70's Sears (new guy here)

M3ch

New Member
#1
Hey guys, I'm new here. I picked up a 70's Sears and Roebuck minibike I don't know much about it. I picked it up about a month ago for 50 bucks from a guy who just wanted it gone. He said it has sat for "a few years" I took it home poured some fuel down the plug hole and nothing. Pulled the plug and check for spark. It had an intermittent spark. I pulled the cover reset the points to roughly 2 business cards spark returned bright and strong. I replaced the spark plug and tried again, it showed signs of life. I pulled the carb (I wish I would've taken pictures of it) and soaked it in carb cleaner. It was one of the nastiest carbs I have ever worked on. Reassembled the carb and it almost started. While working on it I lost the jet, it fell on the ground and I couldn't find it so I ordered a new carb for it. The carb isn't anything like the original but its stated to be a direct replacement. New carb and a few pulls later it almost wants to start. I've had it idle but as soon as I touched the gas it died. I think the governor may be not adjusted properly and that's the only thing I cannot figure out.

Anyway I plan on doing a swap to a predator 212 although I may be ruining something. What do you guys think? Any advice or suggestions on possible fixes for the old engine?

Once I figure out how to upload pics I will lol
 

Steve73

Well-Known Member
#4
Welcome to the OldMiniBikes. The main mixture screw on the bottom of the float bowl on your carb needs adjusting. When you put the new carb on did you set the mixture screws to factory preset and then start and adjust your carb? Or did you just put the new carb on and tried to start it?

 
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M3ch

New Member
#5
I have set them to factory and tried to adjust from there but it was still doing the same exact thing. It did idle high for a bit but when I gave it gas it just wanted to die right away
 
#6
Nice find , It is ( I believe ) an ARCO , Alexander Reynolds Co. , if you put a Predator on it just keep all the original parts as the bike appears to be a very nice survivor ! I'd get the Tec running and leave it alone !
 

Steve73

Well-Known Member
#7
I assume your air filter is good.. and on installed while adjusting your carb. man I was going thru the exact same situation. I turned my mixture screws to preset and could hardly get the engine to idle. So I set the idle mixture 1st to keep the engine running and then it kept dying when I would give it gas. I kept messing with the main mixture screw by hand while moving the throttle with other hand. Until it was smooth on wide open throttle. You can do it, I believe in you!
 
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#9
I read of your problem before and it had to do with ignition timing. The coil assembly is mounted by two bolts and when loosed, the coil can be rotated a little left and right. I can't remember the exact proper procedure to set it but a search on it might reveal the thread.
You can experiment though to see if it runs any better. Turn the coil counter clockwise to advance the timing and clockwise to retard it. Try one way then the other :)
Also the idle mixture screw on the side of the carb sounds like it could be to lean. Try 1/4 turn counter clockwise at a time to see if you can get it to rev up off idle.
It could be possible you got a "bad" carb. I assume this is an Ebay cheap carb for $10 or $12. They work great when they work but some guys Have gotten bad ones. There is an internal passage with a needle or something that is supposed to be free to move around inside the passage. With the float removed see if you can shake the carb and hear something moving around inside of the carb. If you do, then that needle if free and should be good to go. If you don't hear anything flopping around in there, then the carb might be bad. I don't know if needle is the proper term for what is in there as I never cut one open to see it. I know I spent WAAAAyyyyyyy too many hours trying to get a real Techumseh carb to run right and failed. I bought a cheap Ebay carb and it ran Great. Pissed me off that I spent so many days and hours F-ing with that original carb when a cheapy solved it. Live and learn.
The only thing you might have an issue with is the choke lever arrangement on the cheapy carb. Get one with a long skinny choke arm and you can bend it up, give it a twist and then bend it back over the air cleaner and it will work out just fine. There is an old thread on that lever mod also. Try searching for it. When you see it you will say "Oh yea, that will work"... it is a great idea.

Danford1
 

markus

Well-Known Member
#11
Nice :thumbsup: you dont see the the Sears sold ones all that often. It was a pretty brief period they offered them, should be around a 1974/1975. you'll find engine info numbers either top of the shroud lightly stamped between the head and Head bolts, or on the front of the engine shroud on a little tag. It looks pretty much original, here is the catalog info:

 

Steve73

Well-Known Member
#12
Markus where do you find this info? You must have a library of history material.. and to m3ch, I hope you get this mini. That’s a great deal..
 
#13
what Marcus said.he's the research expert... sears had different mfg. at different times. looks like arco made for sears....they had bird,manco,murry.roper etc....Mick
 

M3ch

New Member
#18
So pretty much everything everyone is suggesting is stuff I have done/tried minus the timing thing. The only thing that I have done as far as the spark related issue was clean and set the points.
The motor is an h30.
As far as the carb goes I did order a brand new one (cheap Chinese) that's pretty solid. I may tackle the original carb one of these days. My main issue is getting this motor running.

On my to-do/buy list is new rear sprocket. New tires if these ones don't hold air. New clutch, new chain, clean the frame good probably with degreaser because the frame is filthy. Maybe I'll try to find some paint and touch it up a bit.
 
#20
I'm not saying you don't have other issues, because troubleshooting from 2000 miles away is impossible.

By adjusting the points and not verifying the timing (inches of piston in the hole BTDC) you have knocked it out of time.

Yes, cleaning the points got you a big blue spark. The manual is on line, and the process is tedious. Here are the procedures, and I've inserted my own words to make it a bit easier.

You need to find TDC, (both valves closed) and using a dial indicator (or something else accurate) set to zero inches. Rock it, or do what you need to do to take up any slop. Set points to .020 gap.

Now back off the piston (Crankshaft CCW when looking at Mag side) until the piston is .065" in the hole. (Watch for slop in rod, etc)

Disconnect all wires from your points. Reconnect nut to points with no wires on it to maintain the points arm tension.

Loosen stator plate bolts, and connect one lead of a continuity light, or ohmmeter to the point terminal and the other lead to a good ground. Rotate the stator until the continuity light or ohmmeter indicates a break in the circuit. Torque down the stator bolts while maintaining the stator plate position and the timing procedure is completed.

Note 1: It is common to run out of stator plate slot room before timing is achieved. If this happens, reduce TDC point gap. I've gone as low at .016 and had it fire fine.

Note 2: Tecumseh 3 to 11 Four Cycle L Head manual is easy to find on line in PDF format.
 
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