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New (to me!) '77 CB400F - US model
petermigreen:
As regards foot brake and gear lever if the US variant is different then only in later modes as mine is American and has the standard items
The carb drain screw shouldn’t be too tight that you can’t release it but caution is required as it is brass and soft as doodoo. I’d get a good fitting screwdriver with a shank that will take a spanner and get extra leverage that way or if really stuck maybe get a pair of grips on them and be prepared to replace with new.
The silencer can be brazed but not welded as far too thin but looking at yours I think replacement is probably the best option.
Keep plugging away they require endurance
Peter
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mattsz:
--- Quote from: petermigreen on October 26, 2018, 12:41:05 PM ---As regards foot brake and gear lever if the US variant is different then only in later modes as mine is American and has the standard items
--- End quote ---
Your statement checks out, based on these paragraphs I found on page 42 in the April 2012 issue of your Classic Bike magazine...
--- Quote ---There is some confusion over model designation. Only the CB400F and the CB400F2 came to the UK. The F1 is a USA- and Canada-only model introduced in 1977. The F model is the original 1975 model year machine with Pillion footrests mounted on the swingarm and an unlined fuel tank in either Light Ruby Red or Varnish Blue. For 1976, the pillion footrests were mounted on a loop coming off the rear subframe and the fuel filler gained a lock, but the model was still called the CB400F in the UK and Europe.
Many US F models were modified with higher 'bars, but the 1977 F1 has a single (rear) stay on the front mudguard, slightly higher handlebars, a locking cover to the fuel cap and foot rests re-positioned a little further forward than on the UK and European models. Rare in the UK.
--- End quote ---
Mine matches the latter description...
--- Quote from: petermigreen on October 26, 2018, 12:41:05 PM ---The carb drain screw shouldn’t be too tight that you can’t release it but caution is required as it is brass and soft as doodoo. I’d get a good fitting screwdriver with a shank that will take a spanner and get extra leverage that way or if really stuck maybe get a pair of grips on them and be prepared to replace with new.
--- End quote ---
I think I'll wait until I remove the carbs to proceed. I found a thread here where, IIRC, someone sheared the head off, then broke an easy-out in the remainder, then finally cracked the float bowl while trying to remove that drain screw. So I wondered if it was a common problem, and whether a pre-application of heat and/or penetrating oil might be in order...
K2-K6:
On the carb float bowl screws, the problem appears to be of corrosion between the two metal parts forming a particularly strong bond which ends up similar to the structural integrity.
As you've posted, it can easily go wrong or be all but impossible. Really it's in the realms of experimentation, maybe if you leave them to soak in something like turpentine/paraffin (think that's kerosene over there) for a week or so then get them in an ultrasonic cleaner before attempting to undo them?
They may of course be easy but you never know when they were last removed.
mattsz:
--- Quote from: K2-K6 on October 26, 2018, 03:22:38 PM ---On the carb float bowl screws, the problem appears to be of corrosion between the two metal parts forming a particularly strong bond which ends up similar to the structural integrity.
As you've posted, it can easily go wrong or be all but impossible. Really it's in the realms of experimentation, maybe if you leave them to soak in something like turpentine/paraffin (think that's kerosene over there) for a week or so then get them in an ultrasonic cleaner before attempting to undo them?
They may of course be easy but you never know when they were last removed.
--- End quote ---
This sounds about right.
I'll basically be readying the bike for winter storage; I was told it last ran really well, but that was two years ago. So, I'll focus this winter on making sure the fueling components are in good order, and also the front brake components, since I know they're knackered, so I can try to evaluate the rest - safely - on the road in the spring...
Bryanj:
I will try a basic "how it works"
The piston seal is a square cross section O ring whilst the groove it fits into has a slightly angled base, this means that when the seal is fitted it turns into a "diamond" shape so that only one corner is rubbing on the piston surface.
When the brake is applied the seal "twists" slightly and it is this twist which retracts the piston from the pad. Thus any crap in the groove or on the seal, or tighteness on the piston stops the piston retracting and the brake sticks.
Secondly look at the bracket bolted to the fork with two small bolts at the muguard stay and one big one lower down. The big one has a steel pinthat goes through the swinging part and locates in the top bracket held by the two small bolts, this pivot also gets corroded and the pin pluss hole in the swinging bracket need thourough cleaning and copperslipingso they move very freely. The two bolts you ringed are the ones that split the caliper(no fluid will be lost) the 750 started with bolts you have to undo through the wheel spokes but 550/500/400 do not.
Hope that helps, if in doubt of assembly look at parts book
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