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Cr125 af

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Hi there am a newbey on here am just interested to see if anyone has built a 125 AF if so any decent

Tips on wot to and wot not to do have a 09 crf 250 rolling chassis and a 98 125 motor am just building it for pleasure as I ride a 07 cr250r and a 12 crf450 any help would be much helpfull

Edited by che2498

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That's a tough conversion if you don't have good fabrication and welding skills. It requires removing the front single downtube and replacing it with dual downtubes to create a path for the two-stroke pipe, and fabricating engine mounts.

 

TTMcr5001stday6-30-09019.jpg

 

 

TTMcr5001stday6-30-09020.jpg

Edited by Chokey

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Yes mate that is not a problem as my mate at rolls Royce will do that for me at a price ;-) any more info would be great measurements and diagrams are always usefull

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Yes mate that is not a problem as my mate at rolls Royce will do that for me at a price ;-) any more info would be great measurements and diagrams are always usefull

 

If the fab is no problem, just get the engine and the frame, line the axle pivot of the engine up in the frame, measure where you need the mounts and where to cut the down tube, and start cutting and welding.

 

You're going to run into issues with things like the air boot and pipe mounts, etc., but that's the easy stuff. People do two-stroke AF conversions on here all the time, do a search and you'll find all the info you could ever need.

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Sound pal going to do a log on here with all my progress from start to Finnish

  • Like 1

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I have a AF with a newer CRF chassis ('09 CRF 450 to be exact which is basically the same as the CRF 250 up to '13)

 

I can only rave about how this bike rides. The new chassis gets you back on track. The "old" HPP engine is still a very potent engine. Me too i am using HPP engines but have them outfitted with even older '90 Mugen kits. Even though my engine is basically 24 years old i can still compete with new '14 KTMs ....my bike really is on the same level !

When i had my bike assembled at home i started investing in taking off some excess weight. Without spending in expensive titanium bolts/axles i still managed to take 9 lbs out of my bike!! The only advantage we have with a 125cc is the little weight. We can brake later and manhandle the bike way easier than the heavy thumpers....by having an even lighter bike this advantage is now on a level that makes my bike even more competitive. My AF is about 12 Kilos ( 26 lbs!!) ligher than a CRF 250 !! If i now try some of my friends fourstrokes they remind me of Paris-Dakar bikes with huge gas tanks...they are all so heavy!! My bike is incredibly flickable and so cool to throw around.

 

You are lucky to have someone doing the aluminium welding but there are more problems to solve:

-the main bone with that Y-shaped part needs to be cut and that y-part needs to be rewelded higher up to make room for the exhaust.

-cylinder head mount

-spacing of the slimmer engine between the swingarm bearings. On my chassis i could swap the right side center tube of the main swingarm needle bearing to the left and instead mount a wider right side spacer tube of a 2005 CRF 250 on the right side.

-obviously some pipe and silencer fittings/adapters need to be made

-you need some adapters for the waterhoses as well. The CR 125 has slimmer hoses than the CRF so you need some adapters to connect the tubes from the radiators with those off the engine.

-some re-routing on the radiators might be needed.Re-welding of some tubes to get the hoses to where they belong.

-you need to fit a CR airboot to the airbox but you still need kind of a spacerplate in between as those airboots are all too short. On my bike that spacerplate between airbox and airboot is around 18-20mm thick if i remember right.

-you need to close the bottom of the gas tank

 

My CR 125 AF with '09 CRF chassis, 1998 5 speed engine and 1991 Mugen kit (actually right now i'm using a '90 Mugen):

9426047325_907dda07b6_c.jpg

 

It might be 24 years old but it is easily as fast if not faster than a new '14 KTM SX 125 ;)

8992869541_1a5c4c9644_c.jpg

 

9428814960_5b0d0f9287_c.jpg


 

 

Below some pics of parts that were needed for AF modifications:

14042244089_d1172d6cb5_c.jpg

 

But in the end all that counts is that you have biiiig fun with a nice 125

13363155814_6c6a918b72_b.jpg

 

Edited by nino
  • Like 4

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Can't wait I have hallways been a Honda man and wanted a 125 as I ain't rode one since 1999 so can't wait to get mine done it might take me 12 month as I plan on something special black and gold going to be the theme I think

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Hmm - honestly i don't know if i would do the conversion this way!

Your 125 looks great and is still a nice bike. The advantage going to that already "older" aluminium CRF chassis won't be all that big. IF i would do it i'd rather get the most recent CRF chassis possible OR look out for just a HPP engine!

This way you would still have that sweet CR in the garage and just build yourself a 125 AF next to it.

 

But tearing apart a nice and running 125 ? I think personally wouldn't do it.

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To be honest I was just doing it for pleasure as I have these sat in my garage so it's not pressing to get it done might break to crf and buy a newer rolling chassis to do the build ImageUploadedByThumper Talk1400764331.552315.jpgImageUploadedByThumper Talk1400764350.541308.jpgImageUploadedByThumper Talk1400764418.813186.jpg

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To be honest I was just doing it for pleasure as I have these sat in my garage so it's not pressing to get it done might break to crf and buy a newer rolling chassis to do the build attachicon.gifImageUploadedByThumper Talk1400764331.552315.jpgattachicon.gifImageUploadedByThumper Talk1400764350.541308.jpgattachicon.gifImageUploadedByThumper Talk1400764418.813186.jpg

You must have a good job to support all your bikes Lol

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