Noisy engine at low revs

[zacher]

We have some experience in rebuilding the "beast" but could not really solve one problem over the years. That is the noise when the engine is idle. By now, we have two engines, one of them is in great condition, probably the nicest bike in the country (out of less then 10 in total in Hungary). So, the problem is always there when the engine is running at low revs. We had three ideas for the noise:



- the primary chain connecting the crankshaft and the transmission (gears),

- the clutch,

- the carburation is not perfect when idle.



I think that all 3 might be blamed for the noise but we have no idea to what extent.



Does anybody have a suggestion which way to go further?



I read that a later clutch (82 ?) might solve the problem. Is it so?



I was also told by service people in Germany that the primary chain is a "sickness" of all CBX and it is quite normal that the engine is making noise at low revs. Personally, I think that the primary chain is not the best part of the engine. It is not tight enough. Any solution on this?



Thanks for the answers in advance.



Greetings from Budapest, Hungary

[fasterspider]

We have some experience in rebuilding the "beast" but could not really solve one problem over the years. That is the noise when the engine is idle. By now, we have two engines, one of them is in great condition, probably the nicest bike in the country (out of less then 10 in total in Hungary). So, the problem is always there when the engine is running at low revs. We had three ideas for the noise:



- the primary chain connecting the crankshaft and the transmission (gears),

- the clutch,

- the carburation is not perfect when idle.



I think that all 3 might be blamed for the noise but we have no idea to what extent.



Does anybody have a suggestion which way to go further?



I read that a later clutch (82 ?) might solve the problem. Is it so?



I was also told by service people in Germany that the primary chain is a "sickness" of all CBX and it is quite normal that the engine is making noise at low revs. Personally, I think that the primary chain is not the best part of the engine. It is not tight enough. Any solution on this?



Thanks for the answers in advance.



Greetings from Budapest, Hungary

Our motors make alot of noise but you are on the right track with your assessment.

Your primary chain may be stretched beyond limits or it could just be the spring is sagging in the tensioner.

And here is the killer, you need to syncronize those carbs.

Once you have the carbs dialed in, the bike should run fairly smooth even with the loose primary chain.

Boost your idle a little bit to compensate for now but, I would do the carb work needed to smooth out the idle if I were you.

[zacher]

Thanks for the quick answer. I will go Your way and do a proper synchronization.



2 more questions on this:



1. You were not mentioning the clutch. Is there any improvement possible?



2. I was reading a website of an ICOA member (5190) about synchronization. http://www.1980cbx.8m.com/



Is there any other useful source of knowledge which You would recommend?





Thanks

[fasterspider]

Thanks for the quick answer. I will go Your way and do a proper synchronization.



2 more questions on this:



1. You were not mentioning the clutch. Is there any improvement possible?



2. I was reading a website of an ICOA member (5190) about synchronization. http://www.1980cbx.8m.com/



Is there any other useful source of knowledge which You would recommend?





Thanks

What kind of improvment to your clutch?

If the clutch is old, change it out for a new one.

Replace the discs and the steel plates. Also put in heavier springs.

I want a hydrolic clutch like Tom N. has.



The carb sync works wonders on smoothing these motors out.

If she rattles and makes too many noises at 900 rpm where they will idle at, then raise the idle a little bit to smooth it out.

I did that to my X and she idles around 1100 rpm and sounds so much more smooth. I still have a little sync work I could do to mine, but it really is a little too intricate for my shaking hands to get.

I am actually happy as a pig in shit that my bike idles the way it does, I thought I was gonna have to rebuild my motor, but it was just the choke cable sleeve in the wrong place and too big of a valve lash on 8 valves.

I properly adjusted my valve lash and fixed the choke cable and now my bike runs like a Raped Ape.