spark plug question

My bike is an RM250. I just bought an Iridium tip spark plug. Its a br7eix and the last one I had in there was a br8 something. Now what will this hotter plug do to the bike? Should I not run it? Another question I have is I fouled the br8 probably because I am running 32:1 becasue it is a pretty much brand new motor. Should I lean out my gas to oil mixture or should I lean out my air to fuel miture? Thanks

keep runnin 32-1 got back to a br8, and actually rejet the bike for your altitude and riding conditions. dont ever lean out oil to fuel ratio to adjust jetting, jet your bike for 32-1, also the air fuel screw really only adjusts from idle to 1/4 throttle so getting the right jet is what matters most also clip position.

I think i might keep the br7 in there because im just breaking the motor in and wont be "goin' hammer down" with it. As long as I dont get it too hot I shouldnt have to worry about detonation I think.... and as for the 32:1 Im only running that for break in I plan on going 40:1 or 50:1 with a good synthetic oil. And yeah I know the thing needs to be re-jetted bad but im going to let a professional take care of that lol I dont really like screwing around with that stuff.

Follow Jamaracing's advice. If you are fouling plugs, its a jetting issue. Only idiots change their fuel ratio thinkinhg it will solve a jetting problem. Why? IT DOESN'T WORK. And 32:1 is the proper ratio, no matter what different oil companies say.

Im not really talking about changing my fuel to oil ratio to fix a jetting problem.... Im going to jet it for 50:1..... and anyone who really knows anything about motors would know that it is the gas that keeps the piston and everything cool.... if you displace the gas by adding more oil then your going to have over heating problems... and it is the fuel vapors that ignite so no matter how much you mess with the jetting to allow more air your not going to burn the oil because it separates from the gas when it enters the base of the motor to coat moving parts and if you have too much it is going to over whelm the plug and foul it. Also the reason im having this problem is I bought the bike blown up so I have no idea how it ran or what its jetted for.

Two stroke oil burns. I would never run a bike 50:1. 32:1 is proven as a great mixture ratio time and time again.

I had a 250R quad once (2t), and I tried out one of those iridium plugs. After the bike got hot, it started to rev uncontrollably and wouldn't die with the kill switch or even when I pulled the plug boot. I had to rib the carb out for it to stop running. It had a tach on it, and it kept rising and rising slowly since the bike didn't have a rev limiter - It got up to 14,500 RPM before I killed it. What happened was, the surface area of the iridium tips is very small, so it got red hot much more easily than a regular plug. It got so hot that it started burning the fuel without actually having to produce a spark, effectively making the quad run like a diesel motor. A week later I was riding through the woods and the crank bearings seized up.

Just something to think about. I realize tons of people have run these plugs (I even run one now in my 4 stroke) and never have a problem with them, but it does happen because it happened to me.

I would never run over 40:1 in my bike. I'm just breaking mine in too. It's worth paying someone for jetting your carb then throwing away money on fouled plugs

I had a 250R quad once (2t), and I tried out one of those iridium plugs. After the bike got hot, it started to rev uncontrollably and wouldn't die with the kill switch or even when I pulled the plug boot. I had to rib the carb out for it to stop running. It had a tach on it, and it kept rising and rising slowly since the bike didn't have a rev limiter - It got up to 14,500 RPM before I killed it. What happened was, the surface area of the iridium tips is very small, so it got red hot much more easily than a regular plug. It got so hot that it started burning the fuel without actually having to produce a spark, effectively making the quad run like a diesel motor. A week later I was riding through the woods and the crank bearings seized up.

Just something to think about. I realize tons of people have run these plugs (I even run one now in my 4 stroke) and never have a prYouoblem with them, but it does happen because it happened to me.

You are completely wrong about the tip of the plug causing your run-on simply because it was an irridium plug. An "8" heat range is an "8" heat range, regardless of the type of metal the electrode is made from. An "8" standard nickel-alloy plug will run at the same temperature as an "8" platinum or irridium plug.
A week later I was riding through the woods and the crank bearings seized up.
That tells me the your crank bearings were shot, and the resulting slop in the crank assembly was causing air leaks through the crank seals that produced an extreme lean condition. That's probably what caused your overheating and run-on problem, not the irridium plug electrode.
You are completely wrong about the tip of the plug causing your run-on simply because it was an irridium plug. An "8" heat range is an "8" heat range, regardless of the type of metal the electrode is made from. An "8" standard nickel-alloy plug will run at the same temperature as an "8" platinum or irridium plug.

That tells me the your crank bearings were shot, and the resulting slop in the crank assembly was causing air leaks through the crank seals that produced an extreme lean condition. That's probably what caused your overheating and run-on problem, not the irridium plug electrode.

I'm 90% sure there was no play in the crank. I had it apart about a week before that doing a top end rebuild. Also, I'm fairly positive that it was the plug that caused the run on. No matter the plug range, there is still less surface area on the electrode tip in an iridium type plug. It comes to a point, and the point can very easily get red hot I'm sure. It had never happened before with a regular plug and it never happened again after I took it out.... I can't think of something else that would cause it. Also, if there was slop in the crank, 30 seconds of 14.5k RPMs would have been all it needed to come apart.

Follow Jamaracing's advice. If you are fouling plugs, its a jetting issue. Only idiots change their fuel ratio thinkinhg it will solve a jetting problem. Why? IT DOESN'T WORK. And 32:1 is the proper ratio, no matter what different oil companies say.

If this is true then im going to run 1:1 and rejet so I don’t foul plugs.

............ so how does the oil separate from the gas??

Im not really talking about changing my fuel to oil ratio to fix a jetting problem.... Im going to jet it for 50:1..... and anyone who really knows anything about motors would know that it is the gas that keeps the piston and everything cool.... if you displace the gas by adding more oil then your going to have over heating problems... and it is the fuel vapors that ignite so no matter how much you mess with the jetting to allow more air your not going to burn the oil because it separates from the gas when it enters the base of the motor to coat moving parts and if you have too much it is going to over whelm the plug and foul it. Also the reason im having this problem is I bought the bike blown up so I have no idea how it ran or what its jetted for.
So....if you aren't going to burn the oil, where does it go? Does it just continue to accumulate in your crankcase until the entire engine is full and you have to sell the bike, kinda like selling your car when the ashtrays get full? Or do the oil fairies come spirit it away?

I'm sorry, there is just so much wrong with what you said that I'm not even sure where to start. How about we just start with the basics?

Pre-Mix 101

Looks like it's time for a little pre-mix 101. I don't usually get into ratio discussions, because mix ratios are like religions to most people, and they tend to be closed-minded and hard-headed on the subject, but I'll put in my $.02 here anyway.

Anyone that believes that spooge and plug fouling are caused by too much oil in the mix is flat out wrong. If you know how to jet, you can run any amount of oil you choose, and have absolutely zero spooge.

There is a prevailing myth that less oil is better. This simply isn't the case. While there isn't a magic "one-size-fits-all" mix ratio, and it is possible to use too much oil for your conditions, generally speaking, more oil is better, within certain limitations.

When an engine is jetted too rich, the excess fuel leeches heat from the combustion process, causing the combustion chamber temperatures to be too low to effectively burn the oil, or even completely burn all of the fuel. The result is spooge and deposits. The spooge is nothing more than unburned fuel and oil passing out the exhaust.

If you have a spooge problem, you have a jetting problem. You don't get rid of the spooge by reducing the oil, you get rid of it by fixing the jetting. Correct jetting will produce an air/fuel ratio of about 14:1, which will produce combustion temperatures in the 6000F range and exhaust temperatures in the 1200F range. This will provide sufficient heat to consume the premix oil.

The same goes for plug fouling. Rich jetting does two things. First, it promotes incomplete combustion of the fuel and the oil due to reduced combustion temperatures. The incomplete combustion of the fuel and oil promotes deposit formation inside the engine. Second, rich jetting reduces the combustion temperatures, which in turn reduces the engines ability to burn off deposits. Combine increased deposit formation with reduced ability to burn off those deposits, and what do you get? Spooge and plug fouling.

You don't choose a mix ratio based on "spooge" or plug fouling, you choose the ratio based on the amount of oil your engine needs to provide sufficient protection and adequate ring seal. The common misconception is that mix ratios are "one-size-fits-all", when in fact nothing could be farther from the truth.The amount of oil that is correct for one rider on his bike may not be enough oil for another rider/bike, or it may be too much oil. It all depends on engine displacement, riding style, and how hard you push the engine. A trail rider on a 500 that never reams the bike out is probably fine on a diet of 50:1, where a super-fast up-and-coming young future pro that screams an 85 'till the dogs howl the entire time he's on the track might not get a full day of racing out of an engine on less than 30:1. Your engine's oil needs are determined by displacement, rev range, and the loads you put on your engine.

When you shut your engine down and let it sit, much of the oil drains down into the crankcase and forms a puddle in the bottom. The depth of this puddle is your indicator of whether you are running the correct amount of oil for your engine's needs. Ideally, you want this puddle to be between 1/8 and 1/4 inch. If it's less, you need more oil in your mix. If it's more, you are running more oil than you need for your conditions.

With that said, to have that amount of residual oil in the crankcase at 50:1 (a ratio made popular by magazines and oil bottles), you can't be riding very hard, or your bike is jetted richer than necessary simply to deliver enough oil. I arrived at 32:1 for my bike with my riding style because that is the amount that gives me the proper amount of residual build-up. Small-bore engines require greater oil concentrations than larger engines to achieve the proper amount of residual build-up, because they rev higher and have higher intake velocities. Along the same lines, someone that pushes the engine harder, and keeps the revs higher, also needs to use higher oil concentrations to achieve the proper residual build-up.

When I was much younger and a lot faster, 32:1 wasn't enough oil for my conditions. I needed 26:1 to have enough oil.

To understand why the mix ratio is so important, you have to understand what happens to the oil in your fuel when it goes into the engine. While the oil is still suspended in the liquid gasoline, it can not lubricate anything. It has about as much lubricity at that point as straight gasoline. When the gasoline enters the engine, it evaporates, dropping the oil out of suspension. Now that the oil is free, it can lubricate the engine. The oil mist is distributed throughout the engine by the spinning crankshaft and the moving air currents to coat all the internal surfaces.

People believe that the oil just rushes right through a two-stroke along with the fuel, but that just isn't so. It can take 90 minutes or more for the oil migration through a two-stroke to result in a complete oil exchange on a slow trail ride, and even as much as 5 minutes for a full-throttle 20 minute moto.

The oil eventually makes it into the combustion chamber, where it is either burned, or passes out the exhaust. If the combustion chamber temps are too low, such as in an engine that is jetted too rich, the oil doesn't burn completely. Instead, some of it hardens into deposits in the combustion chamber, on the piston, and on the power valve assembly. The rest becomes the dreaded "spooge". The key to all of this working in harmony is to jet the bike lean enough to achieve a high enough combustion chamber temperature to burn the oil, but also still be able to supply enough oil to protect the engine. If you use enough oil, you can jet the bike at it's optimum without starving the engine of oil, and have excellent power, with minimal deposits and spooge. At 50:1 in a small-bore engine, you simply can't jet very lean without risking a seized engine due to oil starvation.

One small point. No one ever broke an engine by using too much oil.

Now we come to the issue of ring seal. Simply put, the rings alone can not effectively seal the cylinder. They also need oil to provide a complete seal against the bore surface. And up to a point, more oil will provide a better seal.

I have run Dyno tests on this subject, as a school project in Tech School. We used a Dynojet dynamometer, and used a fresh, broken in top-end for each test. We used specially calibrated jets to ensure the fuel flow was identical with each different ratio, and warmed the engine at 3000 rpm for 3 minutes before each run. Our tests were performed in the rpm range of 2500 to 9000 rpm, with the power peak of our test bike (an '86 YZ 250) occuring at 8750 rpm. We tested at 76 degrees F, at 65% relative humidity. We started at 10:1, and went to 100:1. Our results showed that a two-stroke engine makes its best power at 18:1. Any more oil than that, and the engine ran poorly, because we didn't have any jets rich enough to compensate for that much oil in the fuel. The power loss from 18:1 to 32:1 was approximately 2 percent. The loss from 18:1 to 50:1 was nearly 9 percent. On a modern 250, that can be as much as 4 horsepower. The loss from 18:1 to 100:1 was nearly 18 percent. The reason for the difference in output is simple. More oil provides a better seal between the ring and the cylinder wall.

Now, I realize that 18:1 is impractical unless you ride your engine all-out, keeping it pinned at all times. But running reasonable ratios no less than 32:1 will produce more power, and give your engine better protection, thus making it perform better for longer.

The bottom line? Choose a mix ratio that is adequate for your needs, and jet accordingly. You don't fix plug fouling and spooge by adjusting your mix ratio.

This is an interesting read that also supports my "more oil is better" claim.

http://www.bridgestonemotorcycle.com...oilpremix6.pdf

And this is a good article as well:

http://www.maximausa.com/technical/l...summer2001.pdf

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