DoodleBug Performance Jackshaft
- Thread starter ProMod
- Start date
- Tags doodlebug jackshaft performance
Wow Brad,
That is a nice mod. My 8 yr old son and I just finished his bike (new style DB30) and you put a smile on his face! The acceleration is perfect for that bike and engine. The mod is well thought out and easy to install. (We are going to install the second JS on my other son's old style DB30 when the warranty work is done at Northern Tool). The 2.8 is working effortlessly with the JS. I am a believer in your theory that the 2.8 is a decent engine that was not geared right. Your mod fixes that at less than half the price of a correctly installed 6.5.
Tom
That is a nice mod. My 8 yr old son and I just finished his bike (new style DB30) and you put a smile on his face! The acceleration is perfect for that bike and engine. The mod is well thought out and easy to install. (We are going to install the second JS on my other son's old style DB30 when the warranty work is done at Northern Tool). The 2.8 is working effortlessly with the JS. I am a believer in your theory that the 2.8 is a decent engine that was not geared right. Your mod fixes that at less than half the price of a correctly installed 6.5.
Tom
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Just as a side note, I really think this jack shaft is a good solution for younger kids vs the 6.5. I have a 6.5 that is "throttled down" so the kids can ride it and it is still to fast at the top end. I am guessing that I only have about 3/8 inch of throttle at the handle and it does limit the dangerous bottom acceleration (the wheelie problem) but the top end is still very fast. I can not limit the screw further or it would have no bottom end pick up.
I figure the 6.5 conversion can be done for about $235 to $265 depending on the parts. The kits I am considering are both worth every penny and well priced at $120-$125. With tax at HF you will walk away with a 6.5 anywhere from $106 - $140ish depending on your coupon status AND your trip to HF (mine is 50 mins to 1 hr with traffic) This JS is delivered to your door for about $120 and is even cheaper when you combine shipping for more than one!
I love the 6.5 for me and I am going to HF tonight to try every code in the book to get a 6.5 for the wifey, but to cut the kids loose out of sight with their friends would be kind of scary. Kids can lose judgement in "packs" and the 6.5 could get dangerous fast particularly with "friends" that you do not know well. My 11 year old has been forbidden from riding the 6.5 because I have caught him unscrewing the throttle stop!
wink: Secretly, I had to laugh because it was exactly what I would do as a kid, but he already did an out of control wheelie or 2 on it "by mistake" with one crashing into my 8 yr old's bike)
The 2.8 is a funny engine. There are some bad ones from the factory, but it seems like most of the bad ones are carb problems including self induced problems with bad gas (ethanol). I did take one back to Northern tool with a mechanical knocking (Rod, Bearing, Piston slap, who knows?--its under warranty:thumbsup BUT the 2 that are running are pretty sweet. I am really impressed with the engines. I am in the "Lowcountry" of South Carolina and there are little or no hills. The performance was OK here with no jack shaft. We camp upstate a lot so I knew the JS's were needed. Now that I have one installed I am confident that the JS will add life to the 2.8. I also agree with a poster (I forget who it was) that stated that this jack shaft would be a great fix for project bikes that wanted to use the Harbor Freight 2.5 Lifan engine for the little ones.
It is almost like they should have renamed the "new style" Doodlebug something else and kept both frame styles. The new style fits my 8 year old perfect, but it was a little compressed for my tall gangley 11 year old so he has the "old style". My 8 yr old weighs 60 and my 11 yr old is 100. The js conversion got them both excited and ready for hills, plus it was a great mechanical engineering lesson having them fight to loosen bolts and figure out how to put it all together again.
I can see the scenario where a lot of frustrated parents are going to flood Craigslist soon with out of warranty Christmas Doodlebugs (and their brothers) and I would think this would be a great opportunity for folks to grab up those bikes for cheap and order this jack shaft!
Tom
I figure the 6.5 conversion can be done for about $235 to $265 depending on the parts. The kits I am considering are both worth every penny and well priced at $120-$125. With tax at HF you will walk away with a 6.5 anywhere from $106 - $140ish depending on your coupon status AND your trip to HF (mine is 50 mins to 1 hr with traffic) This JS is delivered to your door for about $120 and is even cheaper when you combine shipping for more than one!
I love the 6.5 for me and I am going to HF tonight to try every code in the book to get a 6.5 for the wifey, but to cut the kids loose out of sight with their friends would be kind of scary. Kids can lose judgement in "packs" and the 6.5 could get dangerous fast particularly with "friends" that you do not know well. My 11 year old has been forbidden from riding the 6.5 because I have caught him unscrewing the throttle stop!
wink: Secretly, I had to laugh because it was exactly what I would do as a kid, but he already did an out of control wheelie or 2 on it "by mistake" with one crashing into my 8 yr old's bike) The 2.8 is a funny engine. There are some bad ones from the factory, but it seems like most of the bad ones are carb problems including self induced problems with bad gas (ethanol). I did take one back to Northern tool with a mechanical knocking (Rod, Bearing, Piston slap, who knows?--its under warranty:thumbsup
BUT the 2 that are running are pretty sweet. I am really impressed with the engines. I am in the "Lowcountry" of South Carolina and there are little or no hills. The performance was OK here with no jack shaft. We camp upstate a lot so I knew the JS's were needed. Now that I have one installed I am confident that the JS will add life to the 2.8. I also agree with a poster (I forget who it was) that stated that this jack shaft would be a great fix for project bikes that wanted to use the Harbor Freight 2.5 Lifan engine for the little ones. It is almost like they should have renamed the "new style" Doodlebug something else and kept both frame styles. The new style fits my 8 year old perfect, but it was a little compressed for my tall gangley 11 year old so he has the "old style". My 8 yr old weighs 60 and my 11 yr old is 100. The js conversion got them both excited and ready for hills, plus it was a great mechanical engineering lesson having them fight to loosen bolts and figure out how to put it all together again.
I can see the scenario where a lot of frustrated parents are going to flood Craigslist soon with out of warranty Christmas Doodlebugs (and their brothers) and I would think this would be a great opportunity for folks to grab up those bikes for cheap and order this jack shaft!
Tom
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We installed the new jackshaft aluminum plate on this brand new doodle bug today it didnt take uch time at all everything went easy as the doodle bug never had gas in it yet everything was brand new lol. We got it all done went to put the gaurds back on and they failed to put the new bolts and spacers in the package with the jackshaft we rode it without the gaurd and its run pretty good for a 97cc mtr
Qudaman:
When removing the new doodle bug clutch to install jackshaft,
How did you remove the stud that screws into the drive shaft?
This has to be removed before the remainder of the clutch can
be pulled, is this correct?
I'm trying to get mine out now with no luck.
Thanks for any help.
afarmer
qudaman
When removing the new doodle bug clutch to install jackshaft,
How did you remove the stud that screws into the drive shaft?
This has to be removed before the remainder of the clutch can
be pulled, is this correct?
I'm trying to get mine out now with no luck.
Thanks for any help.
afarmer
qudaman
outlawsr,
What bolts and spacers were missing in your kit?
If you were missing something feel free to PM me or call our contact number on the website for help.
As far as the JS bolt and spacer kit go...The bolt and spacer kit for the new DB should come with one 8mm by 1.25 allen bolt to retain the bottom of the plastic clutch guard along with a nylon spacer to space it out. (this is shown in the top row of the pic next to the clutch retaining bolt) The top of the plastic cover is retained using the triangle shaped bracket and screw that come on the engine from the factory.
This is detailed in the instructions.
Here is a pic of the hardware kit you should have received.
Here is how the factory bracket is re-used for the top cover mount as per pics and instructions in kit.
afarmer,
The threaded stud on the end of the crank is actually part of the crankshaft and not removable. (don't know why they did this??) Your clutch assembly should come off with the removal of the nut and washer. If it's stuck it's more than likely due to thread locking compound on the crank. Use of a gear puller and maybe a little heat will make the job easy if it's stuck. If you use a puller,Thread the special nut supplied in the kit back on the crank stud and push on it with the puller so you don't wreck the threads or mushroom the stud. It should only take a small amount of pressure with the puller. If you have to pull to hard something else is wrong and you may wreck the clutch. Clean up the clutch bore and crank good after getting it apart so you can slide the clutch on and off the crank with ease. This will make it easy to remove when servicing the clutch later.
What bolts and spacers were missing in your kit?
If you were missing something feel free to PM me or call our contact number on the website for help.
As far as the JS bolt and spacer kit go...The bolt and spacer kit for the new DB should come with one 8mm by 1.25 allen bolt to retain the bottom of the plastic clutch guard along with a nylon spacer to space it out. (this is shown in the top row of the pic next to the clutch retaining bolt) The top of the plastic cover is retained using the triangle shaped bracket and screw that come on the engine from the factory.
This is detailed in the instructions.
Here is a pic of the hardware kit you should have received.
Here is how the factory bracket is re-used for the top cover mount as per pics and instructions in kit.
afarmer,
The threaded stud on the end of the crank is actually part of the crankshaft and not removable. (don't know why they did this??) Your clutch assembly should come off with the removal of the nut and washer. If it's stuck it's more than likely due to thread locking compound on the crank. Use of a gear puller and maybe a little heat will make the job easy if it's stuck. If you use a puller,Thread the special nut supplied in the kit back on the crank stud and push on it with the puller so you don't wreck the threads or mushroom the stud. It should only take a small amount of pressure with the puller. If you have to pull to hard something else is wrong and you may wreck the clutch. Clean up the clutch bore and crank good after getting it apart so you can slide the clutch on and off the crank with ease. This will make it easy to remove when servicing the clutch later.
ProMod
Thanks for the help. I did finally figure this out for myself this afternoon
once I took the engine into the sunlight. After that, the jackshaft installation
was easy. Good kit. Sell a lot of them before Baja sees the light.
Now I guess I'll go get that eye test the wife tells me that I need.
Thanks for the help. I did finally figure this out for myself this afternoon
once I took the engine into the sunlight. After that, the jackshaft installation
was easy. Good kit. Sell a lot of them before Baja sees the light.
Now I guess I'll go get that eye test the wife tells me that I need.
I really think the jackshaft is a great idea, but for that price i'll just turn the throttle stop screw on the clone damn neer all the way when my 8 year old cousin rides my bike. If it was 60 bucks I would deffinetley jump on it, but by the time I get it shipped up here to Canada I may as well buy a clone for $100 and a clutch for $50.
I would like to suggest that any one interested in comparing the JS 2.8 mod to the 6.5 engine swap should go back a few pages to read what I wrote on 12-8-10.
We sell kits to install the larger engine as well as the JS systems which can be used on both applications. They both improve the bike but have different purposes.
As stated before it is my opinion that the 6.5 install is a great mod and allot of fun but not a good starting point for new riders.
And as far as the 6.5 goes, Turning in the throttle stop screw does not make the bike suddenly kid friendly. The actual throttle opening is more so controlled by the governor.
Even with the throttle screw ran all the way in the governor may still apply full throttle off idle under a load. Any one who does not believe this is how it works should watch the actual throttle shaft at work on the carb as they hold the brake and twist the handle bar grip a little. There are ways around this of coarse. But it's not a simple turn of a screw.
The 6.5 still has allot of take off torque which is the problem. Especially for a light rider. These engines and there governor controls were really designed for steady state RPM operation. In which case a small amount of throttle grip twist may result in full throttle below the governors set RPM limit. You can play with Gov springs, longer throttle screws and linkage what nots to try to tame the thing down. But you must also consider that the clutch requires a certain amount of spool up RPM to get engaged which may cause a new set of problems.
I realize some kids are more likely to learn faster than others and also may have ample experience and be responsible enough to handle a high powered mini bike, But some are likely to stay out of trouble more than others too.... Things to think about....Heck if my Dad would have brought me home a 6.5hp powered DB at age 10 I probably would have wired the governor spring with a bread bag tie when he wasn't looking and proceeded to harass the neighborhood at eye watering speeds. My Son learned how to ride on an old traditional mini bike. He later graduated to taking his thrill seeking to the MX track on a KX60 at age 10.
We still kept the old mini bike around for years, I taught allot of neighborhood kids how to ride with it, My son and his friends still had many a good time with it even though it was not his race machine. It was nice to know he would not attempt to do some of the things on the minibike that he did on the racetrack as the little 3hp engine was just enough to keep them entertained and out of trouble. It had it's purpose and gave us allot of enjoyment through the years.
We sell kits to install the larger engine as well as the JS systems which can be used on both applications. They both improve the bike but have different purposes.
As stated before it is my opinion that the 6.5 install is a great mod and allot of fun but not a good starting point for new riders.
And as far as the 6.5 goes, Turning in the throttle stop screw does not make the bike suddenly kid friendly. The actual throttle opening is more so controlled by the governor.
Even with the throttle screw ran all the way in the governor may still apply full throttle off idle under a load. Any one who does not believe this is how it works should watch the actual throttle shaft at work on the carb as they hold the brake and twist the handle bar grip a little. There are ways around this of coarse. But it's not a simple turn of a screw.
The 6.5 still has allot of take off torque which is the problem. Especially for a light rider. These engines and there governor controls were really designed for steady state RPM operation. In which case a small amount of throttle grip twist may result in full throttle below the governors set RPM limit. You can play with Gov springs, longer throttle screws and linkage what nots to try to tame the thing down. But you must also consider that the clutch requires a certain amount of spool up RPM to get engaged which may cause a new set of problems.
I realize some kids are more likely to learn faster than others and also may have ample experience and be responsible enough to handle a high powered mini bike, But some are likely to stay out of trouble more than others too.... Things to think about....Heck if my Dad would have brought me home a 6.5hp powered DB at age 10 I probably would have wired the governor spring with a bread bag tie when he wasn't looking and proceeded to harass the neighborhood at eye watering speeds. My Son learned how to ride on an old traditional mini bike. He later graduated to taking his thrill seeking to the MX track on a KX60 at age 10.
We still kept the old mini bike around for years, I taught allot of neighborhood kids how to ride with it, My son and his friends still had many a good time with it even though it was not his race machine. It was nice to know he would not attempt to do some of the things on the minibike that he did on the racetrack as the little 3hp engine was just enough to keep them entertained and out of trouble. It had it's purpose and gave us allot of enjoyment through the years.
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^Well said ProMod^. As a parent I can relate to what you are saying.
I have both setups...a DB with a 6.5 clone (for myself) and a 2.8 powered DB for my 11 year old with a promod J/S kit.
They are apples and oranges. It's really not about getting the most power for the money, rather more about tailor suiting the bike to the rider as I see it. She is not ready to ride flat-out on mine and her's is still a bit under powered for me (I weight 225) and I'm fine with that.
For an a teen or adult, the 6.5 is the best way to go with no doubt.
But for younger riders it seems many here forget that the 2.8 once geared and tuned properly can run decent enough to keep up with a 6.5 when there is a 100 lb+ weight difference between riders, at least for cruising around. While at the same time not as touchy or over powered as a 6.5 with 100 lb rider.
The way I see it, this J/S kit simply gears the 2.8 properly making it fun and ridable as it should have been out of the box. Simple 20 minute install and you are ready to roll with what feels like a different bike. Do a few more simple mods as well - throttle limiter, tire pressures, drill the muffler if desired and now the 2.8 with a 100 lb rider it is plenty fast enough for casual riding.
Later, when the kid is older wiser and heavier, the same J/S kit used on the 2.8 can then be re-used on with a new engine upgrade using it to fine tune the gearing on a future build.
To me, for those not ready for a 6.5 DB, this promod J/S is the best money spent to make your kid's 2.8 run like it should :thumbsup:.
I have both setups...a DB with a 6.5 clone (for myself) and a 2.8 powered DB for my 11 year old with a promod J/S kit.
They are apples and oranges. It's really not about getting the most power for the money, rather more about tailor suiting the bike to the rider as I see it. She is not ready to ride flat-out on mine and her's is still a bit under powered for me (I weight 225) and I'm fine with that.
For an a teen or adult, the 6.5 is the best way to go with no doubt.
But for younger riders it seems many here forget that the 2.8 once geared and tuned properly can run decent enough to keep up with a 6.5 when there is a 100 lb+ weight difference between riders, at least for cruising around. While at the same time not as touchy or over powered as a 6.5 with 100 lb rider.
The way I see it, this J/S kit simply gears the 2.8 properly making it fun and ridable as it should have been out of the box. Simple 20 minute install and you are ready to roll with what feels like a different bike. Do a few more simple mods as well - throttle limiter, tire pressures, drill the muffler if desired and now the 2.8 with a 100 lb rider it is plenty fast enough for casual riding.
Later, when the kid is older wiser and heavier, the same J/S kit used on the 2.8 can then be re-used on with a new engine upgrade using it to fine tune the gearing on a future build.
To me, for those not ready for a 6.5 DB, this promod J/S is the best money spent to make your kid's 2.8 run like it should :thumbsup:.
I ordered the JS kit last night. I was going to head to HF and buy the 6.5 clone, but decided the JS kit was likely the better choice for my kids right now. I will upgrade to the 6.5 sometime in the future.
I have also been reading about maximizing the potential of the 2.8 engine. I am trying to order the carb kit as well. But my real question is should I upgrade the clutch if I am using the jack shaft kit? If so, what clutch is recommended for use with the kit?
Thanks for the advice for a newbie.
I have also been reading about maximizing the potential of the 2.8 engine. I am trying to order the carb kit as well. But my real question is should I upgrade the clutch if I am using the jack shaft kit? If so, what clutch is recommended for use with the kit?
Thanks for the advice for a newbie.
Question on the jackshaft Kit.
I've tryed finding the answer myself going back and reading older posts
but no help. So Sorry if this question has been answered.
Doe the jackshaft Kit come with a chain Guard ?? I saw the kit didn't have it,
so where does this guard come from.
Guard covering the clutch and JS. ???? :shrug:
Thanks..
I've tryed finding the answer myself going back and reading older posts
but no help. So Sorry if this question has been answered.
Doe the jackshaft Kit come with a chain Guard ?? I saw the kit didn't have it,
so where does this guard come from.
Guard covering the clutch and JS. ???? :shrug:
Thanks..