Doodlebug 6.5 speed problems

[Jrdragbike]

I have a db30 and I put a 6.5 (clone) and it gets up to 45-50 and it just stays at that speed and dosent go up at all I tried a bigger carb but same problem
Any suggestions on what to put in it :shrug:

 

[cheezy1]

Details details details......:shrug:. Without any details of your gearing, or pics or info about motor mods...its like guessing a fat mans weight.

 

[Jrdragbike]

Engine upgrades:
18 pound springs
Air filter kit
Header
Jetted carb

 

[cheezy1]

Ok..whats your gearing? Meaning...clutch teeth number and sprocket number

 

[Jrdragbike]

Clutch is 12
Sprocket is 72

 

[cheezy1]

So for more speed...you need about a 60tooth sprocket for the back. Obviously..the smaller the rear sprocket the more top speed you will have. But you will sacrifice on the bottom end during take off. They sell the adapters for DB on OldMiniBikes and you can change the sprocket to any size you prefer.

 

[creia]

With (only) those performance mods and that 6:1 gearing, I'm surprised that you can get as high as 45-50 MPH? That engine is turning some HIGH RPM- you need to do some internal performance mods (flywheel, rod, etc.) before that engine comes apart.
Michael

 

[Jrdragbike]

I'm 240 and I hit 45 on it

 

[Jrdragbike]

I let my 100lb cousin get on it and it runs 50

 

[cheezy1]

With the 12t into 72t....it is 6.00 to 1 ratio overall...with 12t into 60t it is a 5.00 to 1 overall. The lower the number when you divide the driver into the driven the more top speed you will get. The higher the overall ratio...the lower top speed and more take off you will have. Class over:hammer:

 

[creia]

I let my 100lb cousin get on it and it runs 50

Assuming that you are running stock size (diameter) DB wheels and tires, to attain 50 MPH that engine would need to turn around 7,000 RPM.hmy: If you have not done any internal mods so that engine can (SAFELY) turn at that speed, please immediately take out a 1 million dollar life insurance policy and name me as the beneficiary?ut:
Michael

 

[vwfan79]

18# springs will start to float around 6200 RPM IIRC, not to mention the governor will only allow 3600 RPM. With your gearing you would need to turn 6500 to hit 45 and at 200+ #s, good luck. I would be happy with what you got or break out the wallet and start buying some real performance parts.

 

[Jrdragbike]

I'm ordering these and I'm gonna put them in this winter
Billet rod
Billet fly wheel
26 pound valve spring
18cc head
Other things but I can't remember

 

[vwfan79]

That will make a difference, get a timing key, your going to have the flywheel off anyways.

 

[Jrdragbike]

I wanna get a piston but I don't know how to pick them out like it says that they are like 0.9 0.10 shorter do you guys have any info on what kind and size I should get

 

[bpeltzer]

I'd be interested to know how you clocked your speed. I have a stock 6.5 in mine with a 13 toothe clutch 72 sprocket and I've clocked myself at 40. I'm 225.

 

[Jrdragbike]

Raced next to a scooter that has a top speed of 40 and I blew past him

 

[Jrdragbike]

I'd be interested to know how you clocked your speed. I have a stock 6.5 in mine with a 13 toothe clutch 72 sprocket and I've clocked myself at 40. I'm 225.

Your bike is stock and it goes 40

 

[Stangrcr1]

My Predator is stock internal, only air filter, jetting and exhaust, TAV2 and 12/66 gearing and hit 40 easy by GPS.

 

[93notch408]

my bike with a 60 rear and 12 front did 46 mph at 240 pounds its rejetted airfilter and adapter aluminum flywheels 4 dagree timing and a 3 stage pipe and no gov