1985 Honda 500r

[Queef Chief]

I have been reading some posts about ATC 500r here, and first off, I'd like to say i realize there weren't any pre-production 500r bikes(sheww, that was a long thread).
I picked up a 1985 CR500 over the weekend, and was toying with the idea of building a 500r out of my '85 250r roller.
Is there any advice you guys can give me on this build? Are these bikes even ride-able with such a massive power-plant?
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[keister]

Several members 500 conversions. I've ridden a couple. They are obviously a real handfull. They certainly excel in drag racing and hill climbs. People love them in the dunes too. Louis does very well on the MX track with his.

[250rRoostmaster]

Yes they are rideable, depending on your skill.. The frame will need gusseted and the lower motor mounts will need moved for starters. I've rode a few and they are cool, but I'd take a puma or sphinx 363 or bigger all day long over a 500 motor. The coolest thing about the 500 motor is how it builds so much torque at such a low rpm. They are tractors to say the least.

[tecaterob]

Man I wish we had choices like the 250r guys. I'd buy a puma for T3 in a heartbeat.

[John_Neary]

Problems when we put a 85 CR500 motor into a 85 250R frame was mostly vibration that would turn your hands into a blur on long straights, having to remove the fuel tank to get to the spark plug and the exhaust pipe did not fit very well since its a good bit longer than the 250 pipe is and there is not much extra room to work with.

The 250R fuel tank barely clears the 250 motor and the 500 engine is a lot taller so plan to have work there as well.

Sadly i do not have any good photos of that bike and we only raced it once at the 85 Score Off Road world Championship but it got mangled in practice crash after i hit a downed rider's bike and we parked it and i raced another bike. To be honest i did not like the combo and had no interest in the machine after having ridden it, mostly due to the vibration at high RPMs.

[oldskool83]

I'd just redo the dirtbike and ride it as it is. I can go more places with less power normally then more power...except for hillclimbs that's about it.

[Queef Chief]

Problems when we put a 85 CR500 motor into a 85 250R frame was mostly vibration that would turn your hands into a blur on long straights, having to remove the fuel tank to get to the spark plug and the exhaust pipe did not fit very well since its a good bit longer than the 250 pipe is and there is not much extra room to work with.

The 250R fuel tank barely clears the 250 motor and the 500 engine is a lot taller so plan to have work there as well.

Sadly i do not have any good photos of that bike and we only raced it once at the 85 Score Off Road world Championship but it got mangled in practice crash after i hit a downed rider's bike and we parked it and i raced another bike. To be honest i did not like the combo and had no interest in the machine after having ridden it, mostly due to the vibration at high RPMs.

Did you balance the crank? I've read a lot about them not being counter balanced, and tearing motor mounts to shreds. Just curious if it's still a rattle trap when balanced...
This is great info! I'm on the fence about the build, so I appreciate all the pros and cons I can get from people in the know.


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[John_Neary]

No we did not balance the crank and i suspect that was the core issue as other open class engines like our KTM495 did not bother me at all with vibration.

[barnett468]

Did you balance the crank? Just curious if it's still a rattle trap when balanced...

in general, balancing a single cylinder crank doesn't change how much it vibrates, it only changes where in the rpm range it vibrates.

you can not add a counter balancer to an engine.

stick two wires in a light socket and then grab both ends and that will be about how it feels...at least after you are doing riding it.

[barnett468]

Problems when we put a 85 CR500 motor into a 85 250R frame was mostly vibration that would turn your hands into a blur on long straights,

Hey John . . you're lucky it wasn't a KX500 engine . . NOBODY, knows how to make an engine vibrate better than Kawasaki . . They were so good at it that even their engines that had a counter balancer vibrated.

The first time I rode an ATC250R I thought it was broken because after riding the Tecates, it didn't feel like it was hardly running. :lol:
.

[John_Neary]

I had a 85,88 and 90 CR500 and they detuned the engine with each year, the 85 was by far the most brutal 500 i ever rode. I also had a 90 and 91 KX500 and honestly they felt much smoother and easier to ride and the power valve gave the engine a dimension the CR500 never had. Likely why the KX500 was considered the greatest desert bike ever made while no one in their right mind would ride a CR500 in a race like the Baja 1000.

[barnett468]

I had a 85,88 and 90 CR500 and they detuned the engine with each year, the 85 was by far the most brutal 500 i ever rode. I also had a 90 and 91 KX500 and honestly they felt much smoother and easier to ride and the power valve gave the engine a dimension the CR500 never had. Likely why the KX500 was considered the greatest desert bike ever made while no one in their right mind would ride a CR500 in a race like the Baja 1000.

sorry, i didn't specify . . i was referring to the lovely 84 and 85 X500's

[Red Rider]

you can not add a counter balancer to an engine.Somebody here did this very thing to a CR500 mill for their TRX. I want to say his screen name was Mart?

Yep, I found the thread, and it was Mart: http://www.3wheelerworld.com/showthread.php/105221-Project-counter-balanced-cr-500-engine?highlight=counter-balanced+cr500

[Daddio]

Somebody here did this very thing to a CR500 mill for their TRX. I want to say his screen name was Mart?

Yep, I found the thread, and it was Mart: http://www.3wheelerworld.com/showthread.php/105221-Project-counter-balanced-cr-500-engine?highlight=counter-balanced+cr500
Actually, he is converting the 450 into a 2stroke. He's definitely a mad scientist.

[tecaterob]

Wow pretty cool counter balance on that 500!!!!!! BIG DIFFERENCE

[yaegerb]

Somebody here did this very thing to a CR500 mill for their TRX. I want to say his screen name was Mart?

Yep, I found the thread, and it was Mart: http://www.3wheelerworld.com/showthread.php/105221-Project-counter-balanced-cr-500-engine?highlight=counter-balanced+cr500


Good Lord, I just watched those videos. He is brilliant. Love watching him build.

[onformula1]

Actually, he is converting the 450 into a 2stroke. He's definitely a mad scientist.

Link or info?

[Daddio]

It was from a post on his Facebook wall. He is one of my FB friends. I guess I could copy and paste his original post, but it would be hard to do all of the comments.

[Daddio]

Here is his FB post minus pictures and the following comments.

(Post will be boring for my non Moto head friends lol sorry)
I wasn't going to share this one until nearly complete due to a high chance of me not being able to pull it off, but I've now got past most hurdles the project had for me and am very confident I can make it work.
My aim has allways been to have a counterbalaced cr500 two stroke quad engine and did actually achieve it until it blew itself apart ( whole other story that one)
My new engine I've been working on is a combination of a trx 450 fourstroke with a cr500 two stroke cylinder and crankshaft. So basically turned the fourstroke into a two stroke.
I've managed to weld various things machine this and that and basically am at a point that I have the cr500 crank fitting and spinning in the 450 bottom end.
Next step is to cast some alloy for transfer tunnels and match the cylinder to the bottomend ( actually the easy part lol)
The advantage of all this is a counterbalancer, no more dreaded vibrations, strong gear box,and to the af500 bike guys no more cut up frames just bolt either either engines in of choice

[onformula1]

I think the hardest part is separating the transmission from the crankcase and coming up with the correct volume, Very Cool.

Thank You for sharing.

Funny the first modern Husqvarna, Husaberg and prototype Maico 4 strokes had a 2 stroke bottom ends with 4 stroke top ends.

[Daddio]

The TRX 450 already has a separate crankcase and transmission. That along with the fact that it is counterbalanced, was why he chose this engine.

[onformula1]

The TRX 450 already has a separate crankcase and transmission. That along with the fact that it is counterbalanced, was why he chose this engine.

Ah, I just had CR450F on my mind, should have read more closely. :lol:

[tecaterob]

That's awesome work!!!! I believe he also built a 200x with a cr125.

[Daddio]

He also built the laydown 250r for the atc70. He's done some pretty hard core, mad scientist, type stuff.