Muruyama Blower/sprayer

[KE4AVB]

Not sure if this is important but when I tested for spark with my light, I couldn't see the light-up until it started. In other words, 3 or full good pulls with no indication of spark. Then it would fire up and I could see the light. I was inside my garage at the time so there wasn't any light pollution to contend with.

It does sound like you have a weak spark. It may the spark plug so if you haven't changed try a known good plug. Or it could be weak flywheel magnets or too large air gap between the coil and the flywheel. Here I use a standard business for a gauge as most coils are gap at around .010"-.012". Also use my repair tag card stock as a gauge.

Is there a ballpark for the proper resistance?

As I said I only work one of these Muruyama units. But being a coil with the electronics inside it usually you can not test them other the secondary (Plug side). If there is problem in the primary side it is more likely to be the electronics anyway as the coils that I have taken apart have a fair robust primary windings.

If anyone out there that has one these Muruyama and has the time please check you coil resistances and report them so we could have at least basis for testing purposes. I would hate for Lefty have to buy a $100 ignition coil just fine out that his is good. But something is definitely off with the primary resistance reading he is getting. May have an internal colder solder joint.

[bgsengine]

Not sure if this is important but when I tested for spark with my light, I couldn't see the light-up until it started. In other words, 3 or full good pulls with no indication of spark. Then it would fire up and I could see the light. I was inside my garage at the time so there wasn't any light pollution to contend with.

It does sound like you have a weak spark. It may the spark plug so if you haven't changed try a known good plug. Or it could be weak flywheel magnets or too large air gap between the coil and the flywheel. Here I use a standard business for a gauge as most coils are gap at around .010"-.012". Also use my repair tag card stock as a gauge.

Is there a ballpark for the proper resistance?

As I said I only work one of these Muruyama units. But being a coil with the electronics inside it usually you can not test them other the secondary (Plug side). If there is problem in the primary side it is more likely to be the electronics anyway as the coils that I have taken apart have a fair robust primary windings.

If anyone out there that has one these Muruyama and has the time please check you coil resistances and report them so we could have at least basis for testing purposes. I would hate for Lefty have to buy a $100 ignition coil just fine out that his is good. But something is definitely off with the primary resistance reading he is getting. May have an internal colder solder joint.

Methinks its a red herring, though, unrelated to his original problem noted on this thread... however if his problem was "it wont shut off when I turn switch off" , then it'd make sense.. but if unit seems to run fine otherwise, I rather doubt that it'd be the ignition module, (Although not impossible) or the primary stop wire (unless it seems to mis-fire, and/or not shut off with the switch)

[lefty]

I've tried to figure out how these magnetos work but have been struggling. I understand generally how the electrical circuit works but can't seem to locate any info on how current travels through the circuit and what the kill wire is actually doing, more precisely, when it is doing it and how it disrupts the flow. But logic tells me that no current flows through this wire while the engine is running. So it shouldn't be impacting how it is running, just how it's stopping?

So here's my guess simplified of course. As the magnet passes the armature, current flows through the armature to the primary coil, which generates a field and subsequent current in the secondary coil, which is connected to the spark plug wire. That current then jumps the gap in the plug, and reaches ground. The kill wire is connected to the primary circuit so when closed, the current coming down the armature, rather than traveling through the primary coil, travels directly to ground terminating before it can travel down the spark plug wire. This is probably 100% wrong. I've been researching for days and can't seem to find anything that fills in the gaps I have in my knowledge.


So if it was the coil, the problem should be showing up in the secondary test? It shows 1.9k resistance so I guess I need to find out if that's within spec.

Or I'm back to checking the carb needle lever adjustment. Is this something you would suggest doing even with a new lever, needle, and pin being installed?

[KE4AVB]

The basics of the primary circuit is a low winding that produce around 200 volts grounded on one end. The control circuit which acts much like a on/off switch ground the other end of the primary winding via a resistor and transistor or SCR. This controls the timing of the pulse that goes through winding inducing a magnetic field in the secondary winding that produce a high voltage depending the turns ratio which can be as much 20,000 volts. The kill terminal is directly connected to the ungrounded side of primary winding so when it is grounded no voltage can be produce as it is sent directly to ground. Hopes this makes some sense.

As for the meter lever they should be set when installed as they are not when manufactured just close to the right setting.

[lefty]

Thank you for that.


I was going at this one again and found the problem I think. A problem that was likely overlooked due to the fact that ya'll would have automatically assumed I checked this...but I didn't...due to my inexperience of course. But I pulled off the muffler and the exhaust port is 90% choked off with carbon buildup. That has to be it....right? I've never seen one this bad.

I have some instructions to reference on another post that you guys were kind enough to give to me last week for a Husqvarna I was working on with some minor build up in the port.
http://ppeten.com/forums/viewtopic.php?f=3&t=3475

But my ears are open for any additional advice on this one. It's thick.

[KE4AVB]

Clogged spark arrestors are common of a problem but I have ran into a couple Echo trimmers this year where the exhaust port itself was halfway blocked with carbon build up. I would clean it up and see how things go. Also check the muffler itself for clogging since this one sounds badly plugged port-wise. Must have been running extremely rich or had a too much oil in the fuel/oil mix.

Lefty, It takes a lot experience with 2 cycles to get in a set troubleshooting routines and even then you can get tripped up by a seldom seen problem.

[lefty]

So this seemed to work. After cleaning the port, the rpm came right up. Thanks to all.

One thing I noticed when this came in is that the air filter was wet with fuel. I'm thinking that this was also due to the clogged exhaust port. Maybe inadequate exhaust caused excessive pressure and back pressure through the fuel port blowing back through the carb?

[lefty]

The owner reported to me that he religiously utilizes a 50:1 mix, but also just reported that the air filter was only recently changed for the 1st time. Meaning that this machine has been running commercially for almost 4 years on the same filter. Could each issue have lead to the other? Meaning, the air filter is wet because of the clogged exhaust and the exhaust port is clogged because of restricted intake airflow?

If not, what kind of advice should I be giving to reduce carbon buildup in the port? I know that the machine is run full throttle all the time. I've read that not running at full RPM can also lead to carbon buildup in the exhaust port as well.

[bgsengine]

very well could be - dirty air filter leading to clogged exhaust.. the general recommendation (IMHO) would be - replace air filter, spark plug, fuel filter, and all fuel lines every year.. whether they "look" good or not,and that machine should last just about forever....(or 5-8 years in daily commercial use) which has been my experience.. and yes, constant operation of these units at less than full throttle for extended periods, you'll see lots of carbon build-up - and even over-heating... at part throttle, engine may have more of a load to overcome, plus reduced air flow (since flywheel/cooling fan speed affects air cooling, right?) so you gonna see overheating, poor performance, carbon build-up, etc - and on units like trimmers and saws, with clutches, overheating and failing clutches and drums

[KE4AVB]

very well could be - dirty air filter leading to clogged exhaust.. the general recommendation (IMHO) would be - replace air filter, spark plug, fuel filter, and all fuel lines every year.. whether they "look" good or not,and that machine should last just about forever....(or 5-8 years in daily commercial use) which has been my experience.. and yes, constant operation of these units at less than full throttle for extended periods, you'll see lots of carbon build-up - and even over-heating... at part throttle, engine may have more of a load to overcome, plus reduced air flow (since flywheel/cooling fan speed affects air cooling, right?) so you gonna see overheating, poor performance, carbon build-up, etc - and on units like trimmers and saws, with clutches, overheating and failing clutches and drums

I'll 2nd that...

I got one commercial client that regularly have their equipment serviced and still they wear out the Echo SRM-225 about every two to three years. I retired two of them last year due PNC damage, wore completely through the cylinder plating. I only kill off one the Stihl trimmers but was due to be straight gassed a second time.

Now of course the operators at that client only know a few things. One is they either run wide open or idling. When equipment comes for repairs the only reported symptom reported is "It no work.". Most of the operators are Mexicans so language is a barrier. As solution I go over the whole units each time they come in.