May 29, 2015 at 2:46 pm #49094
Hi all, new member here. I’m looking to get a shifter kart some time in the next year or so and came across this article talking about shifters with the CRF250 4 stroke engine: http://www.on-rails.com/tech-honda-crf250-4-stroke-for-us-shifter-racing/
I was just wondering if anyone has any other news on these karts? As in do many clubs let them run alongside the 125s and are many out there racing? Are they competitive? The only article I found in that regard was this one: http://ekartingnews.com/2014/04/22/lone-star-grand-prix-adds-honda-crf250-to-open-shifter-class/
Thanks!May 30, 2015 at 12:44 pm #49110
haven’t heard of any races with those engines. seems stock moto is most common (cr125). would probably have a hard time finding competitionMay 30, 2015 at 7:21 pm #49114
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…
94yMay 31, 2015 at 9:58 am #49122
Interesting. I figured I’d just stick with a stock moto cr125 anyway, but thought these were interesting. I design, calibrate, and test 4 stroke engines for my day job, so I’m way more familiar with them.June 1, 2015 at 10:37 am #49157
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.June 22, 2015 at 7:39 pm #50345
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”.June 29, 2015 at 9:40 am #50669
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…
CRJune 30, 2015 at 12:26 pm #50749
Yeah, but in this case the tuning would be to just adjust AFR and spark timing to pick up more power than with the standard calibration……..not adjusting hardware just to maintain similar performance in different environmental conditions. The tuning is therefore no longer necessary just to get the thing to run right at different tracks and the engine will be much more consistent. Sure you might want to tweak the spark tables, but it will be more like tuning a street car, where you tune it once after all modifications and then you’re set to drive it wherever you want.July 2, 2015 at 5:42 am #50847
Kyle, I believe your missing the point…
EFI is not magical, it will adjust within the parameters for weather conditions, that’s fine and good once the baseline is established.
The baseline tune is the magic that a good tuner creates and that can make a world of difference, matching the track, weather and driver…
If a “spec” class came of it, they could just have a standard baseline map, and load it to every EFI box, or rent a box for an event…etc..
I love my CR125’s, lets hope they are the KT100’s of the shifter class, but I also love my thumpers!!!
CRJuly 24, 2015 at 11:32 am #51832
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.July 24, 2015 at 6:40 pm #51851
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…
CRAugust 12, 2015 at 8:15 am #52743September 24, 2015 at 6:45 pm #54719
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.September 25, 2015 at 4:56 am #54726
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 $1000 or more in parts!!!
I love them both, I still have a bunch of 125’s… It is what it is…..
CRSeptember 25, 2015 at 11:05 pm #54750
Hey Chris, your experience and mine is vastly different in both cost and time on both 4strokes and 2strokes. I have to change my top end on my YZ250 at least once a season, I am unsure of how much you ride or how hard
Admittedly my Karting experience is limited but my mechanical experience isn’t. I have an Italkart (shifter) with a K9c motor. I replace my top end after 30 litres or roughly 3 hours. That process takes about an hour going slow, cost me 125$ (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” ).September 26, 2015 at 9:50 am #54754
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…
CRSeptember 26, 2015 at 8:42 pm #54789
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.September 27, 2015 at 7:58 am #54805
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!!!
CRSeptember 27, 2015 at 8:35 am #54806
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.September 27, 2015 at 1:46 pm #54828
John, K9’s are cool, but they’re are outdated if you want to competitive, so their cost is a mute point..
I never replaced valves in one of 450 kart motors unless they broke, and that was the least of the cost… Cranks I’ve used Falicon’s, and a few others with HD rods, I’ve gotten several seasons out of those, completely different than a seized two stroke puking piston material through the bottom end…. Just the fact that a 4 stroke always has oil on the crank, gives it a better life expectancy..
You have a lot of great experience, but it really doesn’t relate to karts….
Four stroke shifter kart motors are no where near as bad as you paint it, I know, I’ve done it for a lot of years….
CRSeptember 27, 2015 at 7:55 pm #54845
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?September 28, 2015 at 9:20 am #54862
The class was introduced this year for us. HPD is backing the program with a lease program and HPD bucksSeptember 29, 2015 at 3:06 am #54882September 29, 2015 at 10:21 am #54922
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
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.September 29, 2015 at 10:36 am #54923
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 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 😀
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….
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