Author Topic: How far to go with engine strip downs - being sensible about old seals etc  (Read 957 times)

Offline McCabe-Thiele (Ted)

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 Now that my little engine has run I'm turning my mind as to how far to go with an engine strip / down rebuild.
My original thought was to remove the cylinder head for valve grind, valve stem seals if they have them and checking piston tops etc.
That got me thinking about stuff like crank oil seals etc if they have them.

Without going OTT on cost what do folk here do in terms of knowing how far to go with a rebuild - any pointers / advice  as to essentials whilst the engine is out sought here. I will have to strip the clutch as the plates are bound to be stuck plus I am not in a situation to know if the gearbox is in good condition. If the piston tops look good I'm not keen to remove them unless its essential as part of the rebuild

I'm not afraid of the work involved more of an eye on cost and time involved in engine / gearbox strip downs.
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html

Offline Nurse Julie

  • 1977 CB550/4 Mongrel Brat. 1974 UK 500/4 K1. Honda CD250u.
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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #1 on: September 25, 2020, 07:20:44 PM »
Personally, I would advise stripping the complete engine Ted. Fit all new engine seals, hyvo primary and cam chain, make sure the cam chain horse shoe pivot is free and working, check gearbox over etc.
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Offline Skoti

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #2 on: September 25, 2020, 08:23:32 PM »
Of course Julie gives good advice.

But you may want to follow the principle of "if it's not broken don't fix it".

When my old CB750F1 was resurrected I first serviced the motor, then run it and addressed issues as they appeared.

But for example loads of stuff including crank and gearbox oil seals etc are still original and working fine.


Good luck with your project.


 
 
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Offline Laverda Dave

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #3 on: September 26, 2020, 09:43:52 AM »
I think once you remove the rocker cover and inspect the cam and rocker condition they will provide a good indication of how the engine has been previously looked after.  The top end of the engine is what suffers most when oil and filter changes have been neglected.
Once you remove the head to inspect the pistons and bores you will really know what you have on your hands.  Any signs of rust/scoring etc will point to a full stripdown.  As a minimum I would remove the sump pan to check the primary chain, cam chain tensioner horseshoe and the tensioner plunger. The contents of the sump pan will also provide a good indication of the state of the engine.
Read Julies rebuild thread for a good example of what may be lurking around the piston area as an excellent example of how to inspect the engine and what may be lurking within.
Not to worry if you find various nasties, lots of help and advice on here. I sense a nice winter rebuild coming on....................
Good luck :)
Dave
1976 Honda 400/4
1977 Rickman Honda CR750
1999 Honda VFR 800FX
1955 750 Dresda Triton
1978 Moto Morini 350 Sport
1978 Honda CB400/4 'Rat' bike
1982 Laverda 120 Jota

Offline McCabe-Thiele (Ted)

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #4 on: September 26, 2020, 09:47:23 AM »
Of course Julie gives good advice.

But you may want to follow the principle of "if it's not broken don't fix it".

When my old CB750F1 was resurrected I first serviced the motor, then run it and addressed issues as they appeared.

But for example loads of stuff including crank and gearbox oil seals etc are still original and working fine.


Good luck with your project.


 

That was my late Fathers maxim - if it aint broke dont fix it - when I was a teenager I  ignored it of course dismantling things that sometimes I could not put back together. lol
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html

Offline McCabe-Thiele (Ted)

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #5 on: September 26, 2020, 09:57:55 AM »
I think once you remove the rocker cover and inspect the cam and rocker condition they will provide a good indication of how the engine has been previously looked after.  The top end of the engine is what suffers most when oil and filter changes have been neglected.
Once you remove the head to inspect the pistons and bores you will really know what you have on your hands.  Any signs of rust/scoring etc will point to a full stripdown.  As a minimum I would remove the sump pan to check the primary chain, cam chain tensioner horseshoe and the tensioner plunger. The contents of the sump pan will also provide a good indication of the state of the engine.
Read Julies rebuild thread for a good example of what may be lurking around the piston area as an excellent example of how to inspect the engine and what may be lurking within.
Not to worry if you find various nasties, lots of help and advice on here. I sense a nice winter rebuild coming on....................
Good luck :)
Dave

I like the suggested starting points though I am loath to remove pistons from a bore if there is no obvious piston damage, bore scoring or top lip.

I would have been in a position to do the engine strip whilst the frame is being powder coated following full strip down - this was planned for this year. Rather than trying to rush the engine removal before I have my surgery that's scheduled within 21 days I will have to just leave things until after Christmas. My BIL has offered to help but really I want to do it all myself as its potentially  challenging then rewarding taking it apart.

It will be difficult having the restraint not to get on with some of the easier jobs.

« Last Edit: September 26, 2020, 09:59:33 AM by Macabethiele »
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html

Offline Trigger

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #6 on: September 26, 2020, 10:23:10 AM »
If you have pulled the head off you, would of disturbed the base gasket and you will need to remove the barrels to change that  ;)

Offline McCabe-Thiele (Ted)

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #7 on: September 26, 2020, 10:42:32 AM »
If you have pulled the head off you, would of disturbed the base gasket and you will need to remove the barrels to change that  ;)

So to fix a blown head gasket involves removing the pistons anyway - I didn't realise that on my Honda.
That is food for thought.

Can you remove the barrels with the pistons in place by undoing the con rod caps or is that more trouble than it's worth Trigger?

Thanks Ted

PS I will always have a Plan C - that would be to pay to get the engine professionally rebuilt.
« Last Edit: September 26, 2020, 10:44:38 AM by Macabethiele »
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html

Offline Trigger

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #8 on: September 26, 2020, 06:07:02 PM »
Base gasket NOT head gasket  ;)

Just pull the barrels off, you won't find a dead body under them  ::)

Offline Athame57

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #9 on: September 26, 2020, 06:53:11 PM »
Just pull the barrels off, you won't find a dead body under them  ::)
How do you know? The Japanese have been hiding dead grandparents for decades!
I brake for animals!
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Offline McCabe-Thiele (Ted)

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #10 on: September 27, 2020, 12:06:08 AM »
Base gasket NOT head gasket  ;)

Just pull the barrels off, you won't find a dead body under them  ::)

I am confused if I understand you right if you remove the cylinder head you also have to replace the base gasket by removing the barrels - can you remove the barrels with the pistons in place or do you have to then when replacing the base gasket then somehow get the pistons back in place surely not from the bottom? On cars I have only put pistons back in from the top of the engine block?

On the one hand I can see the benefits of checking the condition of the pistons by removing them but if compression is good, oil consumption is okay why run the risk of breaking a ring when you put them back?

Forgive me if I sound thick but back in prehistoric times when I was a teenager I have done a few bike cylinder head removals for decoking etc but never removed the barrels. Maybe that's why my old Triumph 21 always leaked oil !!

Ignore my question above I've just read NJ's rebuild section circa P25 and  seen the brilliant photos - made me gulp a bit!
I'm very impressed with the cleaning & engine assembly posts.

« Last Edit: September 27, 2020, 07:22:50 AM by Macabethiele »
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html

Offline Bryanj

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #11 on: September 27, 2020, 07:42:13 AM »
Multi cylinder Hondas are better built than old brit stuff and when you release the head bolt tension you also release the clamping force on the base, when you wiggle the head off chances are you move the cylinders a bit so the base gasket will leak.
I dont understand your question about pistons, you cant do anything to them without removing cylinders first

Offline McCabe-Thiele (Ted)

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Re: How far to go with engine strip downs - being sensible about old seals etc
« Reply #12 on: September 27, 2020, 05:55:08 PM »
Multi cylinder Hondas are better built than old brit stuff and when you release the head bolt tension you also release the clamping force on the base, when you wiggle the head off chances are you move the cylinders a bit so the base gasket will leak.
I dont understand your question about pistons, you cant do anything to them without removing cylinders first
[/quote
Not sure what my question was now about the pistons either  as NJs post answered it anyway.

Today I fired her up for a few minutes then checked that oil was reaching the valves etc. As I was replacing one of the tappet cover caps I was reminded how hot front pipes get!  Nice little burn mark on my right little finger..... all the Missus Wendy  did was laugh at my stupidity.
Honda CB500 K1 (new pit dug out ready)
Honda CB400 four super sport (first money pit)
Link to my full restoration http://www.sohc.co.uk/index.php/topic,23291.0.html

 

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