bicycle engine tear down

Egor

New Member
Jan 30, 2008
714
0
0
Hurricane Utah
Norman, what do you think of that engine? I have one like it from Kings. The reason I am asking is that I see it is a one piece crank, in that the flywheel weights do not come off. All the other engines I have the part that goes out over the bearings is attached with three screw's, I am thinking that the engine like yours vibrates more! On the other engine there are hollow places near the big end to compensate for the extra weight, that engine doesn't care. Have fun, Dave
 

Attachments

Norman

LORD VADER Moderator
Staff member
Jan 16, 2008
2,605
2
38
67
pampa texas
The engine with the bolt on weights have came apart( weights coming off) so I should not have to worry about that on mine. You could balance any crank by drilling it but I'm not worried about it, mine seems to vibrate at idle and runs good when under power. I'm happy with it so far. These engines are in my opinion, the bottom of the barrel rejects, but they are fun and cheap.
Just right for a motor assisted bicycle not meant to be a moped or motorcycle.
Norman
 

Egor

New Member
Jan 30, 2008
714
0
0
Hurricane Utah
10/4 that is what I think also. I have the one like yours in a Schwinn cruiser, the avatar. That bike has the most vibration but it has the worst mounts also. I have the diamond frame bike with a Dax engine and that has the removable weights, also the best mounts but still not the best for smooth. The bike I call the Green Hornet is as smooth as a good motorcycle also a Dax, I am thinking the mounting is an important factor, I am going to do an extra plate to pick up the bottom of the engine on one of the bikes to see if it helps. Working for Honda years ago there was a problem with the MT250 the motor mount was in a bad place and would crack and then would just about tear the bike to pieces welding was not good, the metal was so brittle it would just crack again, very hard to fix. Thanks for being a good sounding board, if I talk things through I solve the problem. These engines are a good place to relieve tension. I have not had a problem with the weights coming loose yet. Have fun, Dave
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,813
209
63
up north now
I found the diamond frames to be smoother running between itself and the cruiser type, coincedence?

I think it has to do with frame geometry and tube wall thickness/diameter.
 

Egor

New Member
Jan 30, 2008
714
0
0
Hurricane Utah
Look at the (Moon Dog), my Green Hornet, I think that is what it is called, from W Mart. The reason I am saying this is that the frame is so small the engine just fits. I needed to take the top end off and had to take out the studs to get it off with-ought taking the engine out. What I am thinking is that, it being so small that it has strength! I used one of those flat plates to hold the engine in the front, I don't like them, but it is still smooth running. I would like to exchange the engine from the Schwinn but I don't want to mess up the paint, I would like to see if my idea is correct. Have fun, Dave
 

Bikeguy Joe

Godfather of Motorized Bicycles
Jan 8, 2008
11,813
209
63
up north now
Your right Dave, smaller opening/stiffer frame.

Funny thing is, I looked at the Moon Dog today at W-Mart, and the frame is completely different...it's more of a "schwinn type" without the dip like the (older) Moon Dog has.
 

Egor

New Member
Jan 30, 2008
714
0
0
Hurricane Utah
Yea, I was over there today also and noticed the bars are not reversed any more. The next bike I want to make, I want to try and put an engine on a full suspension bike. I want to try and put it out in front of the frame completely and use the top of the engine and the rear of the engine for a mount. If I use a steel frame I can weld on it, I need to change the fork angle to get a little more room. Ill keep you posted. Have fun, Dave
PS: I am in Utah now and all the bikes they have at W mart are under 100 bucks, that Moon Dog is 89.oo.
 

sailor49618

New Member
Mar 29, 2008
5
0
0
New to this.
I have a 70cc 2 cycle and bought a pull start for it but cannot get the nut and washer off the shaft in front of the magento because it keep's turning,tried holding the gear's but still turn's?
It's a little different from the look's of you're photo's or if you know somebody that could help me.
Thank you.

sailor49618

[email protected]
 

Norman

LORD VADER Moderator
Staff member
Jan 16, 2008
2,605
2
38
67
pampa texas
take off the clutch cover and as you trun the nut on the mag side you can take a shop rag and let it jam in the gears of the clutch side. It will stop the crank in its tracks and will do the same thing when you put the nut back on just stick the rag in the gears and it will lock it up don't stick your fingers in there with it or you will learn all kinds of new cuss words and all the neigbhors will too.
 

Down_South

New Member
Aug 28, 2008
140
0
0
North Carolina
I'm having trouble removing the little gear on the clutch side of the engine, I have the special tool, but it pulled the threads right off the tool! I'm stuck, tools are too expensive to break so easily. Should I whip out the blow torch and hammer?
 

Norman

LORD VADER Moderator
Staff member
Jan 16, 2008
2,605
2
38
67
pampa texas
that is something you are going to have to decide for your self I'd try to get another puller and make sure its threaded all the way on use anti seize on the threads of the puller and the gear.
you might be able to use a torch and hammer its not going to be pretty you have a seal behind the gear and you might destroy it getting western on it.
Norman
 

Norman

LORD VADER Moderator
Staff member
Jan 16, 2008
2,605
2
38
67
pampa texas
make your self a big screw driver blade out of flat steel stock grind it to fit the slot precisely and if you can heat treat the blades tip(google heat treating steel DIYS) its not going to be easy if you don't have the right tools. If you live in a town that has harbor freight you can get an impact driver/remover that you use with a hammer they are not expensive about $10.00 some auto parts stores or cycle shops might sell them. You can lock up the gears with a rag so the gears don't spin while your trying to turn the screw off so don't take all the gears or nuts completely off until you have all fasteners loose holding on the gears and the sprocket.
Norman
 

Denver Dave

New Member
May 26, 2009
30
0
0
Queen City of the Plains
Howdy Norman,

I'm looking at post #3 of this thread where you are using the sprocket puller to remove the outer bearing race.

I have my engine completely torn down, and all of the nuts and bolts holding it together are out, but when I went to pull this part off, my tool stripped. From looking at diagrams, it appears I can (carefully) pound out the clutch shaft from the other side (where the drive sprocket was).

Is there anything mechanically holding this in preventing me from doing so? Thanks!
 

baja221

New Member
Jul 28, 2009
1
0
0
so-cal
Re: total tear down

after removing the nut and lock washer pull the clutch off with the puller. Well greased isn't it the clutch didn't slip so the grease was not getting on the pads

magnet holding the key. can't see them but there is 2 shims on the shaft and what a nasty thing.
when using the puller how do you keep the middle part from just spinning?
great thread by the way
 

Norman

LORD VADER Moderator
Staff member
Jan 16, 2008
2,605
2
38
67
pampa texas
you hold the outer puller with a wrench and turn the inner part of the puller with a wrench. You have to use both hands and 2 wrenches.
Norman
 

Matheneyr3

Member
Jun 4, 2009
100
0
16
Carolinas
Wow-Thanks!

Awesome post, and pics as an added bonus.
Just followed along with you to change out the seals on my little moondog project- and I found it invaluable to refer to...Thanks again, after finding that both of my crankshaft seals were rather...unseated, sorta. One of them had sheared into two seperate seals, and the other had simply pulled away from the seat.
Great to have your assistance on this one! I'm sure that I'm not the only Homebuilder to refer to you for help.
Richard- Orange Moondog- 29mph uphill cruise-Afterwards.
 

aspireonescs

New Member
Jan 4, 2010
64
0
0
34
Saint Marys county, Maryland
Re: total tear down

after removing the nut and lock washer pull the clutch off with the puller. Well greased isn't it the clutch didn't slip so the grease was not getting on the pads

magnet holding the key. can't see them but there is 2 shims on the shaft and what a nasty thing.
norm, for the life of me i cant figure out how to get the nut off the clutch so i can remove the big gear. every socket i have fits the nut but wont fit in the space between the nut and big gear? aalllthoughthe sparkplug tool that came with my engine is the right size for the nut, i again have the same problem as the socket. it wont fit in the space, i was thinking that i could sand the tool down a bit so it will fit in the space, but how do you keep the sproket on the drive side from turning when you are removing the big gear? what tools/ sizes did you you use? thanks in advance :)
- steven