Modified hi-torque starter help needed

[Beck]

I built a 1/5 scale r/c tractor puller. It is powered by a Stihl chain saw engine. To mount it the motor had to be removed from the case which also removed the recoil starter. After trying 2 underpowered attempts at starters I grabbed a used SBC hi-torque starter to modify. I thought it was all ready to go so tried it this am. No luck.

Here is the issue. When I push the start button the starter starts and turns the motor over once or twice. Once the starter comes to full rpm the starter output disingages. The starter motor continues to spin but the output quits spinning. When I let off the start button the starter motor slows down and again the output turns over once or twice.
I removed the arm inside the starter that pushes the drive gear out. I did this because I didn't want my output shaft poping out into the center of my chain saw flywheel. (This the issue?) Since the arm was removed I installed a stiff over length spring to hold the drive gear/shaft in place. The photo shows the removed arm and the stock spring that I replaced.

I have missed something really simple here, but I'm at a loss.

[Beck]

Try this again with a smaller photo.

[Beck]

This is the flywheel of the tractor motor. The orange nylon part plugs into the center of the flywheel.

[Beck]

This is the stock spring and retainer. I replaced this spring with a much heavier and longer one. The one I sinstalled was the max length that I could still compress it enough to install the retainer cup and ring.
The gear and shaft is where this spring installs. This was an attempt to limit the travel of the drive mechanism, since I didn't want it to "punch" against the flywheel when I engaged the starter.

[BFS57]

Hello;
I don't know about your spacific problem, but it might help to go to a hobby shop that has giant scale aircraft to see what exactly they use to start their engines with. What you showed reminded me of an electric starter for a model airplane.

Bruce

[wayne petty]

i am kinda lost...

normal operation is the solenoid plunger pulls in... drives the gear out into the stationary flywheel teeth..  as the teeth are fully engaged the plunger bottoms out and shoves the Disc across the contacts in the cap of the solenoid to send power to the starter windings spinning the starter..

when the key is released from the crank position. the power to the solenoid is released... this allows the return spring under the plunger to disconnect the contacts and then extract the drive gear from the flywheel teeth..

i don't quite understand what you have done... is that a socket on the end of the shaft that engages the flywheel nut to start the engine???



or is your overrunning clutch kicking out... during the attempted start...  so the engine stops turning but the starter motor armature is still spinning..  no drive to the crank...

is the orange device locking onto the crank nut.. to spin the motor.. or does the orange device grab into the teeth inside the bell device held to the flywheel???

there should also be a way to SHIM the back end of the drive gear to reduce or limit the outward stroke...

[Beck]

normal operation is the solenoid plunger pulls in... drives the gear out into the stationary flywheel teeth..  as the teeth are fully engaged the plunger bottoms out and shoves the Disc across the contacts in the cap of the solenoid to send power to the starter windings spinning the starter..

when the key is released from the crank position. the power to the solenoid is released... this allows the return spring under the plunger to disconnect the contacts and then extract the drive gear from the flywheel teeth..

I didn't want the gear to drive out since I don't have to engage any teath. I removed the arm that pushes the gear out. I didn't have to consider engaging the teath. I didn't want the starter to be pushed back (because of the gear pushing out of it) for fear of loosing my grip on the starter handle or pushing the motor/tractor off of the starting surface. I left the solenoid plunger spring in place to return the plunger when removing power.

is that a socket on the end of the shaft that engages the flywheel nut to start the engine??? Is the orange device locking onto the crank nut.. to spin the motor.. or does the orange device grab into the teeth inside the bell device held to the flywheel???

The orange sleeve grabs the raised ribs inside the flyweel. The OD of the orange ring is a slip fit into the center of the flywheel hole. Slots were cut into the orange ring with a Dremel tool to allow insertion into the flywheel. These slots engage the ribs in the center of flywheel to couple the two pieces.

is your overrunning clutch kicking out... during the attempted start...  so the engine stops turning but the starter motor armature is still spinning..  no drive to the crank...

I believe this is exactly the problem

there should also be a way to SHIM the back end of the drive gear to reduce or limit the outward stroke...

That is what I attempted to do with the longer heavier spring. The stroke on the drive gear was reduced to about 1/8 inch.

While trying to get this all sorted out I returned the starter to stock, installing the original spring and the arm.
Now the battery is down. Maybe that was the whole problem. I called it a night and put the battery on the charger. Hopefully I will have time some night this week, but it is doubtful.

Thanks Wayne

[wayne petty]

perhaps this will help..

its a starter drive catalog...

just starter drives...

there are other companies out there who sell them also... sometimes you can get these right from your local alternator shop...   these guys also have the one wire voltage regulators and the 50amp 200PIV diode rectifiers to increase life span in delco alternators..

http://wagneralt.com/images/Cat47.pdf

because of the single piston construction of your engine.. once it starts to fire.. it might be enough to disengage the overrunning clutch rollers and cause your issues..

i don't know which drive yours  takes right now.. (lost my thinking hat earlier today) .. but you might end up needing to increase the tension on the roller engagement springs.. ir possible... there are starter drive rebuilders who might be able to do this for you... if they are in crimped cans..    or you might end up splitting the covers on a lathe to slide each side off.. to get to the rollers.. then figure some way to either screw them to the outer ring.. or TIG/tack weld them back together...

you might also be able to get a starter repair kit.. az stores have a few left in stock... they were slow sellers.. so you will need to talk to the manager or you will get a HUH!!! what..


look at the big headed gears on page 41 and 42... those are almost big enough to drop directly into the bell on the flywheel...

there seem to be 2 clutches for these removable drive gears...

w475-110 and W475-130  on pages 37 and 38


i have never had the reason to tear down one of these units... the clutch might be assembled with snap rings or spirallock rings..

[Beck]

because of the single piston construction of your engine.. once it starts to fire.. it might be enough to disengage the overrunning clutch rollers and cause your issues..

.. but you might end up needing to increase the tension on the roller engagement springs.. if possible...

You were right on the mark about the overrunning clutch disengaging. That is exactly the problem.  I disassembled the starter again and figured out how to take the clutch apart. It is built in the gear that is motor driven. When I took it apart it appeared all the springs were "standing up". They should have been laying flat pushing against the rollers. I stretched each (5) a little bit, but when I compressed them to reinstall it seemed they returned to original length. It was a pain to put back together, but I got it. The clutch is much tighter now.
I want to do a little work on the "push the output gear forward upon engagement" portion. I plan to put a solid sleeve in place of the retracting spring and use a E-clip retainer. Hopefully I will have a little time tomorrow.

[Beck]

I have the starter all back together with the mods. It seems to be working just as I want it to. Tomorrow I put some fuel in that motor and see if I can get it to run. Then a hectic timing adjustment.