New (to me!) '77 CB400F - US model

[mattsz]

I think I'm ready to try and start it up!  Should I use my small auxiliary fuel tank, or better to install the proper tank and use a decent amount of fuel?

[Bryanj]

If you have bench synced the carbs properly fit the big tank and ride it round for the 500 miles till first service then vaccume sync after checking everything else

[mattsz]

Thanks Bryan!  I did my best to follow your bench-sync instructions - I presume I did it correctly, as the instructions seem very clear and it's not a difficult job.

I haven't done major open-engine work, so I don't think there's a particular 500 mile service to do, but if it runs and seems ok, I'll definitely ride it and keep an eye on things!

What I did do (relevant to engine running):

• Removed and opened up the carb float chambers (I didn't separate the bodies from the rack), removed all the floats, jets, etc and cleaned everything as best I could without access to an ultrasonic cleaner.  Reassembled and adjusted the choke mechanism so the plates moved together and the lever bumps the throttle linkage per manual specs.  Reinstalled carbs using rubbers that aren't as soft as they could be, but I was still able to use them with effort.  I tested the float valve function with the carbs on the bike: all four bowls filled with fuel, and over the next hour they didn't leak or overflow a drop.  I don't know if the fuel levels are correct, but I did measure and adjust the float heights to spec (21mm per Honda manual) on the bench.
  
  
• Fresh oil and new oil filter.
  
  
• Checked and adjusted the static timing - I found the points a bit pitted, so I ordered new (aftermarket - I know!) points and condensers, which didn't even fit, so I ended up returning them and reusing what I had, after cleaning up the points contacts a bit.
  
  
• I examined the function of all the cam chain tensioner bits - they appear to be doing something, so I set it with the engine not running using the Bryanj method. http://www.sohc.co.uk/index.php/topic,1784.msg3029.html#msg3029
  
  
• Checked and adjusted the valve clearances.
  
  
• New plugs.
  
  
• Cleaned and de-rusted the fuel tank - it really was in pretty good shape, but there was a little minor surface rusting, so I decided to take care of it.  I also installed a new petcock/filter.
  
  
• You may recall there was some, ahh... discussion... about some compression test results being quite low, but uniformly so.  Gotta start somewhere, so I'm not worrying about that for the moment.

If it runs, I'll do the usual checks - listen for strange noises (not like I'd know which noises are strange!), check for uniformly heating exhaust pipes, look for smokey exhaust... any other "first-run-after-sitting-for-a-few-years" things to keep an eye out for?

[Bryanj]

I would still do a 500 service as its been sttod and what you have in now will, hopefully, collect any unwanted stuff and put it in filter and/or sump

[mattsz]

I would still do a 500 service as its been sttod and what you have in now will, hopefully, collect any unwanted stuff and put it in filter and/or sump

Gotcha!

Anything I've missed I should be watching/listening for when I try to run it?

[mattsz]

A few recent photos - I forgot the mirrors!

[taysidedragon]

Looking good. 👍

[AndyD]

Matt,
Bike looks great - hope it runs as well as it looks when you push the button.
 
Cheers,
Andy

[Nurse Julie]

Nice to see it out in the sun Matt, enjoy.

[mattsz]

Thanks guys!

I took it for a spin around the block, and gradually expanded my range to about a 20 mile ride the other day.  Since using the manual adjusting rig, the cam chain noise didn't get any worse in those 20 miles.  I briefly touched 8K rpms during the ride, no drama.  It does make a public statement spinning up there, though, doesn't it?

It runs pretty well; it doesn't like to start moving in 1st gear with anything less than about 3000 rpm, but maybe that's normal for these small, high-revving engines?  I'm used to my newer daily rider which has plenty of low-end torque.  Plus, while the clutch pull has improved a lot in those 20 miles (getting the plates well-oiled after years?), it's still not what I would call an easy pull, so maybe I'm not able to finesse it the way I should be able to.  But once under way, the throttle seems well adjusted throughout the rpm range.  The throttle grip is also more difficult to turn, and to hold, than I'm used to, but I think that's down to the spring action of four older carbs vs two newer ones.

The brake lever action feels very good.  It just doesn't slow the bike all that well, which I've been told to expect - all four fingers on the lever and a good kick at the rear pedal does a pretty good imitation of a quick stop, but cruising along with two fingers covering the front lever doesn't quite cut it!

I finally got the new shocks sorted, so I hope to get a longer ride in today if the weather holds (looking very cloudy at the moment).  I'll keep an eye out for smoke from the exhaust, of which I saw a little bit at idle during one of my stationary test starts.

You may recall my run of very low - but uniform and consistent - compression tests... the conclusion was that it could be all four chambers were badly compromised - or that my testing tool/method was inaccurate.  I never got any result above 100psi.  If the bike is running reasonably well, does it seem likely that the compression isn't as bad as my test indicated?  What symptoms should I be keeping an eye out for?

[taysidedragon]

The only obvious sign of low compression would be a lack of power and lower top speed.
From your description it seems to be running ok.

[mattsz]

You, sir, should be asleep!

But... thanks!

[Bryanj]

Add inability ti idle at a normal revs

[taysidedragon]

You, sir, should be asleep!

But... thanks!

😊 I'm a night owl. Not a morning person! 😉

[mattsz]

Hi guys - it's been awhile!

I've got the bike out of storage and back on the road... it's where I left it last autumn... starts well, idles well, stumbles mightily when pulling away from a standstill unless I rev it up to 3k-5k rpm as I slowly ease out the clutch... once underway it pulls well through all the gears and normal rev range.  I'm actually quite happy with how it runs... except for that stumbling.

When I cleaned and bench-synched the carbs, I set the pilot screws to two turns out which seems to work well for the most part, other than the above - I followed some advice here and tried screwing the screws in 1/4 turn... which didn't seem to make a difference.  Any other thoughts?