Continuous Big Cruncking Noise after Engine Start

[Maverick Lin]

Dear all,
I used the wrong battery instaed of Yuasa half years ago. In the period the small eletricity happened and I got many times of very big single cruncking sound when I pushed the start button. After I replaced into the right Yuasa battery, the big cruncking noise when starting my bike disappeared and my bike ran smoothly everytime I rode it.

Few days ago, the day when I firstly started the engine, a contious big cruncking noise happened. I attached the video for your reference.   And I have checked the follows:

(A) Copper paticles like inside engine oil?...Unloaded all the engine oil and Checked. Nothing found. 

(B) All 4 engine cyliders ingnitted? .....Checked. 4 engine cylinders heats up normally soon after it started.

(C) Engine oil pressure? .....Checked. I reload the engine oil and observed the normal oil pressure and smooth engine oil cycling.

(D) Any sound change when pulling the clutch handler?......Checked. Nothing changes.

(E) Engine easily stars or not...Checked. Easily to start the engine.

Then I used a stethoscope to hear.

I found:  it seems the continuous big cruncking noise comes from the starter clutch side or upper side of the No.3 cylinder or the No.1 cylinder....  

I guess..possibly
1. Starter motor or its sigle way clutch failed
Or 
2.  Engine timing chain loosen

If any suggestion could be available,it would be so appreciated !!

Maverick

 

 

[saddlebum]

Have you checked your valves for a damaged or excessively worn rocker arm. Also you may want to check the starters Sprague clutch. It may have a broken spring allowing the rollers to clatter away.

[Maverick Lin]

Thanks to your suggestions ,Saddlebum ! I will try it. (Maverick)

[Marcarl]

Starter clutch I bet.

[Maverick Lin]

Dear all, 
The reason of the strange crunckind sound was finally found...

Leaking fuel pump together with leaking carburetor made gasoline filled the engine cylinder when engine was in off status. Again when I started the engine,too big inner pressure made the con rod of Cylinder 1and Cylinder 3 bent.....That caused bottom part of piston hitting engine crank case and cracked. And the cruncking sound happened.

[Marcarl]

YEP! that all makes sense. If the starter don't turn the engine over, best to stop and find out why.

[saddlebum]

Wow not pretty at all.