ES2 exhaust valve

Perhaps the valve is seizing in the guide due to the extra heat riding up hill and alsothe valve lifter cam is wrongly set up. Do you still have the 'secÃ?teur ' type return spring fitted against lifter arm pushing it forward? Fiddling with the lifter gives the valve time to cool and re-set it's self.

Sounds very much like modern tollerances have been used on your old chuffer!.Its common to hear of power fading on hills, loss of compression etc when this has been done.It may sort itself out with a bit of wear or you will have to get the guide reamed out .If fitted Bronze guides should be soaked in oil for a few days before use,and need more oil than cast iron.

Previously william_pryde wrote:

The lifter spring is fitted and working and the lifter arm cannot be adjusted anymore than it is. As I say it only happens at high revs when the lifter mechanism is blown out of position and has to be reset.

If the valve seats were replaced during the re-build, you may want to check thay are not moving in the head. any movement here will = a loss of compression.

cheers Steve

When you say "the lifter mechanism is blown out of position " are you sayingthe valve lifter shaftis partially moving out to the left of the rocker box? If you are, this would account for the exhaust valve being held open a tad, as the internal clearance cutaway in the shaft wouldn't line up anymore with the top of the rocker. If this is the case, there is supposed to be a small screw on top of the box, the end ofwhich locates in the groove on the lifter shaft holding it in position to stop it from being "blown out".

OK! now we know, sounds as ifthere is a carbon/burnt oilbuild up in the guide reducing the running clearance to zero. The valve heats and expands enough for itto jamb. You will have to remove the head and clean out the guide or replace it if worn, your choice. You will find that the carbon is probably compactedrock hard and verypolished and hard to see.

this sounds like lack of oil is getting to the rockers the oil to the rockers is controled by a smaller diamenter pipe on the tank side of the rocker pipe has this been altered on the rebuild .hope this helps DICK RICHARDSON.

I just re-read your initial post William, and realise youprobably have new valves andguides?, if this is the case, the exhaust guideneeds to be opened up a thou or two to give it a little more running clearance.

Ensure your exhaust valve is non magnetic, I find stainless best.

Previously william_pryde wrote:

Thanks for the info, the thought about the oil supply is interesting, I am awaiting a response from the chap who rebuilt the engine to establish what was replaced. I decided not to open the head until I have this information but have changed the oil with a mix of Castorol R and valve lifter lubricant which seems to have reduced engine noise and the valve hasn't failed yet...

HI WILLIAM I could have explained the oil supply to the rocker box better the more Iread your problem the more Iam convinced it is lack of oil to the rockers .the oil return to the tank hits aconstriction Ihave been involved with es2 for 55 years a smaller size pipe witch makes the oil rise to the rockers if you put your finger over the return pipe in the oil tank you will forse oil up to the rockers a possible way of getting you home start with somthing simple examine the retun pipe to see the diamenter of the pipe if it ok move on to the head. Ihave been involved with es2 for 55 years I am on with will be my last re build YOURS DICK RICHARDSON.

It sounds exactly like the symptoms of friend of mine had on his ES2.

His problem was caused by the exhaust valve seat dropping out of the head. He had had lead free valve seats put in, but the installer had made them slightly to small, so that when pulling up a hill or fast cruising the head would expand enough to let it drop down onto the valve

blimey 60mph! I have a 35 frame & forks with 52 eng & gearbox with afterburners lit only see 55 max, suspect I am under geared, do you have any idea what sprockets you have on? I do see to get through the gears quick for an old bike, regards Paul