The problem with diaphrams? It's really hard to tell if they are any good unless you see hole in them. So of use can guest by looking at them and again it just guest? The diaphram is the fuel pump. Gives the initial squirt of fuel for the saw to rev. and unseats the needle against the seat for fuel flow in conjunction with the vacuum of the pistion going up and down pulls fuel up to and through the carb. Other problem You said you cleaned the carb. But didn't eleborate on how and what you did. Under the diaphrams there are welch plugs this provided a path to clean the three main jets. IF the saw will idle and won't rev up sometimes the mid and full throttle main jet has become blocked with something dirt, gum,or whatever. Most of use don't miss with the welch plugs due to special tool for installation being it's just hammer seal conformed to the opening in the housing. Mostly likely the main jet is clogged. you can try to spray can carb. cleaner in ALL the little holes when you have the carb. apart, but that don't garrantee it will clean the main jets passages. Again assume you have checked the filter in tank all fuel line aren't cracked and you have got all the air out of the fuel system?

Your F400 Tiller has the Honda G150 3.5hp flat head engine. Last made in the early 1980's and replaced by the GX120-140-160 series. Good engine, but "old school". Your engine has breaker points and condenser, which are located under the flywheel. A few later engine were fitted with transistorized ignition. If your coil is outside the flywheel, you have electronic ignition and your life got earier, but not necessarily less expensive. No coil visible means breaker point style coil, and everything under the flywheel. You have to pull the flywheel to get at the points. That's why Honda suggests a dealer. You need a tool to hold the flywheel while you remove the crankshaft nut, and then you need a puller to remove flywheel. Can be done without special tools, but if you haven't done it before, you can damage the crank, flywheel, and/or block. And, as I'm sure you know Honda parts prices will curl your hair. Once points are exposed you either need to replace, or if only lightly burned, file or burnish. Use an automotive point file. Don't take off anymore metal than need to clean up. Adjustment is to .020 gap at highest point. adjustment is done to the "fixed" contact. There will be a hold down screw and the point frame will have an oversized slot to allow adjustment. Could also be a bad condenser, so after I did the points, I'd dry fit back together to see if you have spark, before you crank everything down to full torque. You may have to go back under the flywheel to replace condenser. As for fuel system, the G150 has a petcock under the tank, and then a fuel line to the carburetor (Keihin is mfg). I believe it has an "OFF", "ON", and "RESERVE" position. There is no primer or return line. Carb has a choke plate, and I'm not sure whether it is manual, or integrated with the throttle cable and governor assembly. In my judgement, best practice is to close the fuel petcock after every use and then run the engine dry. Others will disagree, but I have generally had less trouble with varnish and corrosion build up in my carburetors.

The PTO clutch on the tractor is electro-magnetic and takes a lot of current to operate. If you have a low battery condition this will stop the tractor because you don't have enough voltage to run the ignition system with the PTO turned on. First, check the battery voltage with the tractor off. You should have about 12.75 to 13+ volts (depending on the age and condition of the battery). If the battery voltage is low you could have one or more of the following problems: 1. Old battery that will not hold a charge - needs replacement. 2. Bad voltage regulator - battery is not being charged and electrical system is running on low voltage when the engine is on and the PTO draws enough to shutoff the tractor. 3. Bad stator - battery is not being charged. Of the three possibilities - 1 & 2 are the most common. A bad stator is the least likely but, you can easily narrow this down. Start the tractor and check the battery voltage. If the stator and voltage regulator are working correctly, you should have 14+ volts at the battery. If you do not have 14+ volts with the motor running, then the battery is not being charged - and there is probably not electricity being supplied to run the electro-magnetic PTO clutch + ignition. You can sort this out by starting the engine and pulling the connector from the voltage regulator and looking for AC voltage using a multi-meter. I do not know the exact terminals on that engine - but, you should be able to find a service manual on line in electronic format for about $8.00. Otherwise, you can do this by a process of elimination. Put the probe in the top left contact and check the other contacts sequentially. What you're looking for is about 30 Volts AC from the stator. Then go to the second contact, repeat, etc. If you don't find the voltage - bad stator. This really isn't as likely as a bad voltage regulator. Voltage regulators have diodes in them and other semi-conductors and after being continually exposed to heat, vibration, etc. - they go bad. So, check the voltage regulator with a multi-meter on the Ohms setting. Most of the resistances should be in the 4.5 mega-Ohm area. If you find opens or low Ohm readings between contacts on the voltage regulator - it needs to be replaced. My guess - it's the voltage regulator and you will find several "open" conditions. I just replaced the voltage regulator on a John Deere garden tractor because the PTO would not stay engaged and the battery was always low. If you find the voltage regulator is bad, in your case I would replace both the voltage regulator and battery if the battery is over 2-3 years old as constantly running it in a discharged state has probably compromised the battery's ability to hold a charge.

Hi again Fred. First, do you have auto dimming headlights? If so, unplug the connector from the rear the rear view mirror and see if your lights go out. Now that's the last "silver bullet" that can be thrown out. All too often I see people make light of what a tech has to do today to repair someones car. You don't have to read too many threads right here in this forum and you will see just how rare it is to get respect for what we do. We DON'T just swap parts as you did by playing musical relays in order to figure out a problem with someones car. You should have noticed though, that when you were plugging the relays in, they probably clicked because they are "being commanded on". This command could be a false one such as a grounded wire. We don't actually call that a short because shorts blow fuses, that's not happening here. Looking at the schematic, and not knowing for sure which system you have (there are two designs, one with auto dimming, and one with just Daytime Running Lights) makes it impractical for me to type out each step to lead you to diagnose this thing. Seriously, it would take me about 1/2 an hour to diagnose it, and three hours to type it all out. Average pricing for a tech/shop to diagnose this issue around here would be in the $100 range. Keep in mind things like "Flash to Pass" and the fact that the multifunction switch is a significant part of the circuit. Any aftermarket alarm systems, could also be in play. I'm not going to be able to go into great detail, make sure there are NO blown fuses in any of the vehicles fuse blocks. A blown fuse would of course be evidence of a short occurring somewhere, and this can result in a back feed which can command a relay on. Later today I can look closer at what you have written here again. But if you don't have the skills to do the diagnostics on electronics at this level you should plan to have a tech repair this. JMHO.