• Don't overlook our Welcome Package, it contains many links to important and helpful information about functions at VHT like posting pictures and sending PMs (private messages), as well as finding the parts you need.

    AD

1972 CL350 New Engine Refresh - Acceptable Noise Level?

davidevoss

davidevoss

Veteran Member
Joined
Feb 22, 2022
Total Posts
216
Total likes
41
Location
Dallas, Texas, USA
You probably thought you were through with me for a while but I need some advice. I have a newly refreshed engine on my 1972 CL350 - new rings, new valves (lapped in by me), new cam chain, new cam chain roller and rubber, new gaskets, new seals and most recently new carburetor boot gaskets installed with Hondabond (on both sides of gaskets). While I was doing the carb boot gaskets I took the opportunity to readjust the cam chain tensioner and readjust the valve gap to a snug 0.002 and 0.004 gap all according to the FSM.

Here's the problem - I'm an old guy and I wear hearing aids and they are extremely sensitive to certain noises - especially high pitch metallic sounds. With my hearing aids off the engine sounds pretty quiet and tight with a little valve "tapping" similar to what I experience with the mid-60s push rod Hondas I have rebuilt. However, with my hearing aids on - and with videos taken with my I-Phone the engine sounds extremely loud - like the valve are way off or the timing chain is slapping. Therefore, I have taken a video with sound of the engine at idle and would like someone with younger and better ears to let me know if this engine is alright or not.

Probably a pretty weird request but thanks in advance for listening.

Here is the YouTube link to the video:


David Voss
 
Being taught that tight valves burn and loose valves only lack power, as well as the saying, "slappy valves are happy valves", a little noise can be a good thing. I'm a novice noise interpreter though.
 
I'll be interested to hear what the pro's say about this one.

I have a CB350 that I believe has got 2000 original miles on it and has never been touched since it left the Honda factory. When I got it a few months back the rocker noise was almost non detectable, in fact the lack of mechanical engine noise was night and day compared to what it sounded like 'after' I did the adjustments. Perhaps Honda set the clearances closer at the factory to allow for initial wear?

Anyway mine now sounds like yours. Thanks for posting that.
 
A few thoughts here:

1) glad the Hondabond worked out

2) it’s an old bike, you’re never “done” and we never expect you to take off forever - cue “one of us one of us” chant

3) the iPhones pick up high pitched sounds better than low, much like your hearing aids, it makes these YouTube videos a little tough to work with.

4) if you’ve adjusted many a valve in your day, don’t sweat it, your feel is probably better than we can diagnose over the inter webs.

5) did you adjust the cam chain tensioner at 90 degrees past TDC for the left cylinder’s compression stroke? The old FSM said at TDC, but the correct (purple cover) FSM for your bike says it should be 90 degrees past.

6) nice looking bike.


-Ed
1972 CL350
1985 VF700F
 
The engine sounds good and this listening to it with Cochlear Implants. Your hearing aids as mentioned amplify high frequencies, by design. That's where most hearing loss takes place so the programming for them is biased in that direction.
You can try using a mechanics stethoscope w/o your hearing aids and that will probably help with picking out the light ticking noise from the valves that I hear. You can actually tell which valve is looser than the others by sound with experience. I still have and use the feel in my fingertips on running engines to check valves, does get a bit hot doing that though.
 
LongDistanceRider said:
The engine sounds good and this listening to it with Cochlear Implants. Your hearing aids as mentioned amplify high frequencies, by design. That's where most hearing loss takes place so the programming for them is biased in that direction.
You can try using a mechanics stethoscope w/o your hearing aids and that will probably help with picking out the light ticking noise from the valves that I hear. You can actually tell which valve is looser than the others by sound with experience. I still have and use the feel in my fingertips on running engines to check valves, does get a bit hot doing that though.
Click to expand...

Please expand on the finger method. My finger goes exactly where on the engine? I want to practice the fine art of 'clearance by touch' method too!

Also, do you buy into the 'by ear method' when done by an experienced ear? I know it is a controversial method but...
 
ausman1000 said:
Please expand on the finger method. My finger goes exactly where on the engine? I want to practice the fine art of 'clearance by touch' method too!

Also, do you buy into the 'by ear method' when done by an experienced ear? I know it is a controversial method but...
Click to expand...
If you have sensitive finger pads you simply lightly touch the head as close to the valve location and feel for the tap, it's best used for looser than spec valves.
The fine art of listening is also used as a check. The sound is best described as a "snick" vs a "tap". But this again is purely a check. No noise means tight valves and a louder tap means loose.
The only way to practice these check methods is after you've adjusted the valves, some at spec and some .001"-.002" loose, to the best of you ability and then feel/listen to the differences between them. Of course this means another cool down to cold and reset the loose ones to spec.
Don't feel bad if you can't feel or hear the differences, it's all in sensitivity and not everyone can do it.
 
ballbearian said:
Being taught that tight valves burn and loose valves only lack power, as well as the saying, "slappy valves are happy valves", a little noise can be a good thing. I'm a novice noise interpreter though.
Click to expand...
Thanks ballbearian. I have always been a "snug" not "tight" guy on valve adjustments.
 
ausman1000 said:
I'll be interested to hear what the pro's say about this one.

I have a CB350 that I believe has got 2000 original miles on it and has never been touched since it left the Honda factory. When I got it a few months back the rocker noise was almost non detectable, in fact the lack of mechanical engine noise was night and day compared to what it sounded like 'after' I did the adjustments. Perhaps Honda set the clearances closer at the factory to allow for initial wear?

Anyway mine now sounds like yours. Thanks for posting that.
Click to expand...

Thanks ausman1000. Good to know that someone else's sounds like mine.
 
Thanks Ed.
1. The Hondabond worked out perfectly - no more "chirping" from the carburetor boots.
2. "one of us... one of us" - that makes me feel at home! You are right about never being done but we don't choose these bikes because they are easy it's because they are awesome.
3. A video taken on my iphone sounded terrible - just like my hearing aids. The video I posted was off of a Cannon digital camera and sounded completely different.
4. I have adjusted many valves over the years - street cars, race cars and small motorcycles. I have a lot of confidence on setting a valve to spec and as I responded to ballbearian I tend to be a "snug" but not "tight" guy.
5. I did adjust the cam tensioner by the Purple Cover FSM method - left intake valve open then closed, then to LT, then 90 degrees past LT (all counterclockwise). While I was there with the tank and carburetors off I removed the cam tensioner, inspected it's operation, reinstalled it (compressed and locked down), then released the adjustment bolt and could hear it "slap" back into place. I think I got this right!?!
6. Thanks for the compliment. Like I have said before it's a rider not a show bike but it looks pretty good driving by at 60 miles an hour in the dark.
Thank you for your continuing help!
 
LongDistanceRider said:
The engine sounds good and this listening to it with Cochlear Implants. Your hearing aids as mentioned amplify high frequencies, by design. That's where most hearing loss takes place so the programming for them is biased in that direction.
You can try using a mechanics stethoscope w/o your hearing aids and that will probably help with picking out the light ticking noise from the valves that I hear. You can actually tell which valve is looser than the others by sound with experience. I still have and use the feel in my fingertips on running engines to check valves, does get a bit hot doing that though.
Click to expand...

Thanks Jim. I am glad to know that you think it sounds good. I probably need to do all of my engine listening without my hearing aids in. I used to use a tube in my ear to locate engine noises and even to synchronize twin SU carburetors on old MGs (maybe that's why I have hearing aids now). However,, it seems like with this 350 engine it's really difficult to pinpoint the source of the sound in the top end. Of course this is the first Honda Twin I have ever worked on so maybe I just need more experience.
Thanks for your help.
 
davidevoss said:
Thanks Jim. I am glad to know that you think it sounds good. I probably need to do all of my engine listening without my hearing aids in. I used to use a tube in my ear to locate engine noises and even to synchronize twin SU carburetors on old MGs (maybe that's why I have hearing aids now). However,, it seems like with this 350 engine it's really difficult to pinpoint the source of the sound in the top end. Of course this is the first Honda Twin I have ever worked on so maybe I just need more experience.
Thanks for your help.
Click to expand...
Oh, you had to bring up SU carbs didn't you.:lol: Next up is Strangleburg carbs, aka Stromberg.(n)
 
ancientdad said:
LOL... so you're saying the old 3 deuces manifolds with 3 Strombergs on them, umm, sucked? And here all that bench racing talk of Stromberg carbs back in the day must have just been urban legend...
Click to expand...

I was referring to the side draft Strangleburg CD carbs used mainly by Triumph and Rover but with emission laws all the Brit cars went to them. SU's are very basic gas passers, you tune them by changing the needles which aren't a straight taper but a wavy taper. I used to have a book covering every needle, well over 700 variants. I still have the "special" synchronizing tools :lol::lol: which is essentially 2 wires you drop into the tops and measure the height of each piston.
 
DSC03510.jpg

I modified my feeler gauges as shown and get better results when setting the clearances. I use a pair of forceps clamped to the feeler gauge for the intakes.
 
David, personally I think I hear one tick that is a little louder than usual, but with the way most videos seem to accentuate the high pitched sounds it would have to heard in person to truly verify. Either way it's a small thing and is unlikely to be a problem. And best I can tell the cam chain sounds like it's properly adjusted too.
 
ancientdad said:
David, personally I think I hear one tick that is a little louder than usual, but with the way most videos seem to accentuate the high pitched sounds it would have to heard in person to truly verify. Either way it's a small thing and is unlikely to be a problem. And best I can tell the cam chain sounds like it's properly adjusted too.
Click to expand...

ancientdad: Thanks for the review and advice! I think I'll just ride it for now and get 100 miles or so on it then change the oil and reset the valve clearance again.
 
davidevoss said:
ancientdad: Thanks for the review and advice! I think I'll just ride it for now and get 100 miles or so on it then change the oil and reset the valve clearance again.
Click to expand...

If any of the rocker arms are dished a bit from wear it will be more difficult to get the clearance right, but to repair the problem requires pulling the engine and disassembling the top end. Ride it and see how things go with a watchful ear for any change in top end sounds.
 
ancientdad said:
If any of the rocker arms are dished a bit from wear it will be more difficult to get the clearance right, but to repair the problem requires pulling the engine and disassembling the top end. Ride it and see how things go with a watchful ear for any change in top end sounds.
Click to expand...

Will do. Thanks.
 
davidevoss said:
Well this is my first 350 so I don't know what it's supposed to sound like - but "an old sewing machine" is one way to describe it! Ha!
Click to expand...

I've said this several times. It's like that old parable about 4 blind men feeling a different part of an elephant and each coming to different conclusions about what an elephant looks like.
 
Update on 1972 CL350 engine noise. I put 100 miles (over 10 or 15 trips/heat cycles) on the refreshed motor (at under 5k rpm) and then changed the oil to get rid of the assembly lube, grease and oil use to put it together. I readjusted the valve lash with new improved (cheaply made but effective) feeler gauges to a snug .002 and .004. Here is what the engine sounds like now:

I think it's much improved. Thanks for all of the help and best regards, David
 
Last edited:
Other than sounding like it's idling about 1500 rpm or so, possibly higher (certainly a bit on the high side), it sounds good and certainly better than it previously did. Tach cable looks pretty hideous though :)
 
ancientdad said:
Other than sounding like it's idling about 1500 rpm or so, possibly higher (certainly a bit on the high side), it sounds good and certainly better than it previously did. Tach cable looks pretty hideous though :)
Click to expand...
Yes, I need to go through the carburetor adjustment procedure again and that will sort out the idle. The tach cable is pretty ugly and on the list for replacement but it actually works - surprise, surprise! Thanks for your help. David
 
LongDistanceRider said:
The shield looks so much better than when I sent it.
Click to expand...
A little sandblasting, hammering, straightening and painting did help. I am still searching and collecting to get a set of chrome shields some day but there's a limit to what I will spend. Chrome shields don't stop me from enjoying every minute I spend on this bike! :)
 
davidevoss said:
A little sandblasting, hammering, straightening and painting did help. I am still searching and collecting to get a set of chrome shields some day but there's a limit to what I will spend. Chrome shields don't stop me from enjoying every minute I spend on this bike! :)
Click to expand...

Are y'all talking about the black exhaust shields? If so, looks pretty spiffy in black.
 
You must log in or register to reply here.
Back
Top Bottom