OK, I've had this motor for about 7 years and it ran well for the first 5 although it has always been a bit temperamental on cold starts. The troubles started when I lost a coil a couple of years ago. I replaced it with the proper Sierra replacement but have been plagued with hard starting ever since. Sometimes it starts right up, others it acts like it's not even attempting to fire. Usually if it doesn't start right away the plugs will wet foul and I have to pull them out and dry them, over and over and over again. Once it starts the idle is unstable and it usually dies as soon as you put it in gear. If I can keep it running long enough to get it in gear and above an idle, everything is fine from there.
The carbs have always been kept clean, I have done a deep engine decarb more than once and I run a can of Sea Foam though the first tank every spring. Last year I completely rebuilt all three carbs and put on all new fuel lines, did link & sync, still the problem persisted. The last time I used it a second coil failed (They were originals BTW). I didn't get a chance to mess with it again so it has now sat for 9 months.
OK, so this springs so far I have replaced the remaining two coils, disassembled and cleaned all carbs, fresh fuel. Someone suggested that the powerpack was probably on the way out and likely producing weak spark, so I replaced that as well. I pulled the flywheel to check for a sheared key, it was fine but I put a new one in anyway. Also checked the stator for cracks and the sensor coils for cracks and oozing, all look fine. Also inspected upper crankshaft seal, it was not oily but I sprayed soapy water on it anyway, replaced flywheel and cranked it a few times. Pulled flywheel and no bubbles.
So all this got it running well on muffs in the driveway but it idled incredibly high, like 2000 + RPM. I attributed it to the fact that there was no back pressure on the exhaust and the air silencer box was removed. Hit it with a timing light while it was running and found that it was timed at exactly TDC at the throttle pickup point. Buttoned everything up and went to the lake assuming that I would only need to adjust the idle speed stop and throttle linkage and everything would be fine.
Once again, hard to start and sounds like it is not timed right. At idle it misses and sounds like one coil is cutting in and out. Give it gas and it goes. Top end is great (it always has been), but back to idle and it starts missing and will eventually die. No amount of throttle linkage adjustment seemed to help at all. Took it to the lake again yesterday to mess with it and could not get it to start at all.
I finally decided that maybe the reeds weren't sealing well until crankcase pressure increased so I pulled them to inspect and they look fine. I did find that the gasket between the air silencer and the front of the carbs was a bit messed up. Take a look at the attached photo and tell me what you think. This is at the bottom carb and as you can see I'm definitely sucking air through the gasket at each of the screw holes. I cannot see where this is the problem however because this air leakage is before it enters the carb throat where fresh air supply is still unrestricted. But if you look close at the upper right you can see that the slipped gasket is covering half of the opening to the port that is to the starboard of the idle air bleed orifice. I'm not certain, but I think this port is the fresh air supply to the idle orifice. I have new gaskets on order but wanted to get some opinions. Do you think this is my sole problem at this point or does it sound like there may be something else going on that I'm missing?
BTW, my compression is 150, 150, 140 and I have good blue spark on an air gap tester set at 1/2".
The carbs have always been kept clean, I have done a deep engine decarb more than once and I run a can of Sea Foam though the first tank every spring. Last year I completely rebuilt all three carbs and put on all new fuel lines, did link & sync, still the problem persisted. The last time I used it a second coil failed (They were originals BTW). I didn't get a chance to mess with it again so it has now sat for 9 months.
OK, so this springs so far I have replaced the remaining two coils, disassembled and cleaned all carbs, fresh fuel. Someone suggested that the powerpack was probably on the way out and likely producing weak spark, so I replaced that as well. I pulled the flywheel to check for a sheared key, it was fine but I put a new one in anyway. Also checked the stator for cracks and the sensor coils for cracks and oozing, all look fine. Also inspected upper crankshaft seal, it was not oily but I sprayed soapy water on it anyway, replaced flywheel and cranked it a few times. Pulled flywheel and no bubbles.
So all this got it running well on muffs in the driveway but it idled incredibly high, like 2000 + RPM. I attributed it to the fact that there was no back pressure on the exhaust and the air silencer box was removed. Hit it with a timing light while it was running and found that it was timed at exactly TDC at the throttle pickup point. Buttoned everything up and went to the lake assuming that I would only need to adjust the idle speed stop and throttle linkage and everything would be fine.
Once again, hard to start and sounds like it is not timed right. At idle it misses and sounds like one coil is cutting in and out. Give it gas and it goes. Top end is great (it always has been), but back to idle and it starts missing and will eventually die. No amount of throttle linkage adjustment seemed to help at all. Took it to the lake again yesterday to mess with it and could not get it to start at all.
I finally decided that maybe the reeds weren't sealing well until crankcase pressure increased so I pulled them to inspect and they look fine. I did find that the gasket between the air silencer and the front of the carbs was a bit messed up. Take a look at the attached photo and tell me what you think. This is at the bottom carb and as you can see I'm definitely sucking air through the gasket at each of the screw holes. I cannot see where this is the problem however because this air leakage is before it enters the carb throat where fresh air supply is still unrestricted. But if you look close at the upper right you can see that the slipped gasket is covering half of the opening to the port that is to the starboard of the idle air bleed orifice. I'm not certain, but I think this port is the fresh air supply to the idle orifice. I have new gaskets on order but wanted to get some opinions. Do you think this is my sole problem at this point or does it sound like there may be something else going on that I'm missing?
BTW, my compression is 150, 150, 140 and I have good blue spark on an air gap tester set at 1/2".
