Spark plugs are simple-looking little devices, but in reality they're highly-engineered components lying at the heart of an engine's combustion process while living in an unimaginably harsh environment.
Fortunately for us home mechanics, they're simple to deal with. I'm re-installing the plugs in Project 17 in preparation for test running the engine, and my basic tools are a plug gapper and an old tube of anti-seize lubricant. I've had this tube for at least 20 years, so a little goes a long way.
The idea behind the plug gap is to afford the largest gap that your ignition can fire, thus giving the largest flame to ignite the combustion mixture. But with use, the spark plug gap will increase so it's best not to go with the widest gap at initial setting — give the plug a little extra to work with. The range on our plugs is .03-.04" so I set mine at .035".
A word about heat range. The specified NGK plug for the '86-87 VFR 700/750 is DPR9EA-9. The letters and numbers are fitment and resistance values, but the middle number, 9, is the heat range value. NGK numbers their plugs higher for "colder," lower for "hotter" (some manufacturers are the opposite). Hotter vs colder is simply the ability of the plug to dissipate heat. A hot running engine needs a cooler plug, and vice versa. Honda specifies either a number 8 or 9 for this model. Why would you choose one over the other? If you run consistently in an unusually cold environment you may want to choose the number 8 if your engine exhibits some carbon fouling or sooty deposits. This was much more of a concern in the old days of air-cooled motors, not so much anymore. What you don't want to do is run a hotter plug 'cause someone on the internet said it's "higher performance" or some such nonsense. Not true in any sense and too hot a plug can cause engine damage. To consider a plug heat range change for performance modifications is unlikely — it would require an increase of about 75 HP to warrant a cooler plug. So, a K&N air filter, slip-on mufflers and a jet kit DO NOT require a plug change. This is a case where the engineers at Honda are smarter than us.
Fortunately for us home mechanics, they're simple to deal with. I'm re-installing the plugs in Project 17 in preparation for test running the engine, and my basic tools are a plug gapper and an old tube of anti-seize lubricant. I've had this tube for at least 20 years, so a little goes a long way.
The idea behind the plug gap is to afford the largest gap that your ignition can fire, thus giving the largest flame to ignite the combustion mixture. But with use, the spark plug gap will increase so it's best not to go with the widest gap at initial setting — give the plug a little extra to work with. The range on our plugs is .03-.04" so I set mine at .035".
A word about heat range. The specified NGK plug for the '86-87 VFR 700/750 is DPR9EA-9. The letters and numbers are fitment and resistance values, but the middle number, 9, is the heat range value. NGK numbers their plugs higher for "colder," lower for "hotter" (some manufacturers are the opposite). Hotter vs colder is simply the ability of the plug to dissipate heat. A hot running engine needs a cooler plug, and vice versa. Honda specifies either a number 8 or 9 for this model. Why would you choose one over the other? If you run consistently in an unusually cold environment you may want to choose the number 8 if your engine exhibits some carbon fouling or sooty deposits. This was much more of a concern in the old days of air-cooled motors, not so much anymore. What you don't want to do is run a hotter plug 'cause someone on the internet said it's "higher performance" or some such nonsense. Not true in any sense and too hot a plug can cause engine damage. To consider a plug heat range change for performance modifications is unlikely — it would require an increase of about 75 HP to warrant a cooler plug. So, a K&N air filter, slip-on mufflers and a jet kit DO NOT require a plug change. This is a case where the engineers at Honda are smarter than us.
After checking the gap, I smear a bit of anti-seize on the threads, being careful not to allow any near the tip which could cause a hot spot and pre-ignition. To make certain that I don't cross-thread the plug I use a short piece of rubber hose to thread the plug in place. Dealing with a cross-threaded plug hole in your cylinder head will have you rethinking your life decisions.
Final tighten with a socket wrench. If you don't have a feel for proper spark plug torque, use a torque wrench till you do. See the life decisions discussion above. A stripped plug hole from over-tightening or a popped plug from too loose a plug will also ruin your day.
Final tighten with a socket wrench. If you don't have a feel for proper spark plug torque, use a torque wrench till you do. See the life decisions discussion above. A stripped plug hole from over-tightening or a popped plug from too loose a plug will also ruin your day.
I like to put a big dab of di-electric grease on the end of the plug wire. This lubricates the fitting making it a little easier to remove in the future and also forms a water and humidity seal.
Next up; carburetors.
Next up; carburetors.
RSS Feed