Head Bolts

[K2-K6]

   "Thanks. I have a dry sump system on my 850 Commando, so I know about 'sumping'
This was variations whilst still hot. I'll watch it, but I think it's probably fine."

Yes, worthwhile monitoring as these generally don't do it. Maybe not as strong as "never" to describe, but when healthy and with regular usage its not a risk as they are particularly reliable in that respect, with any significant swings giving cause to investigate further.

[Martin6]

OK, thank you.

I will have another look at the carbs. I used a carb refurb kit when I first got the bike (as it was non-running) from David Silver. I kept the needles, jets and screws the carbs came to me with, so I'll clean them and the carbs and try the old ones again. No idea whether they're original Keihin brass though. I suppose it's possible, but unlike,y after 47 years and 42,000 miles!

I will monitor the oil level carefully. I think it's not wet sumping. I filled the engine about a week before the first run and it stayed at a constant level in the garage. I'd put 1/2 Litre of oil each side of the head (through the rocker covers) and 2L in the tank. The low dipstick reading was the first check, on the first ride after putting the engine back together. So, I just assumed it was low due to the pump filling all the remaining oilways, plus filter. So, it was surprising to see it back to nearly full when I next stopped. That struck me as odd. On the oil change I did yesterday, after filling the tank (2.9L) , it dropped a little when I ran it for 2 minutes, to 75% on the dipstick. I'd guess that was oil filling the filter and sump. I ran it again and it stayed at 75%. So far, so good. Just that first reading on the first ride that's throwing me. I'll keep checking.

[Skoti]

I never fill the oil tank to the max when doing an oil change as the engine oil seems to expand in volume when hot.
Instead of the the 3.5 litres stated on the oil tank sticker, 2.7 litres of oil does mine when changing the oil and filter.
 
When cold mine shows about 85% dipstick level and when up to normal running temp it's about 100% and seldom varies.

But it's been already mentioned that it's no big issue as long as the oil tank level is some where between min and max.
Over filling could cause other problems.

As regards wet sumping mines sometimes does this when parked up over the winter, as a long suffering Commando owner I've a habit of dipping the oil level before each journey...

Hope you manage to iron out the post rebuild issues and enjoy miles of Honda reliability.
 

[Martin6]

Thanks @Skoti.
You may have already seen this, I use it on the Norton, it enables emptying the sump with the small drain plug, without wearing the threads in the crankcase: https://andover-norton.co.uk/en/shop-details/16995/magnetic-crankcase-sump-filter-kit

Yes, 3.5 Litres would also take me over max with the CB750. Not surprising I guess, as we'll never get all the old oil out, without a strip down. My factory manual suggests 2.9Litres as a start point for an oil change, run the engine for 2 minutes, then check the level. I did this and it was fine.

I'm sure I'll get there. I've really enjoyed my post rebuild rides, so I have every incentive to get it sorted. 👍 I'm in my late 50s. These 70s bikes were what I saw as 'the ultimate' as I was growing up, with no prospect of riding them at the time. The Norton and the Honda are still ideal bikes. Both quick enough, but in very different ways, so each is a different riding experience. At least, what I lose in the cost of parts, I save in depreciation and hopefully, at least one of them will be in working order at any one moment!

[Martin6]

OK, thank you.

I will have another look at the carbs. I used a carb refurb kit when I first got the bike (as it was non-running) from David Silver. I kept the needles, jets and screws the carbs came to me with, so I'll clean them and the carbs and try the old ones again. No idea whether they're original Keihin brass though. I suppose it's possible, but unlike,y after 47 years and 42,000 miles!

....

I dusted off the needles and jets I had taken out of my carbs, when I replaced them with the refurbishment kit from David Silver (Keyster branded). I ŵas surprised to see the difference in the profile of the main jet needles. The old ones are a thicker diameter. I assume, at identical height setting, the old needles will allow a lower volume of fuel through, compared to the replacements. I thought this might explain the rich exhaust at open throttle and the bogging down. The jets and emulsion tubes look the same. I left the new jets in and went back to the old (clean) needles and emulsion tubes. Initial runs show an improvement. Must say, if this does solve it, I'm a bit annoyed that something sold as a direct replacement has caused me to chase my tail for 6 months.

When the weather warms up a bit, I'll look at carb balance. I was close on the workbench, but it shows signs of the revs hunting a bit on tickover. I have spare fuel line, can anyone recommend a solution for a remote fuel reservoir? I'd prefer to keep my tank safely out of the way!

[Skoti]

Martin,
You need to renew the needle jets as well, they are a press fit into the carb body under the emulsion tube you refer to.
Just tap them out with a pin punch from the top.

The needles will be worn as well, when compared to new ones you will see the lower part shiny where it enters the needle jet.
 
Genuine Honda needle kit 16012 392 004

I change mine at 12-15000 miles, by that time the consumption has gone up and it'll start almost without choke.

Good luck

Skoti

[Martin6]

Martin,
You need to renew the needle jets as well, they are a press fit into the carb body under the emulsion tube you refer to.
Just tap them out with a pin punch from the top.

The needles will be worn as well, when compared to new ones you will see the lower part shiny where it enters the needle jet.
 
Genuine Honda needle kit 16012 392 004

I change mine at 12-15000 miles, by that time the consumption has gone up and it'll start almost without choke.

Good luck

Skoti

Does that kit work for a K6, do you know?

[Skoti]

Yes,
Listed on CMSNL web site as CB750K6 fitment as well.

[McCabe-Thiele (Ted)]

When the weather warms up a bit, I'll look at carb balance. I was close on the workbench, but it shows signs of the revs hunting a bit on tickover. I have spare fuel line, can anyone recommend a solution for a remote fuel reservoir? I'd prefer to keep my tank safely out of the way!
[/quote]

I bought a small plastic petrol tank off e bay it came with a tap& & pipe for around £12 a couple of years ago. Like below other similar ones on fle bay

https://www.ebay.co.uk/itm/276208145748?hash=item404f49d554:g:mcYAAOSwZ9tlbNIY&amdata=enc%3AAQAIAAAA8CD6Js4CpXVvA3gz1gwA1BJz0x53toQQ6l0zawe8klchV2Yyxq306AtZZJt8slKyqt9CRBks7GvzC4hZIZct%2FSRuIQnYx9aTBrXD%2FlCvVMRtau%2Fqj1nbNpreviuOLEKt3GwfwZEhCAq8f4tbwVwSElS1e0qOb5kRrY82AWe3O4%2B9KUfzWyKeE7uYK0%2BOsPDXy78rUtNbA5DOvvTMzbtL%2BEPFKwozYnbZ1jA0F0kJxtLrm9OU41CXbXF0StOA3KUuXB8s7an%2F7i%2BjhNATO5HmWSyAvP1pio90M6wCdVOdztbcJrbyoOQLYJVf5vXlpNdG0Q%3D%3D%7Ctkp%3ABk9SR5z1yZKkYw

[Johnny4428]

https://www.ebay.co.uk/itm/275326163846?mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338723872&toolid=20006&customid=7XVaJu4bAAAAQYXzERG60rlTZbkhAAAAAA

This is what I have Ted very handy with the hook up facility.

[McCabe-Thiele (Ted)]

https://www.ebay.co.uk/itm/275326163846?mkevt=1&mkcid=1&mkrid=710-53481-19255-0&campid=5338723872&toolid=20006&customid=7XVaJu4bAAAAQYXzERG60rlTZbkhAAAAAA

This is what I have Ted very handy with the hook up facility.

Ideal if you are in a shed or garage with rafters - otherwise an old Hospital drip stand!

[Martin6]

Thank you, ordered the Sealey version, to hook on the rafters. 👍

[taysidedragon]

Thank you, ordered the Sealey version, to hook on the rafters. 👍

I hook mine on the left hand handlebar. Similar height to the bike's tank.

[McCabe-Thiele (Ted)]

Thank you, ordered the Sealey version, to hook on the rafters. 👍

You might need to watch the header tank height as too high might cause the float valves to leak.

[Johnny4428]

Never thought of that Ted. 👍