Any 85's in 125 frames?

EvanR127
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EvanR127
Edited Date/Time 1/27/2012 3:31pm
Hey has any1 seen any 80 cc conversion in adult size bikes?

I know it would be slow as hell and probably not reliable but dam that thing would be light!

Seems like a cool project.

http://www.fanticmotor.it/pop/cbregcmp50.jpg
like this bike
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ATKpilot99
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ATKpilot99 8/7/2011 8:14pm
8/7/2011 8:14pm
TM used to build one.
SlowOldGuy 8/7/2011 8:23pm
8/7/2011 8:23pm
I cant imagine an 85 motor being much lighter than a 125
Rooster
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Rooster 8/7/2011 8:27pm
8/7/2011 8:27pm
The mini road racing guys do it all the time. Toss a CR85 engine an old TZ or RS 125 frame and they go pretty good. It's a phenomenal way to learn road racing and how to carry your speed through corners.

I suppose the same would apply to motocross. It would be a great bike for anybody to upgrade their corner speed skills with.
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EvanR127
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EvanR127 8/7/2011 8:32pm
8/7/2011 8:32pm
SlowOldGuy wrote:
I cant imagine an 85 motor being much lighter than a 125
r u serious? lol Besides the pipe everything is smaller, and lighter! And it only needs one radiator!!!!

I wouldn't be surpise if you can loose 15 pounds easily. Imagine if the bike was built for the 80 engine, the chassis wouldn't have to be as beefy and it could shed a few pounds.
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yanks_178
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yanks_178 8/7/2011 9:04pm
8/7/2011 9:04pm
You can punch out a KX 100 to 112 and those things rip!!
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haydos25
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haydos25 8/7/2011 9:21pm
8/7/2011 9:21pm
EvanR127 wrote:
r u serious? lol Besides the pipe everything is smaller, and lighter! And it only needs one radiator!!!! I wouldn't be surpise if you can loose...
r u serious? lol Besides the pipe everything is smaller, and lighter! And it only needs one radiator!!!!

I wouldn't be surpise if you can loose 15 pounds easily. Imagine if the bike was built for the 80 engine, the chassis wouldn't have to be as beefy and it could shed a few pounds.
Imagine if the bike was built for an 80 engine?? Then it's be the perfect size for a 12 yr old kid. If you're not strong enough to throw a 125 around then hit the gym mate. Little engines are meant for little bikes.
EvanR127
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EvanR127 8/7/2011 9:25pm
8/7/2011 9:25pm
EvanR127 wrote:
r u serious? lol Besides the pipe everything is smaller, and lighter! And it only needs one radiator!!!! I wouldn't be surpise if you can loose...
r u serious? lol Besides the pipe everything is smaller, and lighter! And it only needs one radiator!!!!

I wouldn't be surpise if you can loose 15 pounds easily. Imagine if the bike was built for the 80 engine, the chassis wouldn't have to be as beefy and it could shed a few pounds.
haydos25 wrote:
Imagine if the bike was built for an 80 engine?? Then it's be the perfect size for a 12 yr old kid. If you're not strong...
Imagine if the bike was built for an 80 engine?? Then it's be the perfect size for a 12 yr old kid. If you're not strong enough to throw a 125 around then hit the gym mate. Little engines are meant for little bikes.
lol a 80 in a 125 frame would be harder to ride than a 450....and I do hit the gym but thanks for the tip anyways. Wink
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haydos25
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haydos25 8/7/2011 9:28pm
8/7/2011 9:28pm
EvanR127 wrote:
lol a 80 in a 125 frame would be harder to ride than a 450....and I do hit the gym but thanks for the tip anyways...
lol a 80 in a 125 frame would be harder to ride than a 450....and I do hit the gym but thanks for the tip anyways. Wink
harder to go fast on maybe, harder to ride, hardly.
tobz
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tobz 8/7/2011 11:27pm
8/7/2011 11:27pm
What about a 125 motor in an 85 frame?
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PaleBlue
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PaleBlue 8/7/2011 11:53pm
8/7/2011 11:53pm
ATKpilot99 wrote:
TM used to build one.
Still do - but to built to order. Great for big kids who are on the 85 cc class.
farmerfra
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farmerfra 8/8/2011 3:56am
8/8/2011 3:56am Edited Date/Time 8/8/2011 3:59am
Kawasaki built one for Larry Roeseler to race the ISDE in Germany in 1989. They wanted to cover ALL classes and he did well on it. I attached a link to a page where some one in France i believe has made a rep[lica of Roeselers..........
http://www.leguidevert.com/_V6/viewtopic.php?id=271394&p=1
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dirtbikemike 8/8/2011 9:59am
8/8/2011 9:59am
The 100 class used to be a great transition class with the YZ100 and TM100. There were tons of CR125s and KX125s running sleeved down cylinders too. Shouldn't be a problem with today's technology to develop anything similar.
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Berni
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Berni 8/8/2011 10:09am
8/8/2011 10:09am
EvanR127 wrote:
Hey has any1 seen any 80 cc conversion in adult size bikes? I know it would be slow as hell and probably not reliable but dam...
Hey has any1 seen any 80 cc conversion in adult size bikes?

I know it would be slow as hell and probably not reliable but dam that thing would be light!

Seems like a cool project.

http://www.fanticmotor.it/pop/cbregcmp50.jpg
like this bike
The bike in the link is a Fantic 50cc, very tipical this bikes in europe, you can ride them in the street at 14 (at least that is the required age here in Spain) that is not a 80cc in a 125 frame. These 50cc bikes even if they look like enduro bikes, they are quiet usless for enduro or in a track. Ride them in some trails and the city, not anything harder than that
TeamGreen
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TeamGreen 8/8/2011 10:22am
8/8/2011 10:22am
KX 85 motors are suppose to fit in a KX125 chassis w/o too much fuss...heard the asme about CR's, too.
queen of spodes 8/8/2011 1:34pm
8/8/2011 1:34pm Edited Date/Time 8/8/2011 1:35pm
Didn't Larry Roeseler race one of these things (kx125 w/ kx80 engine) back in the 80s?

NEVERMIND.. I Didn't read the full thread.

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Phillip_Lamb
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Phillip_Lamb 8/9/2023 10:33pm
8/9/2023 10:33pm

its possible but it would be severly lacking torque to get moving on a much heavier chassis vs 85 chassis. 

you would at least need a supermini motor

 

but it may be a fun interesting build. 

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Motocrossjunky 8/9/2023 10:49pm
8/9/2023 10:49pm

Up until 1999 you were aloud to run 125 wheels on your 80 in the Netherlands, so some guys did put 80 engines in 125 frames. I was on 80’s when the rules changes and actually preferred going to the smaller wheels. 

GG121
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GG121 8/10/2023 5:18am
8/10/2023 5:18am

Haven't seen it on a motocross track, but I was in northern Italy earlier this summer and it seemed like most of the supermoto bikes used for commuting around had 85cc engines in a bike bike frame. Lots of TM's and Fantics

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FGR01
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FGR01 8/10/2023 10:10am
8/10/2023 10:10am

In current times, a well-built KTM super mini will out pull a 125 due to power/weight ratio.   There's about a 50 pound weight difference.

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INeedaNewUsername 8/10/2023 10:24am
8/10/2023 10:24am Edited Date/Time 8/10/2023 10:24am

Not the same size chassis though. Be a good time ripping a super mini however. A full size 85/100 doesn't make a lot of sense to most, but they sure are a great time. 

FGR01
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FGR01 8/10/2023 10:47am
8/10/2023 10:47am
INeedaNewUsername wrote:
Not the same size chassis though. Be a good time ripping a super mini however. A full size 85/100 doesn't make a lot of sense to...

Not the same size chassis though. Be a good time ripping a super mini however. A full size 85/100 doesn't make a lot of sense to most, but they sure are a great time. 

Yeah, I'm just making the point, why would you want to put an 85/105 engine in a 125 chassis and make it slower.   It's faster if you just leave it in the little chassis and save 50 pounds.   Anyone big enough to ride a 125 chassis is big enough to ride the 125 engine also.  The only reason I can see to put the little engine in the big chassis is to race some organization/class that has weird rules.

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INeedaNewUsername 8/10/2023 11:00am
8/10/2023 11:00am
INeedaNewUsername wrote:
Not the same size chassis though. Be a good time ripping a super mini however. A full size 85/100 doesn't make a lot of sense to...

Not the same size chassis though. Be a good time ripping a super mini however. A full size 85/100 doesn't make a lot of sense to most, but they sure are a great time. 

FGR01 wrote:
Yeah, I'm just making the point, why would you want to put an 85/105 engine in a 125 chassis and make it slower.   It's faster if...

Yeah, I'm just making the point, why would you want to put an 85/105 engine in a 125 chassis and make it slower.   It's faster if you just leave it in the little chassis and save 50 pounds.   Anyone big enough to ride a 125 chassis is big enough to ride the 125 engine also.  The only reason I can see to put the little engine in the big chassis is to race some organization/class that has weird rules.

After seeing what Carson Brown can do on a super mini, it definitely crossed my mind to get one to play around on. 

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Tumic 8/10/2023 2:13pm
8/10/2023 2:13pm

In sweden there were a pretty common build in the late 80’s and early 90’s before the 125cc school boy class were introduced.

the kids rode 80cc until they were 16 and it was allowed to put the engine in a 125 frame or run 21/19” wheels on the 80cc bike.

 

but it was expensive to build the bikes and plenty of them broke down due to bad welded frames so it just became logical to open up a 125cc youth class instead.

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