cb400-four speed.

[Mikep328]

The red ones were far more reliable; the additional speed from the yellow ones compromised engine integrity!








OK...that's not true of course...

[K2-K6]

Thanks Tricky Mick for the seat info.  I managed to undo the lock and open the seat.   The air Filter looks brand new, so I will have to investigate further.
If the weather holds today I will try some further tests.  I have compared the speedo with a Sat-Nav and they are within 2 mph of each other.

Mine is a Red bike, but I have several litres of JCB Yellow Paint, if all else fails. . . !

Something that may need double checking, some years ago I had a honda that had stood for a while, that air filter looked new, but just would not flow properly, giving rich mixture and "capped" power output.
Whether it had been damp and possibly compromised, or something else that I couldn't readily explain, the result was clear and when swapped it was fine.

Tenuous link, but a possibility to consider.

[Athame57]

The red ones were far more reliable; the additional speed from the yellow ones compromised engine integrity!

OK...that's not true of course...

But is true that the yellow ones are faster, after all Dave told us so! 

[exvalvesetdabbler]

Mine is red and an indicated  110 was regularly achievable in the 80s with my girlfriend on the bach.  It was dead flat where we lived, long straight roads and no traffic.

Not sure if I would be brave enough now. Too many other idiots on the road.

The local bobby only had a hilman advenger so the best he could do was tell my dad in the pub on a Friday darts night.

That was more of a deterrent than being brought before the magistrate.

 Dave

[scifi]

Well after looking at the air filter beneath the seat, I removed the air cleaner top lid and went for another test ride.
This time 70 came up after about 1/4 mile straight, with more to come.
I found that the air intake was masked by the seat, as the following photo may show..
The bit between the screwdrivers is the only bit not obscured by the seat....

[ Guests cannot view attachments ]

[Bryanj]

Something not fitting right there

[TrickyMicky]

If you have the standard seat, are all the rubber spacers fitted as per the photo? These keep the seat base clear of the air intake. If the seat has been allowewd to settle too low, this could also be why the lock jammed.

[scifi]

Thanks Tricky Micky, my seat does not have those 4 rubbers, or anywhere to put them.  So it looks as if I will have to run with the filter uncovered.
Got a new seat lock on order, from China, should be here by end of the month.

[McCabe-Thiele (Ted)]

My 400 has a type of plastic seat base not steel.

I don't know if it's original or not.

[TrickyMicky]

Original ones are steel, Ted. Even the new reproduction ones from DSS have a steel base.

[McCabe-Thiele (Ted)]

Original ones are steel, Ted. Even the new reproduction ones from DSS have a steel base.

On the upside it will not rot away, it has the rubber buffers, the seat hinge and catch work so I assumed it was original. 👍

[Bryanj]

DS first "pattern" seats were plastic based and tended to rock a bit front to back, i have an unused one somewhere for a 500

[Laverda Dave]

If you fit a pattern seat from DSS make sure the hinge and seat lock brackets are in the correct place, mine were miles out to the extent the front of the seat was so far forward when I fitted the hinges it fouled on the back of the fuel tank with big rucks in the cover. I sent the first seat back and the replacement still needed the seat lock and the hinge plate modifying to elongate the mounting holes by 8mm to fit properly.
To be fair to DSS though he accepted the original seat back despite me adding the Honda logo on the back using a stencil so I can't complain and he was very fair about it.