Baja Warrior Build - Drag Race Build

gran_pann

gran_pann

Member
#1
#1
Good morning gentleman.

I've got the tools and a little extra $$ right now to build up my baja warrior (the black one). Now I have three of these things, that I have built up for trail riding, and I Am wanting to build this to drag race a bit. And I have a deadline to meet October 8th.

I have a little bit of experience building engines and have put the whole jackshaft/torque converter setup on other baja heats with the whole 6.5 hp /30 series setup. Which was fun. But I'm wanting to build this up to another level.

Now i am here to document my build for a mini bike show/drag race coming up in the Ft. Worth Stockyards on Oct 8th.

Here's what I got

Engine: honda gx340
Transmission: 40 series torque converter or ?
mini bike baja warrior
a brain and some money, and some fab skills (tubing bender & genereal fab skils

Here's what I want
reach 40-50 mph as fast as possible. Anything above that would be a bit scary

Here's how I plan to do it:

Frame
replace front and rear tires with more road worthy: im considering the following:
kenda K572 19-7.00-8 for rear, or
Kenda K547 19-8.00-8 for rear, but am worried about clearance issues since ill be adding what, a half inch on both sides? Also seems square ish, which i am worried about handling.
kenda K572 19-7.00-8 for front, or
kenda k546 19-7.00-8 for front

replace front and rear wheel bearings with 'better' bearings. Ceramic options?

replace front and rear brakes - e.g. hydraulic rear disc or other options? Weld or secure disc to rear drum housing, come up with some sort of front brake arrangement as well (i can tig weld, but am worried about screwing up the fork somehow by warping? - thoughts)

replace fork seals with better ones, and get 'stiffer' front fork travel somehow. Mini bike seems to bottom out easily.

Fuel: I have already welded a little hoop to the rear of the mini bike and have a spun aluminum tank on it, so im wanting to stick with gravity fed.

frame modifications I have seen people add these 'torque bars' of some sort and cut out that main support beam. Im still figureing that out. bottom line, will be to keep the frame from flexing too much, and to accomodate the engine

Engine work and gearing:
target rpm? now here comes the tricky part. I dont want to wheelie off the line, but want excellent pulling.

Ive built other honda gx390s for torque, and gx390 strokers.... and im thinking this may spiral into a full blown build, but I do want to avoid building the engine up excessively:

32mm mikuni or something like that
custom exhaust, probably 1" ID
mild port job
HD single rate springs
stock length billet rod
cam - 275, 306, 208? im wanting to keep compression ratio below 10.2:1 and run on pump gas, can get the compression ratio correct by either boring to 88-90mm with flat top piston, and or milling head.


Now ive run the 40 series torque converter I have on a gx390 with a 280 cam and the engine tops out at 5500 rpm due to the 1) cam 2)stock carb. I have had issues with the 30 series torque converters holding the smaller engines back....

So.... will the 40 series torque converter rev high? will it hold the bike back?


Also, gearing will be a bit of a challenge. im planning on welding a tube to act as the jackshaft and having the rear sprocket on the opposite side to keep everything centered weight wise.


Anyway, let me know thoughts/ideas regarding front forks, and whatnot. Should be an interesting build by the time I finish.
 
madtom421

madtom421

Member
#2
#2
Not the best picture but I'm building a baja with a predator 301 and 30 series tav. No frame cutting but I did need to buy a engine plate from gopowersports.com to properly fit it in the frame. It's a very tight squeeze to the point that the engine will need to be removed to change the spark plug but I didn't want to alter the integrity of the frame. These are the tires I ordered, someone on here linked them. Waiting on the engine plate to get welded and figure out a quiet exhaust (lol) and she'll be up and running.


Sent from my SAMSUNG-SM-G930A using Tapatalk
 
noseoil

noseoil

Active Member
#3
#3
The Kenda 572 tires are what I run on the street & off-road. You might look at something narrower on the front & a bit more square on the back for traction, but they work well enough for general use for what I do.

Figure out some type of wheelie bar for the back of the bike, you will be launching hard & pulling the front end up when the engine grabs.

Weight vs. HP are what you need for drag racing. The lighter the bike & rider, the faster you will accelerate. Get rid of the fenders & any extra weight you can on it to get there quicker. A warrior frame isn't very light, but you need some strength to keep the engine in place & pulling, so it should work out ok. Strip it to the bare essentials & good luck on the build. Get rid of the handle bars & use some 7/8" round stock instead.
 
gran_pann

gran_pann

Member
#4
#4
I thought about getting those tires pictured as they are a common tire up on the interwebs, but they are a little 'cheap' for what I am wanting. I had a bad experience with wear with previous chinese tires. Granted, other brands are made in china, but the Kenda tires i have just are amazing and even though they are 2 ply, they are a lot thicker than the 4 ply chinese ones i got. So it looks like there might be enough room after all with the engine. Cant wait for the weekend when I can start figuring out how to get the engine on there.
 
gran_pann

gran_pann

Member
#5
#5
noseoil said:
The Kenda 572 tires are what I run on the street & off-road. You might look at something narrower on the front & a bit more square on the back for traction, but they work well enough for general use for what I do.

Figure out some type of wheelie bar for the back of the bike, you will be launching hard & pulling the front end up when the engine grabs.

Weight vs. HP are what you need for drag racing. The lighter the bike & rider, the faster you will accelerate. Get rid of the fenders & any extra weight you can on it to get there quicker. A warrior frame isn't very light, but you need some strength to keep the engine in place & pulling, so it should work out ok. Strip it to the bare essentials & good luck on the build. Get rid of the handle bars & use some 7/8" round stock instead.
Click to expand...
oo i didnt even think about the handle bars.

This is what i will probably get for the front
Kenda K546 Speed Racer ATV Race Tire Front 19 X 7 X 8 | eBay

This is what i will get for the rear if it fits, plus is just looks so good!
Kenda K547 Speed Racer 19-8.00-8 ATV Tire (4 Ply) 19x8-8 Hard Surface 28-5651

I am considering this for the rear, especially since ill take the bike off road a little bit in the future, but it reminds me of ninja turtles for some reason.
Kenda - K572 Road Go Tire - front or rear - 19x7x8 19x7-8 19 085720840B1

Or just another one of these for the rear
Kenda K546 Speed Racer ATV Race Tire Front 19 X 7 X 8 | eBay
 
Last edited:
FOMOGO

FOMOGO

#6
#6
gran_pann said:
oo i didnt even think about the handle bars.

This is what i will probably get for the front
Kenda K546 Speed Racer ATV Race Tire Front 19 X 7 X 8 | eBay

This is what i will get for the rear if it fits, plus is just looks so good!
Kenda K547 Speed Racer 19-8.00-8 ATV Tire (4 Ply) 19x8-8 Hard Surface 28-5651
Click to expand...

The 19 x 8 -8 will not fit the rear without spacing the sprocket out for the chain to clear the tire sidewall.







And the original drums work just fine with the correct shoes. GBC grooved shoes for a Honda 100 are a perfect fit.

Doug
 
Raskin

Raskin

#7
#7
I put 18x6.50-8 turf on my ct200u i like the smaller stretched look and works well with my 6.8 to 1 clutch drive and steering is lighter..there are others i considered for the front like the kenda hole n one..yeah i know the name :lol: but it's kenda 4 ply sawtooth type and maybe nice for a front tire coz steering lighter if your gonna run pavment..are tc ok to drag race? People talk about rpm issues w a tc...I'd enjoy seeing someone build a weekender drag bike 1) 18x6.50-8 18x650-8 18/6.50-8 Kenda Hole-N-1 K389 Limo Golf Cart Tire 4ply
 
Last edited:
SAS289

SAS289

Well-Known Member
#8
#8
Raskin said:
I put 18x6.50-8 turf on my ct200u i like the smaller stretched look and works well with my 6.8 to 1 clutch drive and steering is lighter..there are others i considered for the front like the kenda hole n one..yeah i know the name :lol: but it's kenda 4 ply sawtooth type and maybe nice for a front tire coz steering lighter if your gonna run pavment..are tc ok to drag race? People talk about rpm issues w a tc...I'd enjoy seeing someone build a weekender drag bike 1) 18x6.50-8 18x650-8 18/6.50-8 Kenda Hole-N-1 K389 Limo Golf Cart Tire 4ply
Click to expand...
I have seen opposing comments on whether it is ok to drag race with a TAV. Some have said that TAV's are not for racing with one guy on you tube calling them kids toys. Yet, Super Nate launches his TAV 30 at 4000rpm on the wheelie bars and turns 7800rpm in the eighth mile trap at 60mph. Based on that alone it sounds to me like TAV's are ok for racing.
 
TheDullCarbide

TheDullCarbide

Active Member
#10
#10
The TAV2s top out much better with the 7" driven than the 6" in my kart. The 7" just revs better at top ratio. I guess it has to do with how far the belt sinks into the driven :shrug:. And yes, I compensated for the difference of the top ratio between drivens.

Then again, is this information even relevant since he's going with a 40 series?
 
gran_pann

gran_pann

Member
#12
#12
FOMOGO said:
The 19 x 8 -8 will not fit the rear without spacing the sprocket out for the chain to clear the tire sidewall.







And the original drums work just fine with the correct shoes. GBC grooved shoes for a Honda 100 are a perfect fit.

Doug
Click to expand...
Does the fender clear the tire? I noticed you dont have a rear fender on there. Just curious.
 
FOMOGO

FOMOGO

#13
#13
gran_pann said:
Does the fender clear the tire? I noticed you dont have a rear fender on there. Just curious.
Click to expand...
The tire tread is wider than the fender... So the fender will have to be cut and widened to be used.

And the only reason the fender is not on it is because I hadn't gotten to it at the time. It is just mocked up in the photos. It is also stretched 5 inches with a 420cc Predator and a 40 series Torque Converter.
 
gran_pann

gran_pann

Member
#14
#14
Ok great. Thanks so far for the input. I ordered the
Kenda K547 for the rear Kenda K547 Speed Racer 19-8.00-8 ATV Tire (4 Ply) 19x8-8 Hard Surface 28-5651 | eBay
Kenda K546 for the front Kenda K546 Speed Racer 19-7.00-8 ATV Tire (4 Ply) | eBay

Front forks are getting lucas 15 wt synthetic fork oil (heavy engine plus me)

Making this push to start with a simple button 30 amp is plenty
30 Amp Momentary Push Button Chrome Starter Horn Kill Switch | eBay

also, have burning questions on the mikuni flat slide. What throttle cable works for it? Im ok wiht getting a new twist grip, or should i go atv style push lever?
 
P

Patrick_Moore

New Member
#15
#15
FOMOGO said:
The 19 x 8 -8 will not fit the rear without spacing the sprocket out for the chain to clear the tire sidewall.







And the original drums work just fine with the correct shoes. GBC grooved shoes for a Honda 100 are a perfect fit.

Doug
Click to expand...
i just put a set of the ebc on my daughter's warrior. mine is next :


Sent from my Pixel XL using Tapatalk
 
Daniel Coop

Daniel Coop

Well-Known Member
#17
#17
gran_pann said:
Ok great. Thanks so far for the input. I ordered the
Kenda K547 for the rear Kenda K547 Speed Racer 19-8.00-8 ATV Tire (4 Ply) 19x8-8 Hard Surface 28-5651 | eBay
Kenda K546 for the front Kenda K546 Speed Racer 19-7.00-8 ATV Tire (4 Ply) | eBay

Front forks are getting lucas 15 wt synthetic fork oil (heavy engine plus me)

Making this push to start with a simple button 30 amp is plenty
30 Amp Momentary Push Button Chrome Starter Horn Kill Switch | eBay

also, have burning questions on the mikuni flat slide. What throttle cable works for it? Im ok wiht getting a new twist grip, or should i go atv style push lever?
Click to expand...
The Mikuni's use either a ball or barrel end throttle cable. But in my personal experience and preference, the money is better spent elsewhere. The Mikuni's seem problematic and are a little difficult to tune for a novice. Seems like most of them being sold to guys like you and me are Chinese knockoffs anyway. Not sure if that has anything to do with it? With some proper jets, the stock carbs are more than adequate for a mildly built motor, and if you need more, you can go with a big bore, stock carburetor. There's just something to be said for their ease of tuning and reliability. I use big bore, stock carburetors on almost all my builds, ranging from .650 bores to .675 bores. They usually start around .580(?) stock for comparison.
The throttle control all comes down to personal preference. If a drag build, you probably only need a standard 1/4 turn throttle, because you're just going from a dead stop to full throttle.
I like your build so far, keep it coming...
Guess I should have read in a little better detail, because I thought you were talking small block... Big block with a 32mm is a bit of a different animal I imagine. I'm thinking you'd probably have a real 32mm Mikuni as most Chinese knockoffs are the smaller VM22's. Anywho...
 
Last edited:
gran_pann

gran_pann

Member
#18
#18
yep, the stock gx390 carbs are decent carbs on mild builds. This build is a bit different, just a quick rundown of my build:

gx390 bored to 90mm - milled piston head to be.005" in the hole at tdc
forged piston
stroker crank
i forget the cc,s but its around the 420 vs the 389
10.2:1 compression ratio measured and calculated on the dot
.043" head gasket
unmilled head
stock billet rod
electric start billet flywheel
275 wlc cam
chrome moly pushrods cut to length,
1.2:1 ratio rockers
stainless valves
ported head
3 stage header
mikuni flat slide 32mm
valve cover spacer
top ring gap .008
2nd ring gap .010
oil rings .010-.015 iirc

the carbs are easy to adjust if you know what you are doing (or with enough research). i definitely have a genuine mikuni. there are basically three areas to kind of think about, the idle pilot size, the jet needle height, and the main jet. You can jack around with the jet needle (needle jet?) height to get the right amount of fuel. Low to mid range throttle are more about the idle pilot and jet needle, and the high wide open is all about the main jet. So you gotta tune each one of them separately if that makes sense. Plus y ou dont have to jack around with any stupid top plate or weird throttle linkages, just hooks right up and adjust the cable in the middle of the cable with a wrench. for proper length.

Mikuni American Corporation
Mikuni Pocket Tuner - Temperature & Elevation
Dan's Motorcycle Carburator theory and Tuning
 
Last edited:
You must log in or register to reply here.
Top