How To: Valves
Today’s project was to work on the valves in the 1913 Premier. It is a sidevalve motor, and fairly standard except for a few special features that Premier did differently than other builders. More on that later… First step was disassembly and measurement. The valves were in good shape, but the inlet guide fell out of the head. I’m not sure if it was an original part or if a previous owner made it too small. But it is easy to make new guides on the lathe. Shown in the first photo from left to right are the old guide, a new one in aluminum bronze and a new one in cast iron. CI is a good material to use, as it doesn’t wear too quickly, and keeps the valve lubricated OK on early motors with a spotty oil supply, and is thermally matched to cast iron heads.
Bar stock chucked in the lathe, with one shoulder left to machine.
Parting off the work. It is tempting to part it to the exact final length, but it is bad practice. The parting tool typically will not give a perfect length. Just leave an extra .030” when parting, and then chuck it up and face it off to length afterward.
The valve stems and heads had years of carbon gunk on them. These aren’t too bad considering that it is a constant-loss oiling system. In these motors, the oil splashes all around the inside of the motor, then leaves by going out the combustion chamber (there are no oil rings on the piston). So a certain amount of burned oil does get deposited in the combustion chamber and on the valves. A quick spin in the lathe with some rough and fine sandpaper cleaned them off. I measured them before and after, to make sure that there were no steps worn into the valve stem where it contacted the guide. Worn valves will often have a visible change in diameter where the contact the guide.
The fine grooves on the tulip section aren’t great, but they had been in there for years before I bought the bike, so I didn’t put in too much effort to fully polish them out.
Installing valve guides may seem like a tough job for the amateur mechanic, but it just takes a bit of effort and tools. These guides are cast iron, going into a cast iron head. So they will all heat up and grow in size the same amount as the motor warms. (due to CTE effects) The fit between the guide and head can then be just a light press fit. .0005” or .001” works if the hole in the head is nice and round. If it isn’t round, ream it out first, then make the guide to fit the hole. Size the hole in the guide to fit the valve, but it will tighten up just a bit from the press fit operation. So you might need to open up the guide with a reamer after fitting it into the head.
Before pressing the guide into the head, cover it with grease, then drop it into a ziplock baggie and put it in the freezer overnight. When ready, heat the head with a blow torch or in the kitchen oven to around 212F or 100C. Make sure that you have already gathered up any tools needed and wear gloves. Shown in the photo above are a punch and a socket that I used to press the guide into place. The socket fit down onto the flange of the guide, so that it wasn’t pressed on the end of the guide. The punch was used only because the socket was a little too short to reach past the barrel flange. The punch only contacted the socket, not the guide. A hydraulic press is the best way to force the guides home, but a bench vise or careful hammer blows will work. Do the work quickly, as the guide will heat and swell up quickly when it comes in contact with the hot head.
Shown below is a tool that can be used to remove valve guides. It fits loosely into the guide say, .005” clearance, and its OD is about .020” less than the guide, so it can slide right through the head without damaging the bore.
Once the guides are in place, it is time to check the fit of the valve to the seat. If the guide was made well, and installed well, the valve will fit into the existing seat. If it doesn’t, you can make and install a new guide, or cut the seat to fit the guide. I prefer to use existing seats as much as possible, since cutting them repeatedly will eventually pocket the valve down into a hole. Off center seats can also be a problem if they hit the cylinder bore or the adjacent valve seat.
Valve seat cutters come in different angles and with replaceable spindles. These cutters are 45 degrees, and about 2” in diameter. The spindles fit various different valve guides; the Premier uses .312” These ones are from a swap meet. Some nice motor rebuild tools can be found at Goodson.
The Premier’s valves fit the seats well, and didn’t require any cutting on the seat. So the next step was to grind in the valves. If you read the old motorcycling manuals from the 1900-1930’s, they talk about doing this like it was a monthly exercise. I’m sure there was no need to do it very often but it isn’t too difficult to do. First clean off the valves and seats so you can see what you are doing. Then apply coarse grinding compound the edge of the valve, and install into the guide. With the suction cup stuck on the valve head, rotate it back and forth a little, lifting it up and turning 90 degrees every 20 seconds. Then clean, inspect and do it again if needed, or move to the fine compound. Be sure to clean all the coarse compound off all parts before changing to fine.
When the valve and seat both have a uniform dull grey surface, the grinding is done. Shiny silver surfaces would show that more grinding is needed. In extreme cases, a large portion of the seat will stay shiny, maybe 1/3 of the circumference. This indicates that the seat is not concentric to the valve guide. The remedy is either a new guide, or re-cutting the seat; both followed by more grinding.
To check your work, install one valve onto its seat, but without any valve springs. Invert the head and pour a cup of fuel or solvent into the port via the opening for the carby or exhaust pipe. With just a light bit of finger pressure, the valve should stay on its seat. If the solvent doesn’t pass the valve into the chamber, it is a good, tight joint. If it very slowly seeps in, it will probably be ok (but I’d go back for more grinding). If it comes gushing in from one area on the seat perimeter, you have more work to do.
Be sure to get all the grinding compound washed and wiped off the parts. Don’t forget to clean down the cylinder bore and down the valve guide holes. That compound will wear out your motor if it is left in there.