Inlet valve seals

Has anyone used a valve stem seal that has a spring around the top? Looking on RGM and Norvil sites seem only to stock the normal VITON seals.

I've just had a +20 rebore and rebuilt the head 200 miles ago and I'm still running in but it would seem that the R/H one may have decided to give up the ghost!

I'm having fouling problems on the R/H side only and I'm running a single Mk1 Amal so I think I can rule out carb setting.

I've swapped over the coils to see if it manifests itself on the other pot but I've not been able to get out on it yet to see. The bike runs fine when the plugs are clean and I've not noticed any ominous smoke from the exhausts.

I'm running Boyer ignition and have a good voltmeter that shows the battery is always supplying enough juice.

I'm using NGK BP7ES but not yet tried going to a 6, any info on anything else I could try would be helpful.

Strange, I rebuilt my 750 this spring with new rings and pistons, valve guides and springs and valves. Rebored to 20 over and after 1800 miles I have fouling in the right cylinder also. I plan to pull the head and the barrels in about a month and take a close look at the problem. I believe that it started about 100- 200 miles ago. Noticed blue grey smoke from the right pipe at a stop and immediatly on arrival at home pulled the right plug. Yessir, fouled with oil. If anyone else wants to speculate as to the cause I would be grateful.

If it smokes on the overrun (decceleration) then its valve guides, and if it smokes on acceleration its rings. (generally, sure there will be exceptions).

Rebuilt an 850 quite some decades ago now, with the little rings around the valve guide seals, and it soon started smoking on the left cylinder - on the overrun, as it happens. Black looking plug on that side. A stripdown revealed the inlet valve guide seal had 'fallen off'. Seemed to have shrivelled up, I seem to recall. Other one showed no sign of moving or problems. Fitted a new one, and all was well.

What do these viton ones look like ?
Anyone used them for big mileages ?
Are they all the same ??

Right hand side oiling up could mean the oil drain way at the rear of the right cylinder is responsible. Had a head gasket leaking oil from that drain hole towards the combustion chamber once many years ago. Result: smoke from r.h. exaust.

I had the same problem on the right side a few months ago after a rebore and head refurb. Turned out to be a popped inlet valve seal(which were new). You can't really see if it has come off with the springs in the way so I removed the spring and retainer using a slightly modified version of Ludwig's technique.
The seals seam to be very soft and may struggle to stay on the small ridge on the valve guide as this seams to be a fairly common problem.
HTH.

willy mac said:

Has anyone used a valve stem seal that has a spring around the top? Looking on RGM and Norvil sites seem only to stock the normal VITON seals.

I've just had a +20 rebore and rebuilt the head 200 miles ago and I'm still running in but it would seem that the R/H one may have decided to give up the ghost!

I'm having fouling problems on the R/H side only and I'm running a single Mk1 Amal so I think I can rule out carb setting.

I've swapped over the coils to see if it manifests itself on the other pot but I've not been able to get out on it yet to see. The bike runs fine when the plugs are clean and I've not noticed any ominous smoke from the exhausts.

I'm running Boyer ignition and have a good voltmeter that shows the battery is always supplying enough juice.

I'm using NGK BP7ES but not yet tried going to a 6, any info on anything else I could try would be helpful.

Click to expand...

Ok a nice 70 mile run out yesterday showed a slight display from the R/H pot on the overrun so I'll be making up the tools to change out the valve stem seal in the near future.

Is it feasible to do so with the head still in situ?

Ok a nice 70 mile run out yesterday showed a slight display from the R/H pot on the overrun so I'll be making up the tools to change out the valve stem seal in the near future.

Click to expand...

If its only a little smoke you may have just nicked the seal top when compressing the spring for retainer and collet assy etc. I'm not saying you have but it's possible. I fitted a pair of oversize seals many years ago and it smoked like a steam train on acceleration. A well known happy fellow from the Midlands didn't argue and replaced them. That made a change so maybe he knew he'd sold some bad ones which was more like him :x If the standard parts are fitted OK they don't cause problems, in my experience so you shouldn't need to go hunting anything special. Just ensure they are fully down on the guide and the retainer underside does not squeeze the seal when compressing the spring.

Mark F said:

The seals seam to be very soft and may struggle to stay on the small ridge on the valve guide.
HTH.

Click to expand...

Actually I got that ass about face. The ridge is on the seal. The guide has a groove in it to locate the seal in.
J.A.W. it is not too difficult to do it without removing the head and a lot easier than going through the head retorque procedure.

Mark F said:

Mark F said:

The seals seam to be very soft and may struggle to stay on the small ridge on the valve guide.
HTH.

Click to expand...

Actually I got that ass about face. The ridge is on the seal. The guide has a groove in it to locate the seal in.
J.A.W. it is not too difficult to do it without removing the head and a lot easier than going through the head retorque procedure.

Click to expand...

Did you do the seal change with the engine in the frame? I've had a look and might only have to take the head steady off to get more access!

Willy no need to remove engine or head. It all stays put. That is the beauty of this method.
Basically you need a means of holding the valve up while you remove the valve springs so you can get at the seal. The rocker adjustment hole is used as a means of compressing the valve spring to remove the valve collets then the valve spring retainer. The rocker shaft then needs to be removed to allow the springs room to be removed but instead of removing the rocker and shims completely, replace the shaft with something thinner to allow the springs a bit of room for removal. Sounds awkward but not too difficult. Beats removing the head!
Here is Ludwigs explaination. I didn't have access to a Mustang brake spindle so I used a piece of bent 6mm rod bent to fit through the plug hole and held down with an occy/bungee strap to hold the valve up. Any old 1/4"(BSA side cover bolt) bolt will work in the rocker along with a 'U' shaped stirrup to compress the valve spring.
valve-seal-replacing-t7362.html

Made up the tools today and followed Ludwig's brief with no problems, the head steady had to come off for access but it was easily done in the frame.
When the springs came out the valve seal just lifted off the guide so I guess that was the problem right there, rather than putting that one back on I've just replaced it and made sure it got a good push down onto the guide using a suitable sized socket.
If the weather permits I'll get out on it tomorrow for another blast round the Kingdom.

R/H valve stem replaced yesterday, out for a run today and the L/H one started smoking, same thing again the seal had popped off the guide, and to top it all off the bottom of oil tank has sprung a leak.

Has anyone had their oil tank crack round the bottom mount? If so and apart from having it welded up did you do anything to stop it happening again?

willy mac said:

and to top it all off the bottom of oil tank has sprung a leak.

Has anyone had their oil tank crack round the bottom mount? If so and apart from having it welded up did you do anything to stop it happening again?

Click to expand...

Popular remedy is to cut off the bottom bolt boss and braze a sheet metal patch right under the bottom of the tank. (See Colorado Norton site). Then just fit a nice rubber pad on the tray. My 850 has only the front tab mount fixed, the rest of it is jammed in with rubber pads and that has been no problem for many miles.