Basket case DB revival

#21
Before and After

DB_Before_After.jpg

Got the pipe finished up last night and went for my first real ride in the parking lot at work. I think a steering damper will be on it before I top it out. It will smoke the 15x6 with ease :thumbsup:

I still have some odds and ends to do, but it's pretty cool.

Looking at a washer frame Ruttman tonight...maybe I've caught the bug
 
#22
Did some trail calculations and I was just over 2". I flipped the offset triple trees around "backwards" giving me 4.5" of trail and the wobble is gone.

I'm not sure how all these guys ride short wheelbase, short tire minis so fast around here...must be a ride!
 
#23
Had it out for some decent run time this weekend.

I adjusted the TAV driven to the tight hole, its been a while since I have had one apart...that was fun...

Made a CHT sensor out of some thermocouple wire and a 1/2" ring terminal I drilled out. Works well, but my TC reader zip tied to the frame was less than elegant.

According to my phone, it hit 33mph, but I was running out of real estate and let off before it was topped out. The TAV was not opening all the way, but it is pretty close to my calculations with the gov in place

I tried a few launches, getting more aggressive with each one, until the thing pulled a wheel stand and tried to throw me off the back...haha. With the TAV my SLR is 12:1, so it can get out of the hole decently.

I have ordered some a billet flywheel and a BMJr with 26# springs. After an event at the dragstrip on the 29th I will pull it apart and measure for the rod and head gasket and order the rest of the parts. So much for leaving it stock...
 
#24
For some reason I feel the need to be different and ordered a slipstream flywheel instead of an ARC. I was going to wait, but I couldn't resist throwing that gold eye candy on. (I still have gov hooked up...)

Before I pulled it apart, I verified the stock timing was ~24deg with a timing light and degree wheel.

I lapped in the new flywheel and checked timing, a hair under 30 deg with the stock key. I torqued it to 70 ft-lb

I read with the aftermarket flywheels, that the magnets were stronger and I'd need to increase the coil gap to avoid burning up the coil. I set it at 0.035 to start, and the thing did not want to fire. Once it did, it was running pretty rough. I closed up the gap to 0.025 and it seems a lot happier. The flywheel came with zero paperwork so I'm just guessing here. I did find a guy on a kart forum who said he could only run 0.028 gap with the slipstream, but the raceseng unit was ~0.040....

I'm on my phone now, but I'll throw some pics up later...it sure is purty.
 
#25
A little update...

The local hardware store/mini bike shop, Studz, was hosting a night at the dragstrip, and this seemed like a good idea, as I cannot ride around my neighborhood too much, and security started patrolling my testing parking lot.

I picked up a 7" driven for my TAV2 after seeing many people have issues with the 6" OD driven not revving out. This then required making a new belt guard, as the plastic one will not fit.

IMG_2868.JPG

I have not topped this thing out yet, so I didn't know what to expect. My first couple passes Friday night were made with the 7" driven. The first pass I let out because I must have gotten out of the groove and induced head shake. The second pass I stayed in the groove and it was smooth sailing to a 15.2 @ 37. I don't have a tach, so I couldn't tell where the revs were, but I decided to see how the 6" driven would work, and ran another low 15 @ 37 after the swap. I decided to stay with the 6" for the rest of the night.

I started to work on my launch, and had mixed results. Putting it "up on the converter" helped my reaction times and cut the 60' time, but too much and it yanked the front wheel to the point I had to let out of it. Once I found the happy spot, I ran a couple 14.8 @ 37. Being fairly consistent, I thought I was set for the bracket race, but I am an ET chaser at heart...I pulled the air box lid and filter element, and got after the launch fairly aggressively. I was rewarded with a wheelie of a couple inches and a 14.3 @ 38. I tried to duplicate this, but could not nail the launch, and ended up with a coupe 14.50's. I chose 14.50 as my dial in for the bracket race.

IMG_2892.PNG

I took out one of the faster bikes (google "Pizza Boy") in the first round, by luck, as he broke out by 0.03. I ran a 14.58. I beat a seasoned racer in round 2, he went red after waiting 3 seconds at the line after I left. He ran 0.008 over his dial, I went 14.58 with a 0.03 light. I got a bye in round 3 due to having the best reaction time in round 2. in my bye, I really tried to nail the light, and did with a 0.008, but it pulled the front wheel and I had to get out of it...luckily no one was in the other lane. Next round was against another 14.50 bike. A heads up race! I knew he had me up top by a few MPH. but my TAV would kill him off the line. I knew it was a good launch, but went red by 0.02...I ran it out the back to a 14.42 @ 38.8 shaking my head the entire way, to his 14.40 @ 41. He had a 0.2x light, I would have easily had him covered, but got ambitious and missed out on the money. The air at 11PM must have gotten good judging by the increase in MPH

I never thought I would have so much fun doing 38MPH...haha

I thought my bike was loud, but some of these things really pop. I would say mini night was louder than car night...

There really isn't much info on ET for "stock" predators. I guess it depends on gearing and weight mostly. I also suppose mine it not so stock anymore...closer to "Stage 1"
My setup is:
Hemi Predator
NGK plug
Homemade step header, ran with no muffler
35 main jet, 20 pilot
Slipstream Flywheel ~30 deg timing
Governor spring tension increased ~4100 RPM
Knock off TAV2 with increased tension on stock spring
12/54 gear
15x6-6 tire
bike is 105#
I am 215#

IMG_2898.JPG


I couldn't leave well enough alone though. There is another event that includes minis on October 28th...so I decided to tear into it.
IMG_2905.JPG

IMG_2861.JPG
 
Top