Dirt Racer Continued...

Chain Linkin

Chain Linkin

Member
#1
#1
Since the Build-Off is long over I figured I would move this to a section more geared toward the DB mini bikes. The progress has been slow but I finally got my new engine built and installed. I just need to hook up the throttle, electrical, and put the chain on and I'm ready to test. My only BIG concern is going to be the twist grip travel with the new 22mm carb. Right now my new twist grip is about 100 degrees to WOT which is great. Anything less then that (with the added power) will make racing on dirt tough. Wheel spin is NO good...



 
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Chain Linkin

Chain Linkin

Member
#2
#2
When I first bought the bike it was stock. I had to quickly race prep it (#3 version) for our first season. Here's a quick summary of what happened during (after) the build-off:

Hyd. Brakes
Lowered/extended fenders
Shaved reflector brackets off
New twist assembly and grips

For the engine:

CL1 Cam
18 LBS springs
Stock length ARC Rod
Raceseng flywheel
22mm Mikuni w/ small air filter
Robertson Torque Tube (loop) header

The gear ratio I'm going with is 1:5.58 (67 driven and 12 drive).

My plan is to use the new power + gear ratio to find a happy place where the acceleration is improved over stock but below the wheel spin threshold. A new clutch will be one of my last purchases so I will have to reconsider all of this again when I get to that.

I'm finally at a stage where the end of my to-do list is in site. Other then small details (hose clamps, etc.) the last big project is a new fuel tank. All of the parts have been collected but it's not high on my priority list right now... will probably finish it over the winter.
 
KMC3420

KMC3420

Member
#6
#6
Your gear ratio is similar to mine and low enough to not spin much at all, but it still gets into the power quick.

I have the below twist grip on my Gilson and really like it. It has several notches for different length throttle cables. I have a 1/4 turn throttle that I took off as it was balls to the wall or nothing. It had zero cruise capability. The below throttle is about like your throttle, except it is maybe 90 degrees to WOT.

Throttle

Nice bikes BTW, your racing circuit sounds like a blast.
 
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KMC3420

KMC3420

Member
#8
#8
Chain Linkin said:
Thanks! I just bought a Motion Pro CR Pro a few months ago so I'm going to try it first.
(highest twist to pull ratio - https://www.motionpro.com/motorcycle/articles/view/301/throttles_and_throttle_kits/)
Hopefully I'll get around to hooking the throttle up this weekend to test it.

Here's some picture's of our racing -

https://www.oldminibikes.com/forum/...inal-lombra-race-season.html?highlight=lombra
Click to expand...
Thanks for the motion pro link. I like those, they look like good pieces, and they list the wrist action required! Good luck with your throttle hookup, wont take long, just gotta say, I'm doing this! Music on, 10 minutes later, done.
 
Chain Linkin

Chain Linkin

Member
#13
#13
Baja_brandon96 said:
i need a place like that to race
Click to expand...
Daniel Coop said:
Don't we all, cuz? Don't we all...
Click to expand...
It helps when you grow up in a town of less then 200 people.

Not to brag, but if you've seen the FB group go back before 2014? We used to race on an empty lot near my parents house. That place was incredible. We started our first year with an oval like track, and eventually built the lot into more of a mini bike park. At the end we built a road style course in the infield (a roval...lol) and had a .5 kilometer four wheeler trail we would run rally style races. It was smooth enough for minis but the ruts made it impossible (and dangerous) to run standard races though there. We also had two golf holes and added a fire pit. Spent a lot of time there before I moved away (school, work, life etc.)

We've been very lucky to have a friend buy a house with large piece of land so we can continue our "association". We don't have as many options for racing but it is nice having a garage and proper fridge on site.
 
Chain Linkin

Chain Linkin

Member
#14
#14
Went riding today. The twist from 0-WOT is about 90 degrees so that's good. Power is good but the carb needs some adjustments still. The engine dies when I try to launch, it idles well and pulls strong once I'm moving... it's just the in between that's not so great. I also need to work on my chain tensioner, I can hear my chain slap under hard braking and ended up throwing it off today. Projects for next weekend.

Until then, I just wanted to emphasize how important free stickers are

 
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