ES2 compression and valve guides

I would say the carbon coating is not  especially unusual so i dont think you have a real  problem with piston or inlet valve, I think its most likely that you have oil leaking through the joint between ex guide and head ,you could try sealing this with silicone .I also think that you could be troubled with compression issues caused by insufficient clearance between ex valve and guide . Usually this shows itself when under load going up hills etc with a sudden power loss. Sounds  familiar? I also suspect the guide is a little loose in the head so replacement a couple of thou bigger might be the best.

If the bore is now 80mm, that is the same (almost) 40 thou overbore.  That seems more likely than 80thou over.  And it has no '+' sign.

ES2 surely normally had iron guides.  There are lots of 'bronzes'.  The traditional phosphor bronze is often described as being best for racing because it has better thermal conductivity, but also wears faster than cast iron and needs direct lubrication into the valve guides (as used in Inter engines).  Modern metals like Colsibro seem to be better.. or different...and all seem to need particular valve stems (chromed, stainless etc)

I'm adding questions since I need new guides for my cast iron head Inter, and I'm tempted to use cast iron.  It's not going to be raced.

Mixing cannot matter...if you want to change only one...it can't tell what its neighbour is.

... that cast iron guides have a self lubricating character so are better for road bikes with minimal lubrication like the ES2.

I also see tat there are carbon deposits on the inner annulus of the head surface  My (earlier) ES2 with cast iron head has the head joint ground in so that this is the mating surface. It seems wrong to me that you're getting carbon in there but I'm not familiar with the alloy head.

hello,   mine turned out to be a worn cylinder bore . the engine burned a lot of oil, it provided me with a smoke screen as i rode along . the oil also dripped from the exhaust rose.

thinking valve guides,  thought i would have the cylinder head done first so as to repair the exhast rose thread and have valves and guides fitted same time . had that done. popped the head back on, ran the engine the smoke was still the same . as you sat there on tick over you could watch the smoke build up and get slowly worse.

thought it must need a rebore. so stripped the head and barrel off, piston off, i placed a piston ring into the bore and you could get a feeler gauge inbetween the piston ring and the cylinder bore front and rear of the piston the bore had gone past its limits size wise. so i had a liner fitted with new piston. i put it all together, spot on now.

barry

The shape of the removed guide is wrong, the flat top of the guide will pool oil on the top of the guide and then will be drawn down the guide and burnt, The tapered shape of the original guide prevents a lot of this 'pooling' and can be improved further by machining the top of the guide so their is just a small flat to the top of the guide, say 1.5 mm. Those bronze guides were probably made by an amateur who didn't know how to taper turn. There are a lot of grades of bronze and almost all of them are not suitable for making valve guides out of. Cast iron is the original material they were made from, it is self lubricating and hard wearing and is my material of choice to make replacement guides from. Your head obviously has had replacement guides fitted in the past which has probably ruined the 'fit' of the guides in the head leading to oil burning/loss of compression. It (the head) will need the hole in reaming true and a new custom sized guide making to fit said hole.

Piston wise, putting your hand over the top of the barrel and turning the engine over to check for oil passing the rings is laughable. It won't tell you anything. Measuring the bore for taper and ovality and the piston for clearance as well as the ring land clearance is what is required. If the rings can move up and down in the ring grooves then the piston/rings are worn out (the movement of the rings in this direction 'pumps' oil past the rings themselves. Running these engines without effective air filtration promotes this wear massively.     

Having a load of invoices for bits is one thing, how they were fitted is another. The last three singles heads i,ve worked on for people had loose/badly fitted bronze guides, in two of them one of the guides fell out upon valve removal!   

Can you borrow or beg a bore gauge before doing something expensive that doesn't need doing? I thought ES2 had rudimentary drain arrangements from the rocker box, which might cause oil to run down.  But exhaust gas is much more likely to run up!

Does it smoke worst when on pulling away from tickover?  Wear in inlet guides allow oil to be sucked in and cause smoking when pulling away, and oil deposits inside the cylinder and exhaust ports as the part burnt oil is pushed out.  Worn guides don't affect compression.

Does it hold your weight on the starter pedal when decompressor isn't used?  If so  bore cannot be too bad.

A quick test for poor compression is to pour a small quantity of engine oil down the plug hole (enough to 'seal' the rings) refit the spark plug and see if compression is improved, if it is, it points towards poor ring sealing. You should have done this first.  

hello,  John,

you would think with that amount of work carried out on the engine it would be spot on. just a thought is there a gap in the exhaust valve top and the decompressor spindle flat. with the rocker cover fitted

barry

Re reading your first post, In 5. i suspect you have burred over the end of the guide when you removed it, so giving the impression that the valve is now a tight fit in the guide. Exactly how did you remove the guide? Punched out after heating the head using a hammer? If so what punch did you use? 

Hi John,

   The later OHV engines have extended quitening ramps on the cams which, when the engine is cold, can give the impression the engine has low compression. This information might be a bit late now you have stripped the engine, but a quick check can be done by slacking off the tappets half a turn then try the kick-start test and see if there is any improvement. 

   Looking at your head, the inlet port looks quite clean. My guess would be the piston rings causing the excessive oil. The piston looks to be a modern replacement with it being marked 80mm and it might be possible the rings could be incompatible with the piston. 

   As Ian says, you should do away with the head gasket and double grind the head joint. The gasket was only fitted to speed up manufacturing time and is a poor short-cut to doing it properly.

Hi John. I am still of the opinion that the guide was not sealing in the head ,your photo shows some shiny area where the guide could have been revolving when hot , this would give a smoky engine but not a very  oily combustion chamber as the oil gets blown out by the exhaust ,your carbon on the piston is not unusual. The exhaust seat looks like it has had some blowby perhaps the revolving guide is not truly concentric and has caused it to leak and lost compression.The photo also seems to show oil on the guide when in the head ,usual with a leaky guide hole.I think a new well fitted guide will put you right.

This is a bit like reading about health ailments on the internet, will turn you into a hypercondriac .