Is it possible?

Any one out there think I could mount a 1979 RM 125 engine on a 2005 RM125 frame?

yes, you could...

Yes, its quite possible.. But why?:smirk:

Yes, its quite possible.. But why?:smirk:

Well I love the 79' engine but hate the style and I don't have enough cash for another bike so I thought I'd do a fram rebuild. Would I have to get a new subframe too?

doesn't the entire process have the potential to be more expensive than another bike?

doesn't the entire process have the potential to be more expensive than another bike?

I just dont see it being more than a few hundred dollars. Ive already got all the fenders and such I just need the frame, sub frame and swing arm which i already found for cheap on ebay.

you could, but why, that old air cooled motor is no where near the same, the bike's balance and geometry will not be what it should be, unless it's just something you are just going to beat around on..........whats wrong w/ the 05's motor.

are you sure that the engine will just bolt in? it needs to line up at 4 places (2 mounts on the bottom of the frame, one at the top, and at the swing arm), and I can already tell you that upper frame mount won't be there because your engine is air cooled

my guess is that it will need some fabrication and welding, which if you don't have, might cost a lot of money to have done

but regardless, how much are you paying for the frame and sub frame on the 05? I have one from a 1998 model, and I can try to beat their price and save you some money

Go for it sounds like a great idea to me.

are you sure that the engine will just bolt in? it needs to line up at 4 places (2 mounts on the bottom of the frame, one at the top, and at the swing arm), and I can already tell you that upper frame mount won't be there because your engine is air cooled

my guess is that it will need some fabrication and welding, which if you don't have, might cost a lot of money to have done

but regardless, how much are you paying for the frame and sub frame on the 05? I have one from a 1998 model, and I can try to beat their price and save you some money

Well I have a welder actually but this may be a dumb question would a 2005 gas tank fit on the 98' frame? If it will then I will buy from you for a decent price.

Go for it sounds like a great idea to me.

By any chance was that sarcastic? Haha

hmm, I actually am unsure...but '01+ plastics have been fit on older bikes...you might want to ask the guy who did this one:

http://www.thumpertalk.com/forum/showthread.php?t=845192

Well before I ask the guy how much would you want for the frame plus ups ground shipping to zip code 60010?

I'm not 100% sure what a fair asking price would be. I posted in a thread over in general bike related about shipping frames, so let me find out what the cheapest way to ship is. I will also stop by the post office tomorrow, with the frame and see if they can advise me on how to ship it, and I'll try to come up with a fair price based on how much shipping is.

how much is the other guy charging you?

also, I'm not trying to discourage you, but I just thought about the swing arm, forks, and wheels. The cheapest I see a swing arm on fleabay is $41 shipped, the wheel can become pretty expensive, plus you need to make sure the airbox (built into the subframe) lines up with your carburetor to be used. I'd be happy to help you get a newer generation frame, but for about $750, you can get a used RM125 from 1993-2000 that's ready to ride.

I'm not 100% sure what a fair asking price would be. I posted in a thread over in general bike related about shipping frames, so let me find out what the cheapest way to ship is. I will also stop by the post office tomorrow, with the frame and see if they can advise me on how to ship it, and I'll try to come up with a fair price based on how much shipping is.

how much is the other guy charging you?

also, I'm not trying to discourage you, but I just thought about the swing arm, forks, and wheels. The cheapest I see a swing arm on fleabay is $41 shipped, the wheel can become pretty expensive, plus you need to make sure the airbox (built into the subframe) lines up with your carburetor to be used. I'd be happy to help you get a newer generation frame, but for about $750, you can get a used RM125 from 1993-2000 that's ready to ride.

Well I picked up the Swing arm, Rear shock Linkage, Subframe straight for $50 plus $28 for shipping. All parts came off a 1998 rm 125 and they are all in great condition.

The good: Well the real deal is that when the project is finished it should be about 5 "maybe" 10 pounds lighter mostly because you will not be using the radiators.

The bad: The engine on the '79 uses two bolts on the rear, not the swingarm pivot like the newer RM's (from about '81 on), so you will need a new rear mount. Plus it uses a side exhaust port so you are going to need to rework the front of the newer frames engine cradle.

The ugly: The '79 exhaust is going to run right into the gas tank and air box, and the newer exhaust won't fit around the old engines cylinder fins. And even after you manage to snake the exhaust around the air box you are still going to need a completely different gas tank unless you somehow manage to make the newer system fit.

Even worse: The '79 RM125 "might" make 30hp and without a power valve (it never had one) what powerband it does have, it'll only be about 1500 rpm wide.

In the end it won't be easy but it will be a great learning experience, and it will easily be a sub 200 pound bike (minus gas). And if you decide to do it, please post pictures and keep us updated on your progress.

So exactly what chassis are you going to use??

Well I picked up the Swing arm, Rear shock Linkage, Subframe straight for $50 plus $28 for shipping. All parts came off a 1998 rm 125 and they are all in great condition.

wow, ok, good work

so that means you don't need the sub frame? that might make shipping easier since both the frame and sub frame are long, and awkwardly shaped. Shipping one item won't be nearly as bad...

hopefully I can just wrap the frame in bubble wrap, slap an address on there, and let it go, I'll get back to you on that

wow, ok, good work

so that means you don't need the sub frame? that might make shipping easier since both the frame and sub frame are long, and awkwardly shaped. Shipping one item won't be nearly as bad...

hopefully I can just wrap the frame in bubble wrap, slap an address on there, and let it go, I'll get back to you on that

Did you get a shipping quote?

The good: Well the real deal is that when the project is finished it should be about 5 "maybe" 10 pounds lighter mostly because you will not be using the radiators.

The bad: The engine on the '79 uses two bolts on the rear, not the swingarm pivot like the newer RM's (from about '81 on), so you will need a new rear mount. Plus it uses a side exhaust port so you are going to need to rework the front of the newer frames engine cradle.

The ugly: The '79 exhaust is going to run right into the gas tank and air box, and the newer exhaust won't fit around the old engines cylinder fins. And even after you manage to snake the exhaust around the air box you are still going to need a completely different gas tank unless you somehow manage to make the newer system fit.

Even worse: The '79 RM125 "might" make 30hp and without a power valve (it never had one) what powerband it does have, it'll only be about 1500 rpm wide.

In the end it won't be easy but it will be a great learning experience, and it will easily be a sub 200 pound bike (minus gas). And if you decide to do it, please post pictures and keep us updated on your progress.

So exactly what chassis are you going to use??

Right now I'm debating on a 98' frame or 07' frame which the auction for the 07 frame ends Wednesday and the bid is at $27 plus shipping right now so I'll see where it's at Wednesday before it ends

this sounds like a horrible idea.

rebuild a 79, and leave the 05 alone. have two.

i would think you would want to have an 05 engine on a 79 frame.... oldschool with power?

79 engine will struggle to make 27hp

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