Drill Starting your HT

Discussion in '2-Stroke Engines' started by pucksterpete, Dec 30, 2010.

  1. pucksterpete

    pucksterpete Member

    Has anyone ever started their HT engine with an electric drill? If so, how well does work and can it cause any harm by starting it this way? I am running a 66cc Grubee w/SBP Jackshaft. Too lazy to pedal on the cold starts. From what I have read pull starts are still too weak. Thanks for the input.


  2. wheelbender6

    wheelbender6 Well-Known Member

    Great idea. They crank Indy cars and dragsters in a similar way.
  3. MikeJ

    MikeJ Member

    This is a yes and no answer.

    Yes, it does work to start the engine. You place a 14 mm socket on the magneto hex nut and with a drill (powering the socket extension), spin it clockwise. BUT... when the engine fires, the engine crankshaft will begin turning a lot faster than the now-dragging 1800 rpm of the driving socket. The end result: the magneto hex nut UNSCREWS itself right off the threads of the magneto crankshaft and will drop out of your socket and go spinning across the floor into some dark crevass in your shop. It happened to me. (Also, be sure to get a no-slop socket fit, else you will round the edges of the 14 mm hex nut. Then you have to purchase some new hex nuts.)

    If someone comes up with a freewheel arrangement like the cassette on the back wheel, he will have himself a unique invention I would seriously consider purchasing. My 2-stroke engined jackshaft bike is a royal pain to start after sitting for a week or better; hence I don't ride it as much as I would like. Being able to start it in a stand in a shop would be worth a reasonable price.

    Last edited: Dec 30, 2010
  4. pineiroadrian

    pineiroadrian New Member

    I don't know if the same applies but what the above post says is why this wouldn't work, what you need is a one way bearing. That way when the engine starts, it can spin freely. I was able to rig up a simple drill start using a one way bearing for one of my nitro Rc trucks. But I dont see how you could do it to one of these engines
  5. pucksterpete

    pucksterpete Member

    I have the same problem, for now I have been using a indoor bike trainer for a stand start. You still have to pedal your a s s off, but not the worry of dealing with it out on the street. They are a pretty penny 'new', but you can find them on craigslist for cheap.

  6. motorpsycho

    motorpsycho Active Member

    man, all i do is coast down my driveway about 10 feet and pop the clutch, no peddling involved.
    but, i don't have a jackshaft and i am unsure of how a jackshaft affects the starting due to the gearing.
  7. MikeJ

    MikeJ Member

    Pineiroadrian -

    So you have the concept in practice? I take it larger versions of that one-way bearing exists. When there is a will, there is a way. If I can get a drill on one side of that bearing and a 14 mm socket on the other side, the rest of the effort is trivial.

  8. Ghost0

    Ghost0 Guest

    I too have done the drill trick on new engines because they are a bear to start the first time. I have yet to lose the mag nut though but I suppose it is possible. I have also heard the newer pull starters are much improved.

    Still having a hard time understanding the difficulty in starting a cold engine though. I can get mine to fire after sitting for 6 months in less than 50 ft. The problem with the cold start is no fuel so what I do is put the choke on full, press the primer button until I see a few bubbles come up the fuel line, this means I am replenishing the empty float bowl. Then she always fires right up. I must say good ignition helps too. Good plug and good plug wire are a must. Although I haven't tried one, Pablo says the NGK iridium decreases the starting time significantly.
  9. pineiroadrian

    pineiroadrian New Member

    yes actually, there are larger versions of that bearing. but the tiny one i use for my rc truck is $25. i already have an idea for a setup that would start these bikes right up without unscrewing the magneto nut.

    look at the below diagram i made :)

    Attached Files:

  10. MikeJ

    MikeJ Member

    Hi Ghost0 -

    Thanks for the words of experience. I admit my difficulties are most likely fuel delivery related, especially during startup efforts. I have to spend some more time on that. Once I get the engine started, I have been known to ride my SBP-jackshaft bike over 100 miles in a given day, repeated no less than eight times.

    Pineiroadrian - Thanks for the drawing. I'm going to have to pursue a duplicate. Imagine... Take this on the road and claim to have an electric starter (ie, small drill). You would have to demonstrate to the non-believers!

    I have been sidetracked with work at a remote site for the past seven months and have been working on another build. I will try posting pictures in a week or so...

  11. MikeJ

    MikeJ Member

    Hi Guys -

    I put one together. . . An electric drill driven one-way clutch starter assembly for the 2-cycle engines. There should be some pictures attached.

    The one-way clutch roller bearing was made by Torrington. I got it from a local industrial parts supply house. It measures 1/2 inch internal diameter, 3/4 inch outside diameter, and about 4/10 of an inch wide. I paid just under $13 for it and out the door I went.

    I cleaned the mating surfaces of all oil and grease and used a small vise to press the bearing into an Ace Hardware shaft collar, 3/4 inch internal diameter and 1 1/4 inch outside diameter. The collar has a setscrew. The bearing purposely gives a tight fit so it will not rotate in the collar. I am surprised they assembled so well.

    The big socket is the cheapest, most beat-up 1 1/4 inch socket I could find. An adapter allows this to be driven by a 3/8 inch shaft. The smaller shaft is driven by the electric drill.

    The bolt was 3 inches long and less than $2 from Ace Hardware. It is .496 inch diameter. Take the one-way clutch bearing with you when testing which bolt best engages the clutch bearing. A .498 inch diameter shaft engages more reliably than a shaft of .496 inch diameter (measured with a micrometer). I cut off excess bolt thread and used a Scotch Brite pad I had to polish the bolt just a bit. A file and an hour of effort can trim down the end of the bolt to 3/8 of an inch square. My bolt is not perfectly square; it is even a little sloppy. Place a layer or two of electrical tape over the end sides before putting on any socket and the socket will stay on without a problem.

    To keep the shaft collar in the large socket, back out the set screw until two threads or so are visible, then press the collar into the socket with a little force. When assembled, the drill will spin the big socket, the collar can't avoid spinning with it, the one-way clutch engages the filed bolt, which drives the smaller socket. (Expect a little wobble when spinning; this is not precision-made equipment.) When the engine starts, the smaller socket and bolt spins fast, and the one-way clutch disengages. Now just slowly pull the starter assembly away from the magneto nut. (I recommend you wear leather-finger gloves from Home Depot to avoid skin injury.) Note there is no hole drilling or thread tapping involved on the starter assembly.

    I am going to cut a hole in the magneto cover to get to the 14 mm nut. Then cover the hole with velcro or tape while the engine is running.

    I have not tried my assembly on my engine yet. But I know the one-way bearing will easily hold 10 ft-lbs of torque, a lot more than necessary to start an engine. I have no doubt it will work just fine.


    Attached Files:

  12. pineiroadrian

    pineiroadrian New Member

    Nice! Did you do this cause of the plans?
  13. MikeJ

    MikeJ Member

    Hi Pineiroadrian -

    Your plans put me on the right track. I just did the leg work: discovering what a "one-way clutch" was, what to mount that in, what to mount that arrangement into (tin can? Hole saw? Socket?), machining items that are not at any hardware store, using common and simple hand tools, and how to secure everything. Almost all of these steps are discoveries along the way. This is fairly typical of producing a prototype of anything. But having a vision of the finished product is the first thing that has to occur.

  14. pineiroadrian

    pineiroadrian New Member

    Let's patent it and start selling them! Whe can make
    Themnpermanent by takin new magneto covers and mounting them on it. Sell as a kit to give all the bike guys out there drill start capable rigs :)

    Wish I still had my bike so I could try this :(
  15. MikeJ

    MikeJ Member

    We could always claim patent pending. But the Chinese government hackers probably have already stolen your concept, sold it to the underworld and will amplify it as a way of starting their own version of the Hummer. If they can get into the U.S. Gummit-all computers, this little web site won't stop them. The U.S. Air Force had a version of this for a long time. They used souped-up Buick 454 cid engines to start the SR-71 engines. They used bigger bearings. . . . .
  16. Pablo

    Pablo Motored Bikes Sponsor

    You guys are great!!
  17. srdavo

    srdavo Active Member

    ditto !!

    be sure the hole seals up good.... If your mag gets wet it won't matter how you try to start it.
  18. goodtime65

    goodtime65 Member

    I tried a drill on a gas scooter and at first it worked fine but the threads ended up stripping
  19. ibdennyak

    ibdennyak Guest

    That's what happened to my last HT... ..worked for a while and then stripped. Wouldn't have been so bad if it was the nut, but the shaft stripped its threads.

    Still be a good idea if the threads could be protected somehow.

    Also, I used a plug for an electrical box to fill the hole...the ones that you use to fill unused holes in junction boxes.
    Last edited by a moderator: Jan 8, 2011
  20. MikeJ

    MikeJ Member

    Hi Goodtime65 and Ibdennyak -

    Thanks for the heads-up. I will have to use a variable speed drill and gradually bring the shaft up to speed. Maybe there is a way to engage the clutch plate using a cut-down large diameter socket to make it kinda resembles a castle nut. Take the clutch plate off and drill mating holes into it around the shaft. Someday I will explore that. . . .