Crankshaft Replacement

J

JRMN

Member
#1
#1
I need help replacing the crankshaft in a DoodleBug DB30. The engine is the stock 2.5HP 98cc engine. I used mineral spirits to clean the area around the crankshaft cover. I got the crankshaft cover off without a hitch, but I'm not exactly sure how to get the old crankshaft out and the good used one in. Looking at the good used crankshaft and the bad one inside the engine, everything looks straight forward as far as how it works. However, I just want to ask because I don't want to screw anything up considering I'm not much of a mechanic. What's the best way to proceed from here?

Oh and before I forget, is there some type of timing with this engine? I looked for timing marks and didn't see any.

 
J

JRMN

Member
#4
#4
Ok I got the bad crankshaft off and the good used one on. The first odd thing I noticed was that the bearings slid on and off easily on the bad crankshaft. However, it didn't with the good used crankshaft. Because the original bearing was still attached, I removed the bearing off the good used crankshaft with a hammer. Then I noticed that the crankshaft wasn't lining up correctly so I hammered it back on. Is that normal?

I was so busy keeping track of the nuts, boltss and scews that I didn't take photos of how everything fit. Also when I was pulling the camshaft off I wasn't paying attention and the two little piece fell out. On actually looks longer than the other. Are they supposed to be the same length? If so, which goes where?



Anyway, are these the only 3 parts for the camshaft? I thought I heard something fall but I didn't see anything.



Or am I missing a piece because it's not lining up correctly? Or maybe it has to do with the bearings not sliding on and off easily?

 
old-timer

old-timer

Scamming Member
#5
#5
Those two pieces are your valve lifters . Those need to go back in and then install the cam. Easiest way to do that is turn the motor upside down when installing, in order to keep the lifters from falling out while you slide the cam back in.
 
J

JRMN

Member
#6
#6
Yup got that. Is the camshaft gear supposed to sit up higher than the crankshaft gear? It currently sitting lower, but I thought it sat higher?
 
J

JRMN

Member
#7
#7
Ok, I got the good crankshaft in yesterday. I haven't finished resembling the engine yet. I still have to add oil, tighten the flywheel, connect the fuel tank and cross my fingers and hope I did everything right. lol
 
old-timer

old-timer

Scamming Member
#8
#8
JRMN said:
Ok, I got the good crankshaft in yesterday. I haven't finished resembling the engine yet. I still have to add oil, tighten the flywheel, connect the fuel tank and cross my fingers and hope I did everything right. lol
Click to expand...

:thumbsup::thumbsup::thumbsup:
 
J

JRMN

Member
#9
#9
I finally got the engine reassembled. To my surprise it started up. Although, I am still having the issue with it pulling. I believe it's the idler. Going troubleshoot that issue in my other thread. Thanks for helping me get the crankshaft installed.
 
Txpowdercoater

Txpowdercoater

New Member
#10
#10
see what you accomplished! you tore it apart and rebuilt it! and sounds like you knew very little to nothing about engines, so that being said, I salute you for jumping right in there! Fear not, its just a doodlebug motor, have fun and learn as you go, the same basic technology applies to the bigger engines.
 
old-timer

old-timer

Scamming Member
#11
#11
Congrats on your first motor project :thumbsup:
As Txpowdercoater said, this is how you learn that it's fairly basic and somewhat straight forward. Now next time, you'll know just what to do and how to do it.

Whenever you get stumped, ask questions. The folks here have done it all and are always willing to share their knowledge and help get you on the right track.

Vic
 
J

JRMN

Member
#12
#12
Yeah it was a good experience, couldn’t have done without you all. I did manage to get the chain back on with the extra links that WrenchDad gave me. Now all I have to do is work on a chain tensioner. I will let you all know how I make out when I actually get to drive it.
 
J

JRMN

Member
#14
#14
I believe the clutch was never the issue. After replacing the crankshaft, I started the bike without the clutch and a chain. When I saw the crankshaft spinning, I thought I still had the issue with the bike pulling. However, someone pointing out that the crankshaft is supposed to spin when the engine is running and that the clutch shouldn't engage until a certain rpm is reached. So I put the clutch and the chain back on and started the bike and it didn't move. So the issue with the pulling had to because of the cracked crankshaft.
 
old-timer

old-timer

Scamming Member
#15
#15
JRMN said:
I believe the clutch was never the issue. After replacing the crankshaft, I started the bike without the clutch and a chain. When I saw the crankshaft spinning, I thought I still had the issue with the bike pulling. However, someone pointing out that the crankshaft is supposed to spin when the engine is running and that the clutch shouldn't engage until a certain rpm is reached. So I put the clutch and the chain back on and started the bike and it didn't move. So the issue with the pulling had to because of the cracked crankshaft.
Click to expand...

:thumbsup::thumbsup:
 
You must log in or register to reply here.
Top