Coleman Drag Bike

[Truax]

Well I think this one is outside of the parameters for the 2018 build off, but there is still plenty of time to start something for that . This one has been a longer term evolution of a CT200U. I'll post some pictures of what it started with and where we're at. Currently waiting on a Noram Stinger clutch to come in and then this current phase will be complete. Haven't had a lot of time recently to be on the forum, so I figured I'd create a quick thread.

 

[bob58o]

Which exhaust pipe is that?

And a drag bike surely needs a cam, right?

 

[landuse]

Very nice!!!

 

[Truax]

Which exhaust pipe is that?

And a drag bike surely needs a cam, right?

The header in the pictures is just a AKRA weiner pipe. I've since switched to a different header which is pretty cool, runs outside the the frame and splits into two. I'll post some updated pics when the new race clutch comes in any day now. Right now it has the F-275 from Dynocams in it. Really nice cam for the top end, thing just screams. Kind of an awkward idle though, that could be from the blueprinted carb being a little rich at idle though too.

 

[bob58o]

The header in the pictures is just a AKRA weiner pipe. I've since switched to a different header which is pretty cool, runs outside the the frame and splits into two. I'll post some updated pics when the new race clutch comes in any day now. Right now it has the F-275 from Dynocams in it. Really nice cam for the top end, thing just screams. Kind of an awkward idle though, that could be from the blueprinted carb being a little rich at idle though too.

Idles like its got a cam! LOL
People pay for that awkward idle sound.

And if doing a drag bike, you may want your clutch to engage at a higher RPM.
Unfortunately that rough idle means the engine isn't making very good power at low engine speeds. Guessing a race clutch can be tuned for higher RPM engagement. Something like 4k RPM engagement would be good for a drag bike and that camshaft. BUT with those big tires, a high RPM engagement means a high wheel speed at engagement. That is hard on the crankshaft and clutch. You could play around with the engagement RPM to find what works best.

However, I'd be very interested in timeslips comparing the Torque Converter to the Clutch.
With the big tires, the TC is your buddy.
People always say clutches are better for drag racing, but I'm just not sure I buy it. People say lots of things. Plus most drag bikes don't have those big tires.

Guessing you are going to gear about 8 :1, giving you 55 -60 mph at 8200 RPM?

 

[Truax]

I think the Noram Stinger I have coming is setup out of the box to engage about 3500 rpm I want to say. Yea I'm a little worried about the high wheel speed at engagement, but kind of a trial and error process it seems. I'm actually going to try 9:1 initially, this frame doesn't need to surpass 56mph lol. That is right around where I had my top speed set at before the newest mods. The cam I had before was a higher torque cam from NR racing, think the target rpm on that was like 5500. The 30 series with beefed up springs held up alright with that, but felt it was pretty much at the limits of what it could handle. Not entirely sure why I'm continuing to build this thing out lol.

 

[Quinc]

1/8 mile drag? Do you know what kind of speeds you need to hit to be competitive?

 

[Truax]

1/8 mile drag? Do you know what kind of speeds you need to hit to be competitive?

At this point I've just doing this as a hobby without competition in mind. Not that it wouldn't be cool to take it to a drag strip or do some flat track with it, but it hasn't been the goal by any means. Just a hobby I really enjoy, that being said who knows what I'll end up doing with this little thing.

 

[Joe-405]

Competitive drag minis.......... you need to be at 80mph+ in the 1/8 these days. Anything slower wont get you anywhere but a first round loss usually.

 

[Truax]

Competitive drag minis.......... you need to be at 80mph+ in the 1/8 these days. Anything slower wont get you anywhere but a first round loss usually.

That's wild, good to know!

 

[2SlickNick]

I have a Baja warrior that I use as my drag bike. It's about a 10 second bike in the 8th mile. 58 60 mph.
I was going to use the Coleman frame from the CT 200 I had, but I went this route instead. It's a pretty heavy frame and the frame you are using is more appropriate. But you will need a smaller back wheel. I have the 16 inch rear wheel, and the 60t with Axel sprocket.

I know I'm not the fastest, but still competitive and I am only running 91 octane since I milled my head and added ratio rockers.
https://youtu.be/YxyTSHxCl48
I am now running a 6 to 1 gear ratio and able to achieve 8100 rpm's

 

[Truax]

Pretty good numbers in my book Nick, like your videos man!

 

[Joe-405]

That's wild, good to know!

My 2016 buildoff entry currently still holds the 1/8 mile Oklahoma record and the 60’ and the 300’ mph. Lol. Which is why I know and that was in 2016. They are running over a 100+mph now.

Mine went.........

60’ - 2.08
330’ - 60mph
1/8 - 10.46 @ 59mph

It Locked up the 40 series magnum driver somewhere around the 300’ mark as you can tell. If you do the math that was a mid 9 second pass easy. It also registered the 60’ with the back tire as it was on the wheelie bars through the 60’ as you can tell by the pics in the thread.

Build thread with YouTube videos........

http://www.diygokarts.com/vb/showthread.php?t=32896

I’m gonna build another one as soon as this years buildoff entry is finished ! I want the single digit pass and 80+mph badly still.

 

[Truax]

My 2016 buildoff entry currently still holds the 1/8 mile Oklahoma record and the 60’ and the 300’ mph. Lol. Which is why I know and that was in 2016. They are running over a 100+mph now.

Mine went.........

60’ - 2.08
330’ - 60mph
1/8 - 10.46 @ 59mph

It Locked up the 40 series magnum driver somewhere around the 300’ mark as you can tell. If you do the math that was a mid 9 second pass easy. It also registered the 60’ with the back tire as it was on the wheelie bars through the 60’ as you can tell by the pics in the thread.

Build thread with YouTube videos........

http://www.diygokarts.com/vb/showthread.php?t=32896

I’m gonna build another one as soon as this years buildoff entry is finished ! I want the single digit pass and 80+mph badly still.

I have seen your videos too Joe, really good stuff!

 

[Truax]

https://youtu.be/1gKnI5IiF4A

https://youtu.be/Tl99VVoBHq8

 

[bob58o]

I know you got the linkages, air filter adapter, prefilter,....
but I'd like to see you lose that stock carb. Or at least replace it with a bored out one.
https://www.arcracing.com/dj-2229-g-cnc-bored-675-box-stock-carb-for-gas/

The cam description says it likes a bigger carb.
Use bored stock or Tillotson carb. - translates into Use larger motorcycle style carb when I read it.


Watch some of Jody's videos from ARC and he'll tell you the carb is the key to making power. Need to let it breath.

My 8000+ RPM engine has a 24mm slide carb
Stock carb is like 15.6mm.
Bored out Stock Appearing carb is only going to be about 17mm.

This manifold is cheap, but no pulse fitting. Not 100% sure you need a fuel pump anyway and you have fitting in the valve cover already.
http://www.gopowersports.com/manifold-for-6-5hp-clones-predators

I've purchased a bunch of these Keihin PWK knockoff carbs.
24mm -26mm should be good for your cam.
https://www.aliexpress.com/item/ZSD...63c6-441f-96bd-2ac36a243978&priceBeautifyAB=0

$20 for the manifold, $20 for the carb, $15 for a throttle cable, and $5 - $20 for an air filter.
So an upgrade should cost less than $75.


The cam probably does ok with stock carb. It hold the valves open a long time. Allows the low cfm of the carb to fill up the cylinder. But a bigger carb should do much better.

 

[2SlickNick]

Looks and sounds nice!
If you are ever wondering about
Gear ratios use
App.kartcalc.net

Also subscribed to your channel...

 

[Truax]

I know you got the linkages, air filter adapter, prefilter,....
but I'd like to see you lose that stock carb. Or at least replace it with a bored out one.
https://www.arcracing.com/dj-2229-g-cnc-bored-675-box-stock-carb-for-gas/

The cam description says it likes a bigger carb.
Use bored stock or Tillotson carb. - translates into Use larger motorcycle style carb when I read it.


Watch some of Jody's videos from ARC and he'll tell you the carb is the key to making power. Need to let it breath.

My 8000+ RPM engine has a 24mm slide carb
Stock carb is like 15.6mm.
Bored out Stock Appearing carb is only going to be about 17mm.

This manifold is cheap, but no pulse fitting. Not 100% sure you need a fuel pump anyway and you have fitting in the valve cover already.
http://www.gopowersports.com/manifold-for-6-5hp-clones-predators

I've purchased a bunch of these Keihin PWK knockoff carbs.
24mm -26mm should be good for your cam.
https://www.aliexpress.com/item/ZSD...63c6-441f-96bd-2ac36a243978&priceBeautifyAB=0

$20 for the manifold, $20 for the carb, $15 for a throttle cable, and $5 - $20 for an air filter.
So an upgrade should cost less than $75.


The cam probably does ok with stock carb. It hold the valves open a long time. Allows the low cfm of the carb to fill up the cylinder. But a bigger carb should do much better.

I am running a .625 bored/blueprinted carb from ARC, it seems to be making pretty good power with it. At this point I'll probably just stick with that. Thanks for the recommendations though.

 

[65ShelbyClone]

Without getting into technical details like valve flow area over time, area under the lift curve, and all that, it's generally desirable to have the carb throat area at least match the valve curtain area or be larger. Yours is 45% larger, so I tend to think it's probably not choking the engine.

 

[Mrturbo458]

Looks clean! I like all those shiny billet parts, too!