xr70 to ultimate all around motorcycle
 

Hello everyone Ive got most of the parts together, and more on the way.This will be my biggest most expensive build ever.I'll list the cost of the parts I have bought and future purchases.

Ok well I picked this 2000 XR 70 up off craigslist for 100 bucks complete but not running.Well I didnt care as I never planned to run the 70cc ever anyway.Well I kept looking for a motor and saved .Then the other day on ebay my motor popped up, a piranha 150cc . It came up with a buy it now of 300 , I looked at i and I seen it still had a aftermarket big foot peg bar. I sent him a question if it had a oil cooler hooked up? Well 45min of it being up I ht Buy it now. the next day he informed me that yes it had always had a oil cooler and if I wanted he would throw it in the box for me. Well that saved m some cash a well cause you have to get a bigger foot peg bar to fit the wider motor. The one that came was the super heavy duty thick one. The stock xr one was fine but I never wanted to jump with it no problem now. I plan on using a 27mm pumper carb ,but thats just to get it running. I been wanting bad to put fuel injection system on. I found a few on tao bao ,I registered and have a agent so I'm good there. I bought a ton of stuff thats on its way.

Im going to be swapping in a cr80r shock and spring its a fully adjustable showa and I'm going to use another swingarm. I have a few to choose from and I want to extend it to keep the wheelies down a bit because I'm going to make big power. I'm building up the 150cc to really run. All help is welcome ,I will add to this one only til its done.

The XR70 (and the Yamaha PW80) uses a swingarm with a different design to most; the forward end of the shock is quite far forward, and the angle is very shallow. The only way you'll get a different style of swingarm on the bike is to weld on a new upper shock mount that is closer to the rear wheel. If you were going to that trouble, perhaps it would be better to just lengthen the stock swingarm.

A shock in the stock location that is too long will push the rear end down and change the steering angle, which might make the steering a little too twitchy for your liking. The only way to combat that would be longer forks. Costs really begin to add up. Check out some of the fiddy sites; those guys put cubic dollars into their bikes.

I'm looking forward to watching this build! :D 150cc in an XR70 is going to be crazy fun.

BTW, chromed steel rims will turn into egg shapes after serious jumping; you might want to upgrade to aluminum rims. This is a good opportunity to master lacing and truing.

I don't know the specific numbers, but I suspect the XR70 steering is a little lazy to begin with. Perhaps you should measure rake and trail of the stock bike, to use as a reference as you make changes.

Son of Weldangrind had a PW80 clone (with a four stroke Honda clone engine), and the steering angle was quite shallow and slow. He quickly began to outgrow the bike, so I made a simple adapter that lengthened the stock shock. The result was a higher seat, better ground clearance and quicker steering. He loved it. I can't remember the length of the adapter I made; perhaps around 1.5" long.

I've seen more than one horizontal Honda engine clone crack the crankcase after a jump with too much weight on the pegs. Some engines don't have enough aluminum around the top engine mount hole, but I don't know about the Piranha. Something to consider though if you're a big guy.

I weigh about 180 -200 depending on food around. I have a big footpeg bar that came with motor. Yeah weld thats what I was planning was to extend the top mount over to position it. I bought a kx 65 swingarm and going to flip it and wait til you see! I plan on putting in heavy duty springs in the forks.Im 5 ' 10" and it fits me perfect. I want to raise it a little so its still this height with the motor . I got a kickstand off a 91 suzuki bandit 400. I want to use the cr80r showa shock because its adjustable.

One thing Im going to do is race it on a drag strip,I figure at a 1/8 mile I should be able to use all gears.This is why a extended swingarm is needed. I'm going to modify the kx 65 plus 3 inch maybe four. I bought a 14 inch xr80 rear rim and I have a kenda jungle master for dirt and I am buying motard 12 inch front and rear. I have a 17 inch I was thinking about 17 front/14 rear or 14 /14?

Im thinking of using cr80 forks for the front , I got the 14 inch wheel it way to heavy .Im going to just swap with cr80 forks,so I can put the 17 inch front wheel on.With the rear at 14 , I gotta figure out the rear swingarm situation. I have three swing arms to choose from I have stock,cr80r,xr80r and kx 65 . I want more travel so I can jump I have a cr80r 17 aluminum wheel for the front. I want this so the bike will be bigger ,taller, and big able to jump.

Will the CR80 forks slide into the XR70 triples?

Im not sure if they will the xr 80 ones will . But I need the cr80 forks for the disc brake holes in the fork. Is there a way to put disc brakes on a drum brake fork.

Not an easy way. The best way is to just change the forks, as you've planned.

I can get a set of piranha front forks right now ,I don't know how to put those on I think I will keep drum brakes and put heavy duty springs and atf fluid in them it will raise them an inch. I'm going to start putting it together.

You can probably swap the cr forks and triple to get what you want ,or the piranha forks and triple that goes with them .Most of those forks are made for pit bikes and small mx bikes ,you will have to mod them to work well for an adult or heavier rider but stiffer springs ,and messing with fork oil formulas and levels will make them usable for you .The cr forks are probably around 38 mm diameter ,the original xr forks are 27mm in my 2002 xr70 ,so doubt you can fit the fork tubes into the original triples even with a bit of time at the machine shop .

well I got most of it together but I have to figure out the wiring the piranha has to many coming out of it and not enough plug ins. I bought a piranha swingarm thats aluminum,skid plate, clutch lever and cable, a 28mm mikuni with a special intake .

I think I will use xr70 forks with heavy duty springs and xr80 dampening rods. Next question what are dampening rods? How would I get these ?How to install?

Can you take a picture of the wiring? In general on one side of the engine you should have your stator wires probably 5 of them and on the other side of the engine should be the shift position wires. I think thats pretty much it.


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Here I hope the pics are sharp enough , I tried to get it in the one .The swingarm is on it way right now to the house , as I wait with wrenches in hand.