How do I remove the magnet and the crankshaft?

GatorGuy · #1 02-23-2009, 06:16 PM

I have a 69cc (advertised as an 80cc) motor. How do I remove the magnet from the crankshaft screw?

As soon as I can get the magnet off, I can remove the crankshaft and connecting rod (piston rod). I have already removed the clutch side of the crankcase, but the magnet is still on the magneto side of the crankcase and I cannot remove the crankshaft.

Also, there is a bearing/bushing in the crankshaft at the bottom of the connecting rod. How do I get the crankshaft apart to access this bearing/bushing?

I have read Norman's post on engine disassembly, but it does not cover removing the magnet or whether or not the crankshaft and connecting rod can be separated.

GatorGuy · #2 02-24-2009, 07:01 PM

I was able to remove the magnet, but I cannot figure out how to access part number 29 on the included schematic. If you know how to "pull" number 30 and 20 from number 28 I would greatly appreciate any assistance.

robin · #3 02-24-2009, 07:19 PM

you have to get a small wheel puller--thats how i dissassembled mine---today i was talking to spooky tooth cycles order desk and i bought their tool kit which is supposed to have a wheel puller i beleive

robin · #4 02-24-2009, 07:20 PM

you can pull it with 2 bent screwdrivers too

**Norman** · #5 02-26-2009, 05:56 PM

to remove the magnet I use 2 small pry bars that have a 90 degree angle on them or if you have it a small 2 prong puller will work most of the magnets will come off by hand. When I tore my engine down for the posts you will notice I didn't split the crank I have done it but I get ugly with a 12 ton press and heat. Best bet is don't take the crank apart it will be tough to get back together and to run true if you don't have some special tools like a dial indicator and a stand or lathe to mount the crank in to true it. I have not heard of a rod bearing failing on the big end of the crank yet but I'll bet someone has had that happen I just haven't heard about it.

Gatorguy
you are the first one who I know has had a big end rod failure I'm glad to know that the seller is standing behind their product and replacing it for you free of charge
Norman

GatorGuy · #6 02-26-2009, 08:12 PM

Well mine had failed. It is a roller bearing and a few of them have turned sideways. You can spin the connector rod about 3/4 of a turn before it hangs. You can then drag it through the "rough spot" for a 1/4 turn before it frees up again. I am wondering if this was the cause of my original piston failure... Either way, I contacted the company I purchased the engine from, zoombicycles.com, and they are sending me a new crankshaft... Yeah!!! Because of that, I ordered two more engines from them. I think this was just a faulty engine (I hope). Thanks for your help Norman. Your post on disassembling an engine came in quite handy. I have been reading up about proper break-in techniques and will take care to break it in a bit more scientifically.

I am going to put one of my new engines on a Schwinn Delmar Cruiser and another on a trike.

fm2200 · #7 03-26-2009, 10:03 PM

Gator, would you say that the break in period was short lived, or is it fair to say there was hardly any break in period, and that you just rode it as though it was a regular thing to do. I'm only curious about this, I don't mean to sound rudimentary or anything like that. I had friends of mine that rode their motorcycles hard right from the start yet they had no problems at all. It's really hard to determine what causes the burning of bearings, inadequate fuel mixture, improper installation, or just poor quality.

GatorGuy · #8 03-27-2009, 01:22 AM

fm2200,

It's hard to say if it was poor quality. I know I rode it harder than I should have during the (if you cal it that) break in period. I have rebuilt the entire engine (literally- had it in a thousand pieces like the schematic | very cool). I also ordered two more engines. Already installed one of the new engines on my bike and I am 40 miles into the break-in. It seems to be running well, though I have not brought it above 20 yet. First 25 miles were pedaling while holding my clutch and revving at various speeds with the occasional release of the clutch. I have tried not to let it stay at one rpm for more than a few seconds. I am hoping that the first was just a bad engine. Still running at 16:1 until this tank is empty (probably 35-45 more miles) then switching to 24 or 32:1 synthetic.