'77 CB400F - it runs!

[mattsz]

See subject heading...

First start - fired right up on the second button press, with a barely-there puff of smoke - not surprising, as there was oil in the cylinders.  All 4 cylinders heated up quickly and uniformly.  No obvious oil leaks, yet.  With a bit of juggling choke lever and idle screw, I quickly got it down to a steady 1200 rpm idle with the choke off.

The front end sounds very rattly - is this a loose timing chain?  I know it's hard to hear sometimes on a video, but I've posted a couple.  Would you guys check them out and give me some opinions?

The first one is the start video (because I had to!), just over 1 minute long.  It ran until I shut off the choke and it stalled:

https://youtu.be/PoMMEqoxnK0

The second video is a shorter (about 25 second) "running" video to highlight the noise. It's running without the choke at this point:

https://youtu.be/fzLM4dWA_lE

[Nurse Julie]

Sounds like cam chain rattle. Well done for all your work so far, it's great to hear it running.

[mattsz]

Sounds like cam chain rattle. Well done for all your work so far, it's great to hear it running.

To be honest, I'm shocked it went so smoothly!  But I'm not there yet!

I tried to adjust the cam chain tension using Bryanj's method of "putting pressure on the [crank] so that the engine is just about to turn but not quite turning."  I don't know if I did it right, or if the adjuster isn't working correctly.  Any advice on how to proceed?  Dare I follow Honda's recommendation and let it adjust itself while the engine is running?

[Nurse Julie]

Sounds like cam chain rattle. Well done for all your work so far, it's great to hear it running.

To be honest, I'm shocked it went so smoothly!  But I'm not there yet!

I tried to adjust the cam chain tension using Bryanj's method of "putting pressure on the [crank] so that the engine is just about to turn but not quite turning."  I don't know if I did it right, or if the adjuster isn't working correctly.  Any advice on how to proceed?  Dare I follow Honda's recommendation and let it adjust itself while the engine is running?

Yes, I would have a go Hondas way. If it doesn't make any difference to the rattle, it would diagnose either a cam chain stretched well beyond spec or a seized horse shoe pivot, or even both.

[mattsz]

Thanks Julie!

I did investigate the function of the tensioner based on the advice of another forum member.  I did get some results, but I never got an answer as to whether my results were normal.  If you wouldn't mind, would you take a few minutes and read this short post and the three which follow it to see what was suggested, and my results?

http://www.sohc.co.uk/index.php/topic,17461.msg205855.html#msg205855

[Nurse Julie]

Nigels method and your result proves there is a little movement but it does not prove if the chain is beyond spec, or if the horse shoe has minimal movement before it seizes.

[mattsz]

Nigels method and your result proves there is a little movement but it does not prove if the chain is beyond spec, or if the horse shoe has minimal movement before it seizes.

True.  I was hoping to hear from Nigel about whether he thought the amount of movement I discovered was ok or not.  No matter now... my attempts at Bryanj's adjustment method didn't have a satisfactory result, and I just tried Honda's simple "idle the engine and loosen the adjustment bolt" technique which didn't change anything.

Worth trying to adjust the tension by removing the upper bolt and pushing on the plunger by hand?

[mattsz]

When I ran it again just now, it still started and ran well, but I had some steady whitish smoke out the exhaust this time... and a surprising amount of water dripping out of the joint between the silencer and header collector - no wonder they rust out!

Should I not take it out on the road with that rattle?

[Nurse Julie]

You will get condensation unless you ride the bike and get it hot enough to dry the steam out. My personal view, others may disagree, I wouldn't ride the bike with the chain rattling like that. Others may take a risk at a ride up the road but whether you choose to or not, that chain and adjuster need replacing.

[mattsz]

You will get condensation unless you ride the bike and get it hot enough to dry the steam out. My personal view, others may disagree, I wouldn't ride the bike with the chain rattling like that. Others may take a risk at a ride up the road but whether you choose to or not, that chain and adjuster need replacing.

Understood.  By way of investigation, I'm tempted to try manually adjusting the tension by accessing the pushrod through the opening just above the proper adjustment bolts.  If I do, can I try it with the engine running, or will removing that upper bolt spray oil out?  It looks to me like that's open to the unpressurized crank case, so oil shouldn't be a concern...

[Bryanj]

I admit my method takes practice but it does work, oil will not spray out of that plug you talk about but i will lay odd you will burn several bits of yourself on the exhaust

[mattsz]

I admit my method takes practice but it does work, oil will not spray out of that plug you talk about but i will lay odd you will burn several bits of yourself on the exhaust

I will not take that bet... 

[taysidedragon]

Wear protective gloves if working near hot exhaust headers. The one time I didn't bother, "I'll be careful,  it'll be fine" , i thought, and ........

[mattsz]

Ouch!  thanks for the reminder...

[AndyD]

Gareth,
Looks familiar!!!
When I finally got the 400 running the other week I was so keen to just sit on it I forgot that wearing shorts isn't a great idea near a piping hot exhaust - nice burn to remind me next time!
Cheers,
Andy