Oil pressure issue / motor rebuild

[MrDavo]

Thanks Ash, though do check the thread for the ignition stud. While I realise they should not be taken as an authority on compatability, one crank DK had was listed for  CB750K 1970-77, another they have is listed as only for a K6. Confusingly, according to John Wyatt's book, F1 comes in at 1976, so does K6, so there could be a change to something around then, it certainly needs checking out.

If it will fit, I'd certainly take you up on your offer, subject to what carnage I uncover, if you have a few rods I'm sure we could pick one out with the same / similar weight code letter, I can print out the Honda service bulletin (which you may have put online) saying which rod goes with what.

[AshimotoK0]

I had to nip home at lunch as the missus is away and I thought I had left the steam iron switched on  , so I checked my cranks. It's defo got the 8mm thread same as the other one ... so over to Trigger  , the F1 engine was one with the more domed 392 pistons.... Thinking about it, I may have a couple or more of it's original rods. Bryan is correct, when the big ends go the shells move in the rods and scuff the surface... it happened on my K0 engine. Are you in Yorks or Lancs?

You don't want the con-rod that I caught the wife using as a litle hammer to hang a picture hook 

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[Trigger]

I did show you that the cranks are different Ash, so how they are the same part number is only something that MR Honda can explain

[royhall]

The F2 crank appears to have the same part number as well but I'm sure they are unique to the F2?

[AshimotoK0]

I did show you that the cranks are different Ash, so how they are the same part number is only something that MR Honda can explain

But mine both have the M8 thread on points side ..so are they OK for the early bikes?

[AshimotoK0]

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[Greebo]

I had the braded hoses made when doing the rebuild.

Click image Link to enlarge

[MrDavo]

Very neat Greebo, they look like the ones I have now. A mechanic I do work for tells me I could have had mine made up by a local firm using my ends.

My original kinked pipe looks more like the 'molded' one in Ash's service bulletin, the bend they put in it is where it kinked. Unfortunately the feed pipe is the one that's hidden behind the return hose and oil tank - it's something everyone should check at least once.

Once bitten twice shy, as Ian Hunter said.

I've been in touch with Ash, it looks like his F2 crank will fit OK and we can look in his parts box for a matching rod (assuming only one is fubar). Can I split the cases to get the crank out without disturbing the clutch, gears and gearbox sprocket, or does it all have to come out so I can get the crank free of the primary chains? I'm guessing so.

[K2-K6]

It's easiest to have the cases upside down,  lift the gearbox mainshaft with clutch up and withdraw it from the primary chains, the you can put the mainshaft back in if you want to. The crank is then easy to lift it out, I wouldn't try to thread the crank through the chains while they are still round the gearbox shaft and don't think it'll go anyway.

[MrDavo]

Thanks, that just what I wanted to hear, it means I don't have to dismantle the gearbox, clutch, selectors, sprocket etc unless I need to.

[hairygit]

Thanks, that just what I wanted to hear, it means I don't have to dismantle the gearbox, clutch, selectors, sprocket etc unless I need to.

That could prove a false economy. Personally I would totally strip the cases, and check all the oilways are flushed through and blown through with compressed air, seeing as you found metallic filings and nasties in the oil you drained. Think hard about it, do you want the possibility of having to do it all again and more for the sake of not completely stripping it now?

[Trigger]

When you get that far, you may as well do the chains and look at the chain tensioners, rebuild the oil pump and so on.

[AshimotoK0]

They are money pits to rebuild properly agreed. It's an  F1 crank I have BTW not F2. One way of getting it to you safely would be to ask my mate as he goes on Sunday, at least twice a month,  buying his mobile phone parts from a wholesaler in Manchester. You are always welcome here though. As I said, I also have a really nice early gearbox inc primary drive. Also a large box of gears but of unknown condition.

[MrDavo]

I'll see where I'm at when I've got it in bits, I take the point that it all wants to come out for a good clean. From experience I'm very aware of 'mission creep', I don't want to get carried away if I can help it.

From the external condition, and the lack of mechanical noise (other than the death rattle when hot!), I think the motor had been rebuilt when the bike was restored, so I'm hoping that most of it will be good. I checked the oil pump out at the weekend, it all looked OK. I could do with fixing the wet sumping though, Trigger you said on the other oil pressure thread that you do the stopper kit yes?

Another 'while I'm in there' job will be to fit the heavy steel 'case protector' around the drive sporcket, which is absent - anyone got one?

@ Ash, your mate might be a good way to go, but I need to see what rod(s) I'll need first, in the hope that you have one (or more) the right grade to make a matching set. I'll fit new shells and mains after miking all the journals up, that doesn't look to be a cheap undertaking.

Any recommendations on gasket sets? some don't have all the O rings, yamiya do one at great cost, but I'm sure good quality.

[Trigger]

I'll see where I'm at when I've got it in bits, I take the point that it all wants to come out for a good clean. From experience I'm very aware of 'mission creep', I don't want to get carried away if I can help it.

From the external condition, and the lack of mechanical noise (other than the death rattle when hot!), I think the motor had been rebuilt when the bike was restored, so I'm hoping that most of it will be good. I checked the oil pump out at the weekend, it all looked OK. I could do with fixing the wet sumping though, Trigger you said on the other oil pressure thread that you do the stopper kit yes?

Another 'while I'm in there' job will be to fit the heavy steel 'case protector' around the drive sporcket, which is absent - anyone got one?

@ Ash, your mate might be a good way to go, but I need to see what rod(s) I'll need first, in the hope that you have one (or more) the right grade to make a matching set. I'll fit new shells and mains after miking all the journals up, that doesn't look to be a cheap undertaking.

Any recommendations on gasket sets? some don't have all the O rings, yamiya do one at great cost, but I'm sure good quality.

yes, I do the stopper kit and have stock. PM me with your requirements