Restarting a Power Mac 6

[04HemiRam2500]

I was using the old power mac 6 a few days ago just for fun. The saw has a lot of power in a tiny package. The only issue I have with it is no primer bulb. If I run out of gas and then refill it starting the thing is difficult.

Without a primer bulb how do you restart a saw like this? Do you flip the choke on even if it us to operating temp?

 

[dougand3]

You shouldn't have to choke a hot engine. If you run out of gas, you have introduced air into the fuel line and carb. May have to pull rope 15-20 times to replace air with fuel. May help to crack gas tank cap initially. Ensure the fuel filter is positioned as low as possible in the tank, so that it stays submerged. Of course, position changes as saw changes. And best is not to run out of gas. I refill at 3/4 empty tank - I may orient saw differently and make fuel filter pop out of gas. Fuel filters do have weights that keep them low in fuel but can pop out if 1/4 tank or less.

 

[04HemiRam2500]

Thanks dougand3, I just wanted to know if pulling it 15 times was the right way to start a saw without a primer bulb.

One more thing that I wanted to ask was about vapor lock. Maybe it was the way the saw was positioned. But this has happened about 3 times to me now. When cutting the saw will stall out with WOT. I open the gas cap tank is 3/4 to half full then close cap and give it 5 pulls and it starts back up again. I am thinking that there is a vapor lock issue going on? Maybe it is the gas cap? Or is something else causing this?

 

[dougand3]

Gas tank caps have a small valve to let some air in to replace fuel leaving. It could be stuck closed. Also, above could be fuel filter bobbing up out of gas.

 

[Jags]

Do you hear a suction sound when you crack the gas cap? If so it is probably the vent in the cap.

 

[04HemiRam2500]

I apologize to revive this thread but I am having issues again after it has been working. When using it I get it up to temp and if I shut it down it does not wan to restart. After it cools down it will fire up and run again.

Today, After it would not restart I let it cool then it started but was not reving up. I loosened the cap with it running and it worked great. So, I am guessing the gas cap is bad. The gas cap just has a tiny hole for air to come in in the middle. I blew air in the hole but still no luck. Before buying a gas cap is this my issue or am I missing something? Thanks.

 

[dougand3]

I loosened the cap with it running and it worked great.

That is a big clue. Worth buying a new gas cap.

 

[04HemiRam2500]

Yeah, I think gas cap too. Although I blew air into the hole and I feel it coming out on the inside of the cap so how can this cause vapor lock that I am experiencing. This saw is a nice little saw. This is really the first issue I have had with it.

 

[dougand3]

Fuel system doesn't generate as much pulling pressure as your mouth generates pushing pressure is a possibility.

 

[04HemiRam2500]

I should have mentioned I took the cap off and used an air compressor to clean the hole on the cap. Than put the cap on loosely.

 

[smokedragon]

Gas tank caps have a small valve to let some air in to replace fuel leaving.

Either clean the cap good in some solvent (to try and remove whatever is clogging the air inlet) or buy a new cap.

When using it I get it up to temp and if I shut it down it does not wan to restart. After it cools down it will fire up and run again.

You may also be having some carb issues......I have seen saws in the past that would act just like this - a through cleaning with new diaphragm and gaskets made it like new. If your gas cap doesn't solve your issue, a carb rebuild might. Often there is a clog somewhere that is only apparent when you try a hot restart.

 

[04HemiRam2500]

It is just weird to have a sudden issue with it as I used it about a month ago in cold weather. Messed with it more today it will run and restart if cap is loose as soon as I tighten the cap the saw will struggle to idle and boggs down. Also, if I tighten the cap the saw is not flooding itself cause pulled plug and it is bone dry. I wonder if I should drill out the hole on the gas cap a little bigger to make it work better. It is going to get colder again here so it will be interesting to see what it does.

Personally, I am thinking that in heat the gas in the tank is expanding too much for that little hole on top of the gas cap. A little bigger hole might solve my dilemma?

 

[TreePointer]

You didn't answer Jags' good question:

Do you hear a suction sound when you crack the gas cap? If so it is probably the vent in the cap.

...Personally, I am thinking that in heat the gas in the tank is expanding too much for that little hole on top of the gas cap. A little bigger hole might solve my dilemma?

The sound will be an indicator of vapor lock. It's not excess pressure in the fuel tank; it's the opposite. It is a relatively low pressure (vacuum like) in the tank that indicates this condition--hence the suction sound. Engine consumes fuel, but the breather valve doesn't let air in to replace it. The low pressure can starve fuel to the carb. The low pressure also can cause your fuel to boil at ambient temperature (boiling point depression), and in extreme conditions, you can actually see the fuel boil in the tank immediately after removing the fuel cap

 

[TreePointer]

Sometimes your symptom can be caused by your engine running too lean. This causes overheating, which would be similar to a very hot summer day that would push certain saw models into vapor lock.

Solution: try richening LOW carb adjustment up to 1/8 turn (towards richer running).

 

[04HemiRam2500]

Sorry I did not answer Jags question was trying to work on it while typing. I did hear a slight suction sound. Although it has always been like that. AS far as setting the low screw I have it at one turn out of the carb. Maybe this is not even? I re tune the saws during mid summer and mid winter to factor the temp change but maybe this saw just wants the L out more.

Should I tun it out a full turn more or how much?

 

[dougand3]

Smaller turns - 1/8 turn is good. CCW is richer.

 

[TreePointer]

Try 1/8 turn to start. Going a little too rich won't hurt the saw like going too lean, so feel free to experiment a little.

I've seem some saws respond with as little as 1/16 turn out, but my Makita 7901 needed a tad over 1/8 turn to solve this hot restart problem and sound really good.

 

[04HemiRam2500]

Okay, so I will turn the low 1/8 turn out from all the way in. Although, should I change the high before trying to start it cause the low affects the H as well?

 

[dougand3]

No, no, no. Starting point is 1-1.5 Full turns out (CCW) from LIGHTLY seated. Or from right where L is currently - 1/8 turn from there.

 

[04HemiRam2500]

Okay yeah I mis understood what was said. I was thinking wait just 1/8 turn out is lean not rich. Got it now. What about the high are you thinking leave it and see how it goes.

 

[dougand3]

Leave H alone until you get L tuned in. And if this is vapor lock from plugged gas cap vent, tuning carb won't fix.

 

[04HemiRam2500]

Typically i tune the h first. So with the l screw am i wanting it to idle faster to help keep gas in engine?

 

[dougand3]

The T or Idle screw should be way in...CW. Better to do L and then H. And H is tuned with WOT.

 

[TreePointer]

Adjusting the IDLE screw will change the throttle butterfly to increase or decrease the amount of fuel-air mixture going to the engine.

Turning the LOW adjustment screw CCW will add more fuel to that same fuel-air mixture while your saw is running at idle speed. In addition to providing combustion components (fuel + oxgen), this fuel-air will provide cooling and also add lubricants to the engine. The goal is to keep the engine from getting too hot.

 

[Jags]

I did hear a slight suction sound.

Fix or replace the darned cap before you do anything.