Big and small bevel gear alignment

[Toby woodman]

My engine makes a fairly loud consistent mechanical grinding noise when idling. It sounds like some gears are not meshing properly. When I took the clutch cover off I was a bit concerned as the bevel gears were out of alignment. Is this normal. I am fairly new to these motorised bikes.

 

[Toby woodman]

Is it normal to be able to hear the clutch/other noises while the engine is idling

 

[Gordy]

Honestly, I don't know. I run a bt80. It has a cyntifugal clutch, so only the crank and clutch shoes are spinning at idle.

 

[Street Ryderz]

Unfor

View attachment 190270My engine makes a fairly loud consistent mechanical grinding noise when idling. It sounds like some gears are not meshing properly. When I took the clutch cover off I was a bit concerned as the bevel gears were out of alignment. Is this normal. I am fairly new to these motorised bikes.

Unfortunately yes that's quite normal for them to be misaligned, and yes you hear the them!
The best way of fixing this is to chuck the crank in a lathe and cut the tapper back and elongate the wood ruff key slot so that the faces of the gears are flush, nothing can be done about the mesh and if the crank is badly untrue it will slowly grind away the bevel gear teeth.

 

[Toby woodman]

Sounds a bit out of my skill range. Thanks for the help

 

[zean]

Street Ryderz excellent explanation will fix the problem (not only the symptom).

I saw a different point of view to fix that issue (I don’t know how to post videos) on YouTube. It is: Fred Corrects Drive Gear Wobble Problem on Half-breed Engine by Fred Chelminski of CR Machine.

One person on this website also suggested to heat up the drive gear and cool the engine to install the gear being careful not to hit the crank seal.

Fred essentially loosens the small bevel then taps it straight with a hammer retightens and checks wobble then repeats until straightened out. Make sure after you remove bolt and washer that the crank is not standing proud of the gear or else the screw won’t make contact with the gear and seat it against the crank taper.

If you remove that small bevel gear you have to look behind the gear when re-installing and hold the key with curved needle nose or whatever and check close that the key is fitted correctly.

I just read this stuff right now then wrote it down. I’m not trying to come off like I know this off the top of my head.

 

[DAMIEN1307]

I saw a different point of view to fix that issue (I don’t know how to post videos) on YouTube. It is: Fred Corrects Drive Gear Wobble Problem on Half-breed Engine by Fred Chelminski of CR Machine.

Is this the video your referring to???


View: https://www.youtube.com/watch?v=d3xmY8Ce0gk

 

[zean]

Yes. Back in the day Fred at CR Machine was highly respected. I believe he invented (amongst other things) the CNC head with the large cooling fins that was later copied.

 

[DAMIEN1307]

(I don’t know how to post videos)

All you need to do is simply do a copy and paste with your mouse cursor.

All I did was go to this video on youtube, highlight and then right click with the mouse to copy what it says on the browser address bar for that particular video, come back to the forum and just right click a paste with the mouse to post your videos.

 

[zean]

Thank you Moderator DAMIEN 1307 for posting the video and the instructions both. When I get a lull in the action I will follow what you said to the letter.