Use Hotter Spark Plugs On the Two Outter Cylinders

[Anonymous]

I have found that using the next hotter spark plug on the two outer cylinders of my 4 cylinder inline 1982 GS850GLX prevents plug fouling.
It only make sense that these two cylinders run cooler since they are more in the air stream. Remember that with NGK plugs the hotter plug has a lower number so I used a B7ES instead of a B8ES on the outer cyclinders and things work much better.

[KEITH KRAUSE]

Re: Use Hotter Spark Plugs On the Two Outter Cylinders

I have found that using the next hotter spark plug on the two outer cylinders of my 4 cylinder inline 1982 GS850GLX prevents plug fouling.
It only make sense that these two cylinders run cooler since they are more in the air stream. Remember that with NGK plugs the hotter plug has a lower number so I used a B7ES instead of a B8ES on the outer cyclinders and things work much better.

I know you think you've done the right thing, but what you've done is found a way to compensate for a richness problem or a weak or incorrectly timed spark. The outer two cylinders do run just a little cooler than the middle two. Some models run a step richer jetting in the middle cylinders to keep them running cooler. If changing the outer two plugs to hotter plugs was the answer, then the manufacturers would have done that.
The hotter 7 plug does not shed heat as easily as the 8. This extra heat in the cylinder will help a rich cylinder to spark better, but there may/will be consequences as there always is when compensating. You can get away with doing shorter trips with the hotter plugs, but if you go on a long ride you risk melting the plugs and all the damage that can cause. If you go on a long-high speed ride, you will melt the hotter plugs.
I would put the 8's back in and find whats causing your problem. I would start with checking the ignition timing to #1/4 cylinders. If the timing is good, I would check the coil and all connections.
If that's OK, I would check compression and valve clearances and then sinc the carbs. Also, make sure any mixture related screws are set correctly.
If you still are running rich in those two cylinders, I would clean and inspect the carbs for rich related problems. Incorrect/worn jets, loose jets, float height, worn float valve needles, etc.

[Anonymous]

My Clymer manual specifies D9EA plugs on my 1100 but my local Schucks carries only D8EA plugs. So that's what I run. Do you think that's a big problem?

[KEITH KRAUSE]

My Clymer manual specifies D9EA plugs on my 1100 but my local Schucks carries only D8EA plugs. So that's what I run. Do you think that's a big problem?

Most factory manuals will tell you the stock plugs are a good compromise.
They will suggest that if your bike is commonly run at higher speeds and longer trips, you should run a colder plug. If you run shorter trips AND carbon build up is a problem, then you should run a hotter plug.
Like I said to samova, your hotter plugs MAY be allright as long as you stick to shorter trips and/or general cruising speeds. If you go on longer rides, you run the risk of melting the plugs. Higher speeds and a hot day just increase the chances.
If you ride your bike "normal", I would be safe and order the correct plugs.
Only if you have mixture problems or a weak spark, would I understand the change in plugs as a last resort. Even then, that's just compensating for the real problem.

[Anonymous]

Something about this post has been gnawing at the back of my mind since I read it almost a month ago. It seems to me that samova may just be onto something. It is not uncommon for the outer two cylinders to be jetted one step leaner than the inner cylinders because the inner cylinders run at a higher operating temperature. because they cannot shed heat as efficiently as the outer cylinders. It makes me wonder if, as the colder plugs shed heat faster than the hotter ones, it wouldn't make sense to duplicate samova's setup, shifting all the plugs one step cooler and the jets a step leaner. In other words, if the two outer cylinders are to rich when running the standard B8ES, rather than running a higher heat range plug than the motor was designed for, take a step leaner in the main jet. Then, rather than leaving the jets richer in the inner cylinders to compensate for the extra heat, why not match them with the outer jets and then take a step cooler with the plug to a B9ES. It seems, at least in theory, that this would allow for a more consistent cylinder to cylinder operating temperature while eliminating the problems that might be caused by using to hot a plug (B7ES). Just a thought.

[scotty]

Ive gone on a trip with ((covered about 3K miles ))d7 plugs in all 4 jugs with no ill effects. I will always agree with proper jetting though. I was trying to get the fuel to burn more efficiently. I have experimented with the cooler and hotter plugs in the diferent cylinders and almost no diference was visable to me. Maybe i am too far sighted??

[Anonymous]

In 19 years and over 210,000 miles on GS850's and now the 1100GK, I've never fouled a spark plug. Plugs are replaced on my bikes once a year at checkup time, during which my mechanic checks carbs and valves.

By fooling with different heat ranges on plugs, you're treating the symptom rather than the disease.

All stock or near stock GS shafties should run perfectly, day in and day out, mile after mile, on B8ES plugs (all four of them) and regular 87 unleaded gas. Plugs should be the least of your worries when owning and riding a GS850.

Nick

[scotty]

In 19 years and over 210,000 miles on GS850's and now the 1100GK, I've never fouled a spark plug. Plugs are replaced on my bikes once a year at checkup time, during which my mechanic checks carbs and valves.

By fooling with different heat ranges on plugs, you're treating the symptom rather than the disease.

All stock or near stock GS shafties should run perfectly, day in and day out, mile after mile, on B8ES plugs (all four of them) and regular 87 unleaded gas. Plugs should be the least of your worries when owning and riding a GS850.

Nick

Ive heard of hard nosed but you must qualify for hard a s s
210K on a bike=wow

[Anonymous]

I think he meant 210,000 miles combined on more than one bike. 8O
I can't seem to run anything lower than 90 octane a not get pinging :? but, whatever works.

I've set up my bike as an experiment with this theory. Previously, I was running 130 mains with all B8ES plugs. I still had a little fouling on the outside cylinders in stop and go traffic. Now I'm running strainght 127.5s w/BP8ESs outside and BP9ES inside. 600+ miles and, so far, so good, plugs look beautiful tan/brown across the board and the bikes running great. Haven't been doing much driving in town though so I'll run this experiment a little longer and see what happens.

[Anonymous]

I think he meant 210,000 miles combined on more than one bike.

That is correct. I only have 81,500 miles on my GK -- 56,000 of which are mine. The other miles on my four previous GS850's.

We've discussed regular v. premium fuel several times now. I maintain that if your GS1000G won't run perfectly on 87 octane fuel, there's something else that's wrong. I've run nothing but regular fuel on all my GS bikes, and none of them pinged or knocked.

If a stock GS shaftie won't run on B8ES plugs perfectly and evenly, then there's a problem somewhere else. I maintain, again, that one should treat the disease, not the symptoms.

Nick

[scotty]

I think he meant 210,000 miles combined on more than one bike.

That is correct. I only have 81,500 miles on my GK -- 56,000 of which are mine. The other miles on my four previous GS850's.

We've discussed regular v. premium fuel several times now. I maintain that if your GS1000G won't run perfectly on 87 octane fuel, there's something else that's wrong. I've run nothing but regular fuel on all my GS bikes, and none of them pinged or knocked.

If a stock GS shaftie won't run on B8ES plugs perfectly and evenly, then there's a problem somewhere else. I maintain, again, that one should treat the disease, not the symptoms.



Nick

I agree with you Nick but you are still a Hard A ss

[bwringer]

Nick speaks the truth. I don't know about the hardness of his posterior.

My GS850 is bone stock, aside from Dyna coils, and the recommended B8ES plugs are always toasted a perfect grayish-tan color and last many, many miles. I replace mine every year (7 - 12k miles, depending), not that I really always need to. And yes, a lot of my miles are long, fast rides on hot days.

The color of the plugs will tell the tale -- if the plugs are telling you you're running too rich or too lean, something is not right with the carburetion. It's also important to remember that the a "hotter" or "colder" plug has no effect on mixture or cylinder head temperature. (Unless it's failing to fire or something.) Your bike will not run cooler just because you put in hotter or cooler plugs.

The only temperature affected by different plugs is the very tip of the spark plug -- the "temperature range" of a spark plug only has to do with the optimal nose temperature to prevent deposits on the ceramic and electrodes. Again, it has NOTHING to do with mixture or cylinder head temps.

If you plugs are fouling, jacking around with spark plugs without fixing the carbs has less of an effect than rearranging the deck chairs on the Titanic.

The main jets on a stock GS850 are 115 all across -- no wonder you're getting deposits and fouling with 130 and 127.5. (Assuming "theshootist" has a GS850, that is.)

And I use 87 octane gas, too, no matter how hot it gets, and I never get pinging. If you're getting pinging in a GS850, you have a problem with timing and/or carbon deposits. And carbon deposits can be caused by, oh, I don't know...using main jets three or four sizes too big?

[KEITH KRAUSE]

Changing the heat range of the plug will effect combustion. There is some significant temperature change in the cylinder. You can't change the combustion unless the temperature or the mixture or the spark timing changes. The plugs are rated by their ability to shed heat. If a plug runs hotter than another, there will be more heat in the cylinder and it will change the combustion.
I would never try plugs with two different heat ratings at the same time. It may make sense to someone, but it's the wrong thing to do. As I and others here have said, there is something else wrong with a bike that pings on B8ES plugs. As stated, excessive carbon deposits will cause pre-ignition. So will poor timing. Another thing that will cause pinging is using plugs with two different heat ratings. If the ignition is timed correctly and the correct mixture is in each cylinder, then the two different heat rated plugs will cause uneven combustion. Combustion will happen just a moment sooner in the cylinders with the hotter rated plugs. This is like advancing the spark timing on two cylinders. If all four cylinders are not running uniformly, you can get pinging, especially with lower octane fuel, hot days, etc.