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Old 07-17-2013, 03:14 PM   #1
McGoo 69 OP
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XR600 RFVC Engined Honda CRF 600 Supermoto project!

So here it begins!

Basicly i want to build a supermoto that i can road register and ride daily without having to worry about the high costs of running a motorcross engine on the road..

Some of you may be familiar with me already as i started a post a few weeks ago about what engine should i try and fit into a spare cr125 frame i had knocking about.. I had some good ideas sent my way but i wanted to keep the bike Honda engined and prefably have atleast 500-600cc.

http://forums.mxtrax.co.uk/showthrea...rsion-problems

I did abit of research on various motocross engine conversions and there wasnt much out there, ive seen a RXV with a ej6 engine so that made me believe anything was possible!

[media]http://www.youtube.com/watch?v=2CnEYhExAXc[/media]

Then i found the crf/xr440 that has been mentiond on here a few times so i decided i was going to do the same but with the 600 motor!

[media]http://www.youtube.com/watch?v=2EYgwgdk8uI[/media]

Any way, a RFVC xl600 engine came up cheap with loom, carb and exhaust, so i snapped it up and decided that this will be the beast that we will fit to the cr125 frame.

I made the trip to collect the frame and it wasnt untill i got there that i realised how massive the engine is compared to a crf450 and im not even going to talk about the back breaking weight! But not to be put of once ive commited to something i bought the engine and began the project!

The engine isnt pritty, its been painted 3 or 4 times but i have most of the paint of now





So the next step was to cut up the 125 frame to see if it would actully fit in!, so i took it upto a friend who builds alot of bikes and he got it tempory fitted into the frame in the correct position so i can build it up as much as i can before we go any further to see if its actully do-able









I think it fits pritty well considering the size of it!, the next challange is to come up with an idea for the carbs. The xl600 orignaly came with twin carbs, there just isnt enough room for them, its very close mind, the carbs with fit in the frame without the manifold but with the manifold they will need some modification..





with manifold





without manifold











I think the only realistic option is to run a single carb like the xr650's.. but would this mean chainging my duel carb head to a single carb one?

Ive also got an Aprilia RXV swingarm for this, and i know that to fit it to a crf frame you have to mill abit of the swingarm, but from what ive read about other rxv swingarm conversions you dont have to take alot of "meat" of the swingarm to get it into a crf frame but it looks like i may have to take abit more of for it to fit into a cr125 frame, what do you think?

i dont want to modifiy the swingarm too soon then find out this conversion wont work then ill be left with a RXV swingarm thats only useable on a cr125.







And heres the money shot! sup:



So thats basicly how far ive got for now, im curious to hear any concerns or ideas for this project as its a bit of a one of so any useful ideas or input would be appriciated!

thanks for reading if you got this far :goofy:

Matty
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Old 07-17-2013, 06:16 PM   #2
sailah
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Matty,

Wow that's an ambitious project there. That motor is massive for that frame. I assume you have a good TIG welder who can weld on that frame? Even still there's going to be a ton of modification when you get to the softer parts of the build like the airbox and fuel tank.

I'm not going to say it's impossible because nothing is, just want you to think ahead 3-4 steps to try and visualize what interferences you may be creating. Nothing worse than getting half way done and realize you made a massive miscalculation.

Do check the sprocket alignment as that can drive a bunch of decisions about the swingarm.
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Old 07-17-2013, 08:44 PM   #3
Apocalipsis FZR
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I hate to say this, but can you get a CR500 frame or at least check if the CR 250 is a bigger frame?
Or even a Steel XR 250 frame will do the trick...

You have there extremly serious interferences (the XL650 top head will not avoid the fact that you have the frame in the middle of the intake), and after spending a lot of money in gas and electrodes, it will be cheapper to get a bigger frame.

A solution will be to rise the engine inside the frame, but this actually means to weakening the frame by cutting it at the sides, and you will be rising the mass center...

Also in a bigger frame, the swingarm will require less modifications, and the sprockets alignment should be easier (because you have more space, look at the gearbox output, once you install a sprocket the chain will hit da frame).

Sometimes is better to see the trouble comming and take another and more suitable route in order to achieve the objective...

Just my 2 cents.
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Old 07-18-2013, 11:20 AM   #4
McGoo 69 OP
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Quote:
Originally Posted by sailah View Post
Matty,

Wow that's an ambitious project there. That motor is massive for that frame. I assume you have a good TIG welder who can weld on that frame? Even still there's going to be a ton of modification when you get to the softer parts of the build like the airbox and fuel tank.

I'm not going to say it's impossible because nothing is, just want you to think ahead 3-4 steps to try and visualize what interferences you may be creating. Nothing worse than getting half way done and realize you made a massive miscalculation.

Do check the sprocket alignment as that can drive a bunch of decisions about the swingarm.
ambitious yes, impossible no :) im aware this project may never get finished,, but i had a spare cr125 frame which cost me nothing so i decided to give it a go, the engine was cheap so i can sell that for 3x the price once ive tested it and cleaned it up etc.

all im worried about is the carbs right now, if i can get a carb to fit its doable, if not then im nakerd. r.e airbox i can just run some ducting and a k+n or just a metal mesh im not botherd, and for the tank that isnt hard ill either make one out of alli or mod a stock one, it may hold less but i dont care about that either, this project is more of a challenge than a practicaly

my mate john who does the welding has built many bikes and his dad is a bike builder too so i have alot of knowledge on my side

i just realy need to get the carb to fit.

matty
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Old 07-18-2013, 11:23 AM   #5
McGoo 69 OP
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Quote:
Originally Posted by Apocalipsis FZR View Post
I hate to say this, but can you get a CR500 frame or at least check if the CR 250 is a bigger frame?
Or even a Steel XR 250 frame will do the trick...

You have there extremly serious interferences (the XL650 top head will not avoid the fact that you have the frame in the middle of the intake), and after spending a lot of money in gas and electrodes, it will be cheapper to get a bigger frame.

A solution will be to rise the engine inside the frame, but this actually means to weakening the frame by cutting it at the sides, and you will be rising the mass center...

Also in a bigger frame, the swingarm will require less modifications, and the sprockets alignment should be easier (because you have more space, look at the gearbox output, once you install a sprocket the chain will hit da frame).

Sometimes is better to see the trouble comming and take another and more suitable route in order to achieve the objective...

Just my 2 cents.
if this all fails, ive already considerd buying a xl/xr or nx frame and making a supermoto using crf tanks etc but im not giving up on this just yet
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Old 07-18-2013, 12:40 PM   #6
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Quote:
Originally Posted by McGoo 69
I think the only realistic option is to run a single carb like the xr650's.. but would this mean chainging my duel carb head to a single carb one?
Yes, you would need a single carb head (and cam) although i don't think you will gain anything as the cross brace will still be in the way.

If you do end up going with a single carb head you will find that the cam gear won't quite line up with the chain but can be compensated by flipping the gear around.

Good luck
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Old 07-18-2013, 03:43 PM   #7
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40mm downdraft carburetor
90 degree intake boot

or a set of downdrafts
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Old 07-19-2013, 06:59 PM   #8
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Good gosh did godzilla rip that engine out dip it in molases eat it poop it out and sell it to you. Lol. Cool little project
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Old 07-20-2013, 02:21 AM   #9
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Just had a good look at the engine. It has electric start, and red paint which means its from an XL600LMF. The XL600R was kick start only.
Even though Honda called it the XL600LMF, it is actually an XR600 top end, with a bore of 97mm and stroke of 80mm. On the XL600R, the bore is 100mm and stroke is 75mm.
Besides the carb problem, the engine is dry sump which means you'll also need an oil tank of some sort.
Good luck.
Oh, and an XL600R CDI wont work. You'll need a CDI from an electric start motor, an XL600RMG, LMF, NX650 or an XR650L will work.

Homerb screwed with this post 07-21-2013 at 12:32 AM
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Old 03-12-2014, 01:43 PM   #10
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Any updates on this project?

I thought I had an original idea, but after searching it seems like this idea has been kicked around many times but this is the first I've seen of anyone actually attempting it.

I can't think of a better combination of performance and reliability. Old Sk00L bomb proof XR engine in a modern chassis. Lotta fun could be had and still ride it dail.
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Old 03-14-2014, 09:34 AM   #11
Bambi
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Hello there,
just had a quick 'read-through' and I'm wondering that nobody mentioned to tilt the engine a bit forward. This might solve all carb-problems ...
Interesting build, but I have to admit, that my biggest curiosity goes to that point where this big lump of an engine starts to hammer inside that small-size-bike-frame ...
Kind regards, Bambi
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