Factory Karts Introduces FZ Shifter Engines

We’ve discussed this a bit in this thread (250cc two-stroke engines for sprint shifter karting, available soon), but I think this ekartingnews article does a great job of summarizing and detailing the intent of the FZ shifter kart program that Factory Karts is starting. I’m curious to see the retail prices for just the engine packages, personally, and just how it plays out overall. It would be great to have affordable shifter kart racing at the local and regional levels.


I guess my first thought is… for the 125 “adult” engine. What does this bring to the market that RoK shifter doesn’t?

Genuine question.

I’m curious to see how this plays out. I’d like to see a little more Yamaha presence trackside and directly with customers. That I think would really set this apart from HPDs increasingly clumsy handling of the stock moto.

Two advantages to the customer add up to easy at-home top end jobs on the FZ125:
Linerless cylinder that doesn’t have to be honed for scheduled piston replacements
Readily available top-end kits

The RoK is a pretty consistent and reliable package itself so it’s not going to be a night-and-day difference, but the FZ125 can make maintenance a little easier and more predictable. That goes as well for the carburetor - it’s not like Dell’Orto parts are unobtanium and the carburetor tuned by voodoo only under the light of a full moon, but the Nibbi is notably easy for everyone to get close across the range.


Maybe I missed it in the article, but what class will these be racing? Their own or against KZ??? Also, assuming they are their own class, are there any series already lined up for the class this year, or is next year really the target for something like that?

“We are working with select clubs in 2024, hoping to at least meet the minimum entry level to offer the class so that it will be included throughout the season,” Musgrave concluded. “Our hope is to start with Cadet and Junior classes. Our engine platform is already legal in the Open Shifter division that is offered at the ProKart Challenge here in California. However, this is not about running at the Superkarts! USA Pro Tour, or to offer a class at the SuperNationals just yet. This is about bringing affordable shifterkart racing to the customers. We’re not trying to replace or compete against Pro Shifter. Instead, the goal is to revive the ‘Semi-Pro’ and ‘Junior’ classes at the club level.”


The EKN article was disappointing in several ways. Despite Factory stating beforehand their intentions for the FZ85 was to be an engine for both Junior-level and Adults. EKN went back to the old ways of labeling the 85 as a “Junior Class”, no mention whatsoever of it being potentially available for senior (adult) classes as well. Thus reverting back to what held back the 80 gearbox class previously, deeming it only as a kid’s class.


Once committed, Musgrave placed his first order at the beginning of 2023 for 270 engines. The first half of the order is already in the company inventory in California, and the second container arrived recently. A total of 50 FZ65 engines and 50 FZ85 will be assembled for retail along with 150 FZ125 and 20 FZ250 packages. Another batch of engines are scheduled for the start of 2025…

I thought this part of the article was odd. The first batch of FZs for retail are 50 FZ65s, 50 FZ85s, 20 FZ250s, and 150 FZ125s. I know the 125 is without question the most plentiful shifter engine out there. But you’d think they’d emphasize in offering the engine sizes that are not readily available here right now, rather than the one engine size that already has many varieties around; KZs, Vortex Roks, old CR125s. They say later on that they’re…

not trying to replace or compete against Pro Shifter. Instead, the goal is to revive the ‘Semi-Pro’ and ‘Junior’ classes at the club level.”

But they’re only so many karters available to sell to, and I can’t see them establishing their own 125 class without encroaching into the numbers of the current 125 shifter classes. Judging by how many more 125s they are importing right now than the 65s/85s/250s, they’re really focused on setting up this category.


Their reference to top end and bottom end longevity reminds me when Stock Honda was starting to make a presence. I fully believe these YZ Yamaha-based engines will go a lot longer between rebuilds than the KZs can. But their claims of going 20-25 hours for top end and up to 80 hours for the bottom end harkens back to when Stock Honda guys were boasting big numbers like this in the early days of that engine platform… then they weaseled-in the 2001 cylinder and the national-caliber karters started racing them…


Another common line back in the days of the Stock Honda vs KZ wars, was how you can go to your local bike shop and get the parts you need for your CR125. I can’t tell you how many times I’ve went to the nearby (big and well-established) motorcycle dealer only to be told: “…Ah, we don’t have that in stock, we’re going to need to order it…”. Of all the times I’ve tried to get something there for a '99 CR125, I think the only part they had available was a gasket.

Now, I know, unlike the Honda, these FZ engines are from much more recent Yamahas, so possibly more parts should and will be in stock and available, hopefully that’s the case.


I still think these new engines have potential, and there are certain karting segments that could benefit from them, as I alluded to in the previous thread about this subject. But I’m sure they’ll have their challenges.


Carb stuff and honing aren’t really compelling differentiators IMO. People are not staying in other classes because of these. The RoK already has a presence in karting, is a known quantity in terms of tuning, performance, parity and reliability.

The 175 offered KZ performance with reduced maintenance periods but unfortunately saw limited adoption. The Yamaha proposes to also offer longer maintenance periods, (I suspect will) … but less performance compared to the 175. Nothing wrong with less performance, but what I’m getting at is there’s already been two packages that seem to fit the same demo, yet have had limited adoption.

Don’t mean to be a Debbie downer, but at the same time I’ve lost count at the number of times a well meaning person has thrown a new engine package at the market only to lose their proverbial butt.

The 250 in sprint could be cool. We know it won’t be much faster than a 125, but it’ll be a
wild ride. Thats at least something compelling…. Depending on price which is the other missing piece of info.

On the upside, it is cool to see MRC and Yamaha get involved and commit to it. I’d like nothing more than to see it take off with grids in the double digits across clubs all over the US. That would be awesome. I just think the engine itself is not as big of a contributor of low participation in shifters at those levels.

While thats what many in 206, KA or X30 will say, the real reason they are not doing shifters is that they are TOUGH physically and mentally even at the local level. The commitment is at a much higher level.


Yes. The FZ85 is meant as much for the senior and master drivers as the juniors - it lines up perfectly with Wes Lee’s concept for a less-powerful, less-abusive shifter kart engine.

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All it needs is a restrictor and we’ll be in karting utopia.

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Don’t knock the restrictors… We’re about to make people’s heads explode and introduce them in SIRA.

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Hmmm…are you gonna start a separate thread for that, or should I? Need more info.

I’ll go post about it.

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If you want a real restriction and tuning conundrum, write down 91-octane gasoline as your spec fuel (and you’ll get a nice dramatic show of a powersports expert explaining why it’s a bad idea when you call Willy).

While these aren’t being marketed up front as such, but in terms of wider brand recognition Yamaha is a different league. I can see it being easier to market to newcomers, especially bikers fed up of breaking bones, with the phrase “yeah, it’s a Yamaha” as oppose to Vortex which only karters know about.

The issue with ROK and the IAME 175s is the very ad-hoc approach to it all. The 175, for example, doesn’t really fit anywhere and is very emblematic of IAME’s scatter gun approach to their engine line. Then there’s ROK which is kinda KZ, but isn’t, but is, but isn’t. All these things are quite hard to explain and get your head around. These two companies also have competing interests within their own engine divisions. Do they support KZ or ROK Shifter/175? Do they support OK or do they support X30/Rok? What about he VLR? It’s all a bit messy. For all Rotax’s issues, it’s not really diverted too much from the base concept in nearly 30 years. It road derived and ‘simple’. The RM1/DD2 was probably a mistake, but doesn’t really overshadow the core concept.

So anyway, a Yam - 65, 85, 125 and 250 league of engines is much simpler and a widely recognised brand. Road or dirtbike derived engines have tendency to be the most popular form of kart engines. Whether that be the FR125 or gearbox karting back in the day.

Whether it’s a success or not, who knows. It faces inordinate challenges, like all start-ups do, especially in karting. But I do think they have particular market advantages in the ‘spec-engine’ realm.

I happen to think the cadet classes offer the most opportunity. I can see that being popular if they capture an audience early. Not sure how comfortable I am with kids blasting round on a 65, but just looking at it from a pure business perspective.


There’s been a reliable purpose-built KZ in the market for years. Same maintenance intervals as the CR moto.

Even has an electric starter.

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Not technically a KZ?

Either way it’s not listed on their website and not as well known as Yamaha. Nor do they have 65/85 variants. The 250 could come from their 250 MX range.

The FZ things seems like the full-package idea from cadet to adult. I don’t quite understand the negativity. It is what it is. To make this an reasonable business opportunity worth risking I can see why they’ve gone the route they have.

Everyone is always negative about a new engine package.

what engine is that?

The US market is pretty jaded and disillusioned with engines that pop up on the scene as the next great thing. There’s been so many over time in the US. It causes class dilution because combining the engine packages on a grid doesn’t seem to satisfy drivers.

I guess you could call it scarcity mindset too. But folks have been left with paperweights more
than a few times, so early adopters are hard to find in a way that gets a given engine to critical mass.

Anyway, when can I test a 250?