do you have to take the head off to replace valve retainers?

[tranqwhl]

Is it possible to leave the head on a four-stroke motorcycle, compress the valve spring, pull out the old retainer, drop in the new, and be done; without removing the head from the engine?

This is probably an obvious question, but I've never attempted it, and I need to do that soon, and if I don't have to pull the head off, I'd rather keep that gasket fresh on there!

thanks

[Jmoore12]

Not to my knowledge. Most valve compression tools need to push up on the valve and down on the spring in order to remove the keepers. Having said that, it is physically possible, but you need a way to keep the valve itself from slipping into the cylinder.

[KJ790]

I have heard of people putting compressed air in through the spark plug hole to hold the valves up, then removing the retainers to change the valve springs, so it is possible to do without removing the head. I have never tried it personally though.

[daled]

packing the cylinder with a nylon cord thru the spark plug hole is an "old skool" trick.

just make sure to leave a little sticking out !

[Zappa]

I changed out all the valve seals on one of my Dad's old trucks using the compressed air method. (4.9L I6 Ford, as easy as they get). After 20 years, the rubber was as hard as ceramic.

All you need is an adapter for the spark plug hole that you can connect to ~120PSI from a compressor. Holds the valves in place and lets you remove the springs very easily. Just make sure the pressure stays up and the compressor doesn't blow a breaker. I had a valve sitting on top of the piston about to fall into the cylinder, and had to guess which way to turn the crank to bring it back up. I guessed right and flipped the breaker on the compressor. But almost had to take the head off.

Just be careful with the valve, removing the spring won't knock the air seal, but tapping it with a ratchet too hard could.

[tranqwhl]

thanks to everyone who replied for the help

Instead of fashioning the air-hose adapter I'd need to fill the cylinder with air, this idea sounds pretty easy:

packing the cylinder with a nylon cord thru the spark plug hole is an "old skool" trick.

just make sure to leave a little sticking out !

...so is part of the trick that I need to pack it so tight that the valves can't open (for when I compress the spring), or is that nylon cord in there just to hold the valve up when the retainer is gone?

many thanks again my friends

[KJ790]

thanks to everyone who replied for the help

Instead of fashioning the air-hose adapter I'd need to fill the cylinder with air, this idea sounds pretty easy:

...so is part of the trick that I need to pack it so tight that the valves can't open (for when I compress the spring), or is that nylon cord in there just to hold the valve up when the retainer is gone?

many thanks again my friends

Both, the nylon cord will fill the space between the piston and the valve same idea as compressed air) without damaging either part. This holds the valve up so you can push down on the retainer to pop the keepers out, and keeps the valve from falling into the cylinder when there is nothing else holding it.

[HeadTrauma]

Depending on the engine design, the rope is mostly just to keep the valve from falling irretrievably into the cylinder. If there is no way to fit a regular compressor around the valve spring, then it also allows you to push down on the retainer and remove the keepers. Just be careful not to let the crank turn if you're pushing on the valve.

I used the compressed air method when replacing valve seals in a Ford 2.3 turbo a few years ago. I took an old sparkplug from the same engine, knocked the ceramic out, and welded some ¼" pipe to the end so I could thread a quick change air fitting onto it. One caveat; 120psi in the cylinder will exert A LOT of force on the crank and it will be very difficult to keep it from turning. With the above 2.3T, the e-brake had quite a hard time holding the car even in 4th gear!

I also managed to drop one of the valves down far enough that I couldn't grab it. Luckily I used a pen magnet to pull it back up. Won't work with titanium and some stainless steels, though.

[tranqwhl]

it was super hard to push down on those valve springs! I don't know what I was expecting... but there is not much room when the head is in the frame to get any leverage with your body, and it seemed like I was just making things more difficult. I had already selected some rope and had it fed into the cylinder when reality reared it's ugly head.

So off came the head! It's a bummer because that also meant the subframe, carb, pipe, oil lines, water pump guard, and finally drain the coolant. Not super hard, but time consuming.

A friend had "the spring-compressor tool", which made things really easy once the head was off. You compress the spring, remove these two small half-moon shaped inserts, and finally loosen and remove the "compressor tool". Then you can remove the retainer and whatever else you wanted to! It was that easy. Installation was reverse. The only hard part was that the parts are small, but that just meant patience was in order, and the use of my pinky finger.

Again thanks for the advice on this! I am waiting for a new head gasket "just to be safe" to complete the re-assembly.

[KJ790]

Yeah, in the end I think it is easier to just take off the head on a bike, there isn't much room to try and change the springs on the bike. I have a valve spring compressor for bike heads, but I only used it once. I find it is much easier to use a 14mm deep well socket, or a piece of PVC pipe of the right size with a tennis ball cut open and placed on top as a handle. This way you can just push the spring down with the head on top of a rag (it will take quite a bit of body weight) and pop the keepers out. To put them back in I place the keepers in the retainer, and do the reverse. It sometimes takes 2-3 tries to get them to sit right on the valve, but it is still much quicker.