500 thoughts

[Stusmoke]

ok guys thanks for the input really appreciate it, as for the motor i think i will try grab what ever comes up first as there hard to come by in australia.

and for the frame thinking maybe a yz250 frame as there steel correct me if im wrong. and that may nip most of the vibration in the bud.

ive seen it done before heres a link for all that are curious
http://www.ebay.com.au/itm/honda-cr-500-engine-yz-250-frame-/161039279827?pt=AU_Motorcycles&hash=item257eb066d3

but im going to have a while to think before the motor makes its way into my possesion.

The latest chassis for the YZ250 (2005 onwards) Is aluminium. I had a 2001 YZ250 and its handling was great. Bury the front end into the tightest inside line you can find, wick the throttle and she came out screaming. Awesome frame.

With regards to the motor, everyone I've ever spoken to prefered the KX500 motor. If you can find a KTM 380sx motor, that would also be really sweet. Throwing it into a 2011 onwards KTM mx frame would be even awesomer still.

With all due respect Stu, many I've spoken to have also loved and preferred the KX. Having said that, many more I've spoken too prefer the CR for many reasons. Hence the reason for more forums etc. dealing with the CR for various reasons. Both great bikes, but for many reasons, warranted or not, the CR still trumps.

One day I would like to drop both motors into identical chassis and really nail down the reasons. Obivously just as many people prefer the CR over the KX, otherwise the CR motor wouldn't be traded much and anyone who has looked for one knows they sell like hotcakes. Just pure chance that the... 3 or maybe four (Terrible memory) people I've spoken to prefered the KX. They were all oldies that either raced or owned a 500 back in the day.

[adzski]

could you use a later model kx500 expansion pipe? if not ill just wait till something else comes up

[opfermanmotors]

The CR has a much harder hit and is not as smooth as the KX.  The KX has a power valve and that gives it more tractable power than the CR and smooths it out. 

[Marco810]

ok something has come up
http://www.ebay.com.au/itm/Kawasaki-Kx500-Motor-complete-Kx500af-not-cr500-cr500af-/200933917101?pt=AU_Motorcycle_Parts_Accessories&hash=item2ec89841ad

but im curious as to whether i would have to run the stock pipe(HATE THE LOOK) or could i run a new 250 pipe or something similiar?

I would try for a 89+ k5 engine. lots of discontinued parts for the pre 89. also you'll want to run a modded cr500 pipe and silencer

I made a kx500sf and i gotta say if you plan on riding any tight track you better be in good shape cause it will ware you out in a hurry. Vibration+mandatory death grip= numb wrists

[dogger315]

what is the better motor and the pros and cons over each other?

Both are great motors.  Your choice should depend on intended use, parts availability
and to a lesser extent, brand loyalty.

I did a lot of research before starting a similar project a couple of years ago.  The
advantage I had is I raced 500s before the class went away.  I knew what I was
getting into and I knew what modifications were needed to be able to survive a
moto.

To be honest, I didn't even consider the KX as I consider it more of a desert racer
than a MX motor.  The CR is also easy to get parts for and there is a ton of support
available due to the popularity of the numerous CR based  "AF" conversions out there.

With that said, In stock trim, the late model CR is not a good MX engine.  It comes with
a wide ratio transmission and has a substantial hit that will stretch your arms and wear
you out in short order.  It also vibrates pretty good.  The one thing you don't want is a
mid 80s CR500 engine.  Those engines were so powerful that even the factory riders had
them detuned.  Throw in the corrosion problems from Mag water pump covers and the very
long list of NLA parts and you'll have a big mess on your hands.

Here is a partial list of the modifications I performed to correct a 2000 CR 500 shortcomings:

Close ratio tranny
Balanced and trued crank
Aluminum cylinder sleeve
Digital 3D ignition
Port and head work to lessen the hit
Aftermarket pipe and silencer
Aftermarket clutch

I opted for a 2008 Honda CRF250R frame over any of the newer models.  The frame geometry
on the 06-09 CRF250 is very similar to the 93 CR250, which is one of my favorites.  I also like
the slimmed down size and lighter weight over the 450F.  I'm 6'1" and that frame fits me
perfectly. 

What I have now is 60+ of more useable horsepower in a lightweight, modern chassis with state
of the art suspension.  The bike is deceptively fast because you don't have to wring it out to make
power.  All you have is the wind noise in your helmet and the corner approaching way quicker than
you expect - the first mods I made after I finished the bike was a pair of oversized wave rotors.  If
I had this bike back in the 90s, I would have won a lot more races.   

If you are a Kawasaki fan, some of the same mods would apply as well.  Like I said, both are great
engines and both will make an awesome MXer in the right roller.

I would say you have a lot of research to do and some big decisions to make.

My two cents.

Good luck.

dogger

[Stusmoke]

what is the better motor and the pros and cons over each other?

Both are great motors.  Your choice should depend on intended use, parts availability
and to a lesser extent, brand loyalty.

I did a lot of research before starting a similar project a couple of years ago.  The
advantage I had is I raced 500s before the class went away.  I knew what I was
getting into and I knew what modifications were needed to be able to survive a
moto.

To be honest, I didn't even consider the KX as I consider it more of a desert racer
than a MX motor.  The CR is also easy to get parts for and there is a ton of support
available due to the popularity of the numerous CR based  "AF" conversions out there.

With that said, In stock trim, the late model CR is not a good MX engine.  It comes with
a wide ratio transmission and has a substantial hit that will stretch your arms and wear
you out in short order.  It also vibrates pretty good.  The one thing you don't want is a
mid 80s CR500 engine.  Those engines were so powerful that even the factory riders had
them detuned.  Throw in the corrosion problems from Mag water pump covers and the very
long list of NLA parts and you'll have a big mess on your hands.

Here is a partial list of the modifications I performed to correct a 2000 CR 500 shortcomings:

Close ratio tranny
Balanced and trued crank
Aluminum cylinder sleeve
Digital 3D ignition
Port and head work to lessen the hit
Aftermarket pipe and silencer
Aftermarket clutch

I opted for a 2008 Honda CRF250R frame over any of the newer models.  The frame geometry
on the 06-09 CRF250 is very similar to the 93 CR250, which is one of my favorites.  I also like
the slimmed down size and lighter weight over the 450F.  I'm 6'1" and that frame fits me
perfectly. 

What I have now is 60+ of more useable horsepower in a lightweight, modern chassis with state
of the art suspension.  The bike is deceptively fast because you don't have to wring it out to make
power.  All you have is the wind noise in your helmet and the corner approaching way quicker than
you expect - the first mods I made after I finished the bike was a pair of oversized wave rotors.  If
I had this bike back in the 90s, I would have won a lot more races.   

If you are a Kawasaki fan, some of the same mods would apply as well.  Like I said, both are great
engines and both will make an awesome MXer in the right roller.

I would say you have a lot of research to do and some big decisions to make.

My two cents.

Good luck.

dogger

I think your two cents is worth two thousand cents.

[SachsGS]

We don't have pennies here in Canada anymore. I'd say that advise is worth at least a nickle or maybe a thousand (nickels).

[adzski]

i have been thinking pretty hard about it and reading and after muchthought i decided to go with a cr500 engine.
now i just have to find one.

thanks everyone for your input, it gave me much to think about

[Stusmoke]

As Dogger accurately stated, the only real reason the KX500 motor is faster out of the box is because the Honda engineers went out of their way to choke down their 500 monster rather than hop it up. Take away those mods and focus much much more on usability rather than goability.

[JETZcorp]

If you REALLY want to make everyone mad, you could use an air-cooled engine.  I've heard better things about an '83 490 Maico than I have about CR500 or KX500, which is really all I can say as I haven't ridden them myself.  If you want something less exotic (but weirdly, harder to find parts for) you could get a CR480 or YZ490.  I think Super Hunky had some kind of plan to make a bike like this at one point, but I'm not sure if it ever happened.

Advantages of air-cooled:
- Looks bad-ass (although it would be weird with a modern-styled bike)
- No water pump, hoses, or radiators to fail or leak
- Lower center of gravity and slightly lighter overall weight
- Bike is narrower in front slightly
- The looks on 450F riders' faces after you beat them

Disadvantages of air-cooled:
- Parts availability may be an issue if you deviate from the cult-following models
- Cooling isn't as effective
- Potentially louder
- Possible geometric issues, depending on how big your motor (Maicos have BIG fins) and how strangely-shaped your frame is
- The looks on 450F riders' faces before you beat them

[Stusmoke]

If you REALLY want to make everyone mad, you could use an air-cooled engine.  I've heard better things about an '83 490 Maico than I have about CR500 or KX500, which is really all I can say as I haven't ridden them myself.  If you want something less exotic (but weirdly, harder to find parts for) you could get a CR480 or YZ490.  I think Super Hunky had some kind of plan to make a bike like this at one point, but I'm not sure if it ever happened.

Advantages of air-cooled:
- Looks bad-ass (although it would be weird with a modern-styled bike)
- No water pump, hoses, or radiators to fail or leak
- Lower center of gravity and slightly lighter overall weight
- Bike is narrower in front slightly
- The looks on 450F riders' faces after you beat them

Disadvantages of air-cooled:
- Parts availability may be an issue if you deviate from the cult-following models
- Cooling isn't as effective
- Potentially louder
- Possible geometric issues, depending on how big your motor (Maicos have BIG fins) and how strangely-shaped your frame is
- The looks on 450F riders' faces before you beat them

Jetz raises a good point. Honestly when its all said and done theres lots of motors that would be great to have new life breathed into them. Maicos, Hondas early CR480, CR450, YZ/IT 490, WR 4something, obviously the KX500 and CR500, the list goes on. These days one of your biggest concerns is the ability to get the bloody parts. Most of the big bore smokers had issues that could be fixed easily enough. I've never worked on any of them or owned I'm just repeating the things I've read and heard. My brother had a WR 4something I believe it was that was bored out to a 490. He loved it to bits. Monstrously powerful and torquey.

As I said, from my perspective, the biggest thing for me would be the ability to get parts. Hey while all the experienced blokes are looking at this thread, how hard is it to sleeve a big bore motor like the CR or KX500 down to 450ccs? and Obviously finding the piston to fit it and replace said piston when necessary?

[Marco810]

sleeving down the kx wouldnt work too well with how the the powervalves are laid out, unless it was a pre 1989 (they have no center flap)

Also the fact that they are nikasil plated out of the factory

[yota]

If you REALLY want to make everyone mad, you could use an air-cooled engine.  I've heard better things about an '83 490 Maico than I have about CR500 or KX500, which is really all I can say as I haven't ridden them myself.  If you want something less exotic (but weirdly, harder to find parts for) you could get a CR480 or YZ490.  I think Super Hunky had some kind of plan to make a bike like this at one point, but I'm not sure if it ever happened.

Advantages of air-cooled:
- Looks bad-ass (although it would be weird with a modern-styled bike)
- No water pump, hoses, or radiators to fail or leak
- Lower center of gravity and slightly lighter overall weight
- Bike is narrower in front slightly
- The looks on 450F riders' faces after you beat them

finding a modern chassis to put a RH drive motor into could be a challenge.

Disadvantages of air-cooled:
- Parts availability may be an issue if you deviate from the cult-following models
- Cooling isn't as effective
- Potentially louder
- Possible geometric issues, depending on how big your motor (Maicos have BIG fins) and how strangely-shaped your frame is
- The looks on 450F riders' faces before you beat them

[JETZcorp]

You're right, I hadn't thought of the right-hand-drive aspect.  For me, though, that's just all-the-more excuse to use a vintage chassis.

[adzski]

Almost had a 1996 cr500 $1500 was getting shipping quotes and someone snapped it up