Pod Filter Problem

[Arnadanoob]

Your temps are similar to what we have here, it appears to be tropical weather with perhaps the differences being something like humidity which does affect jetting in a negative way.

A 6 range plug is kind of on the hot side for the ambient temperatures you seem to have. On NGK spark plugs, the lower the number the hotter the spark plug. We use NGK B8HS spark plugs here and never go beyond a 7 range plug.

There is a way to check the spark plug's ground strap to determine if your heat range is correct but it can be difficult to see clearly due to the oil we burn along with the fuel for 2 strokes. I can go over this later if you wish.

The problem with using a spark plug of a heat range even 1 range off will affect jetting severely. For example if your engine is supposed to be using a 8 range plug but you're using a 6 (which is a hotter plug), if you rely on plug chops to determine your jetting, in order to get that chocolate brown color you'll almost always end up jetting richer than what's necessary. When you jet richer, temps come down, that's why I think your temps are so low. For example when you used that cone filter and you noticed it gave you immediate problems, that's a symptom of your engine being tuned so rich to the point that the filter restriction was too much and there wasn't enough air volume to burn with all the extra fuel.

Air cooled engines suffer heat soak much worse than a water-cooled engine. When you ride at higher speeds, you have the benefit of extra fuel being fed in to the cylinder, more oil to reduce friction-related heat, and higher air velocity through your fan from the extra rpms. You slow down now you have less fuel to cool the cylinder, the fan speed drops in rpm so all the heat soaks into the bore and everything else which is why temps climb up for a bit, then eventually drops down. That's purely normal behavior.

If you're seeing higher temps with the carb and PG pipe upgrade, that is normal. Higher air flow = more power = more heat generated. The PG pipe is also a higher rev pipe, higher rpms are associated with more heat.

Keep in mind 2 stroke air cooled engines are not like electronics, cooler does not always mean better. Fuel must atomize properly for power, fuel atomizes better at higher temps (which is why engines without chokes on carbs run like crap until they warm up). If the engine is too cold, fuel condensates and sticks to the internal walls of the intake tract instead of atomizing into a finer mist to burn completely. Right now your engine is running cooler than watercooled bikes, that isn't good and should show signs of it when you tear everything down for visual inspection.

Oils require a certain range of heat in order to work properly. Some oils won't reach proper flash points at the temperatures you currently have.

[Arnadanoob]

Why I don't like relying on only plug chops for final tuning.

Plug chops are mostly for getting a general idea not for taking accurate air-fuel checks for the final steps of tuning. When you have a new pipe, different carb, new intake manifold, etc. you can't tell what settings will work best so you use plug chops to essentially avoid blowing up your new engine by getting close as you can initially while you fine tune the rest of the bike first.

A spark plug with a hotter heat range is essentially like running an engine with higher temps, in regards to the insulator. When the spark plug is hotter, it's no different from making your engine run leaner which also leads to higher temps.

Hot plug(hot) + extra fuel(cold) = hot + cold = warm = normal looking insulator.

What this means is if you rely on the insulator color, if you use a spark plug that's too hot, in order to achieve an ideal looking insulator color, you will have to jet richer to neutralize the extra heat retained by the plug. The engine however is experiencing too much fuel which will definitely show its signs when you exceed 1500ft when it starts to sputter under load.

If you are in a cold climate and you use a colder spark plug...

A spark plug with a colder heat range is essentially like running an engine with lower temps, in regards to the insulator. When the spark plug is colder, it's no different from making your engine run richer, which leads to lower temps.

Cold plug(cold) + leaner on fuel(hot) = cold + hot = warm = normal looking insulator.

By doing plug chops you are tuning the fuel ratio to the spark plug, not the engine. That is NOT how you tune an engine correctly.

In order to tune the fuel delivery to an engine properly you MUST FIRST determine the correct heat range of the spark plug before you do anything else. This can only be done through checking the electrode strap.

You can read the basics of it here. http://www.angelfire.com/fl4/pontiacdud ... plugs.html

For modified DIO engines, 72cc and up, your spark plug heat range will almost always be an 8 range NGK plug.


For final fuel tuning, I will make final checks based on what I find on the mixture ring of the spark plug, which is NOT affected by the heat range of the plug and is the most accurate way to determine jetting quality. You will sometimes need a cutting tool to remove the threaded portion of the sacrificial spark plug in order to see it properly.

[jeremydde]

I will change the plug to an 8 tomorrow. I am getting misfiring again. I tried a smaller main jet, and it got noticeably worse. Violent backfires out the back. Pretty much wouldn't move at all. I redrilled my other 132 jet to a 141, and the misfires were still present. This is all with a brand new 6 plug. The next smallest drill I have is a 161 jet size, which I haven't tried. I will try and purchase more jets tomorrow as well. By your explanation, using too hot of a plug should raise my temps (makes sense), but my temps are low. Yesterday I had it to 60mph quite easily. Today, it will barely accelerate down the alley. I checked the plug too. There isn't any signs of overheating either. I was initially thinking that the rich smoke was due to overjetting, but then I thought it might be a weak ignition so I installed a new coil and plug to check ($60 CDN). Perhaps the spark plug is just all wrong, and the lack of a filter was allowing more cool air in to allow for ignition?

Jeremy

[Arnadanoob]

By your explanation, using too hot of a plug should raise my temps (makes sense), but my temps are low. Yesterday I had it to 60mph quite easily. Today, it will barely accelerate down the alley. I checked the plug too. There isn't any signs of overheating either.

Jeremy

The spark plug's heat range won't show up on your CHT gauge and it has no bearing on your engine temperatures. The amount of fuel (your jetting) is what determines the temps you are reading at the CHT gauge. The heat range of the plug will affect your ability to jet the engine correctly using the plug chop method. The reason why your temps are so low is due to an overly rich condition. There's a lot of unburned fuel which is leading to an incomplete burn and a corresponding loss in power and very low temps. Remember, fuel cools the engine from the heat resulting from combustion, not the oil.

In an extreme situation, if you used a 3 range plug for example, that's a very hot plug. If you install that on your engine and ride around and take plug chop readings, the insulator temp will be very high and you'll notice that it'll likely be whitish in color at a low 200F temp, which makes you think "omg my engine is wayyy to lean". So in panic you jet bigger which brings the temp of the insulator down from all the extra fuel, you start to notice that the bike starts to sputter from being overly rich but when you check the spark plug, it's chocolate brown... so the jetting's perfect right? Wrong.


All of the following can be true when you use the plug chop method.

- spark plug insulator can be bright white and your jetting being perfect.

- spark plug insulator can be bright white and your jetting be too rich.

- spark plug insulator can show excessive carbon deposits (which means too rich) and the jetting still being too lean.

- spark plug insulator can show chocolate brown and be too lean on fuel.

- spark plug insulator can show chocolate brown and be too rich on fuel.

[bakaracer]

is it a misfire or stutter at wot?meaning does the engine cut in and out at wot?check to see if the ground cable is loose that comes from the stator because that will cause the misfire too(green wire).

[jeremydde]

is it a misfire or stutter at wot?meaning does the engine cut in and out at wot?check to see if the ground cable is loose that comes from the stator because that will cause the misfire too(green wire).

Will do. It was definately misfiring today. Backfiring out the back of the muffler. Almost like the timing was wrong.

[Bear45-70]

Backfires are almost alway caused by being too lean in a 2 stroke.

[bakaracer]

yeah double check that ground wire.that thing will cause that symptom.you might even have to pull the fly wheel off and check to see if the pickup came loose if the groung wire is tight.

[jeremydde]

I changed the sparkplug to the other new 6 that I had (2 pack) and the misfires are gone and all is well again. The plug I took out looked fine, but was misfiring horribly. I'll get
an 8 tomorrow, and hopefully it won't get fouled up.

[Arnadanoob]

I'm glad you figured to try a different plug.

Moped engines in general like this.

A backfire is usually something that sounds violent with a loud noise that's usually heard through the carb. The cause is usually due to ignition timing. If the keyway of your flywheel/crank gets stripped and the mag position is not aligned with the keyway, the end result is an explosive sounding misfire from being way too advanced or retarded on the ignition point.

A misfire is usually due to a bad spark plug, plug wire, coil or CDI usually checked in that order based on the frequency of problems. A misfire can be heard like as if the engine is skipping a beat. Temps may appear to be normal during this condition.

An overly lean fuel condition will show up as symptoms similar to a misfire but the CHT gauge will show higher than usual temps. Unlike a misfire with proper jetting, a lean condition will spike in temps. To get an idea of what this is like, you could replace your pilot jet with one that is clogged. The bike will tend to hiccup/* when power is applied, and/or make a hollow BWAH sound when you open the throttle. In the most severe cases the exhaust will sound very tinny, zinging with a very sharp sound.

A sputter is the result of an overly rich condition. This is easy to detect because it sounds like your engine is gargling mouthwash or in the most severe case, like it's drowning. The bike will act very lazy, the temps will be normal maybe even lower than usual. Sometimes when the engine has been running for extended periods, the reeds will start to get soft/lazy resulting in this condition. This can be remedied by using low-mass, stiffer reeds like carbon fiber.

I hope this helps.

[burnt_toast]

Arnadanoob you have posted SO much useful info, you're like a book

Thank you sir for you contributions to these forums

[Lunytune]

Arnadanoob you have posted SO much useful info, you're like a book
Thank you sir for you contributions to these forums

Can I wait for the movie?

I noticed another one of those misused words we've discussed, (like carbs?).

Backfire

... Arnadanoob is right on, it's a backfire through the carb. My SIL has had his beard singed more than once looking down a quad at the wrong time.

But we often say backfire when we mean muffler explosion. And you say it is due to lean condition? I would have thought the opposite, unburned fuel exploding in the muffler.

[Bear45-70]

But we often say backfire when we mean muffler explosion. And you say it is due to lean condition? I would have thought the opposite, unburned fuel exploding in the muffler.

I would have too, at school they told us this and I was a disbeliever, except now, experience has shown that to be correct. What hapens is the mixture is too lean to fire in the cylinder and moves into the exhaust, where all of it does not exit the pipe, the next charge comes along and enrichs it and then the cylinder actually fires and the mixture in the exhaust is ignited. Watch the NASCAR guys and see when they get fire out their exhaust, on decel going into the turns on the short tracks and road courses. Decel is always a lean condition.

[Lunytune]

But we often say backfire when we mean muffler explosion. And you say it is due to lean condition? I would have thought the opposite, unburned fuel exploding in the muffler.

I would have too, at school they told us this and I was a disbeliever, except now, experience has shown that to be correct. What hapens is the mixture is too lean to fire in the cylinder and moves into the exhaust, where all of it does not exit the pipe, the next charge comes along and enrichs it and then the cylinder actually fires and the mixture in the exhaust is ignited. Watch the NASCAR guys and see when they get fire out their exhaust, on decel going into the turns on the short tracks and road courses. Decel is always a lean condition.

Okay, you convinced me.

[Wheelman-111]

Greetings:

Bear gave the best (the only, really...) explanation for lean backfires I've ever heard. It's applicable in the 4-stroke world, too. Easy test for Sportster leanness is to take it up to 4500 and chop the throttle... Pa-Pa-PA- POW!!