[Jelly Bolagnuts]

1972 CB 175

1,900 miles

Fresh gas and oil

The bike is running well (starts right up, steady idle, pulls in each gear) but I'm getting some engine noise from the front clutch side of the engine. Another post described their problem as sounding like a "little tractor" which is spot on. It's a steady "clicking" at idle (1,200 rpm) but seems to "smooth out" upon revs. I've read to look into cam chain tension as well as valve/tappet clearance. Considering the milage, could it be as simple as oil type? I've been told "It's just old" but under 2,000 miles and garage kept...?

Any help is greatly appreciated, thanks!

 

[J-T]

Not the oil. If you have a stethoscope you can determine which part of the engine it it coming from. You can also hold the handle of a screwdriver (preferably a long one) to your ear and move the other end around the engine.

 

[Jelly Bolagnuts]

I'll give that a try and see if I can pin point the location. I'll try to post a recording of the engine running as well.

 

[Jelly Bolagnuts]

Thanks J-T. The screw driver tip helped.

The tapping noise is definitely coming from the behind the alternator cover so It would seem like a valve adjustment. I'm also hearing some high octave "shhhhh/hiss" from behind the breaker point cover. Both noises are noticeable up close if you have ok hearing. Has anyone heard similar noises/symptoms from a small twin or vintage Honda?

Thanks dudes.

ps: I'll try to get that recording up soon.

 

[ancientdad]

Just to be sure, the alternator cover is down on the left side of the crankshaft (large round 3 screw cover with Honda embossed in it). The valve noise would be coming from the top end of the engine near the points cover, and the hissing sound is really quite common and usually just the cam chain.

 

[Jelly Bolagnuts]

Just to be sure, the alternator cover is down on the left side of the crankshaft (large round 3 screw cover with Honda embossed in it). The valve noise would be coming from the top end

The noise is coming from behind the alternator cover as far as i can tell. What do you think is going on? Good to know that one noise is normal.

I read during valve adjustment to take off the alternator cover and align the rotor with its index pointer so i guess i jumped to conclusions thinking the noise coming from that area would be valve related.

 

[ancientdad]

I read during valve adjustment to take off the alternator cover and align the rotor with its index pointer so i guess i jumped to conclusions thinking the noise coming from that area would be valve related.

You have to turn the crankshaft there, yes, but the valves are in the top end of the engine and if too loose, the noises would be coming from that area. It's really hard to say what noise you're hearing without a video (and that might not be conclusive either). Hearing it in person is always best

 

[phil71]

If it sat for that long, maybe the starter chain is rusty as hell? Is there fresh oil in the thing?

 

[Jelly Bolagnuts]

If it sat for that long, maybe the starter chain is rusty as hell? Is there fresh oil in the thing?

Fresh oil. I had the cover off and didn't see any obstructions or wear around the alternator rotor. As for the chain, i couldn't get a good view but i might dive into that tomorrow.

I'll get a recording up soon. I added a few ounces oil after putting the cover back on and the noise seemed quieter but It might just be me.

 

[Jelly Bolagnuts]

Here is a link to a recording of the noise.

[video]https://drive.google.com/file/d/0B067KUyGPzXWMFIySGxDYmdPVmR6YWFjbEJYdEtROTAyM1gw/view?usp=sharing[/video]

 

[Jelly Bolagnuts]

Does that sound familiar to anyone? It's pretty subtle so hopefully nothing severe.

I took the covers off to check out the starter chain and sprockets. Everything looked fine. The chain was lubed up and showed no signs of wear or stretch. All of the gear teeth looked perfect. I'll have to get a new gasket for the starter drive cover. Some of those screw heads for the covers softened like butter so it did require an impact wrench.

 

[slofut]

Does it make the noise with the cover off? Definitely a pulsed noise, not a smooth rotational noise like a bearing (though it could still be if there's a bearing surface involved) but like something is touching in one spot per revolution. Run it with the cover off and see if there's something obvious?

 

[Jelly Bolagnuts]

Does it make the noise with the cover off?

I did start it up with just the dynamo cover off the other day and I didn't hear it or notice anything strange. It's hard to get up really close because there is oil in that area that will fling out when you start the engine. I used a piece of cardboard to get as close as possible but didn't hear it. To any inexperienced readers, if you have the cover off don't stick your face down there and tell your buddy to fire it up. There are no dents in the dynamo cover that would obstruct but the seal was shot. I didn't see any signs of wear/tapping on the inside either. I ordered a couple different seals today. Maybe a new OEM seal and the screws tightened at even torque will make a difference.