Honda CB400F oil & fuel?

[denill]

Can someone kindly advise the best oil for that machine and what octane fuel. TIA.

[Grumph]

Can someone kindly advise the best oil for that machine and what octane fuel. TIA.

They were made to run on swill so 91 will be fine - better than the 89 crap which was current when they came out.
Use a mineral oil around 20/50. OE would have been 20/40 but it's old now and will like 20/50 better.
I use and recommend Spectro oil. Modest price and I've found it good in the older motors - but oil is a very emotive subject....

[FJRider]

As said previously ... 91 will be fine.

Whatever oil you choose ... changing it (and the filter) regularly will be of more benefit than the actual oil used.

[denill]

Thanks guys. Have just purchased a John Silver machine.

[merv]

Thanks guys. Have just purchased a John Silver machine.

What year Bill?

[denill]

What year Bill?

75. It's a minter, except it's got some transmission noise?

[denill]

What year Bill?

Image attached

314290

[HenryDorsetCase]

Thanks guys. Have just purchased a John Silver machine.

You bought that CB400F on tardme for $10k? I thought that was seriously good buying BTW given what they did to them when they were building that batch.

Nicely done.

Its David Silver from David Silver Spares though right?

http://www.davidsilverspares.co.uk/index.php

[IkieBikie]

Had an old CB750 once and ran best on Z 95 octane and I would have thought a semi synthetic 20/50 would be better for an older bike than a mineral oil

[HenryDorsetCase]

75. It's a minter, except it's got some transmission noise?

when they say "they all do that" its actually true about every SOHC Honda I have ever had.... not that many. the noise is likely to be the chain primary drive. It is a multiplex chain driven from the crank centre which in turn drives the gearbox shaft. and honestly, they all are noisy to a greater or lesser extent. Careful carb balance helps.

Unless its an actual gearbox noise in which case all bets are off.

[merv]

Image attached



I was so tempted by the red ones back when they were new, but being a poor student then you would have had to give me a very good discount to buy one, so just stuck to the trail bike.

[denill]

You bought that CB400F on tardme for $10k? I thought that was seriously good buying BTW given what they did to them when they were building that batch.

Nicely done.

Its David Silver from David Silver Spares though right?

http://www.davidsilverspares.co.uk/index.php

Yes, It's 'David' of course.

And I'm afraid it wasn't the buy of century. I swopped my 52 Triumph Trophy that owed me $13,000 plus, lol. But yeah, it's a bloody nice little bike.

[denill]

when they say "they all do that" its actually true about every SOHC Honda I have ever had.... not that many. the noise is likely to be the chain primary drive. It is a multiplex chain driven from the crank centre which in turn drives the gearbox shaft. and honestly, they all are noisy to a greater or lesser extent. Careful carb balance helps.

Unless its an actual gearbox noise in which case all bets are off.

Think you're on to it. It is in all gears, so yeah,it's probably in the primary drive. It is a quite loud 'growl' like sound?

[Trade_nancy]

when they say "they all do that" its actually true about every SOHC Honda I have ever had.... not that many. the noise is likely to be the chain primary drive. It is a multiplex chain driven from the crank centre which in turn drives the gearbox shaft. and honestly, they all are noisy to a greater or lesser extent. Careful carb balance helps.

Unless its an actual gearbox noise in which case all bets are off.

Bang on.
The primary chain noise is often an indicator of slop in the primary chain(s) as the PO is oft reluctant to crack the crankcases open during a an engine "do-up" to replace them. The inboard tensioner unit becomes as hard as concrete and contributes to the din....

[Grumph]

Had an old CB750 once and ran best on Z 95 octane and I would have thought a semi synthetic 20/50 would be better for an older bike than a mineral oil

The 750 does need higher octane, yes. The 400 NO.

If the bottom end is still together on original gaskets etc - as the primary noise would suggest - do not use synthetic or semi synthetic. A lot of period gaskets simply will not resist synthetic oil and give up....Even if the bottom end gets rebuilt, I personally still would not use synthetic. I've just built a 454cc version and the first thing I did was the well known oil pump revision to increase capacity. It will still get run on mineral oil.

[rudolph]

I used to have a 1978 CB400F and a 1977 CB750, I used 96 petrol in them and Spectro 20W50 mineral oil,

the 400 was a little smokey, it had a wine in all the gears and made a nunga nunga nuga knocking / flapping sound at idol that was the primary chain.

[HenryDorsetCase]

I used to have a 1978 CB400F and a 1977 CB750, I used 96 petrol in them and Spectro 20W50 mineral oil,

the 400 was a little smokey, it had a wine in all the gears and made a nunga nunga nuga knocking / flapping sound at idol that was the primary chain.

"flapping sound" at idle could also be the cam chain. the tensioners are notoriously shit especially on the 400. they stop automatically adjusting and the bolts strip out and its a major to fix. Its kind of a horseshoe shaped thing to push on the slack side of the chain but mounted on the front of the engine kinda.

http://forums.sohc4.net/index.php?topic=106661.0