Fitting 125cc motocross engine in my derbi senda

[b0unt1 tw1ns]

Hi guys im looking into fitting a 125cc 2 stroke motocross engine in my 2006 derbi senda 50 before buying an engine im going to ask you bike experts for some advice.

Would i be able to make it fit & work with some mods to my bike , also would it be a hard job.

If you can give me some advice to note down i would be very greatful Kind regards Thomas.

[devojunior]

sorry pal but be prepared for abuse,

1, yes it will fit with ENOUGH mods

2,well whos fiiting it that will depend on if its hard or not

3, unless your have a full license you will not be legal blaa blaaa blaa,

4,dont try make a derbi senda fast just buy something faster ,

[P.]

DT125 engine.

Do it

[dangerousdave]

nice idea - but not at all straightforward.

chassis may need modifying to take the mx engine, depending on which was chosen. Also bear in mind that the Derbi chassis is made for a 50cc engine that produces less than 10bhp. Bolting in a 125 motocross engine, making 40hp, is far more than the chassis was originally designed to take.

you'd need to use the mx radiators and adapt/weld mounts to the chassis to suit. The mx airbox will need to be used which may or may not fit in the derbi frame. You'd need to fabricate new mounts for the motocross exhaust.

Once the engine is in, bear in mind the exhausts are louder than road-legal trail bikes so may take some quieting down to get through the MOT, as it is up to the tester whether he thinks its too loud or not.

Also the motocross engine would no longer power the lights or charge the battery as they do not have a charging circuit. (no need for lights on a MX track)

The change of engine would need to be declared to the DVLA, which could involve an inspection.

125 MX engines make 40hp+ so it wouldn't be learner legal. Also many insurers either wont insure or charge highly for heavily modified bikes.

Saying all that, I saw a YZ125 chassis fitted with a tuned DT125 engine, and road registered. That looked great and went well. These things are possible if you put your mind to it and know the right people to get the job done. However, a 50cc Derbi chassis is unlikely to be a good home for a motocross engine.
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1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50

[b0unt1 tw1ns]

Thanks for the advice guys really appricate it , i dont have the funds to go buy somthing like a ktm exc 125 , as i already have a derbi road legal , and i know a mot guy really well i rekon he would pass it with flying colours with a yz 125 engine in , for the dt engine im not a fan.

I can buy a 1987 yz 125 engine in fully working order off a mate for £180 so thats why ihad the idea to put it in my bike. Then i would sell mine to add to my funds on buying the mods i need to get it working.

The only problem i have is getting it checked as im only on a provisonal

[b0unt1 tw1ns]

forgot to mention £180 for the engine and full exhauste system

[dangerousdave]

here's one completed

https://dt125r.activeboard.com/t41245690/epic-derbi-senda-sm-with-yz-125-engine-epic/
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1988 Kawasaki KMX 200

Previous: Yamaha YZF1000, ZZR600, KMX200, DT50, KX80, CG125, PF50