Old tricks to get a few more Micro Ponies out of a Baja 30 Doodle Bug

C

CtMiniBiker

New Member
#1
#1
The baja 30 was major under powered out of the box here’s a bunch of little things we did to get some more micro ponies out of her.
(Remember it doesn't take allot to impress an 8 year old and his friends)

First removed all the annoying stickers, I think we dropped 20 pounds. Did save them on a piece of cardboard though

A little more tire pressure around 20 (remember these also do duty as the shock absorbers)

Bought 93 octane gas, remember to put 5 gallons in your car/truck first so you end up with 93 octane in the can

Got some NOS octane booster. remember this little motor has very only has a compression ratio of 5.6:1 so this probably wont help much if not any but it was cool to see my kids face when I told we were adding the same stuff that rockets use to go into space into his fuel to his tank

Removed the throttle cable stop screw totally see pic

Took off exhaust and enlarged exhaust opening, see pic, didn't want to go to big, might lean out air/fuel and have no idea if i can even adjust it (if any one has any experience please post.

Removed front shroud from cylinder head. not sure on this one but it should keep cylinder cooler

Its fun now.... great top speed, it takes time to get there though but that’s good for a beginner ( you don't have those instant on 2 cycle power band crashes) . I weigh 190 and it gets me going..…down hill, no seriously we had a bunch neighbors over and the adults had fun.

Before I swap out to a larger motor and just to spend time tinkering with my kid I think I need to get a better clutch and some one here hit the nail on the head when they suggested a larger rear sprocket diameter.
This thing is not high end by any means but all in all the best money I ever spent on a gift for my kid.

Thanks again for the forum
Dan & Dylan
 
H

hexhead

New Member
#2
#2
ctminibiker,

With regard to high octane gasoline. High octane gasoline has the same energy content per gallon as low octane gasoline. Simply switching from low octane gasoline to high octane gasoline will not increase the power output of the engine unless you also increase the compression ratio of the engine. The reason high octane gasoline exists is because it is less susceptible to pre-detonation in engines with high compression ratios.

The higher the compression ratio of an engine the greater the efficiency of the engine. A diesel engine has like a 20:1 compression ratio and that is why it gets more MPG than a gasoline engine (everything else being equal).

I am glad you and your child are having a ball with your doodlebug! That is what it is all about.

hexhead
 
Z

zabroluc

New Member
#3
#3
if you make the exhaust bigger, you have to make the hole that comes out of the engine bigger, not the muffler. or you could make it a straight pipe, only problem is that the exhaust comes off the side, but it can be done. good job so far
 
delray

delray

Well-Known Member
#4
#4
CtMiniBiker,my two easy fixs where a large rear sprocket and built a header exhaust system. i also still have kids riding my bike, so i will keep the stock motor on:thumbsup:

 
S

superior

New Member
#5
#5
Sometimes making the exhaust port larger will decrease exaust velocity, negating any desired benefits and quite often, lowering the power output of the engine. In any case,the most extreme modifications to the stock engine will not likely result in a real "seat of the pants " performance increase. The best bang for your buck is a larger rear sprocket to multiply torque for better accelleration off the line. Torque is what brings the front wheel up. Horsepower keeps it up. Your clutch will last much longer as well. Be sure to oil the clutch bushing with 4 drops of sae 30 right behind the snap ring about every 2 hours of riding time. :thumbsup:
 
delray

delray

Well-Known Member
#6
#6
superior right:thumbsup:, the only real thing that can really help a stock(engine) doodle bug is to replace the gearing with a larger sprocket or bolt on jackshaft. like i said before(about 100x)the bike is built wrong from factory or i should say something wong:chinese:
look at how most vintage bikes where built when using a small 3hp motor. the rear sprocket was large or they use a jackshaft setup.
when i went from a stock sprocket to a larger sprocket it made a big differents on how the bike took off and made the clutch lock up faster. i still have the original clutch on my bike:thumbsup:
 
Last edited:
fonz

fonz

New Member
#8
#8
Where are you guys purchasing the larger sprockets at? I've looked everywhere and cannot find a supplier who has a matching bolt hole pattern. Are you just drilling your own holes and modifying them yourself? Unless you have a milling machine in your shop it would be pretty tough to layout and drill the holes accurately.
 
den35

den35

New Member
#9
#9
You won't find a sprocket that matches.Nobody makes them sofar.

You'll need to get a blank sprocket and drill the mounting holes yourself.
 
fonz

fonz

New Member
#10
#10
Thanks for the info Den35. I kinda figured that. To do it right one should indicate the hub hole to keep it true. Evidently a little bit of run out wont hurt on these chain sprockets......chain slack and all. My thanks for your confirmation.
Fonz
 
C

contraption22

New Member
#11
#11
When I got my DB30, the rear sprocket had HUGE runout in it. Trued it up on the lathe as best as we could.

We took the rear wheel and chucked it in the lathe and cut the flange true. Had over .020 runout in it. Then we opened up the center hole on the sproket and made a SS bushing for the center to take up the space. We also had to drill out the 6 bolt holes slightly, as once the rest was centered, the screw holes no longer lined up correctly.

Before modifications, with any kind of chain tension the rear sprocket would pull on the engine so hard it was flexing the engine mount plate.
 
delray

delray

Well-Known Member
#12
#12
WOW contraption22 little china girl must of fallen asleep on the job:chinese: i don't think anybody here has had any problems with there rear hub not being true? good you cought it and have a lathe to fix it. i don't now why they use that type of raise engine mount plate with just welds in the front and back. it lets the engine flex back and forth,causing the bike to vibrate through the front forks little:doah: real bad if your using a stock motor with the factory rear sprocket. bikes are just not geared low enough to lock up the clutch good:doah:
 
M

Mikes Bikes

Member
#13
#13
Some ideas: Since you want to run high-test. Take the head off and get it milled at a machine shop. That'll bump the CR so you can take advantage of the octane. Disconnect the governer to let the rpms run up, just remember that your right hand is now the rev limiter.

Since you like playing with the fuel, stop at your local hobby shop and get some RC plane fuel. You can get it with various % of nitro. You'll have to re-jet for it, but done right, it'll give you lots of power!
 
M

mickeybee

New Member
#16
#16
My brother and I have two DBs' that came with A 70 tooth rear sprocket and 11 tooth clutch. We changed to an 80 tooth rear blank from Jacks small engines and drilled them ourselves with careful measuring. It was still difficult and time consuming and we still had to fine tune the centering with A little grinding. It really helped! We also replaced the stock muffler to A simple straight pipe. We bought A cheap wire feed welder from Harbor Freight that has paid for itself in one day. I have not touched my air mixture at all. My brother has. We both have inceased the gov. tension to get full throttle at A higher rpm. He is running A max-tourque clutch with the stock bell so he can keep the 11 tooth. I decided to run A Hilliard extreme duty with 12 tooth bell. I really like this clutch it has A higher stall so the engine can wind up before it engages,this helps take off faster and its just A way better clutch than stock. The max-tourque is is great too with A higher stall speed but my brother ordered A Hilliard too from Northern tool.These bikes are awake now since we first brought them home. MB
 
X

xxllmm4

New Member
#17
#17
The higher the compression ratio of an engine the greater the efficiency of the engine. A diesel engine has like a 20:1 compression ratio and that is why it gets more MPG than a gasoline engine (everything else being equal)
Click to expand...
Actually Diesel has more energy content per gallon. 147,000 BTU vs gasoline 125,000 BTU... more heat = more energy
 
delray

delray

Well-Known Member
#18
#18
mickeybee, glad see you installed a 80t:thumbsup: almost day and night differents in how it takes off ......:scooter:
different clutch may help little,but it was the gearing that did it:thumbsup:
it's still no racing bike like a 6.5? but still fun to doodle around in:thumbsup:..:scooter:
 
You must log in or register to reply here.
Top