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WesternHunter's picture
Joined: 05/05/2006
Posts: 2374
Any Small Engine Experts Here?

Anyone here an expert on small engine repair? I have a bit of a delemma with conflicting information on my 2 cycle trimmer. It's a Husqvarna 128CD that I bought new last spring. In preparing my lawn equipment for the season as I do at the start of every season I went to restring and tune-up my trimmer and discovered that the spark plug that was factory installed in my trimmer was a Champion resistor RCJ8Y. Okay, nothing odd there, pretty typical plug for a 2 stroke engine of this type. The problem is that in reading the paper manual that came with the trimmer it specifies to use a Champion RCJ6Y resistor plug. That's a cooler plug by 2 heat ranges. I went to Husqvarna's website to view the parts list and schematic for my trimmer. They basically have several models of trimmers that use the same engine. The parts list for my model indicated the plug to be a RCJ8Y, but the updated online owners manual still specifies to use the colder RCJ6Y. To make matters more complicated the manual specifies to use only a resistor type spark plug and I can see no reason why a simple 2 stroke engine would need a resisitor type plug. In fact I can't even see why a simple 4 cycle mower engine would need a resistor type plug. Regarding the resistor plugs I know exactly why some larger and more complicated engines need them, that's not the question.

The three big problems are:
1. Husqvarna really hasn't given me a good answer.
2. I can easily find the RCJ6Y plugs at a number of places. But, there isn't an auto parts store, home center, hardware store, or small engine repair shop locally that sells the resistor RCJ8Y plugs. They all only sell the non-resistor CJ8Y.
3. Will using a non-resistor plug in a 2 stroke engine cause any damage to the coil. I suspect this is the only reason why Husqvarna is specifying a resistor plug in it's engine, to prevent damage to the coil.

In examining the factory installed RCJ8Y plug I can see that it seems to be the right plug with no indications on the electrode of excessive heat or fouling either and it seemed to run great last season. I worry that the colder RCJ6Y might not be hot enough to keep the 2 stroke running reliably and will foul faster. Asking a small engine repair shop about this is a waste of time. Most guys there are on the job trained and it's a lot like asking a gunsmith what his favorite guns are - the ones that break most often and come in for repair. Those small engine shops figure the faster your machine breaks the more business they will have sooner, they're not going to tell you how to keep your machine running best the longest. I know first hand because I once briefly worked in a chainsaw and lawnmower shop sharpening blades and tools a long time ago. Any thoughts or info will be helpful. Thanks.

Location: Florida,USA
Joined: 08/21/2003
Posts: 1585
Re: Any Small Engine Experts Here?

Hummmm, I am certainly not an "expert" and can only offer a guess but admit I know nothing about Husqvarna Trimmers.

Unless there is some sort of electronic ignition or CDI system on the trimmer I can see no reason for "requirement" of Resistor spark-plugs unless there is some sort of FCC regulation that requires the reduction of RFI emissions. Is there an FCC statement in the paperwork that came with the trimmer or stamped label on the trimmer itself?
I would not think that they would have any effect on the heat range of the plug though unless the coil pack is poorly made or the spark-plug wire is not matched with the resistor in the coil and the Plug. Such a mismatch could have an effect on voltage which could increase heat in the plug causing misfires.

Interesting though and I'd be interested in knowing exactly why also.

WesternHunter's picture
Joined: 05/05/2006
Posts: 2374
Re: Any Small Engine Experts Here?

I was able to speak to someone different at Husqvarna and they confirmed my suspicions about the use of a resistor type plug in a modern 2 cycle engine. I speculated that the reason might be to prevent damage to these new ignition modules/coils (spark plug wire) being used on todays engines. Husqvarna confirmed that the industry is using some complicated modules (coils) these days that send info back and forth to the engine, unlike the simple older carbon fiber modules (coil). Sounds like there is a lot more delicate but more sophisticated circutry being employed in the ignition modules today of new outdoor power equipment. The resistor type plugs are used in this manner to prevent damage and premature burn-out of the new module (coil). I also called Stihl and they confirmed that this is true also of their newer 2 cycle engines as well.

The guy at Husqvarna cautioned me that using a non-resistor type spark plug in my trimmer will damage the ignition module beyond repair. I then explained to him that Husqvarna better see to it that all their dealers and repair centers carry those RCJ8Y resistor plugs. I've gone to every Husqvarna dealer within a 20 radius of me as well as every small engine repair shop and lawn mower shop in the area and none of them sell the Champion resistor plugs in the 8 heat range. They all only carry the non-resistor 8 heat range.

Man oh man!! Finding a simple common replaceable part to keep any engine running properly should not be that difficult. Maybe I'm just too anal, but I learned a long time ago that it always pays off in the long run to follow procedures and specifications when it come to keeping any type of power equipment running safely and properly. Luckily I was able to find that particular plug at my local Ace Hardware store. It's the only place in the area that seems to carry them, and while they sell a limited number of gas trimmers, that particular Ace co-op is not a Husqvarna, Stihl, or Echo dealer at all. But the best part is that the guy who runs that store always seems to know what in the heck I'm talking about. Thumbs up

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