Actual Engine H.P.	Recommended Glow Plugs	Engine Break-In	Throttle Response	Recommended Fuel
AAC vs ABC Engine Wear	Remote Needle Valve	Engine Lock-Up	Short Piston Skirt	Connecting Rod Noise
Fuel Shut-Off Mechanism	Prop Shaft Wobble	Throttle Arm Adjustment	Muffler Inlet Is Too Small	(future)

Question:	What glow plugs do you recommend for use with your engines
Answer:	The basic answer is to use a high quality glow plug. For all Sport-Jett engines, the K&B 1L and HP plugs work well. They operate in the proper heat range for these engines. Alternates include the OS #8, and Hanger 9 high performance plugs.

Question:	How do I break in my engine?
Answer:	Please see the tech library document Engine Break-In

Question:

My throttle response is not what it should be. I have tried everything.

Answer:

Please check and read all the tech data and FAQs on setting your carburetor and upon the use of the correct glow plug. These are still the most common cause of slow throttle response and flameouts. Use a hot plug like a K&B 1-L or the Mc Coy 59. If you are not blowing glow plugs and the engine seems to be running right otherwise, you need to check your head clearance. The specifications for head clearance are in the engine operating instructions, located in the tech data section. If you find that the head clearance is not correct, then first try adjusting to the correct dimension. (Read the section on torquing heads in the tech bulletin for your engine). If the problem persists, then try lowering the head .002 to .004". (One or two shims). Sometimes increased compression raises HP and heat enough to improve the mid-range performance. You may need to readjust your needle.

Question:

What kind of fuel do you recommend?

Answer:

We have always recommended PowerMaster fuels. We do this because this is the fuel we use, and believe that it has all the ingredients and quality you should expect. We test on 15% and use the synthetic/castor blend. We like clear fuels better than "dyed" fuels, but the dye doesn't really hurt anything. You should use what ever high quality fuel you are comfortable with. If you have never had a problem with your present fuel, then Jetts will not have a problem either. Most of the fuel available today is adequate for normal flying. There are some problems, however. Let's be frank. The cheapest part of fuel is methanol. The expensive parts are oil and nitromethane. Some fuel manufacturers use other additives or none at all, to reduce the amount of oil and nitro in their product. The trick in making fuel is to get power without heat, and of course, wear. Nitro and oil do it best. Other additives typically generate more heat. Castor oil is cheaper than synthetic so if someone is bragging about castor, then you know what they are selling. I recommend that you get yourself a test stand (everyone should have one) and try a few different fuels. You might find that some run differently from others. If the peak RPM is down, then the nitro is down. Don't let them tell you it is because the oil content is higher-that is not true. Some fuels will run hotter at peak than others, causing the engine to surge to a high rpm, then slow down as it heats up. You can see these things on a test stand. Read our safety instructions before running any engine, in an airplane, or on a test stand. For break-in, I like to run just a bit more oil than that found in standard fuels. The safe thing to do is take your standard blend and add 4-6 oz. of castor, or synthetic (Klotz is good) oil. After you follow the break-in instructions, switch back to your regular fuel. One last thing: You should not expect your fuel manufacturer to tell you his formula and ingredients. I do not reveal the HP of my engines. (See the FAQ on the subject) The bottom line is if I say my oil is 16%, which is about average for sport fuel, then there is always someone out there that will say, "mine is 20%". I have a saying; "It is hard to beat the first liar!" It is not good practice to reveal corporate secrets, period. Don't ask, don't tell. Also, don't believe those home remedies for determining the oil content. People don't know what they are talking about. If someone wants to pay for a "three-ball wear test", then listen, otherwise get a test stand and go to work.

Question:

My front end wobbles when I put the prop on. Is the shaft bent?

Answer:

In most cases, Jett crankshafts do not bend. They are more likely to break underneath the front bearing during a crash (very rare), than to bend. What usually happens is that the front removable stud bends. This is what it is designed to do. The stud should always be replaced after a crash or runaway (sheared propeller), and should be replaced as a maintenance item every year or so. If the front of your engine wobbles after you tighten the propeller, then there are several things to look for. First and foremost, remove the stud, clean the threads in the shaft and replace the stud. Screw the stud all the way in, then back it off slightly so that it rotates freely. If you screw it in tight, then it cocks slightly as it tightens. Second, remove the prop drive and lock cone. Clean them carefully, replace and fit the front end with a new propeller. Tighten the spinner nut and inspect. Unless there is a problem with the fitted parts, it should be aligned. During a crash, it is also possible to damage the cone and prop drive. They may need to be replaced. If the stud still has run out after being cleaned, and fits tight in the shaft housing, then this is the most likely problem. The crank may need to be replaced (very rare). The stud should be loose enough to self align as the prop is tightened. You should return the engine to Jett for inspection.

Question:

How can I adjust my throttle arm without changing the idle needle setting?

Answer:

Since the position of the idle needle is very critical, this is a very important process. First, can the throttle arm be bent to make a small adjustment? It is made from special steel that allows it to be bent around without damage. It also is a very inexpensive part, should you decide to replace it. If you want to shorten the arm (to give you more stroke) it is best to bend the arm over itself, making a sharp "Z". You can avoid some drilling and cutting this way. Now back to the question. Make sure you have a brass stop screw!!! Early Jetts had a black plastic screw. Do not follow these instructions if your stop screw is black!! Follow the instructions included with your engine to avoid damage to your engine. If you have a brass stop screw, then take a marker or pencil and place a small dot on the idle needle face and a matching mark on the brass 3/8" nut. This will tell you if the idle needle has moved during the adjustment of the arm. Loosen the 3/8 nut. Adjust the arm to the new position. Tighten the nut. Since the barrel will rotate during tightening, you may have to use trial and error to get it right. Tighten the nut with about 30 inch pounds of torque (not an excessive amount). If for some reason you wish to remove the brass nut completely, then you must take special note of exactly where the idle NV is with respect to the face of the nut, e.g., one turn inside the nut. It can actually be just about anywhere. After your arm is set, then check to see if the Idle N.V. has moved. It should not have, but if it did, then use a small screwdriver to readjust it to the mark. If the carb is out of adjustment, then read the tech section on "setting R/C carbs".

Question:

The exhaust port on the OS seems massive in comparison to your engines and the inlet on your mufflers. Doesn't this smaller opening restrict power? Do you make a different muffler adapter/header with a larger opening?

Answer:

We get this question so much that I had to include this FAQ on it. Look at the opening on a Moki. It is small. It runs as good or better than the OS. Large exhaust openings are just a way to make the engine lighter and cheaper by using less metal. Exhaust back pressure is better in most cases, especially on a tuned system. The exhaust openings on JETT engines are very small. Since we beat the pants off of the competition, this pretty much speaks for itself. The opening size in Turbo-JETT and Sport-JETT mufflers WILL work properly with your engine. We make a headers for many different brands and sizes of engines. For example, take the Moki 180 and OS 160. In this case, the only difference is the span of the screw holes. If you own the muffler for one engine, you can either change out the header or slot the screw holes to fit the other.