DoodleBug Performance Jackshaft

ProMod

ProMod

#1
#1

So you bought a little Doodlebugger and after your first test ride I am almost positve you were as disappointed in it's performance as I was. Anyone over 100lbs, any kind of hill or even a cruise across the lawn will leave you pedaling with your feet to keep it going. The problem....Way to high of a gear ratio for the little 2.5hp eng causing the poor little clutch some bad abuse.
The solution...
Motor swaps are cool but not for the average person. And although I love to be scared by a Hot Rod Mini Bike.(I have a Hot Rod baja heat that is making around 14hp)
A +5hp engine in one of these frames is not childs play. Even attempting to stop one fast with the little rear disc brake system will require you to add your Flintstones brakes.( scary).
Rear Sprocket changes........
I have heard you can find a larger rear sprocket blank and drill the bolt pattern to fit, But if you get the sprocket to large it will dig into the ground when turning left and has clearance problems
It just depends on how much you want to gear it down.
We have found that a 8.86 to 1 ratio works great with the little 2.5hp eng and with that can offer some suprising performance with the stock engine.
Our Bolt on Jackshaft Kit will allow the engine to actualy rev out to a RPM where it can produce it's rated horsepower and also drasticaly improve clutch life. At 225lbs I can do 27mph on flat ground and climb hills the little bike would never of dreamed of with the stock gearing.
This kit is a major upgrade for those of you that want to keep things simple and turn the little bike into something fun that Dad and kid alike can enjoy!
Mini On !
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Strigoi

Strigoi

#4
#4
some people don't want to put on a 6.5 if their kids ride them (which is a good idea). a setup like this is a good way to get a bit more out of the stock setup without having something that is dangerous.
 
delray

delray

Well-Known Member
#5
#5
nice jackshaft set up and all:thumbsup:,but for $134 ship to my door:doah:
your can buy or bidd and a bolt on jackshaft from bmi for less then $25 and buy couple new sprockets real cheap and chain and your set.unless you already have the stuff laying around:smile:like me. save even more$$
i still like it :thumbsup: looks real nice:smile:.........:scooter:
 
ProMod

ProMod

#6
#6
I have also used the stamped steel BMI style jackshaft plate. It works well. The current list price on there website is $65. It comes with #40 sprockets so you have to buy a couple of $10 to $15 #35 sprockets and chain to complete the project. Clutch and chain alignment also had to be set up by making spacers with the ones I messed with. And then there's the bulky plastic cover that falls off or gets broken. The do it yourselfer can save a few bucks going this way and that is great. And I have also seen some of the old yerfdog stock being ebayed for less. But our kit is a direct bolt on for those who do not want to fuss with gathering up all the pieces and hardware. And its CNC machined out of aluminum and has bearings that hold up well. It also comes with pre-cut chains. I have seen problems with the BMI-yerfdog and baja motorsports china made jackshaft setups having bearing failures time and time again. Its kinda a get what you pay for deal. Not putting down your Jackshaft install. It looks great and you did a nice job. Just voicing my opinion about the difference between The BMI and PMR setup.
 
delray

delray

Well-Known Member
#7
#7
yes there was little little spacing between the sprockets. nothing a machine washer couldn't take care and the B sprockets that i use also had two set screws.(martin sprockets under $10 piece)
the jackshaft unit that i have was made by comet. not sure how people where having bearing problems? first to here that? and yes i did have to trim little plastic to fit,but still easy to do:thumbsup: plastic cover design has been around for away and holds up just find,but just like anything that is made out of plastic it will break. probable better then the real cheap factory baja plastic cover. they start to crack real easy around the bolt holes.
and yes i did save some money doing it my self.
still nice product you have:thumbsup:. it will make it real easy for someone that has no clue how to install a bolt on jackshaft.
goodluck on selling you new product........................:scooter:
 
DEUCE

DEUCE

Member
#8
#8
This is way cool.. I was holding off on the 6.5 upgrade on my daughters DB. This may be just the ticket... :thumbsup: And if I am understanding this right, once we do upgrade to the 6.5, we will be able to attach this to the 6.5 clone on the DB.. Right.?
 
TT

TT

#9
#9
Pro Mod,

This group is a bunch of die hard mini bike people. I for one applaude you for being a supporting member and and a paid advertiser!

Ebay will be the place to sell your product line and I really do believe you are on to something. Drilling slots is difficult. My custom Jackshaft in my album cost $120.00 and was worth every penny! I still had to build it bore it and make it conform to the bike>?

My advice is start working on spring loaded tentioners, custom two stage header's, and a bushing to lower the fenders and slams them against the tire for looks. A million doodle bugs and CJTMINI are far ahead... Six posts and a business idea sends out red flags to the peanut gallery.

I wish you success and hope that a group of buyer's are standing by waiting for your next debut...

Do not get discouraged here, these people are brutal and a 6.5 HP complete set up through CJTMINI with the engine, plate, hardware and clutch is $250 and makes more power, certainly not for the daughter's.

TT :thumbsup:


heifhwiiiojhgt94uhjgg mtunv9unv 9t nt9u9jhiotot4jfopjffpeojpe nice! :scooter:
 
Last edited:
tomsprops

tomsprops

Active Member
#10
#10
I like this idea . Great for kids or could be a serious upgrade for the 6.5 ! Flip it's rear sprocket around and I bet your clone will really some Haul Fast Donkey's ! :thumbsup:
 
T

tdishon

New Member
#11
#11
TT,
Custom bolt-on spring loaded tensioners is exactly what everyone needs on the DB-30. I see it brought up every so often, but you nailed it. I'll buy three...
 
Strigoi

Strigoi

#12
#12
chain tensioners aren't needed. just get it set so there is the correct amount of play in the chain and you don't have to worry about it. if you're using cheap chain, you'll just need to check it every once in awhile since it will stretch.

i'm not even running the tensioner on mine anymore.
 
R

Ronald

New Member
#13
#13
At first glance I thought the kit price may be a little on the steep side but after
Taking the time to look at the kit, I can see the quality machine work that
Went into the plate and can’t weight to get my hands on one for both of
my bikes. I’m 215lbs so it takes the 2.8 a ½ mile to get me up to speed down the back
Lane. I can live with a lot less top end if I gain crawling around bush trails
And I can go across grass at walking speed and have throttle response not bog.

My opinion A 10+ product.
 
bucksboysdad

bucksboysdad

New Member
#14
#14
That's a great looking kit, and sounds like it will do a good job improving performance of the little 2.8hp engine. :thumbsup:

So how about offering the members of OldMiniBikes.com a 20% discount to get the word out how good they are? :biggrin:
 
ProMod

ProMod

#15
#15
I agree with Strigoi about chain tensioners. And adding one can cause a constant load on your clutch drum bushing at idle. The bushing will last longer if the proper amount of slack is kept in the chain and the bushing is kept lubed. MX bikes with massive suspension travel dont even use them. Some freeplay without rattling against the guards is good.
 
ProMod

ProMod

#16
#16
Great Idea Bucksboysdad!
I have 11 kits left from the first production run I will sell to OldMiniBikes members at a discounted price of $114 shipped to lower 48st. I was doing some Baja Motorsports warranty repair work in my shop for about two yrs. This kit was something I came up with to ad to my parts inventory after hearing customers whine over how pathetic the doodlebug performed. I installed a few jackshafts using exsisting backplates but ran into some problems I did not like to deal with. Thus this kit was created. And telling a warranty customer they needed to change there engine to achieve a fun level of performance was not an option. Selling them this upgrade kit and keeping the bike kid friendly/dad ridable was. I have sold and installed lots of these kits in my shop with never one unhappy customer.
 
S

SummerSoFar

New Member
#17
#17
ProMod said:
Great Idea Bucksboysdad!
I have 11 kits left from the first production run I will sell to OldMiniBikes members at a discounted price of $114 shipped to lower 48st. I was doing some Baja Motorsports warranty repair work in my shop for about two yrs. This kit was something I came up with to ad to my parts inventory after hearing customers whine over how pathetic the doodlebug performed. I installed a few jackshafts using exsisting backplates but ran into some problems I did not like to deal with. Thus this kit was created. And telling a warranty customer they needed to change there engine to achieve a fun level of performance was not an option. Selling them this upgrade kit and keeping the bike kid friendly/dad ridable was. I have sold and installed lots of these kits in my shop with never one unhappy customer.
Click to expand...
:thumbsup: Getting more tempting... :thumbsup:

Heres what I am looking for, and if your jackshaft kit can provide it, I think you have yourself a deal:

Through significant tuning, I can get the 2.8 going fast enough for a mini, but ANY positive incline and the bike fails. With my weight approx the same as yours, ProMod, what has been your experience with hill climbing improvements? Thanks!
 
tomsprops

tomsprops

Active Member
#19
#19
I'll give one a try ! :thumbsup:
I'm a big TAV Fan ,but on a bd30 and some other frames it's a complete Do -Over ! I Love the TAV2 on my 6.5 but I'm sure I went thru alot more Fabrication than most people have availible to make it work . Some aplications are tight . This could be a neet alternitive ? Without " Modding " a frame ? I'll PM you .



 
ProMod

ProMod

#20
#20
doodlebug performance jackshaft kit

SummerSoFar, After you install the JS kit you can change the gearing very easily by going up or down a tooth on the JS rear chain output sprocket. This is very easy to do and you usualy do not have to cut down or ad any links to the chain. There is enough travel in the motor plate to ajust for it.
You can fine tune the gearing depending on how steep the hills are that you want to climb. Top speed falls off though. I have found that the supplied 13-18 combo works best all around so you should start there. The top speed stays about the same as with the stock gearing but the little motor RPM's allot harder and hill climbing ability is improved. If you go down to a 11 or 12t sprocket you will have a top speed of around 20 and it gets way more peppy on take off. Just don't remove the govenor, only backoff or remove the throttle stop screw. The engine may not live without the govenor.
 
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