Topic: Burning oil, or unburnt fuel?

[The Lone Builder]

New gasket goes without saying; you can see in the pics, part of the old gasket has stayed on both sides.

I've already ordered bronze guides, so I'll be putting those in. Hopefully the valve stems are in spec, otherwise, I guess they'll be replaced also.

[Tracksnblades1]

Tracks: I think since there was oil on both No 1 and No 4 pistons, that the oil leaked down.

Putting the previous two responses together:

The normal tendency for oil to come up past the rings is aided by the fluttering caused by the uneven torquing. This flutter also reduced compression.
More oil coming up fouls the plugs which then don't fire leading to lower pressure during the power stroke, reduced forced return of errant oil, and cooler exhaust gas.

So the solution is to:
          clean everything up,
          check valve guide clearances, 
          check rings (just in case),
          check/renew my torque wrenches and
          put everything back together, having cleaned the carbs.

What do you think?

Oh, I see…

Don’t forget the cause while you’re in there….

I don't think I said earlier, that the exhaust gas coming from No 3 & 4 pipes was colder that that coming from pipes 1 & 2.

That's because those cylinders were not firing.

So I got my compression gauge hose replaced - it blew out last time and I did the test again, after adjusting teh cam chain and checking the valve clearances.

Cylinder      1          2          3          4
Dry           140      140       125      110
Wet          150                   155      140

This tells me the rings need attention (yes?)

The excess fuel that was getting pumped into the exhaust by the non-firing 3&4 cylinders also washed the oil off the piston rings, reducing the seal until you added oil. Put the motor back in and fix your carburetors.  

Fluttering.. due to uneven torquing…🤔 On through cylinder studs …🤔

Wondering aloud if your cylinder’s bores we’re prepared using a “through cylinder stud” torque plate…😏

Interesting 😁

Let us know how it turns out….

Merry Christmas

[newday777]

While you are in there what is your piston to bore clearances in each cylinder?
Any taper to the bores(internal bore mic is needed)
What are your Ring end gap measurements?

[PeWe]

Check if guides are OK before replacing them.
Easy to do. Remove spring, let the valve open ca 10-15mm, try to move the disc sideways in several directions in chamber.
You should not feel any "cloncing" play.
Just a little, more like a softness with oil in guide.

Exhaust side usually worn most.

[The Lone Builder]

First cleaning efforts - filled chamber with parts cleaner - revealed that exhaust valve on No 3 was leaking badly and No 4 exhaust was also leaking. All others were OK.

Further along, removing the valves revealed the following movement in the guides:

      1          2          3          4
I      -         +         ++        -
E     +        +         +++     ++

Valve stems all measured the same - 6,58mm on inlet and 6,55mm on outlets.
Tomorrow I'll clean teh faces and seats and see what's what.

What are the chances I will need to replace the valves?

[The Lone Builder]

The valves have cleaned up well, and the faces seem to be "lappable".

I'm replacing the guides with APE bronze guides;

Do I have to recut the valve seats now?

And if so, is it better to replace the valves also?

[denward17]

Please wait for more responses (no expert here), but if the valve guides are replaced, the angle changes slightly, so I suspect the answer is yes on the valve seats.

[newday777]

Valve seats are to be recut after installation of new Valve guides, not before.

[The Lone Builder]

So I've found someone to recut the valve seats, and I've decided to order new valves as well; teh supplier will take them back if the machinist thinks the old valves are OK to re-use.

But, not for the first time, I'm confused. The parts fiche for both K2 and K4 engines show a valve guide clip - PN: 12211250310. But when I put this into CMS and DSS parts finder, it doesn't appear for these models, even though it shows on the CMS fiche.

Not shown on the parts fiche is the valve stem oil seal - PN: 12209-300-003, although this appears on the DSS site under the relevant model.

Question is, do I need the valve guide clips, or just the oil seals (which are included in the gasket set along with the pucks)?

[PeWe]

I think you can reuse the old clips.

My shop has never asked for new clips when I have left head with all parts like guides, valves, springs, retainers etc.

The complete gasket kits include the valve guide seals.

[The Lone Builder]

Thanks PeWe.

[newday777]

So I've found someone to recut the valve seats, and I've decided to order new valves as well; teh supplier will take them back if the machinist thinks the old valves are OK to re-use.

But, not for the first time, I'm confused. The parts fiche for both K2 and K4 engines show a valve guide clip - PN: 12211250310. But when I put this into CMS and DSS parts finder, it doesn't appear for these models, even though it shows on the CMS fiche.

Not shown on the parts fiche is the valve stem oil seal - PN: 12209-300-003, although this appears on the DSS site under the relevant model.

Question is, do I need the valve guide clips, or just the oil seals (which are included in the gasket set along with the pucks)?

When you entered the numbers on the David Silver part search, did you enter the dashes in the numbers? The dashes are needed doing a part number search.  I just entered the numbers for the clips, David Silver shows the clips available as does the Honda dealer here in the states I use.
Yes you need both the clips and the seals.
The stem seals are not shown on the head fiche, they are shown on the Valve-rocker fiche, #1- seal, valve stem, is that why you didn't see them?

[The Lone Builder]

Seen, thanks.

I've now got the pistons out and all looks good on them, the bores and rings - except the one I broke on taking it off; the very last one!

There is come discolouration on the pistons around the pins which I'm not sure about. Could this be overheating? The pins are also discoloured.

There is also something amiss with the cam chain.  There are two channels cut out on either side of the chain tunnel, the cam chain guide and tensioner roller look very worn and the guide has two gouges in it at the top; when the engine was rebuilt – some 20,000 miles ago – this channels were not there and all part were renewed, from David Silver.

Is this wear normal and what could have caused the gouges?

[The Lone Builder]

These are the photos of the cam rollers etc; I couldn't get them uploaded altogether.

[PeWe]

Has the cam its washer bolted on left end side at #1?

[The Lone Builder]

Do you mean No 5 on the schema? If so, yes it's there.

The damage is symmetrical, which would make you think the chain is too wide, which it obviously isn't.

[PeWe]

This washer

[The Lone Builder]

That's the one; yes it's there.

[The Lone Builder]

These are the photos of the cam rollers etc; I couldn't get them uploaded altogether.

I found the tensioner, roller and guide that I took out of the motor; they are in much better condition than these ones. I bought them from CMS and DSS in 2017, so I thought they should have lasted a lot longer than this. Has anyone else had similar issues?

[ekpent]

There were some totally junk chinese tensioner rubber wheels that were being sold at one time from a cheap popular parts supplier and the problem was so bad they were offering refunds. Hopefully CMS was not selling any of the off brand crap. Some threads here somewhere about the inferior parts.

[The Lone Builder]

I saw one started by PeWe some years back - about the same time I bought the parts.

http://forums.sohc4.net/index.php/topic,155043.msg1774841.html#msg1774841

[PeWe]

All stock like tensioners are probably junk when not packed in Honda bags.
Honda cost more when order but the cheaper will cost much more in the long run.

I have bought Honda bagged tensioners from DSS after mistake with Taiwan junk.

DSS have crappy aftermarket version too.  Sold as Aftermarket.
Good ones as Honda. So up to the buyer to order right, not cheapest.

Same with carb boots not in labeled Honda bags and all other rubber parts.


I replaced CB750 junk fork gaitors a few days ago. They cracked really quick.
Now Honda version I hope will live at least 100.000 km/10 years.
They cost 3-4 times more but take apart the fork is work to do.

These tricked me jetting carbs a few years ago. Could have damaged engine too. Pistons and valves.

Both 2-3 rubbers. One almost 180* crack the other a little less.
Crack under clamp so not seen until carbs were removed.
Crack were inlet spigot ends against carb.
Max 3 years and 15.000 km.
The carbs were strapped to frame with rubber spacer between as vibration damper and avoid carbs to bend rubbers.

I bought the boots as Honda OEM, all 4 in one bag, not one by one Honda labeled bags. Not at cheap aftermarket alternative.

They looked exact as the new Honda labed carb boots I bought from DSS UK as replacement

Honda version is softer than before.
The set I bought mid 80's used harder rubber. The stock carbs with pods were hanging in them without other support. Rubber did not crack.


#
#
I changed clamps after this failure.
Wider clamps covering the entire end.  12mm.
The groove for clamp filled up with a nylon strap I shaped round before assembly. Around old boot and heat gun.

Ensure to not tighten too hard which can be a contributing factor of the failure.



Overtighten not possible before with harder rubbers. Even if tighten again with warm engine.
I used same clamps as used in the 80's.

My K2 has also straps filling the clamp grooves, but 9mm clamps as before.
The nylon strap protect rubber and help to apply an even clamp force, I hope.

Still not tighten hard when engine is warm and rubber even softer.

I found a set of 4 carb boots with Honda paper labels inside as NOS. Not cheap. A little bit harder rubber, not that sticky.

[The Lone Builder]

I had a similar problem with fork rubbers a few years back.

The problem is when buying parts from reputable suppliers; I think we wrongly assume they have done some QC on the parts they are selling, but it would seem not.

When you start a job that you think is going to be small and quick, and suddenly the parts bill is the wrong side of 500 €, you make those decisions that end up costing more in the long run.

The trick maybe is to balance the cost with potential damage cause by parts failure; so e.g. a pattern clutch cable might be worth the risk but for a cam chain (roller) better to bite the bullet and go for OE.

[The Lone Builder]

So having started out investigating an oil burning problem, I'm now replacing valves, guides, all cam chain tension parts and, because I broke a piston ring, all the rings, which of course requires recutting the valve seats and honing the cylinders.

Unlikely to be much change from 1 000 €! 

[denward17]

So having started out investigating an oil burning problem, I'm now replacing valves, guides, all cam chain tension parts and, because I broke a piston ring, all the rings, which of course requires recutting the valve seats and honing the cylinders.

Unlikely to be much change from 1 000 €! 

I think a lot of us can relate to your situation, I know I can.  Good Luck with the build.