haven’t heard of any races with those engines. seems stock moto is most common (cr125). would probably have a hard time finding competition

They are racing them out here at Sonoma, currently they run with the Heavy (405lbs) and are just as fast. They have awesome bottom end and are easy to drive, tuning doesnt even play into the equation. Honda even uses the 250 in an Indy car commercial so it makes you wonder what direction they are going…

https://www.youtube.com/watch?v=9Hcwoaoqpi0

There was an attempt to race them up here near Seattle when the local zoning guys decided PGP’s permit didn’t allow for 2-stroke karts (there is no sensible explanation, so don’t ask).  It didn’t take off, mainly because of the cost.  Word was that they were close to but not quite as fast as a stock honda and were WAY loud.

I think it would neat to run one of the modern fuel injected 250 four strokes in a stock form, leaving only the exhaust open for mods. No more fiddling with carb jets to “get it just right”.

Bill, there’s plenty of “fiddling” to be done with an EFI motor, hence the HRC programing kit…  It’s easier to do than changing a jet, but there’s plenty in there…

http://world.honda.com/HRC/products/settingtool/crf250r_2013_settingtool/

CR

Honda hasn’t really pushed the CR250 platform. They wanted it because the tooling for the old cR125 engines is wearing out (it wasn’t designed to build engines for 15 straight years), but the big organizers didn’t like the idea.

Lots of people on here hate the idea of switching to 4-stroke. I think it’s a combination of basic fear of change (though everyone says it’s fear of over-revs) and vendors fearing the fact that it has the potential to be much more reliable and potentially puts them out of the tuning business. The over-rev issue can potentially be solved with a slipper clutch, but that does add more $ to the initial investment.

If it does ever happen, the new Yamaha 250 motor is the way to go, not the Honda motor. The Yamaha HP is roughly on par with a KZ motor plus the intake and exhaust are correctly positioned for a kart setup (unlike any of the Honda engines). As far as I can tell though, Yamaha doesn’t sell the engines by themselves.

John, I believe you mean CRF250?

Honda did do a big push a few years back when they put together the whole package and I believe they announced a series, then I heard the 4 strokes were banned from that venue???

The big difference and fear is, you can run a 2 stroke till it blows up, worse case scenario, you ruin a jug, maybe a crank, you’re talking $600-$800 in parts…

You blow up a 4 stroke, worse case scenario, jug, head, crank, maybe cases, could be several thousand dollars in parts…  Ask me how I know.. :)

On the plus side, you never lean, or cold stick a 4 stroke and if you stay on top of the maintenance, they hold up very well.

BTW, over revving has never been an issue, usually stock rods fail on the throttle, or over used slipper piston give it up, and I’ve had after market valves fail…

CR

http://www.tokyomods.com

click on karting.

the finest engines.

Hi all, I am new on here and new to karting and I have been following this thread, it’s interesting. I come from a moto background and I can tell you straight up, 4 strokes cost bucks! If you think maintains 2strokes is bad wait till you have to do a rebuild on those. I have 2 crf 450’s and a YZ250F and a YZ 250 two stroke. All of my 4strokes are for sale, it’s just too much time and cost to justify it, and I do all my own wrenching. They have one good point, torque, that where it starts and ends. For moto it helps for sure, they can mask  your lack of skills, unlike a 2 stroke. One other thing to remember is in moto they aren’t wide open as much as they would be on a kart so valve adjustment time would be more frequent. Also the different manufacturers use different quality TI (Honda cheap, Yamaha expensive)in there valves so depending on the manufacturer valves may not last as long, like Yamaha. My opinion, leave karts with 2 strokes.

John, I started in MX, went through road racing, ended up in karts…

You’re talking apples and oranges…

You can run a whole season on a piston and ring on MX 250 2 stroke, you get maybe 2 weekends on it in a superkart..  Maybe several pistons a weekend if you stick it.  In MX, you’ll never lean them as much as you would in kart, and they’ll never stay wide open as long as in a kart…

I’ve run CRF450’s for several seasons, had one the first ones out there in 2003, I can get about 2 weekends on a piston, if it were a big race, I put a fresh one in just because.  The only failures I’ve had were aftermarket valves, factory valves work very well…  The biggest problem we have encountered was factory rod failures, so we replace the rods with something like a Carillo, problem solved…

The biggest difference in the two is that you can run a two stroke till they blow up, $500 to $600 in parts, back on the road.

You run a four stroke till they blow, could be $1000 or more in parts!!!

I love them both, I still have a bunch of 125’s…  It is what it is…..

CR

Hey Chris, your experience and mine is vastly different in both cost and time on both 4strokes and 2strokes. I have to change my top end on my YZ250 at least once a season, I am unsure of how much you ride or how hard

Admittedly my Karting experience is limited but my mechanical experience isn’t. I have an Italkart (shifter) with a K9c motor. I replace my top end after 30 litres or roughly 3 hours. That process takes about an hour going slow, cost me 125$ (no wrist pin cage) in parts and I am back in the game, pretty cheap. Bottom end after 70 litres or 12+ hours, 300$ and 5 hours of work, again cheap. I guarantee a 4 stroke won’t be nearly that cheap in both time and parts.

As for my CRF 450s, one is SM with a purpose built motor ($5,000 in motor work, yea it’s a grenade,haha) the other is MotoX only with motor work of just a cam and minor head work, pipe and tuning. Run too hot on the stock Honda motors and kiss those shit TI valves good bye, recut the seats and new valves $300 plus time and on 4 stokes it takes WAY more time to do work. After 60 plus hours, bottom end and top end. Piston$350+ bottom end package from hot rods$600, if you need reNik the cylinder ad another $300 we haven’t even talked about the valve train yet. Now on all my YZ250F i have owned I check the valves 3-4 times a season, with at least on adjustment, (more time wrenching). By the end of the season I need a total top end (valves) freshen up valves, maybe be recut the seats, depends. New Crank and bottom end, and have gone through 2 Pistons. All of these are basic needs required to prevent a catastrophic motor failure, and this is at MotoX where we don’t sustaine long periods of high RPM. If I was to run these motors like they would be run in karting it would be safe to say your maintenance  would be double that, and remember I do all my own work, factor is someone who has to pay for labour and I thinking, “stick with the 2 strokes” ).

John, I raced MX for 10 years, and yes a refresh mid season was about what I did also on my 250’s, I know lots of guys that got a full season on a top end.

You’re also comparing a 250 two stroke MX motor, to a 125cc kart specific motor, two very different things.  If you raced a 250cc MX motor in a Superkart, you would never get a 1/2 season from it….

Ask some of the stock moto guys what they get out of a top end, and what that costs…  They are very economical for sure.

I’ve run full on Motard motors in my karts, and lightly mods.  The full on’s were oversized Ti valves, and the ones that were slightly modified had stock valves with bronze seats…  The stock valves held up much better than the oversized Del West valves which are some of the best on the planet…

Just my experience, I’m sure yours was different…

CR

What we have here is a communication issue not tech issues. I was under the impression, given the title of the thread (4 stroke shifter karts) that you, Chris were talking about 250 four stroke motors for karting not 2 stroke, big difference. So with that note I agree with you. My issues was referring to running a 125 smoker to a 250 four stroke.

The bigger issue and the reason why the US didn’t jump into shifter karts as quickly as the rest of the world is the cost of kart specific shifter motors.

That gets back to the CR125 which has been probably the most popular platform, probably the cheapest to run, and currently the only professional platform here in the states.

It’s also something Honda hasn’t built as a unit in 16 years.

So as a replacement, the consideration has been going towards 4 strokes, because they are in production today and can be bought as a complete unit from the factory…

In a kart, well maintained, they are no as bad as you think…  Definitely more complicated to do a top end swap, but not that bad…  They only get real expensive when they go boom!!!

CR

Granted the European motors are way over priced for what they are, but used ones aren’t that bad in price. I have found 2 TM,K9C for $2500 Canadian this is cheap Considering there over all design isn’t that out dated to current models. New top AND bottom end replacements are no more that $1000 C, which would be a full crank rebuild, rod, piston&rings, bearings, seals reNik cylinder (if needed), me doing the work, Cheap!

Rebuild my YzF250 motor top end, $400 just in valves, not including guides, springs, seals, retainers or machine work that maybe required. Realistically $1000 is what your looking at for a full rebuild. This is just to head, I still haven’t touched the borrow end yet, no labour with that price iether. MotoX teams operating cost went through the roof with introduction of 4 strokes purely on motor costs! I have rebuilt so many of both 2 and 4 strokes, there is no comparison to cost, the amount of parts alone used in a 4 stroke tells you there not cheaper.

Just as an added note: I ran an AMA road-race team for 2 full season so I know the cost related to racing. Two riders, 4 bikes all 600s so is fully awear of costs related to racing and motors.

Ok I now get what you are taking about, we were still not on the same page till now. When I was talking 125two strokes, I was comparing the cost of running a 250 four strokes to the 125 two strokes, not 450 four strokes. So if I understand you correctly you are running 450 not 250 four strokes? If that is the case then yes the cost would be lower than a 250f, because the motor is not being run as nearly as hard. So your not running against 125 strokes then? Again my ignorance of this sport is showing, but I have been following the European series which seem to be dominated by KZ and have herd little on 4 strokes except for a Swiss made 250 four stroke that was super expensive.

My 450 I ran in SM did require head work at the end of the season that was around the $500 plus a piston $450, not much considering the abuse but it was purpose built, Falicon Super crank, yo yo dyne clutch, 13.5/1 piston, bla bla bla head work.  But by the end of the second season it was a lot more expensive. So again if you are running on the same tracks as the 125 karts yes the 450 motors will last longer, but when they do go, and they will go, it’s going to be more money than a 2 stroke.

What are the difference with the new KZ that make it that much better than the K9c? I have checked the port timing, combustion chamber, Squish, even the piston I haven’t seen anything I would consider ground breaking the one thing I did see was the intake track and reed cage but really that would be minimal. Am I missing something?

The class was introduced this year for us. HPD is backing the program with a lease program and HPD bucks

http://www.sanzarukarting.com/news/15_03_13.html

$2500 to lease, $1000 to rebuild, doesn’t sound so bad….

Try sending the TM back to the factory for a rebuild, best it costs more than $1000!!!!

CR

[quote quote=54862]The class was introduced this year for us. HPD is backing the program with a lease program and HPD bucks http://www.sanzarukarting.com/news/15_03_13.html [/quote]

I knew somewhere in the US tracks were running a class, thanks for posting this.

What kind of response did you get from drivers?  Has it piqued the interest of more drivers for 2016? Observed almost 2seconds\lap advantage to Stock moto from the times, but that’s just going by the numbers, knowing nothing about the drivers or conditions.

[quote quote=54845]What are the difference with the new KZ that make it that much better than the K9c? I have checked the port timing, combustion chamber, Squish, even the piston I haven’t seen anything I would consider ground breaking the one thing I did see was the intake track and reed cage but really that would be minimal. Am I missing something?[/quote]

The differences in performance are 99% perception from what I’ve seen over the years. Performance improvements between homologations for the most part is very incremental, perhaps not even measurable. Sometimes there will be a breakthrough (like Rotax’s 100 debut), but for the most part the performance difference that one is lead to believe between homolgations is not very big. Each time you’ll hear people claim they found xxx (time) with the latest widget/upgrade/motor. I recond if you go back ten years, add up the claims of time found with each “widget” and compare lap times to today all other things being reasonably equal (track, tires, conditions) one might expect that a modern KZ would be 2 seconds faster than the last ICC. But my guess is that it wouldn’t even be close to that.
Many of the folks that claim big differences are invested in the newer stuff in one way or another :D

Look at how radical the Modena motor is. Thing is a work of art, but yet it has not outshone the competition.

I’m very interested to see where the CRF250 goes….

Jim, I agree with you on both points, the CRF is slower, and the all the new Homologations aren’t all that much better, if any….  The tuner on any particular motor makes the difference…

But, I believe one of the issues of running a 10 year old+ motor is that everything in the motor is warn just a little bit, and all that adds up to a loss of power…  Take a fresh factory new motor, and all the tolerances are where they should be, and that makes up for a lot….

That being said, if the right person was to go though ever inch of the motor and measure everything, they probably would be able to bring everything back factory new spec, but then again, what would that cost versus selling it and replacing it with a new one….

So the CRF is slower? So what, it runs in it’s own class…  Stock Honda is slower than the Mod’s were, and the Stock Honda is probably more competitive than the Mod’s ever were…

I like the idea of lease motor program, you don’t have to worry about some tuner getting more power than the next guy……

I remember when I was road racing, the factory support rider’s used to walk over to the Honda trailer, wheel out a crate, pull their old motors, put in the new ones, pack it back up…  Takes all the guess work out….

CR

The lap times at Sonoma between the 250f and cr125 are much closer than the race results show….  Two different levels of competitors between the classes.

So far we are at round 8 of our series and reliability has been outstanding.  Feedback has been great, it’s a bit less work to drive and tune with the fuel injection and the added torque.  Power and noise are pretty entertaining!

We sold/leased all engines than we had available. Next year we are expecting the class to grow. We have put together 6 of them so far, including the one in the Honda commercial  (-:

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[quote quote=54928]So the CRF is slower? So what, it runs in it’s own class… [/quote]

Oh I agree, in terms of absolute speed, it doesn’t matter a whole lot. Look at how LO206 has grown. I was just conveying what I observed in numbers between the two. From what I understand it’s really nip and tuck between the CR and CRF on the tight tracks, and Josh outlined that the difference I saw was down to drivers.

I like the lease idea too, especially give the (potentially) precarious nature of EFI.

Josh, do you have any videos? If you’ve got some interesting CRF stuff, I’d love to share one on my kartpulse facebook page.

Josh, thanks for the hands on report!!!  Being that I have run 450’s for a long time, I was pretty sure the 250’s weren’t all that bad…

So basically the series is a spec series as the motors come from your shop or HPD?

Is there a particular year that’s been used or is it any of the EFI 250’s??

I have an idea for a new 125 chassis, I was kinda thinking of a 4 stroke for road racing…

CR

Starting in 1994 I was involved in racing 250 road race karts with Terry Ives in NorCal.  When the CRF 450 came out my team owner had an association with Honda through a driver that drove the kart a lot.   They gave the team a couple CRF 450 engines.  They were great, easy to tune and dead reliable, but definately down a power to the 250 2 strokes.  It wasn’t awful, do to the power band we still won most of the time only a really good driver in a really good 2T could beat us.   That being said when the average driver got a 450 they were slower.  The engines started to get modified, then they became very unreliable and very expensive.   The program in Sonoma is definately different as the engines are controlled by the owner HPD.

Mark, the Superkart thing is a whole different deal…

It became a battle of the check books, and everybody was blowing up stuff to stay with it…

Kinda like the same thing that happened to Mod Moto…

Myself and JR Clasen has always talked about a “Stock 450” class, if there was more interest in Superkarts in general, I believe that would have been a good thing…

CR

Yes.  I agree Chris.  When Chaz Lemmon first got the 450 and had Johnny Green driving it that was the whole concept.  Run it stock and reliable.  We ran one bone stock at Laguna with the world superkart races one year and Johnny ran second in the single cylinder class even being down on power.  It was easy to drive with tons of torque (it was doing a wheel stand out of turn 3).  In NCK races Johnny was unbeatable in the 450 or 250 2T.  All the mod 450’s killed the whole deal.

I built a CRF450 a couple of years ago with EFI, I was pretty psyched to run that, I just lost interest in the Superkarts in general…  There’s just not enough interest in the class…

The 250’s have a good chance though, HPD has good program, there’s plenty of chassis and interest….

One thing I believe would move it along though, is some kind of on board electric starter…  I could probably do a remote electric starter mod on those cases and get rid of that kick starter…

CR

<span style=”color: #444444; font-family: Arial, Helvetica, serif; font-size: 12px; line-height: 21px;”>Interesting. I figured I’d just stick with a stock moto cr125 anyway, but thought these were interesting</span>

As long as the CR125 lasts and is supported by Honda, it’s a great platform!!!!

But at some point it will not be, and the CRF250 is a really good replacement for that…

CR