Flushing oil

[Trigger]

Got to ask this Graham, why did you build an engine with no rings?

Experimenting with aftermarket pistons in a engine with no rings on a test rig. This tells you if the pistons clearances are good or if they will seize at Honda clearance 

[Laverda Dave]

😂😂😂

[Rob62]

Such false information !

I remember you advising a guy that he must strip his engine to change a drive shaft oil seal because the “60 psi oil pressure behind the seal would push it back out” if he just tried to press it in..... that was false information mate... and your an expert. Lots of people successfully resurrect old bikes and cars without total engine strips, each project has to be assessed individually.

[Trigger]

And to assess a engine fully, it need to be stripped. Unless you have one of those OEM Honda crystal balls 

Not a drive shaft seal, a crank seal 

[Laverda Dave]

Or...... as what happens in the American car programmes such as Fast & Loud when they dig out a rusty 30's Model A from an old shack and minutes later they utter the immortal lines, 'We put a new battery on it, fresh fuel and oil and it fired up first time'! Yeah, sure it did🤔. Then they rev the nuts off it and do burn-outs and doughnuts around the yard. Such a load of tosh, of course they checked it over before the cameras rolled and I bet this included tacking the head off.
I'm refurbing my original 400/4, it's been stood 10 years in my insulated and de-humidified garage, hardly any sign of corrosion but I've still used an endoscope camera to check the bores (no sign of rust in there), checked all the valve's are moving & not sticking, dropped the sump and going to use flushing oil. This thread Cound not have come at a better time for me. I'm not going to take the head off though as the engine only has 5k on it and the bike has been kept in my garage.

[Laverda Dave]

When the drive shaft seal blew in my CB250RSA I had to split the cases, no way could I have got a new one in otherwise.

[philward]

All the bikes I have built have all had full engine rebuilds - but... its about risk analysis I suppose. I am risk averse and so I am more likely to not take any chances. its down to the individual. If you spend the time and money stripping a motor and rebuilding it compared to 'if' something went wrong after doing precautionary checks (as per previous threads), is there much difference. Particularly the miles most of us do on these old bike.
That said, I will no doubt strip the 500 engine despite me saying I will go the precautionary check route!

[Spitfire]

Left my CB750F1 for 10 years in the garage while I was away working, I covered it in grease and dust sheets, when I came back I was going to give it a quick check over and get it back in the road, however a closer look showed that it needed a lot more work.
I broke a stud on the head getting the exhaust off so I took the engine out, and removed the head to fix the stud.
While I was there I decided to check the pistons and rings as I was concerned about stuck rings and found a stuck compression ring on one of the centre pots, it may have been like that for years before I went away or the result of me leaving the bike standing, who knows, but for the amount of effort required it was worth checking.

Cheers

Dennis

[Rob62]

http://www.sohc.co.uk/index.php/topic,14243.15.html

[Bryanj]

At least you can get the top off the 500 in the frame

[Genniker]

Not looking for guarantees, but if the rings are gummed up and the value seats pitted, is the worst thing that would happen is that it wouldn’t run right; or could it cause damage?

[Bryanj]

Gummed up is not so bad but broken could be disastrous

[K2-K6]

While I'd not argue with any inspection / replacement that were needed to recommission a stored bike, I think flushing oil needs closer scrutiny in this context.

The position, naturally given by the manufacturer of "flushing oil", is that using their products will gently and considerately remove unspecified contaminant along with various wear / worn materials resident inside your engine. Leaving it as pristine as could be and ready for further excellent service from then onward.

It's one of those odd decision,  if there's enough of a problem inside the engine,  then flushing isn't going to fix it.  If there isn't a problem in there that needs flushing out,  then it shouldn't be put in there.  Neat a?

A contra view may give that you are about to put into a Honda engine with tolerancing smaller than most believed possible in a production engine during the era of manufacture,  a mix of Kerosene/Paraffin /Diesel in approximately 85% quantity,  to which is added 10% thin mineral oil, plus solvents like Acetone and MEK (that's more or less the makeup of flushing oilsover the years) in the vain hope of desolving unspecified detritus. This is in the oil system that we agonise over which oil is best to protect our precious engines!  this mix is supposed specifically to break down oil and oil film,  the very quality that the oil uses to keep those fine tolerances apart in the first place to avoid wear.

I seriously doubt that any Honda instructions would call for any product like this to be put into one of their engines. More to the point,  the manufacturer of flushing oil has no idea whatsoever of material composition,  tolerance,  age,  wear characteristics or any other pertinent detail of the engine that's sitting in front of you for consideration. It's most unlikely to fix anything.

Two sides to consider,  whether it would influence a decision to flush or not to flush would be interesting to see, comments appreciated.

[deltarider]

+1. I have never believed in flushing the engine. IMO it has more to do with our desire to care for our bikes. This can lead to overcare. Flushing is one manifestation of it, fitting unnecessary and often problems causing inline fuelfilters another.

[Laverda Dave]

Very intersting read as always Nigel and a very good point made re:tolerances.
I have been reading this thread with added interest as I have been re-commissioning the 400/4 I originally restored 28 years ago over the past month or so.
I havent used the bike for 13 years as its been laid up due to other bikes/work/DIY etc getting in the way.  It was always a case of 'I'll get that running in the spring' only for it never to happen! The bike has only covered 7.5k miles between 1992 and 2006 after the engine was fully rebuilt.  Oli changes were completed every 1000 miles and its always been kept in my garage.  I drained the old oil a couple of weeks ago and it looked like ATF, I remember when I bought it at the time and it was that colour, I have no idea of the brand but it was the correct motorcycle oil and bought from my local bike shop.  The condition of the oil was as-new and so was the filter but I am changing them anyway as the oil is too old to leave in there.
Having read the start of this thread I bought some flushing oil but to be honest, after reading your reply and the potential damage (IMHO) of what flushing oil could do Im not going to use it.  Instead I'll buy some cheap oil (to the correct spec) and run the engine for 200 miles, drain it and change the filter.
I've had the rocker cover off, all the valves are moving and I have no rust in the bores (using my endescope). I'm going to drop the sump and take a look at its contents and check the tensioner horseshoe is ok. I know there has been discussion about sticking rings/ gummed-up rings etc but this is a chance I'll take.