Help getting it to start

[BillNH]

I have set the timing, points and carb by the book. I have a great spark, but it just floods most of the time. Every once in a while , 1 in 40 or 50 tries, it will start and run for a minute or 2. I have cleaned and reset the carb, timing, and points (new). It holds 10 lbs of pressure in the crankcase, and pulls 5 inches of vacuum when turned over. Pulls fuel up from the tank easily. Just will not start 99 percent of the time.
Any more suggestions?

[jayvee43]

Hi Bill
it’s not about how you spin the engine, but about the fire triangle (fuel/air/spark).

Is your sparkplug wet, or dry after a series of no start? What compression do you see when conducting a compression test with W.O.T. (wide open throttle) and finally, how fresh is the fuel. (I know this one is skeptical) but it must be asked.

I have spark, I have good compression but I am using last years "ethanol" (Phazed seperated fuel)

I hear them questions all the time at work. It is very difficult to say why you have such a hard time with your Hirth engine. I know the tell tale of the spark plug tip being wet is too much fuel, and dry is no fuel transfer into the combustion chamber. So If you can provide us with a little more details... It would help.

Jesse

[Barrie2777]

With an issue like this i work backwards. First you have to be sure there isnt a pool of gas in the motor base. It sounds like you have done a lot of cranking so make sure it is gone. There may be enough gas in tbe motor you can pour it out the exhaust. I ve seen this! Once you correct this then eliminate the carb by screwing the needles in til they hit bottom. Now with a dry plug and a dry cylinder squirt some gas down the carb. It should start.

[BillNH]

Jesse, Barrie, thanks for the answers. I have flooding each time I try to start it. The gas is fresh this week. I have 150 lbs of compression.
It may be what Barrie says , too much fuel in the motor base, I'll try to empty that then start over.

[Barrie2777]

If you remove the engine then you can remove the drain plug on the bottom of the crankcase

[Go Go Diablo]

Twice this year, I ran across Tillotson carbs that the needles were not holding back pressure and they were flooding the motor as well. If you have a pop off tester or a pressure tester that can pump and hold air, remove the hose from the carb and pump air into the fuel inlet. The needle and seat should hold air until somewhere between 8 and 12 psi and then "pop" when it should then bleed down a little and then hold about 6 to 8 lbs of pressure.

If you pump air in and it does not hold any pressure, fuel is being pumped right through the carb and into your motor. Give that a try and let us know what you see.

PS, I don't think a Hirth motor has a drain plug.

Bruce

[Barrie2777]

Ooops....thought we were talking jlo

[BillNH]

Twice this year, I ran across Tillotson carbs that the needles were not holding back pressure and they were flooding the motor as well. If you have a pop off tester or a pressure tester that can pump and hold air, remove the hose from the carb and pump air into the fuel inlet. The needle and seat should hold air until somewhere between 8 and 12 psi and then "pop" when it should then bleed down a little and then hold about 6 to 8 lbs of pressure.

If you pump air in and it does not hold any pressure, fuel is being pumped right through the carb and into your motor. Give that a try and let us know what you see.

PS, I don't think a Hirth motor has a drain plug.

Bruce

Yes, there is a plug exactly opposite the impulse port for the carb. I pulled that plug and tipped it up, got a couple ounces of liquid fuel out.
Still haven't got it started. I propped the throttle open and left it sit with the piston at TDC to allow any extra fuel to evaporate.