I would like to check the timing of my engines using Milton's video but I can't find a source for a piston stop. Can one be made from a spark plug or who has them? Dan.
http://www.youtube.com/watch?v=GBXFpxWg7vY

Easier to make them from an m10 or otherwise appropriate bolt. 3w sells custom stops for some of their engines.

Don't need a piston stop, just use a bolt.

Hi,

I have seen piston stops for sale, but I can't remember where. I just gutted a spark plug, and used JB Weld to install a piece of aluminum tubing for the stop. You could use a dowel, but the tubing allows the air to escape and lets the engine turn over easily when doing timing chores.

AV8TOR

As stated above just go to a hardware store and get a bolt that is correct for the size plug you are using.

Milton

Some of my old dirtbikes used a piston dimension from TDC to time the ignition. To that end, I have a piston stop that has a locking plunger and also a micrometer screw that enables you to set the distance from TDC to the ignition point. It has both 14mm and 10mm threads, but I guess it predates the smaller plug threads. So, a threaded bolt will allow you to set the piston stopped where you want it; a fixed tube in a plug body will not. Just a thought.

Sincererly, Richard/Club Saito #635

Yep.

Insert and rotate crank one way to the stop, make a mark on the hub. Rotate crank the other direction to the stop, make a mark on the hub. Halfway between the marks is TDC. From there one can do the math and degree out a spinner backplate or the prop hub and establish all the timing marks they want. Better to use the hub since it is fixed relative to the crank.

I like the wood dowel better. Sand it round on end... not to damage piston. Drill a small dia hole through it to prevent compression. Easy made. Capt,n

I either ues a wood fork between piston and crankcase if I need to support the piston, OR modify a spark plug to use as piston stop (latter for timing purposes)
The spark plug isolator can easily be removed. Then tap the plug body with suitable thread. If you want to guild the lily, make a bolt with sheath that has a scale divided in 10 (metric). This will give you very exact piston stop positions for ignition timing purposes.

For a soft and solid piston stop, just stuff some twine or thin rope down the sparkplug hole.

Re the graduated stop, that is what my motorcycle piston stop has built into it.

Re the rope trick, we used to do this so we could replace valve springs/seals/keepers on car engines way back in the day. The rope kept the valves from falling into the bore while we worked on the other valve bits.

Regards, Richard/Club SAITO #635

Thanks for all your responses. I was thinking about the spark plug gutting trick for some time. I'll work on that to get going on the timing checks. Richard, aka spaceworm, where did you get that sophisticated one you keep mentioning? Dan.

I have several stops that look like Aviator's but anymore, I use Milton's method of finding top dead center. I just feel for it.

Easier than blowing 20 minutes with a dial indicator.

same here... i measure it three times to make sure i get it spot on.....

Same here...just feel will do fine. Capt,n

I have had it since my Yamaha CS3C and DT175 back in the 70's. I have to see if it has any markings on it as to make, and post a picture of it here. That was when points were used (remember them?) and a buzz box was connected across the points to hear when they opened as the crank was turned.

Sincerely, Richard

Before I got a piston stop I just used a allen key. Insert the bent end through the plug hole and hole it at an angle with one hand. (I used the largest one that would allow the bent end of the key to pass through without damaging the threads) With the other rotate the crank and check your readings on the protractor or what ever you are using. Just don't go crazy and it works fine without damaging anything. I came up with the idea a few years ago when I timed my first gas engines. If you do it correctly it is just as precise as using a stop. Common sense prevails here. don't go jambing things around or gouging the key into the cylinder walls etc.

For those who have an excess of $$$. Zenoah makes a very nice machined stopper in both 10mm and 14mm.
PN 20010 10mm
PN 20005 14mm
They are $9 ea.

lol, that is the ones I bought. Very nice.

I hope some newbie is not reading this and thinking that the piston stop is used to keep the crankshaft from turning so they can tighten the prop nut or a hub nut?

If so, hope they have lots of $ LOL

OMG, you never know. That is why many times I am hesitant about what I say on these forums. Sometimes a little information can be dangerous.

What do you mean can be? In this forum it often is.

I'm not that critical. The bolt takes about 45 seconds to locate TDC. Small point Sharpie makes a mark that comes off. After that it's protractor time. Glad someone mentioned not using a piston stop for tightening hubs and props.

Thanks some more for the continuing posts.
tgk, Horizon Hobby had those stops. I sent for one just to have it when needed. Dan.

Between Milton's video and TOM's recommendation to eye ball TDC through the spark plug hole, I did a set up as seen in the attached image. Much to my surprise, the spark plug fired at 28 degrees. Definitely a benificial thread. Dan.