Changing valve stem seals

Last year i talked to a guy who told me that he changed the valve stem seals of his Z in the following way; he made an old spark plug ready (hollow) for a connection to a compressor. Then with the compressor connected in this way to the cylinder head he was able to change the stem seals without removing the head. But...i dont know how he pushed the valve springs down before he was able to remove the seals.
Does somebody knows if this tric is possible and what is the tric of pushing the valve spring down.
Willem

I believe you still have to take the cams and valve springs out. The air in the cylinder just keeps the valves from falling down inside.

It would be possible but not very dam easy.

1st - You would need to fabricate a customer tool to compress the valve springs.

2nd - getting to the inside cylinders to remove the old seals would be a chore.


3rd - pushing the new seal over the guide with the valve stem sticking up would be kind of a bitch to do.

Generally, if the seals are shot it's time to do a valve job too. The leaking seals will no doubt have the valves all gummed up on the back side.

There are 2 ways to approach things....the right way and the corner cutting way....the end result tends to reveal the effort....

I have done this on cars but the valve retainers are a bit smaller than a car so you would need to make a lever system to bolt down to the head and push down on the retainer so you can remove the collets. Once the springs are off you just need to get the old seals off and new ones on, once you have done that then reverse the proceedure. Most compressors will do around 140 PSI so you should not have problems unless you rings are stuffed. If you suspect this do a Dry and Wet compression test and see what the difference is.

Noel

All of these rocker arm engines put a side load on the valve stem during operation. So the chances are VERY high that the guides are shot. When you have the can cover off and cam out, see if you can move the exhaust spring front to back. If you can, take the head off and rebuild it.

Jay

Have participated in doing this a few times- it's NOT easy. The hard part is keeping the spring compressed - we used a tire iron with a hole drilled through it bolted to one of the cam bearing cap holes to lever the spring down.Getting the retainers out and not dropping them into the engine is fun too.

Why would anyone go through all those gyrations to change out the valve stem oil seals? The head can come off in about 15 minutes after the tank and coils are removed. The main job is not the oil seals but cleaning the old gasket up. Whole job can be done in about 3 hours. I suspect it would take a lot more fumbling with the head on the bike.

put nylon cord into the combustion chamber thru the plug hole and bring the piston as close to top dead you can get. this will give you the resistance you are looking for to compress the spring.

it is a wrong thing to do!! you are going about this the wrong way.

remove the head get a valve job replace your seals and check the guides. clean and rebuild

just think if you bought a bike someone did this stuff to and you found out the hard way.

Oke, taking the head of is the best way to do but i was just curious how to do this job without taking the head of.

If you're talking about your 900, getting the head on and off is the easiest part of the job.
-Duck