Kx500 vs cr500 for snowbike?

The two main reasons I went with the KX was the power valve and nikasil plated cylinders. I had it bored to 525 and ported for mid/high by Eric Gorr. It gave it a ton more bottom end and mid range and a decent amount of top end.

The cons of any 500 is old tech, heavier, narrow power range, no e-start, and probably the most vibrations of any bike out there. If you can deal with those, either bike will make some decent power for cheap.

Heavier ? Can you explain

summitboy said:

Heavier ? Can you explain

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vs a newer built 300. I ride fairly regularly with a stock kx500 and a nicely built ktm 300 and its really impressive how well the 300's work.

How much heavier would you say ? Are you comparing dirtbike to dirtbike or snowbike to dirtbike ? If memory serves me correctly the CR was a 222lb bike, KX was even lighter at 220lbs. The newer 300s are 229lbs ?

I don't have numbers for you, but I can tell you that my KX500 motor is physically huge compared to a 300 motor, and you can feel the difference in weight while riding it. Probably more due to the rotational mass difference than anything. Both still feel lighter than a big 4-stroke, but there is a difference between the two for sure.

Having the same question a few years ago, I will give you my .02c worth. The CR and KX 500's are twin warriors of the 80's and 90's. Both are light and powerful. I have owned and ridden, modded and competed on as early as the CR480 and KX420. We built and modded both in about every way imaginable. There are some slight differences, but only slight. We found the CR doesn't have the life when modded, especially compression. There is an old piston rock issue that everyone knows. The soft steel cylinder requires boring and oversizing. The coolant capacity in the cylinder is only 29oz. They do get warm. All bad? Not at all. I just want to give you the honnest reply. There has never been a bigger love for a brutal dirt widow maker than the CR500. Part of the love was the era, "Ride Red". It dominated the world at the time. Was an excellent Moto bike. The CR500 ignition in it's OEM form is superior.

The KX500, Brutally powerful. Uncontested the #1 most powerful dirt bike ever made. It was developed ahead of it's time, "speaking engine". There is an extensive port diagram on cad describing the KX cylinder and it's technology. Common now, but revolutionary in it's time. It has a big cylinder, lots of cooling, Nikasil cylinder and KIPS exhaust valve. You can port, comp, and build that engine up and it will run flawlessly for years. Some old quotes of the day, "indestructible", could swallow a gallon of dirt and keep running. Their frame and suspension were far short of the CR. The KX shined as a desert racer and it's amazing engine. The power valve is huge. Every modern 2 stroke today has an exhaust power valve for all the obvious reasons. Smooth, fuel efficient, huge torque with the valve closed, then a smooth transition as it opens and get's on the pipe. I don't know of any modern 2 stroke engine without an exhaust power valve. The nikasil cylinder is also excellent modern technology. You can keep the OEM bore for life.

I chose the KX for the first big 2 stroke 500 build. "Service KX500 Monster" thread. I had a great time, learned a lot. It ran beautifully all year doing demo's etc without one hick-up. We have come a long way in 3 years. Primer, de-comp, etc. They are a viable option for big HP on a budget.

it almost comes down to what color you like.

the ex valve on the k5 is nice. i ported mine alot and the valve is pretty much gone. the tq is still a mile wide.

electrofusion liner on the kx vs steel on the cr. steel is softer, power fades quicker but is much easier to repair. the electrofusion liner transfers heat better, chips on the corners of the ex port because its shaped stupid, and are expensive to re-do but are much tougher.

parts availability is likely an edge to the CR but i can find everything i need for a kx

you're looking at low to mid 50 horse in stock form, but the tq is flat over almost the whole rpm range. thats a big deal.

i would find the best deal on the best condition bike you can find of either brand.

Another downer for the KX is electrical system. Stock is nothing and the best is a measly Penton system that really does nothing. Some dont need the power, some do and CR has better options for elec power. Everything from factory/after 200watt systems to modified CRF systems etc.

You can Nikisil the CR if you want to. There is a wicked Nik guy in Calgary, forget Milenium and US chrome lol

summitboy said:

Another downer for the KX is electrical system. Stock is nothing and the best is a measly Penton system that really does nothing. Some dont need the power, some do and CR has better options for elec power. Everything from factory/after 200watt systems to modified CRF systems etc.

You can Nikisil the CR if you want to. There is a wicked Nik guy in Calgary, forget Milenium and US chrome lol

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how the heck do you nicasil where a cast liner would be? wow that would be a pile of work. unless the guy is just coating the existing steel liner.

Ya more power would be nice. i'm supposed to have 70 or 80w but its nowhere near that. i have a semi-decent light thats enough to get you home early in the riding season. other than that all i use my power for is running an egt and opening a nitrous solenoid.

Adam does the Nikasil stuff for the 500's. I kept to the cast. Cheap and easy. Adams motor makes power especially torque, thats where it really shines. It doesn't have to be 200psi of compression to make power. I sure like the Pulse over the Smartcarb, runs better, more adjustable, oh and it starts and idles LOL.

I run heated grips, helmet light, gps etc off my 200watt (1 bank of 100w) Honda stator with a Yuasa ytx4 battery. Works pretty good

portgrinder said:

i'm supposed to have 70 or 80w but its nowhere near that. i have a semi-decent light thats enough to get you home early in the riding season. other than that all i use my power for is running an egt and opening a nitrous solenoid.

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That's what I did also. I installed the reg/rec in the air box. The "X" model coil gave me enough for tuning and monitoring data. For a light I use the Vision-X with their 6hr battery. The bat is like that little powerhouse jumper battery. Only 1lb. It stays in my pack. If needed, I pull the slinkey cord out the top zipper and it attaches to your helmet like a go-pro mount. Super bright LED flood. Lights where you look. Works good and keeps things simple.

Brad from Power Sports Tech has his new CR500 hot rod up and running. CPI Pipe, some porting, 40MM Smart Carb, and some other goodies. He said he was blown away with it. Cold start in the morning, two kicks. All day every start was one kick and Idles smooth and beautiful. WOT ,EGT peaks at 1240. It is absolutely a screamer! He said the rev "acceleration" is ridiculous. It's a beautiful bike. Plastics, Graphics, etc. He will be making a post and hopefully a vid soon.

Ill put the Pulse up against a Smartcarb any day. Guys are unloading them for a reason. Ill post up a video of a friend trying to start his 500 Smarty. Its so painful to watch.

So curious why the need for a primer if the Smartcarb starts so great ? Seems like lots of guys having EGT inconsistency on the 300 etc. i know one guy who has a 300 in Revy and it would barely run with the Smarty. He of course was waiting for rods.

Mine sure didnt work well and i tried all the updates and 4 different rods. Also it vibrated like a bastage lol. I have video of that as well, smarty vs pulse idling. You can just see the vibration difference.

Oops must of hit a nerve lol. I dont hate either the CR or the KX. They are one of the most powerful dirtbike made normally aspirated. Not many 4 strokes can touch them. And with the right porting they are torque monsters. You cant go wrong with either.

Having said that MtnDoo, everytime i make reference about the Smartcarb/Yeti your on my back about it. I get it you dont like the fact i dont like the Smartcarb. When something works as poor as that carb im not afraid to say it. I dont put lipstick on a pig. Look up the Smartcarb posts and you can read all about it. I also get you dont like the fact i like the Yeti. Get over it. If anyone is hating take a look in the mirror.

Dont put words in my mouth Randy. I never called Milenium or US Chrome junk, they do good work. I said there is a Canadian company doing Nik and south of the border is not needed because of this option.

As far as your other comments yes i do think there is a need to share honest opinions about some products that you make out to be the greatest stuff since sliced bread. If people didnt tell it like it was some of this junk wouldnt improve or be better scrutinized before it left the shop. Guys work hard to buy these toys and the last thing they need to do is fix someones poor engineering through constant updates or upgrades. I call a spade a spade and not aftaid to do so.

Im glad u admit all your hating stems from that last phone call when we discussed the Yeti. I as u claim truely like competition to make these sports better for the people who pay for them. You on the other hand silently hate anyone that prefers the non TS brand, just look through your protectionist posts.

Wow, this thread has gone downhill. I like the fact that summitboy will call someone out on a poor product. How else would I know not to buy something if there weren't people like this. I guess I fall into the same catagory of people with some of the experiences I have had when I drop thousands on sled parts. I actually was quite interested in your Canadian cylinder repair place as US Chrome and I have been sending cylinders back and forth to each other for the last 2+ months, but they are taking care of me, just can't get my time back.

Now, to get back on topic, I was wondering about the comparisons of an RM500 as I am a Suzuki dirt bike rider and have contemplated doing an AF build 500 mountain horse. Are they as viable of an option as the KX and CR?? :devil:

Smartcarb

I've had this 38mm Billet since last summer. APT did all the upgrades including high flow floats, new needle and bored out choke circuit and it still doesn't start cold unless the bike is tipped over. When its cold out, the only way it will start is with a pickup truck pulling it.
It definitely doesn't run with the .076 metering rod APT recommends, have to go with the .080 to even get it to idle. Then it has a super lean spot 2/3 throttle which can't be tuned out by adjusting the clicker without losing the bottom end response.
Almost all of the CR500riders.com guys have returned their Smartcarbs, a couple guys seem to have gotten lucky. I wished it would have worked, I spend months working with the .074, .076, .078 and .080 metering rods on this new engine. Keihin PWK is back on it now.
https://www.youtube.com/watch?v=k6ENOoh0DBU

Darn, looks like you need the initial set up and tune. Very lean and high slide height is killer to start. I posted a quick reference under the "Smart Carb" thread "balls dropped" for carb discussions.

Any way, back on the thread's topic. The two, CR and KX, are awesome snow bikes. Tons of torque. You can hold a gear without the engine bogging. They will "lock on" and hold it. I have a vid where the bike is in 3rd, getting slower and slower in the deep pow but the RPM's stay the same. Locks on and keeps spinning in 3rd. Super cool. The RM and the YZ490 should both have good potential as well? It would be great if someone builds one and shares the experience. You won't go wrong either way.

I believe the service Honda RM500af is a CR motor