Mini supermoto build thread

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Mini supermoto build thread

Post by milesmiles » Sat Oct 11, 2014 4:11 pm

After fixing a few bikes and having a blast doing it i found myself wanting a bigger project that was more custom than the standard. Not only that, but i have missed track days more than you can imagine(i have my priorities where they need to be, please don't comment on how i don't. I know what it takes to get back out there and when it's time i will be at it again). I was hanging out at motoliberty one day when i saw a flyer for the Texas mini moto GP, http://www.tmgps.8k.com/" onclick="window.open(this.href);return false; , an employee raced in it and pretty much had a friend and i sold on doing it.

My friend(cmra racer) had a TTR125 that he was going to use. After looking on the internet i found one for SUPER cheap and then another SUPER CHEAP.
IMG_2414.JPG
Don't worry, i have a new seat and new tank that came off the other bike(the one with the blown motor). This fit the project bike, race bike, future pit bike and it was cheap and i could buy/trade stuff as i go along(little did i know it was about to become insanely expensive).

The idea was to run GP125 2.5 x17 in the front and 3.5 x17 race slick in the rear, but to do this i had to get rid of the wonky suspension of the TTR!!!

I fixed one and had it running perfect, trading it for a 2003 YZ85 front and rear suspension/wheels only. Sounds stupid, but all these parts come out around 800-1200 used on ebay. They would also be fitted to the TTR to beef up the suspension and give more adjustments to it, not to mention changing out the drum rear brake to disk. This is the new front end with repacked bearings. Fitting it was pretty easy with minimal work.
IMG_2468.JPG
The problem comes in when you try and fit a YZ85 rear in to the TTR frame...it doesn't fit at all! This requires shims, re-drilling holes and cutting of several places in the frame to make it work.

Here is the stock frame and rear shock setup, look closely where the shock tower connects to the frame...
IMG_2437.JPG
IMG_2439.JPG
Here is the new hole for the correct placement of the new shock, notice how i still haven't cut into the frame(gotta make room for the reservoir that the other shock did not have).

I started cutting on the frame to make room for the reservoir...no turning back now! Tons of filing went into making just the right amount of room.
IMG_2481.JPG
While there isn't any photos there was a huge chunk taken out for the spring since it was bigger than the old one, none of this has weaken the frame.

There are 4 people who have done this swap with write ups that i can find, not a single one did the same thing and not a single one had a write up in depth. Of course i went a different route as well. Using some of the new and old linkage i redrilled a hole making the shock sit a little further back and taking some of the angle off to make it not sit so high. Here is the part i redrilled
IMG_2486.JPG
This gave a great stance as you can see. Keep in mind the rear stand holds up the rear about perfect height of what a 17" tire will be. There is plenty of play on the front and rear to work out if needed once i get tires installed. Take a look!
IMG_2489.JPG
I can't tell you how impressed/happy i am with the work, little did i know that wasn't the hardest stuff i was up against....plenty more to come!
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Re: Mini supermoto build thread

Post by milesmiles » Sat Oct 11, 2014 4:43 pm

So how do you get disc brakes work with the existing system? Well the rear end(YZ85) is already setup, but you have to make the master cylinder work with the brake lever. This requires cutting of the old lever, you can see where i started to cut...
IMG_2498.JPG
Now it was time to make a templet to hold the master cylinder. To do this you had to cut a plate to weld to the frame! Below you can see how i marked this out and you can also see the full cut to the brake lever. Don't worry, the brake lever will be welded together later on.
IMG_2505.JPG
Cleaning of the frame to have the metal plate to weld to...
IMG_2510.JPG
Here is my dad welding the plate to the frame. Without his help there was no way this project could be done, huge help!!!
You have to get the underside as well. Once done it was time for cleanup and grinding.
IMG_2512.JPG


The plate was really thick and the frame was pretty thin. This made it fairly hard to weld, but he's a great welder so there really wasn't any problems. The main grinding is done, i couldn't believe how clean and perfect it turned out. Once home it will require some light sanding.

The picture doesn't make it look clean, but in person it looks like it came that way from the factory(of course the whole bike will need power coating...darc )
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IMG_2518.JPG
IMG_2516.JPG
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Re: Mini supermoto build thread

Post by milesmiles » Sat Oct 11, 2014 4:59 pm

Next up was fitting the Master cylinder to the plate that we had just welded. This became a little tricky because while you can mark out the distance between the holes you can't mark the distance needed to make it line up with the newly welded brake lever. We did the best we could with a little measuring and a little eye balling. I'd say we got lucky and drilled it perfect. Take note of the brake lever we rewelded straight...not to mention 1" cut off the end. This gave the brake lever a clean pull and push into the master cylinder.
IMG_2521.JPG
I honestly can't believe i've made it this far. There have been a ton of steps that i have left out and hours of work not mentioned. So what's the next step? Well for awhile things will cool down. The rims for this thing will be a major hit in the wallet(non standard front size) and have to wait until the first of the year. I do have plans to have the stock YZ85 stock hubs powder coated and laced to excel rims.

The current motor is messed up bad, but i have plans to drop a 150 big bore kit in with a hot cam. The crank will be trued up along with removing the balancer to let it spin up faster. Also the flywheel will get a chunk machined out as well, over a pound). Free flow air filter and exhaust should match up nicely with a bigger carburetor being donated from a yz80(26mm over the standard 24mm.) This should be able to feed the motor that should produce double the HP. And that's not even the end of it, there is plenty more with the motor, frame, & brakes that i have to have done.

This is a long project so expect plenty more over the next several months.
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Sometimes you gotta draw the line, but that doesn't mean it can't be squiggly-miles
"it's not a stupid dirt bike, it's a supermoto!"-miles

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Re: Mini supermoto build thread

Post by BeautifulDisaster » Sat Oct 11, 2014 5:40 pm

Wow, this looks like one heckuva project!!! So many technical questions (yes I read it all), will save those for when you're patient (read: have a beer or two).

Looking forward to the updates! Glad you shared, and your dad IS awesome for lending a hand.
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Re: Mini supermoto build thread

Post by U-Turn » Sat Oct 11, 2014 5:49 pm

Ill hafta read it later, when I can comprehend.
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Re: Mini supermoto build thread

Post by milesmiles » Sat Oct 11, 2014 6:04 pm

Stop drinking Karl. I broke it down into sections with pictures just for you.
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Re: Mini supermoto build thread

Post by LonestarCBR » Sat Oct 11, 2014 6:49 pm

Cool dude.
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Re: Mini supermoto build thread

Post by Pooty » Sat Oct 11, 2014 7:08 pm

Bad ass
A lot of time and more to come
Worth it

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Re: Mini supermoto build thread

Post by Firewa11 » Sat Oct 11, 2014 7:39 pm

Dude this is a cool little project!
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Re: Mini supermoto build thread

Post by Stardog » Sat Oct 11, 2014 7:51 pm

Bitchin.

EDIT: Also I saw your dad earlier today in one of our safety CBTs at work. Tell him he needs more PPE. :-D
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Re: Mini supermoto build thread

Post by milesmiles » Sat Oct 11, 2014 8:06 pm

Haha, he's old school.
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Sometimes you gotta draw the line, but that doesn't mean it can't be squiggly-miles
"it's not a stupid dirt bike, it's a supermoto!"-miles

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Re: Mini supermoto build thread

Post by shilka99 » Sat Nov 08, 2014 8:11 pm

TT-R 125s are fun.
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Re: Mini supermoto build thread

Post by milesmiles » Sat Nov 08, 2014 9:32 pm

Sweet! I'm still working I this one. Might get with you after the first of the year with some help on motor work
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Sometimes you gotta draw the line, but that doesn't mean it can't be squiggly-miles
"it's not a stupid dirt bike, it's a supermoto!"-miles

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Re: Mini supermoto build thread

Post by DemonDuck » Thu Nov 13, 2014 1:16 pm

If your getting rid of the balancer then your going to have the crank perfectly internaly balanced? Just curious. If the balance isnt perfect then you can easly spin out main bearings and do more damage to internals.
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Re: Mini supermoto build thread

Post by milesmiles » Thu Nov 13, 2014 1:30 pm

yes the crank will be cleaned up & trued, but not balanced. Really all this means is faster revs due to the weight reduction. Sad part is it will vibrate a lot more and will wear out faster. Not really a huge deal in these small motors though and it's VERY common to do this. I don't mind the trade off, because i will need every ounce of help i can get to go faster.
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"it's not a stupid dirt bike, it's a supermoto!"-miles

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Re: Mini supermoto build thread

Post by LonestarCBR » Thu Nov 13, 2014 1:32 pm

I can testify to that.
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Re: Mini supermoto build thread

Post by milesmiles » Thu Nov 13, 2014 1:36 pm

LonestarCBR wrote:I can testify to that.
You're a funny man Lonstar
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"it's not a stupid dirt bike, it's a supermoto!"-miles

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Re: Mini supermoto build thread

Post by DemonDuck » Thu Nov 13, 2014 2:54 pm

Ok I just know that I had a bored out 302 that threw some main bearings because the crank was not balanced like it was supposed to be. I guess it would make less difference in a small motor like that. Still would it be that much more to have it balanced?
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Re: Mini supermoto build thread

Post by milesmiles » Thu Nov 13, 2014 2:58 pm

Not really a way to do it without the weights on it. Like I said it's a trade off, but not really that bad of deal
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"it's not a stupid dirt bike, it's a supermoto!"-miles

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Re: Mini supermoto build thread

Post by DemonDuck » Thu Nov 13, 2014 3:23 pm

Ok cool. I know places that balance the entire motor when building it so that the crank needs no weights or a balancer. When the shave it they do it in a way to keep it all balanced.
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Re: Mini supermoto build thread

Post by milesmiles » Thu Nov 13, 2014 3:37 pm

It sure would be nice to find a place that could do it. Let me know if you have a place. Not sure if i would do it though, shaving weight off can sometimes hurt things more than help them. With this build so far i've just been going with things that have been proven to work.
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"it's not a stupid dirt bike, it's a supermoto!"-miles

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Re: Mini supermoto build thread

Post by DemonDuck » Thu Nov 13, 2014 3:45 pm

Not sure about small engines but I will check.
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Re: Mini supermoto build thread

Post by LonestarCBR » Thu Nov 13, 2014 4:00 pm

This is either going to make a good "how to", or "how not to"...it's a shame it's not video-taped.
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Mini supermoto build thread

Post by milesmiles » Fri Nov 14, 2014 6:42 am

Image

bought an excel takasago 2.5x17 rim yesterday on eBay for $50. It's finds like these that will really keep my cost down!
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Re: Mini supermoto build thread

Post by Stardog » Fri Nov 14, 2014 1:20 pm

Nice! Lace that bitch. Did it come with spokes and a hub?
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