
a 2021 crf250 with 300cc kit (athena 290).
The red curve is stock bike with HGS exhaust
The green is the 300 kit with HGS exhaust
The orange curve is a 2018 crf250 with the same 300 kit.
If people are worried about overrev you could colpensate that with cams. But as always if you mount something like this, a tune of the ECU would be a good thing to do.
What you gain in low to middle would be a no brainer for the little over rev you loose. Even if it peaks earlier, it still produces more HP than where the stock bike peaks.
Couldn't Yamaha make a 350 without Russell anyway?
I immediately tried changing cams with my big bores in an effort to regain some overrev (I was not impressed). I also switched to a shorter header with no luck. I acknowledge ECU changes may do the trick....I have simply not tried this avenue. Bottom line, if you are a lugger vs a screamer there is no downside to a big bore.
You only lose over Rev if you don't build it to Rev out. Ive never lost any appreciable over Rev on any of my big bores I've built.
I would love a jap 350…ideally a Yamaha…but if any of them released one, it would be in my garage…since the jap brands refuse to build one…after 30 years on jap bikes…my next bike will either be an Austrian 350 or a Beta 300 2-stroke…
Post a reply to: Kailub Russell helping Yamaha develop a 350?