A solution for wheeling of Predator powered DB30

[GustoGuy]

The Doodle Bug chassis with its short wheel base and high center of gravity which is centered over the rear wheel with a rider on it is the reason for the wheelie popping you experience with a Predator 212cc. For example a Baja Warrior bike handles the increased torque of the Predator 212cc with out any issues because of its heavier weight and longer wheel base. Since the concentration of weight and center of gravity is high and near the rear wheel on a Predator equipped DB30 the only way to fix the issue of unintended wheeling is to lower the center of gravity and move it forward towards the front of the bike was to add weight to the bike in front of the engine. I went out and purchased 3 cut pieces of steel each weighing 4 pounds and I placed 8lbs directly over the front wheel bolted on the Number plate bracket attachment on the Badger front fork. The remaining 4lb piece of steel was put down low on the frame just in front of the Predator engine. I attached it by using 3M Body panel adhesive that I had left over to glue the 4lb piece of steel down low on the frame. If you wish you could use a welder to weld it to the frame instead.

I then proceeded to test the bikes stability with the modifications that I made and I found that I could now easily sit on the bike with the kickstand down with out problems. I then took the bike out and proceeded to road test it. I found that the bike has a much reduced tendency to try and pick up it's front wheel when accelerating quickly than it did before. It felt much more stable and I did not have to slide forward on the seat as much or lean forward as much to maintain stability while accelerating. Here are 3 photos showing the steel pieces I added to the bike to improve the stability.

 

[Sinner70]

How's it work? wouldn't changing the gear ratio accomplish the same thing?

 

[GustoGuy]

How's it work? wouldn't changing the gear ratio accomplish the same thing?

Changing the gear ratio would work but unfortunately it would do it by reducing the quick acceleration of the start but you would gain a bit of speed on the top end. My next mod will be a GTC TC2 torque converter which will add about 10mph to the top end without sacrificing the awesome acceleration. The Predator 212 is much more powerful than the original 2.8hp engine and the DB30 has a real short wheel base and that coupled with the center of gravity up high and near the rear wheel means wheelie if your rider doesn't lean forward or slide forward on the seat. The added weight does help by reducing the need to lean forward to keep stability when accelerating. I noticed it tonight when taking off that the front wheel tended to stay on the ground much better when accelerating hard.

 

[Neck]

So....What's so bad about wheelies?

 

[GustoGuy]

So....What's so bad about wheelies?

Unfortunately most of the people who ride my bike tended to lose control and wipe out on it. My stepdaughter rode it last year and whisky throttled it and wheelied it right off the curb and dropped the bike into the middle of the road and skinned up her elbow and bruised her hip. Thankfully a car wasn't coming when that happened. My wife then lost control on the bike about a week later on a gravel road by our cabin and got a bruise. Just a week ago my step daughters boyfriend wheelied it over despite me telling him to lean forward a bit when riding it. He did it while riding it in the grass so he was not hurt at all. With a skilled rider who knows how to control the wheeling it could be kind of fun I guess. I even like it better now because it doesn't seem so squirrely anymore when riding it. And I haven't lost control of it either before I did the modification and I used to ride motocross bikes when I was in my Teens and 20's so I know how to lean forward and shift my weight to keep the little sucker in line.

 

[Neck]

Ah I see, kinda like putting a 16 year old boy on a Hyabusa.

 

[Arthur Kill]

Wow....all I can say is.....uh, wow.

Was Rube Goldberg your engineering professor?

:laugh::shrug::laugh:

 

[GustoGuy]

Wow....all I can say is.....uh, wow.

Was Rube Goldberg your engineering professor?

:laugh::shrug::laugh:

"You mean the cartoonist who drew overly complicated thingamabobs and machines that accomplished simple tasks."

As to being overly complicated it's not really. I just added some weight to the front part of the bike and it doesn't have any moving parts. I just balanced the weight of the bike so that the front wheel has about the same amount of weight on it as the rear wheel with out a rider. The 6.5 hp Doodle bugs are wheeliers because most of the weight is concentrated near the rear wheel and up high once a rider gets on the bike. The steel plates are not moving and there is nothing complicated about it at all.

 

[deejaaa]

i like it and commend you for your solution that caused you problems. you took initiative and figured out how to let others enjoy your machine. maybe others will copy your idea and say something a little more positive.

 

[Toycartony]

I say take all that weight off and get a video camera and let the fun begin???
Now that would be a hell of a thread!!!!!

 

[GTO]

I think the amount of paint alone would have been enough! :laugh:

 

[buckeye]

Wait, GTO?????

 

[Toycartony]

Wait, GTO?????

What??? Is something you should have said?????

 

[buckeye]

Just haven't sen him on here in over a year.:thumbsup:

 

[Miniwood]

Or you can lean over the bars if you are going to lay into the throttle. Its not as bad on the older db30 frame. Also, you can slide your butt forward if you bend the bars
You could also lengthen the frame. Im too tall to fit in the newer frame without doing something to the frame or bars.

Would be fun to make some wheelie bars on the back.

 

[Stangrcr1]

Not what I would do, but you get an A for effort.

BTW, both my DB's are stretched wheelbase....

 

[GustoGuy]

"Or you can lean over the bars if you are going to lay into the throttle. Its not as bad on the older db30 frame. Also, you can slide your butt forward if you bend the bars
You could also lengthen the frame. Im too tall to fit in the newer frame without doing something to the frame or bars. "

"Would be fun to make some wheelie bars on the back.
Not what I would do, but you get an A for effort."

"BTW, both my DB's are stretched wheelbase.... "

Thanks Stangrcr1 and Miniwood and deejaaa for your constructive reply to my concern. The main problem with the old style classic DB30 is that it has a short wheel base and it's center of gravity with a Predator 212cc is rather high and with a rider its almost directly over the rear wheel. This combined with the torque of the 212cc engine often means unintended wheelie. I do like your stretched frame DB30 and I would like to stretch mine but I only have a stick arc welder and would need a good MIG welder to do this. It's not so much for me since I familiar with the need to shift your weight and lean forward over the handle bars when accelerating. When I was younger I would ride motocross bikes and my brother used to own a 1993 CR250 that I would ride quite regularly. I am doing this because I have older children and their friends who are not skilled in riding a short wheeled based relatively powerful mini bike that happens to have a high center of gravity and my stepdaughter accidently whisky throttled it and went off the curb last fall and dropped it into the road because she lost control of the bike when she was accelerating out of a curve. She ended up with a bruised hip and skinned elbow. The DB30 frame was never really designed to run with a 6.5+ hp engine in it and it is not balanced correctly or with a long enough wheel base to channel the power with out having to do some serious rider input by leaning and shifting of your body weight to keep the little sucker in line. I tested it and the 12lbs of added weight does seem to reduce some of the unpredictability in handling of the bike. I hope the modifications I made will be enough to prevent wipeouts from occurring when my family is riding it. The last thing I want is for someone to get hurt while riding my mini bike.

 

[Havasu Dave]

I'd have just put in a smaller motor if I were concerned about the safety of the less-skilled riders in the family.

 

[GustoGuy]

I'd have just put in a smaller motor if I were concerned about the safety of the less-skilled riders in the family.

Well, I like the Predator 212cc engine and its fun to ride. I just am looking for a way to tame the handling characteristics of the Short wheel based DB30 to make it more forgiving to novice riders. I can also adjust the throttle limiting screw too. Every one I let drive has been over 18 years of age so I am not looking to hurt youngsters and children with this. Plus the 2.8hp engine was gutless and would not climb even relatively shallow hills. I would like to get a GTC tc2 TAV and put it in. You have to admit that the DB30 frame with a Predator 212cc is not really made for the Predator 212cc power. Center of gravity and balance is everything when making a bike handle better. Look at motocross riders and how they shift their weight when railing on a powerful dirt bike. If they did that in a seated position with out applying any body English they would be thrown off. I am just tweaking it to reduce some of the unpredictability and when I tested it does seem to reduce the tendency to pick up the front wheel while accelerating because novices will not always listen to you when you tell them to lean forward when riding it.

 

[MiniBike Paul]

Let's see if I get this;

First, add a bigger engine because you like the power!
Second, bolt on a bunch of weight because you don't like all the power!

OK, I have it now!