Cafe Racer Forum banner

1 - 13 of 13 Posts

·
Registered
Joined
·
84 Posts
Discussion Starter #1
Hello everyone...I was lounging around & Kevin yelled out to me, there's a titled RD250 rolling chassis, just went on Craigslist, for $50. Well, I have a couple extra engines...I ran over there in my PU, checked the frame no. on the title, it matched. Funny thing is I was a bit hasty, didn't even look at the frame closely..it's not near an RD frame, actually it's a '74 TX500A less motor. No wonder I didn't recognize the frame no. prefix. LOL damn I'm dumb sometimes!! That's okay, for $50 with the title I can't go wrong. Very little rust & all there except engine, carbs & exhaust. I think the relatively tall, lower slung frame would be ideal to fit a MX motor like that.

Anyway the wheels are turning in my head, I'd like adapt a 2-stroke dirt bike motor into it, like a CR500..it'd be a rocket! What kind of electronic black magic would it take to adapt a motor like that (CR500) to it's system, anyone have ideas here? Designing, aligning and Welding motor mounts would be relatively easy part...
 

·
Registered
Joined
·
8,388 Posts
Interesting looking frame. Yeah, the motor mounts give it away as a non-RD frame. Nice complete roller, though.

CR500 motors are getting a little hard to find. Plus they vibrate ALOT.

Hmmm with the extra room, you could drop in a CB350 motor. Would be nice to have a CB350 motor in a chassis that didn't suck.
 

·
Registered
Joined
·
84 Posts
Discussion Starter #3
quote:
CR500 motors are getting a little hard to find. Plus they vibrate ALOT.
Well, I have a cylinder from I believe an old YZ490. No bottom end or cases. Just how much does a CR500 vibrate? Worse than an RD350? I have a book which explains how to make custom molded rubber pieces. It wouldn't be very difficult to make custom rubber mount dampers for any engine, just offset the placement of the metal mounts wide enough to fit the dampers. I keep around several thicknesses of rubber which could be readily cut & epoxied to them in the same manner.
 

·
Registered
Joined
·
2,595 Posts
I haven't looked closely at a CR500 motor recently, how high up from the case is the exhaust port? Reason I axe is that sometimes a double downtube frame won't match with the exhaust system of a big single...
although it looks like there's considerable space between the downtubes.


FR
 

·
Registered
Joined
·
23,303 Posts
Personally I am a big fan of the old kx250 motor. 10:1 compression, water cooled, 45.5 peak hp, dead nuts reliable, and a nice powerband. A year old one with new parts should cost you $500, less for a couple of years old. The motor is tiny so fitment isn't going to be a problem.

If you want to get really crazy, start hanging around the snowmobile guys and see if one of them has a chain drive motor laying about. I think artic cat has an 800cc parallel twin two stroke that should whip on anything if you can put it in a bike frame.
 

·
Registered
Joined
·
7,125 Posts
Dear Abby,

I've never written to you before, but I really need your advice on what
could be a crucial decision.

I've suspected for some time now that my wife has been cheating on me.

The usual signs... phone rings but if I answer, the caller hangs up.

My wife has been going out with the girls a lot recently, and when I ask
their names she always says, "Just some friends from work, you don't know
them."

I always stay awake to look out for her taxi coming home, but she always
walks down the drive.

Although I can hear a car driving off, as if she has gotten out of the car
round the corner. Why?

Maybe she wasn't in a taxi? I once picked her cell phone up just to see what
time it was and she went berserk and screamed that I should "never touch her
phone again", and "why was I checking up on her"?

Anyway, I have never approached the subject with my wife.

I think deep down I just didn't want to know the truth, but last night she
went out again and I decided to really check on her.

I decided I was going to park my Harley Davidson motorcycle next to the
garage and then hide behind it so I could get a good view of the whole
street when she came home. It was at that moment, crouching behind my
Harley, that I noticed that the valve covers on my engine seemed to be
leaking a little oil.

Is this something I can fix myself or should I take it back to the dealer?

Thanks,

Bob
 

·
Registered
Joined
·
434 Posts
I am reposting this reply as I think there was a problem with my first reply.

Anyways, I've got an 86' CR500 engine that I will sell for $800, or consider any interesting trades. The engine is currently in an ice racer and comes with a lug that can be put in the end of the crank so an electric starter can be used. It also has a brandy new Wiseco piston in it, but I haven't started it because the carb needs to cleaned, got spark, but she just pops after many kicks like she's not getting gas. I haven't had time to dick with it. I've got $1200 in it. That'd be a nasty little Sunday morning rider.

Dgy 518 674 4045
 

·
Registered
Joined
·
8,388 Posts
quote:
Personally I am a big fan of the old kx250 motor. 10:1 compression, water cooled, 45.5 peak hp, dead nuts reliable, and a nice powerband. A year old one with new parts should cost you $500, less for a couple of years old. The motor is tiny so fitment isn't going to be a problem.
Ya know, a while back a guy was selling a KX250 powered RZ350 racebike. Neat idea, ran it in the WERA singles class. Hmmm... I have a roller RZ350... What years did they make the KX250? Wonder if it'd be legal for the USCRA singles and F2 classes. Think the cuttoff on F2 is 1984 or 85.

Yeah, like I need another project.

quote:
If you want to get really crazy, start hanging around the snowmobile guys and see if one of them has a chain drive motor laying about. I think artic cat has an 800cc parallel twin two stroke that should whip on anything if you can put it in a bike frame.
with a auto clutch? That would be... interesting.
 

·
Registered
Joined
·
2,047 Posts
Hey there, good snag!

Check the local wreckers like we were talking about, or CL. I just saw a reletively clean Yamaha IT 490 (complete got for $500. Since you'd need to come up with your own pipe anyway and can always toss a bigger carb on it (38-40mm) you'd end up with a brand similar monster.

Then I wanna ride it!

Lead, follow or get out of the way!
 

·
Registered
Joined
·
8,388 Posts
quote:
I am reposting this reply as I think there was a problem with my first reply.

Anyways, I've got an 86' CR500 engine that I will sell for $800, or consider any interesting trades. The engine is currently in an ice racer and comes with a lug that can be put in the end of the crank so an electric starter can be used. It also has a brandy new Wiseco
Dang, Doug.... what else do you have hiding up there?

The only problems I've heard with roadracing a large dirtbike single is vibration and gearing. Have to either put a tiny front sprocket on or a huge rear. And I've heard of CR500 motors cracking TZ250 frames from the vibration. But they're aluminum frames. A steel frame would hold up better.

That would be cool... CR500... lol
 

·
Registered
Joined
·
23,303 Posts
quote:

Ya know, a while back a guy was selling a KX250 powered RZ350 racebike. Neat idea, ran it in the WERA singles class. Hmmm... I have a roller RZ350... What years did they make the KX250? Wonder if it'd be legal for the USCRA singles and F2 classes. Think the cuttoff on F2 is 1984 or 85.

Yeah, like I need another project.

quote:
If you want to get really crazy, start hanging around the snowmobile guys and see if one of them has a chain drive motor laying about. I think artic cat has an 800cc parallel twin two stroke that should whip on anything if you can put it in a bike frame.
with a auto clutch? That would be... interesting.
The first year of the kx250 was 1985, I think. There have been several generation changes since then but even the '85 motors were strong (a buddy of mine had one, loved that bike).

I wanted to put one in a derbi gpr 50, but I didn't have the scratch to buy the roller from vespa soho at the time. Besides, If I do one now I want it to be street legal. 45.5hp + 224lbs = 4.9 lbs per hp, or roughly the power to weight ratio of a nextel cup car. Formula one cars have power to weight ratios of 3 lbs per hp. Now picture it with some tannermatic carbon fairings and things really start to get interesting....

I saw recently a few bikes with artic cat engines, and most seem to use a HD primary and gearbox.
 

·
Registered
Joined
·
84 Posts
Discussion Starter #12
quote:
I've got an 86' CR500 engine that I will sell for $800, or consider any interesting trades. The engine is currently in an ice racer and comes with a lug that can be put in the end of the crank so an electric starter can be used. It also has a brandy new Wiseco piston in it, but I haven't started it because the carb needs to cleaned, got spark, but she just pops after many kicks like she's not getting gas. I haven't had time to dick with it. I've got $1200 in it. That'd be a nasty little Sunday morning rider.
Dgy 518 674 4045
I'm perusing ideas for the somewhat distant future...like the rest of you, I have lots of ongoing projects and/or items to fix on running bikes. I'd love to buy that engine but my first priority right now besides my caliper bracket design is to start on the RD400F Daytona Special.

I'm not really concerned about having an electric starter, I haven't even looked closely on the TX roller to see if it has one; probably, since just about the only bikes of those years that didn't are RDs and MX bikes! In talking to one of my other vintage friends the main concern seems to be adapting a generator to it, or a bigger one. What type of power generation source does a CR500 motor use to power the (presumably) electronic ignition? Since MX bikes don't have lights, I'd have to have a way to generate power for them. Yep it would be NASTY fast, for sure. Speaking of sprockets, I didn't count the teeth but the rear sprocket that's on it now looks to be pretty big, at least 48T I'd say.

Lee (Swagger) what were the names of those yards? Those were two I hadn't heard of. Can you email me the names and/or addresses.
And hey, if you help me figure out how to adapt the electrics, you DEFINITELY could ride it anytime!

Edited by - Quicklimegirl on Jan 08 2007 8:14:36 PM
 

·
Registered
Joined
·
8,388 Posts
I'm sure someone out there sells lighting coils/rotors/stators/whatever for the CR500. They were the premier desert racing bikes for a number of years.
 
1 - 13 of 13 Posts
Top