FH680V-BS29

[ILENGINE]

Here is one for you guys to ponder. Fresh RN14YC spark plugs, new OEM ignition modules, valves set to .006, and freshly rebuilt carb. Engine will start within about 4-6 revolutions cold, but after running 10-15 minutes won't start with or without choke hot, And will not fire with addition gas dumped into the intake. And the tip of the afterfire solenoid has been removed. And gas is known to be fresh.

 

[txmowman]

Well, first of all, all cutting the tip off a fuel solenoid does is make it a junk part.
Assuming the fuel dumped into the intake is actually making it to the cylinders, you likely have a sticking valve would be where I would check.

 

[ILENGINE]

Well, first of all, all cutting the tip off a fuel solenoid does is make it a junk part.
Assuming the fuel dumped into the intake is actually making it to the cylinders, you likely have a sticking valve would be where I would check.

The plastic tip has been removed. the metal plunger is still intact. And both cylinders are reading 15-18% bypass with a leakdown tester both hot and cold. And the bypass air is coming from the crankcase, so just ring bypass lose. And adding a small amount of fresh fuel into the intake should eliminate fuel flow issues from the carb both still won't start.

 

[txmowman]

As you know, the engine requires fuel, spark and compression. Since the engine ran previous, and given everything you wrote, it is either the coils or possibly the air gap.What the part number of the coils you received and what did you set the air gap to? Try moving the coils closer to the flywheel magnet, without them hitting of course, and retry.

 

[sgkent]

first thing I ask myself when troubleshooting an engine not starting, which is missing:

Air/Fuel
Spark
Compression

Others have said the same.

If all three are present, and there are no changes made like reversed plug wires or cam timing etc., then it may be flooded. If so why? Where is it coming from?

When a hot engine in summer floods, it can be from heat boiling the gasoline in the carb, which can be that the engine cooling is failing - especially on an air cooled engine, and it is running too hot.

One trick if you have spark and compression, and you think it might be flooded, is pull the apark plug and set it aside for a minute to dry. Pull the engine thru three or four times to clear out any excess fuel. Then put the plug back in and try it again. If it starts, that usually means it was flooded.

 

[Rivets]

Couple of things which come to my feeble mind. First, I checked the service manual and it calls for a Champion RCJ8Y plug. Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold. I know the oil pressure switch only triggers a warning light, but if I remember right I did have one that shorted out the ignition switch when it got hot. Replace it and problem went away that time. Manual says the fuel solenoid and pressure switch connect to the same terminal on the key switch. If that were the case I doubt you would hot spark. IL, I know you have been around the block at least one time, but I’ve got to ask a stupid question, please don’t be insulted. Have you checked for hot spark with an adjustable spark tester and can get it to jump at least 3/16”? I’ll keep thinking, keep us posted. I hope this is not a test, if so I failed.

 

[ILENGINE]

As you know, the engine requires fuel, spark and compression. Since the engine ran previous, and given everything you wrote, it is either the coils or possibly the air gap.What the part number of the coils you received and what did you set the air gap to? Try moving the coils closer to the flywheel magnet, without them hitting of course, and retry.

Coils are part number 21171-7034 set to .010. Standard is .008-.016.

first thing I ask myself when troubleshooting an engine not starting, which is missing:

Air/Fuel
Spark
Compression

Others have said the same.

If all three are present, and there are no changes made like reversed plug wires or cam timing etc., then it may be flooded. If so why? Where is it coming from?

When a hot engine in summer floods, it can be from heat boiling the gasoline in the carb, which can be that the engine cooling is failing - especially on an air cooled engine, and it is running too hot.

One trick if you have spark and compression, and you think it might be flooded, is pull the apark plug and set it aside for a minute to dry. Pull the engine thru three or four times to clear out any excess fuel. Then put the plug back in and try it again. If it starts, that usually means it was flooded.

Even after adding fuel and cranking and then immediately removing plugs they are dry. Sometimes it will pop a couple times but still not start hot. Three different spark testers show spark. Something I may need to check but is unlikely an issue is partially sheared flywheel key but that condition on rider engines is rare unless some knothead removed the flywheel and didn't torque it properly. And most of the time a sheared flywheel on a rider engine is way out of time not just a few degrees.

 

[txmowman]

Could be flooded, yes. But, heat is not likely the issue unless the routing of the fuel line has been changed from where MTD originally routed it. I still suspect the coils or if there is spark.

 

[ILENGINE]

Couple of things which come to my feeble mind. First, I checked the service manual and it calls for a Champion RCJ8Y plug. Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold. I know the oil pressure switch only triggers a warning light, but if I remember right I did have one that shorted out the ignition switch when it got hot. Replace it and problem went away that time. Manual says the fuel solenoid and pressure switch connect to the same terminal on the key switch. If that were the case I doubt you would hot spark. IL, I know you have been around the block at least one time, but I’ve got to ask a stupid question, please don’t be insulted. Have you checked for hot spark with an adjustable spark tester and can get it to jump at least 3/16”? I’ll keep thinking, keep us posted. I hope this is not a test, if so I failed.

Compression test not a bad idea even if just for reference.

 

[txmowman]

This model does not use an oil pressure switch, at least not from Kawasaki.

Couple of things which come to my feeble mind. First, I checked the service manual and it calls for a Champion RCJ8Y plug. Second, I know you’ve done a leak down test, but I would perform a compression test, should have a minimum of 57 PSI. I wonder if it is different hot and cold. I know the oil pressure switch only triggers a warning light, but if I remember right I did have one that shorted out the ignition switch when it got hot. Replace it and problem went away that time. Manual says the fuel solenoid and pressure switch connect to the same terminal on the key switch. If that were the case I doubt you would hot spark. IL, I know you have been around the block at least one time, but I’ve got to ask a stupid question, please don’t be insulted. Have you checked for hot spark with an adjustable spark tester and can get it to jump at least 3/16”? I’ll keep thinking, keep us posted. I hope this is not a test, if so I failed.