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xr100/80 cr80 conversion......help!!


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ok in the UK all you are allowed to ride on the road when your 16 is a 50cc bike.

what i want to do is put a xr100 or xr80 engine in a cr80 chassis but have the xr100 or xr80 engine sleeved down to 50cc. and also the stator rewound for a full light kit.

please can you tell me if this will work?

Thanks very much, simon

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I didn't think of that in the XR forum.

your right the valves will hit the cylinder.

you can try to de-stroke it but then your into a lot of work.

you would need to machine down the cylinder make the cam chain shorter. Some how make the cam chain guides shorter too.

you would need a stroke of 22.5mm instead of 45mm

If you used a 80cc cyl you would only have to decrease the stroke to 28.2mm which is 5.7mm less than the 100.

the 80 has a 13mm pin so you need to find a xr80 crank or complete engine.

Why not put lights on a XR50? They make really cool stuff for them and it would be much less work and probably cheeper and much much lighter which means faster.

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isnt destroking when material is removed from the top of the piston?

is this what u mean by destroking?

or do u mean i would somehow have to get the piston not to go as far up in the cylinder so the valves don hit the sleeve?

Thanks very much, si

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yeah i understand now.

so another way to do it would be to get a shorter con rod (and maybe crank shaft) how about off a xr50?

i think this is getting a little too complicated.

i need to find a 50cc motor that will fit in the cr80 frame.

do u think a air or water cooled would work?

but another thing is 2 or 4 stroke if its 2 stroke im gonna have to make sure the pipe will fit.

or maybee have a custom one made.

Thanks for all your help, si

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Guys the motor already exists. An XR50, no not the little kiddy XR50 with the z50 motor but in Japan they have an APE50 built by Honda for Japan. Its a minibike that has 12" wheels and they are legally registered and ridden on the road. I gateher they race them as well. It appears to be a small bore XR80 motor. They are 5 speed etc. The APE 100 is an XR100 motor but the barrel on the 50 looks shorter than the 100, more so than the 80 so it appears that it is a shorter stroke smaller bore built as a 50cc motor. Try talking to one of the grey bike importers in the UK to see if they can bring you in an engine or a complete bike to strip and build the CR80 up. In the ponts XR motors the lighting coil can be brought from Honda Its an XL100 (Same as XR100 motor not the bigger SL/TL/CB motor ) lighting coil. A later CDI one will need coil being made up by a good coil winder. The CR80 / XR conversion is pretty straight foward. Here is a pic of Matts ( 🙂 Mine actually) CRF80ff.jpg

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ACS i love you!!

not litrally but thanks very much uv found me a motor!!

im gonna do loads of resarch into it and then try and buy it.

do u have any idea how much just the motor car and all electics would be?

Thanks very much dude, si

and thanks to minifig-phil for all your help.

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acs, is the ape50 engine the same size (not bore, just pysical size) and has the engine mounts in the same places as the xr100?

and could i use a xr100 exhast with it?

acs do you have a email adress so i can ask u questions?

Thanks very much, si

p.s. in the post above where it says engine car and electric its supposed to be engine, carb and electics.

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Phil That is one of the motors. Good find! Note the similarities but I am not sure if its mounts are the same as the XR80/100. Sigibbons thats the motor you want. remember a custom conversion is custom so if the mounts are not the same it wouldnt matter. Phil can I see a XR50/CR combo?????????

Sorry guys the clamp down on linking is getting to be a pain..................... 🙂

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thanks very much phil!!!

i am enquiring about it now, and hope to buy it.

does anyone know if the motor is exactly the same as the ape50?

and also on the cr80 the swingrm pivot bolt goes through the cases on the engine, will it also do this on the cy50/ape50/xr80/xr100?

Thanks very much, si

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It looks like it. The gear ratios of a road bike motor will suit your project. I'm amazed that there are so many around. I did a search and found that there was a trail 50 as well. Honda must have flooded Europe / UK with bikes with 50cc motors to take advantage of the road rules.

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yeah the motor is in germany i think so i'll have to arrange shipping. could i get it to do like around 60mph around 8hp?

also it looks like the nice finish that comes on honda motors has worn off on this engine, so can i get the motor re painted or watever it is which they out on like xr100 motors?

Thanks, si

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ive also found another cb50 motor actually in the uk for £60 around $85.

it has no electrics just the motor, i may get this one indtead because its from a reputable breakers yard and the other one is in germany so would be alot of shipping charges.

i would need a carb, intake boot, and electics so where would i get them from?

Thanks very much, si

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