2017 - MBX10 Flat Track Racer

[KartFab]

So i recently joined Texas Outlaw Mini Bikes (T.O.M.B), on facebook https://www.facebook.com/groups/1551572811793734/ its a closed group, but anyone can join. So.. they do flat track mini bike racing, pull start only, stock and modified class. No transmissions, clutch and torque converter ok. I took my old baja mini bike out to see what it could do, and got spanked. Just tore up all over the track, almost lapped, and i think it was only a 3 or 5 lap race. After a bit of digging, and questions, i knew i needed to get a smaller tire mini bike to be competitive. This has led me down the path to start a new build. So thanks to $150 and a motovox mbx10, im now starting to do a build that will transform the bike from a kids toy to an adult death machine that wil top out at 30 m ph at 7500 rpm, built for extremely small dirt tracks. So sit back, and enjoy the build! I just may finish it sometime in the future. I have about half the parts I need as of right now, and will post pictures, questions, and video as it moves along.

https://www.youtube.com/watch?v=fwVkZdOB5Ws

[2SlickNick]

Small wheels on those... pegs tend to scrape and cause you to flip in flat track...
You may want to look at these...
https://m.ebay.com/itm/10-WHEELS-SET...-/250568625836

[KingCobra]

That makes me want to buy another mini bike!!! Will be following and drooling........

[bob58o]

I see a fancy head, piston, rod, cam, valve cover, bolts, rockers i think, pushrods i think, maybe a gasket?.... what's in the black box?

EDIT: It's lifters the the box right? I know you like you some billet lifters.

Staying Clutch or going TC? With 13" Tires, 30mph at 7500 rpm is what? 9.5:1 Final Ratio? Seems crazy torquey like wheelies at full speed!!!

[KartFab]

Originally Posted by 2SlickNick

Small wheels on those... pegs tend to scrape and cause you to flip in flat track...
You may want to look at these...
https://m.ebay.com/itm/10-WHEELS-SET...-/250568625836

those are some good wheels, but we are more on very short oval, bull nose, etc loose dirt, and all the winners had these snowblower tires because they grip. They had those front tires through.

Originally Posted by bob58o

I see a fancy head, piston, rod, cam, valve cover, bolts, rockers i think, pushrods i think, maybe a gasket?.... what's in the black box?

EDIT: It's lifters the the box right? I know you like you some billet lifters.

Staying Clutch or going TC? With 13" Tires, 30mph at 7500 rpm is what? 9.5:1 Final Ratio? Seems crazy torquey like wheelies at full speed!!!

1.3 ratio rockers is in the black box. im trying to figure out what carb to use for methanol. Static compression ratio is 12:1 with the 18cc head milled .030" and a .045" fire ring head gasket. hemi short block bored to 2.815"

[bob58o]

Welcome back. What's the bottom of the Grand Canyon look like? LOL
How come no thread moving yet? Wasn't there a "remain in good standing" clause in the rules, Thelma?

[itsid]

very few people around here have such EXCELLENT standing as Grant!
So I'm fairly certain that there is no issue with that clause whatsoever..

Also... I have no idea what you're talking about *strolling off whistling*

'sid

[KartFab]

I’m just gunna leave this here.

[Nosandwich]

Originally Posted by KartFab

I’m just gunna leave this here.

They'll ban anybody around here...for whatever reason they want. It's the ban of the week special!

Love the "not specified".

[bob58o]

Originally Posted by itsid

Also... I have no idea what you're talking about *strolling off whistling*

'sid

Did he spell "Cookies" wrong? Am I the only one bothered by this? Can someone tell me why this thread is still here?
Most oddly satisfying video ever....

https://www.youtube.com/watch?v=I1e6lMA5Bj8

[ezcome-ezgo]

It's like being pardoned.

[KartFab]

Whelp, my nephew has been bugging me about getting a mini bike of his own, so I put my personal build on hold. I found another MBX10 shortly after posting this and we finished it over the thanksgiving break. Still have some filming to to but here is the progress and the final running product.

• got a thoroughly trashed mbx10 roller
• bent front forks into position
• replaced front and rear tires
• did a gopowersports stage 1 kit on a predator 212cc
• cut a new motor mount to size and welded it onto the frame
• replaced the #35 sprocket with a #40/41/420 sprocket (either 50 or 55t)
• took a good tire off of my mbx10, and installed it on the front of his mbx10
• installed a 13" X-Trac snowblower tire on the rear of his mini bike.
• welded up a header from the stage 1 kit, and wrapped it
• installed a new brake lever, using a baja heat brake cable for the mbx10 brake cable
• installed new brake pads
• installed a new twist grip throttle.
• fixed kickstand
• installed new chain guard
• 20 minute break in while my nephew was like HEYYYY WHY ARE YOU RIDING MY MINIBIKE?!!?
• oil change and letting him drive it around at 10 pm

any suggestions for a 1" inlet muffler? Im thinking of chopping off part of the exhaust and putting a decent muffler on this, or possibly welding a bigger end to the exhaust to fit a decent muffler on. Its so frickin loud.

Any thoughts on colors? he wants to paint it and that will be on his own time at his house.

[bob58o]

1" RLV4100
http://www.bmikarts.com/RLV-Muffler-...16-_p_885.html
I have open/modified version of a RLV Silencer. It doesn't quiet it much.
The above is the unmodified version. Not sure how quiet it will be. It needs a clamp.

Not sure what else is out there for clamp on mufflers.

[KartFab]

Originally Posted by bob58o

1" RLV4100
http://www.bmikarts.com/RLV-Muffler-...16-_p_885.html
I have open/modified version of a RLV Silencer. It doesn't quiet it much.
The above is the unmodified version. Not sure how quiet it will be. It needs a clamp.

Not sure what else is out there for clamp on mufflers.

I have that muffler and it takes the 'ear splitting, cracking' sound and tones it down to a 'deafening, bleeding out your ears' sound. Hahaha

[KartFab]

Well, I'm going to put an end to this thread and say it is complete! This is the post where Ill put up the video of my nephews mini bike. Just need to weld on a little adapter for the muffler and film it this weekend.

The reason why I ended this build (in addition to switching to my nephews build) is this bike ill be picking up tonight.

[KartFab]

Here is the final product. Scary and fun! Happy New Year!!

https://www.youtube.com/watch?v=UTUQvR4A9Ds

[KartFab]

So, this is the ORIGINAL BIKE (not the one i fixed up with my nephew).

Decided to put the ol briggs on it with all the goodies inside, ported, dual bearing block, billet rod, billet flywheel, cheetah clutch set to engage at who knows what, im hoping 2800-3200 rpm, i built this fancy motor mount thing a ma jig and painted it with my airbrush. First time unsing an air brush that i had purchased like 5 years ago with AUTOAIR colors and it turned out alright. I havent clear coated it though but oh well.

I also put on a pz22 knockoff 20mm carb on it, redid the seat, gotta put some tires on it. Its geared for 36 mph at 7000 rpm so should be a blast to ride around. Clutch is 15t, jackshaft in is 20t, jackshaft out is 9t, and axle sprocket is 50t, tires are either 13 or 145/70-6

[2SlickNick]

Looks awesome Grant!
Do you use Alec's app.kartcalc.net too?
Is this your new personal flat tracker?

[KartFab]

I used the bmikarts one. I figured the wrong tire size, but that’s okay. I’ll be going a bit faster then. The Briggs 5 hp flathead just doesn’t have the torque to move my 240lb self around,l like I want it to no matter how many mods it has. This one is just for fun and I actually ‘finished’ it tonight with the exception of bending the forks back into place. Going to go ride with some other youtubers tomorrow afternoon and will take this along. Setting engagement rpm was a bit tricky, I set it too low at first, then went to factory 4K rpm engagement. I ended up settling around 3000-3800 engagement. It’s super torquey at start but doesn’t feel like it has a broad powerband. Once I start really hitting the higher rpms the mini bike shakes a lot

[bob58o]

Originally Posted by KartFab

Once I start really hitting the higher rpms the mini bike shakes a lot

I'm not sure if it was an RPM range or a MPH range, but on my last minibike I just had to push through it and then it steadied up.

Just got to go faster. LOL
I love how he crashes and your response is "What the Crap!"