Which ngk plug works on 3.2. My dad has a extra plug off his g38 will it work.

A G38 plug should work OK in the 3.2. I have found that, generally speaking, if a plug will properly screw into the hole it will work if the piston does not hit the plug. This may not be the optinum plug. You also need to make sure it is a resistor plug unless the ignition lead and cap is fully shielded.

For the 3.2 I like a Champion RCJ7Y plug. The NGK equivalent is a BPMR7A. Here is a site with an NGK plug cross reference.

http://www.ngkspark.com.au/

Ken

The plug I have is champion rdj7j the crossreference is a ngk is a bmr6f will it work. I think the r stands for resistor I not sure what the rest stand for any idea ,will it work. Or wil it be hotter.

I am currently running a ngk bpmr6a. But motor seems to run hot.

What is the difference between the bpmr6a and bpmr7a?

On NGK, the higher the number, the colder the plug. Run the hottest plug you can without detonating. On these low comp. engines. the bpmr6a would be best. On champion plugs, their number system is opposite. the higher the number the hotter the plug. And yes, R stands for resistor plug. The other numbers represent the plug thread length, extended nose, electrode alloy etc.

Correct me if I'm wrong. I'm always willing to learn.

Don't you change the heat range to a hotter plug if you are experiencing carbon fouling? The "hotter" plug has a deeper center insulator to allow the center electrode to run at a higher temperature to prevent fouling. If the fuel is combusting properly, the spark plug has nothing to do with the temperature of the engine. Plug related preignition (knocking) has to do with very hot deposits on the plug, piston or head/cyl which can ignite the fuel before the plug sparks. I have never observed preignition with our R/C gassers unless the timing was too far advanced.

Gassers do run much hotter than alkie engines. If you think your engine is running too hot then you need to rethink your cooling air flow. Proper ducting can help with over heating problems.

Ken

I have even tried it with the cowl right off and still the same problem. What temp should a gas run at I got a heat gun for my car I could try. The engine seems rich in the mid transition range it make burb sound then come out off it at higher rpm I think this is normal. I have tried to get rid off the burb sound in the mid range and it will result in a dead stick landing. Thanks for all the help.Another problem might be I was running a 22x10 prop and to keep speed down I was always running real low rpm around mid range with little shots of throttle to clean out motor. Going to go with 22x8 since seeing a vid with a guy using this prop.

Big Bird:
Your right, The longer the ceramic centre electrode the hotter the plug, although engine temp. does make a difference as the only time a plug cools is the heat transfer between the plug threads and the head, so the hotter the head runs, the cooler the plug needed. Ideal temp is when the centre electrode is a tan colour. To cool and it runs black, builds up carbon and shorts out as carbon is a good electrical conductor. If it burns white, its to hot. All this is with a proper fuel mixtureof course, as to rich a mixture can cause the plug to carbon foul and to lean a mixture can cause the engine to overheat and cause the plug to burn white.

The RD series plugs are for a tapered seat, and have no gasket..The RC series have a flat seat with a gasket..You can use either in the engine, but the taper seat plug will have to be tighter to not leak around the bottom...The engine was made for a plug with a washer...

My engine runs around 190 degrees F.
So if you are running more oil than recommended, should you use a hotter plug to burn the oil?

You should not be burning your oil. It should only be carried through the engine while it lubricates. If you are burning it you will have a lot of deposits. Some cheap mineral oil may do a little burning but a good synthetic will not. Some people think that if 50:1 oil ratio is good then 25:1 is twice as good. Not true. More oil can cause more friction which causes more heat build up. It is a very good plan to go by an engine manufacturers oil type and ratio recommendation. The synthetics are made for close tolerance engines and have a very high film strength to prevent metal to metal contact at high temperatures. I am not an oil or spark plug expert but I've been running gassers since 1982 and this is where my practical experience comes from. I run all of my engines on Amsoil 2000 at 50:1 and like Klotz KL-300 at 50:1 equally well. There are other synthetics that work as well as these.

Flypaper 2 also has it right when he says that you are looking for a tan color on your spark plug. It will take several runs before this color will develop. This is really the best way to determine the correct heat range for your plug providing that you are running the correct oil and ratio.

Ken

I treid a synthetic oil but it seemed to get hot, white plug. I changed back to sthil 50-1 mineral oil and seemed better again but still not right. Does your engine burble in the mid range also then clean up at higher rpms.

I thought maybe I would mention a couple things. When you increase the amount of oil in premix for a 2 stroke the jetting of the carb (or needle settings) may need to be opened up or you may have a lean running engine. The reason is that the oil displaces gas and when this is atomized in the carb the fuel-air charge going into the engine has less gas to burn. This can make the engine run leaner. Adding less oil actualy richens the mixture and can make the engine run rich. You have to cahnge the ratio pretty drasticly to see the effect but going from say 80-1 to 32-1 would have an effect. If you change your mixture from 50-1 to 25-1 and the engine runs hotter it's not from increased friction from oil it's from the engine running lean. All the oil does is lubricate and does not add to the combustion. More oil can can cause the rings to seal better leading to more power. For larger 2 stroke engines such as the ones used on dirt bikes 20-1 was found to be optimum with 32-1 to be the a good compromise. Our plane engines don't have the same load as these engines or operate at the 10k or 12k rpm where oil migration becomes an issue so the higher ratios work well. I've found that a lot of the problems with gas 2 stroke engines stems from bad gas more than anything. A hotter plug will not reduce carbon buildup. Good gas and oil with proper needle settings will. I always run the recomended plug heat range for the engine or maybe 1 cooler for the summer if it's hot. If I remember right, going up or down one heat range changes the exhaust temp 50F. Be careful if you go up in heat range or it could get expensive.

My Zenoah 445 twin picked up 200 rpm using 20% oil in the fuel..One quart Pennzoil 2 stroke petroleum based oil, 4 quarts pump gas.....Messy but effective
Don't do this if you're afraid to change your carb from the "factory" settings...

Pedec:
I would richen it up a bit or go to a colder plug. Is it the plug recomended for that engine? If so, more likely a high speed mixture problem. An air leak can also cause lean run problems but show up more with low end problems. Plugged carb filter screen can also cause lean high speed. Might be worth checking the filter. When fuel pump diaphram stiffens up with age can also cause high speed to run lean as it can't pump enough volume.

I just pulled a Bosch plug out of my good running Sachs 4.2. This is what it should look like.