Hellion
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Reposting this superb article written by Doc Sprocket, from this thread.
(edited for spelling ~Hellion)
"This has come up recently, again, so I'm going to post this here. What you are about to read is a couple of articles I wrote sometime back, that address the function of the governor, the exploding flywheel MYTH, and all the crap to go with it. What I have written is based on years of personal experience (not "I heard, read, or was told") as well as extensive research and others' personal experience. It was originally written for the go kart crowd, but the same information applies to all similarly-derived small engines. Take it for what it's worth and insert your favourite fine print here, but I'm telling you--there is so much MIS-information out there, it's disgusting. Grab your favourite beverage, smoke 'em if ya got 'em, and read on...
It is absolutely amazing how often we run into this here--and how often we find ourselves banging away on the keyboard, typing out the same old answers. So, I felt it was a good idea to write up a little blurb on the topic. If requested, I'll sticky it to hopefully save us all some future work. Let's start by outlining the governor's job description. Everyone knows that the governor tries to limit engine speed to (usually) 3600 RPM. But wait, there's more. The reality of it is this: the governor's job is to try to MAINTAIN 3600, not just limit it. The governor reacts to changing loads on the engine; decreasing throttle if it starts to run too fast, and INCREASING throttle if it starts to bog. This is why it is called a "governor" and not simply a "rev limiter".
Now: On to the question: "If I take out my governor, is the flywheel gonna go off like an atom bomb, blowing semi-molten schmutz everywhere, and killing every living thing in a 15-block radius?"
The short answer is no. The long answer: There are many factors involved here, and each must be carefully considered.
1.) I always advise people that IF they are going to run well above governed-RPM, to do it by fully removing the governor's internal mechanisms, and NOT simply bypassing it externally. Many governors are designed in such a way that if over-revved, can suffer component interference inside the crankcase, and/or have internal parts forced right off the shaft and bounce around loose inside the crankcase. Either case can cause severe engine damage. NOT an "explosion", just largely screwed-up internals.
2.) IF you are going to run ungoverned with an otherwise stock engine, keep the factory-spec valve springs in place. At a high enough RPM, weaker springs will cause a condition known as "valve float" or "valve flutter". This occurs when the valves cannot slam closed fast enough before the next combustion cycle. This causes compression losses and as a result, prevents the engine from spinning faster at that point. Valve flutter tends to occur in our engines around 5000-5500 RPM. Your results will vary based on your individual engine, spring condition, etc. Valve flutter occurs at a lower RPM than it would normally take to cause a flywheel mishap.
3.) IF you want to get into RPM ranges HIGHER than this (say 5500+), now is the time to go shopping for high-performance internals. A billet aluminum flywheel, connecting rod, and stiffer valve springs are what's called for. Stiffer springs allow the valves to react faster, so at higher RPM, the valves won't float--NOW things really do have the potential to get a little crazy, so it's time to reach into your pockets for better quality parts.
4.) Your connecting rod is MUCH more likely to fail than your flywheel. I have witnessed MANY more conrod failures than flywheel failures. In fact, I have never seen a flywheel failure. Most here haven't.
5). Contrary to popular belief, a flywheel is NOT going to vapourize at 3601 RPM. This is NOT why your engine is governed to 3600 RPM. Your engine is governed to 3600 RPM because it is an industry-standard operating speed for all the implements these engines are designed to power. Let's NOT lose sight of the fact that these are industrial stationary engines, made and marketed with the primary purpose of powering equipment. Generators, pumps, power washers, welders, cement mixers, tillers, trenchers, tampers (you name it) and the implement are designed to run at 3600 RPM, so the engines are factory-set to 3600 RPM. It's that simple. When a flywheel is manufactured, it is designed to run well above normal operating speed. It's called a safety margin.
6.) NOTHING is 100% guaranteed. You can do everything completely properly, and have a flywheel fail at a "normal speed". OR, you can do everything wrong, and run the hell out of the engine at 7500 RPM on a stock flywheel for a lifetime and never have a problem. Sometimes, there's just no accounting for "Sh*t Happens". Write that down.
7). IF you are running an otherwise stock, ungoverned engine, is it advisable to avoid excessively free-revving the engine. Use proper gear ratios to keep a bit of a load on the engine at full speed, wide open throttle. Don't try to rev the crap out of the engine with the clutch, chain, or belt off. A load on the engine helps keep harmful vibrations (harmonics) in check. If you have an insanely long, steep downhill stretch in your riding route, back off the throttle going down it. If you hear the valves floating or the engine starting to over-rev, apply some braking force. Coasting too fast can force the engine to spin even faster than valve flutter can prevent.
8.) Inspect your flywheel before removing your governor. A previously damaged flywheel can break apart at a completely unpredictable speed. Damage may not be visible (sh*t happens) but if it IS visible, replace it.
9.) If you have to remove your flywheel for repair/maintenance, remove it properly. Do NOT beat the hell out of it with a sledgehammer or pry on it, invest in a flywheel puller. Failing that, try the following: Loosen the retaining nut until the nut is flush with the end of the shaft. Now, hit the nut squarely and sharply a few times with a hammer. Most times, this will do it. You can also aid in loosening the flywheel with mutiple taps around the circumference with a soft-faced mallet or deadblow hammer. Do NOT beat on it with a steel hammer.
10.) If you need to hold the engine from turning while you are tightening/loosening a crank bolt or clutch, do NOT wedge a screwdriver or bar in between the flywheel fins. Although this is not likely to crack the flywheel, a fin could break off. This will throw the flywheel's dynamic balance off. An out-of-balance flywheel is just asking for trouble. Same goes for sawing off alternate cooling fins (an old performance trick). If your fins are cast into the flywheel, don't do it. If you have a Honda, clone or other engine with plastic fins, go for it.
11.) Handle with care. Once you have the flywheel off, don't drop it...
So--Armed with the above information, go ahead and make an informed decision. This guide arms you with what you need to know, to decide whether removing your governor is a feasible idea and how to handle things if you do. And remember (for all the "Armageddon-is-coming-prepare-to-meet-thy-maker-in-a-sintered-metal-flywheel-induced-world-war-3-esque-everybody's-gonna-die-including-the-cockroaches-in-the-cupboard"-nervous-nellies out there): Sh*t Happens. On the one hand, your stock flywheel will very likely be fine. On the other hand, even a performance part could fail. Sh*t Happens.
One last point here: For those that may not yet be ready to dive into their engine and come out with a handful of governor parts, some engines (most notably Hondas and clones) have a VERY user-friendly means of governor adjustment. This adjustment is designed to fine-tune the governed speed to a different specification, but makes it super easy to gain a few hundred RPM. You can usually bring your GOVERNED MAX to 4000-4200 RPM with the turn of a screw. Your governor will still do its job, but you'll run a little faster. Locate the manual throttle control on your engine, it's the little lever you would slide to increase or decrease RPM if you didn't have a remote throttle (gas pedal). Behind that lever is a screw with a spring wrapped around it. Notice how the throttle rests against the tip of that screw when you move the lever to the "fastest" position? Great. Remove that screw. Presto--instant maximum RPM increase, no fuss, no muss.
It is also worth noting that these engines were designed to run at 3600 RPM, day in and day out. If you do run faster, the engine will wear faster. Fact of life. Treat it well, maintain it well, and you'll never notice the potentially shorter lifespan.
(edited for spelling ~Hellion)
"This has come up recently, again, so I'm going to post this here. What you are about to read is a couple of articles I wrote sometime back, that address the function of the governor, the exploding flywheel MYTH, and all the crap to go with it. What I have written is based on years of personal experience (not "I heard, read, or was told") as well as extensive research and others' personal experience. It was originally written for the go kart crowd, but the same information applies to all similarly-derived small engines. Take it for what it's worth and insert your favourite fine print here, but I'm telling you--there is so much MIS-information out there, it's disgusting. Grab your favourite beverage, smoke 'em if ya got 'em, and read on...
It is absolutely amazing how often we run into this here--and how often we find ourselves banging away on the keyboard, typing out the same old answers. So, I felt it was a good idea to write up a little blurb on the topic. If requested, I'll sticky it to hopefully save us all some future work. Let's start by outlining the governor's job description. Everyone knows that the governor tries to limit engine speed to (usually) 3600 RPM. But wait, there's more. The reality of it is this: the governor's job is to try to MAINTAIN 3600, not just limit it. The governor reacts to changing loads on the engine; decreasing throttle if it starts to run too fast, and INCREASING throttle if it starts to bog. This is why it is called a "governor" and not simply a "rev limiter".
Now: On to the question: "If I take out my governor, is the flywheel gonna go off like an atom bomb, blowing semi-molten schmutz everywhere, and killing every living thing in a 15-block radius?"
The short answer is no. The long answer: There are many factors involved here, and each must be carefully considered.
1.) I always advise people that IF they are going to run well above governed-RPM, to do it by fully removing the governor's internal mechanisms, and NOT simply bypassing it externally. Many governors are designed in such a way that if over-revved, can suffer component interference inside the crankcase, and/or have internal parts forced right off the shaft and bounce around loose inside the crankcase. Either case can cause severe engine damage. NOT an "explosion", just largely screwed-up internals.
2.) IF you are going to run ungoverned with an otherwise stock engine, keep the factory-spec valve springs in place. At a high enough RPM, weaker springs will cause a condition known as "valve float" or "valve flutter". This occurs when the valves cannot slam closed fast enough before the next combustion cycle. This causes compression losses and as a result, prevents the engine from spinning faster at that point. Valve flutter tends to occur in our engines around 5000-5500 RPM. Your results will vary based on your individual engine, spring condition, etc. Valve flutter occurs at a lower RPM than it would normally take to cause a flywheel mishap.
3.) IF you want to get into RPM ranges HIGHER than this (say 5500+), now is the time to go shopping for high-performance internals. A billet aluminum flywheel, connecting rod, and stiffer valve springs are what's called for. Stiffer springs allow the valves to react faster, so at higher RPM, the valves won't float--NOW things really do have the potential to get a little crazy, so it's time to reach into your pockets for better quality parts.
4.) Your connecting rod is MUCH more likely to fail than your flywheel. I have witnessed MANY more conrod failures than flywheel failures. In fact, I have never seen a flywheel failure. Most here haven't.
5). Contrary to popular belief, a flywheel is NOT going to vapourize at 3601 RPM. This is NOT why your engine is governed to 3600 RPM. Your engine is governed to 3600 RPM because it is an industry-standard operating speed for all the implements these engines are designed to power. Let's NOT lose sight of the fact that these are industrial stationary engines, made and marketed with the primary purpose of powering equipment. Generators, pumps, power washers, welders, cement mixers, tillers, trenchers, tampers (you name it) and the implement are designed to run at 3600 RPM, so the engines are factory-set to 3600 RPM. It's that simple. When a flywheel is manufactured, it is designed to run well above normal operating speed. It's called a safety margin.
6.) NOTHING is 100% guaranteed. You can do everything completely properly, and have a flywheel fail at a "normal speed". OR, you can do everything wrong, and run the hell out of the engine at 7500 RPM on a stock flywheel for a lifetime and never have a problem. Sometimes, there's just no accounting for "Sh*t Happens". Write that down.
7). IF you are running an otherwise stock, ungoverned engine, is it advisable to avoid excessively free-revving the engine. Use proper gear ratios to keep a bit of a load on the engine at full speed, wide open throttle. Don't try to rev the crap out of the engine with the clutch, chain, or belt off. A load on the engine helps keep harmful vibrations (harmonics) in check. If you have an insanely long, steep downhill stretch in your riding route, back off the throttle going down it. If you hear the valves floating or the engine starting to over-rev, apply some braking force. Coasting too fast can force the engine to spin even faster than valve flutter can prevent.
8.) Inspect your flywheel before removing your governor. A previously damaged flywheel can break apart at a completely unpredictable speed. Damage may not be visible (sh*t happens) but if it IS visible, replace it.
9.) If you have to remove your flywheel for repair/maintenance, remove it properly. Do NOT beat the hell out of it with a sledgehammer or pry on it, invest in a flywheel puller. Failing that, try the following: Loosen the retaining nut until the nut is flush with the end of the shaft. Now, hit the nut squarely and sharply a few times with a hammer. Most times, this will do it. You can also aid in loosening the flywheel with mutiple taps around the circumference with a soft-faced mallet or deadblow hammer. Do NOT beat on it with a steel hammer.
10.) If you need to hold the engine from turning while you are tightening/loosening a crank bolt or clutch, do NOT wedge a screwdriver or bar in between the flywheel fins. Although this is not likely to crack the flywheel, a fin could break off. This will throw the flywheel's dynamic balance off. An out-of-balance flywheel is just asking for trouble. Same goes for sawing off alternate cooling fins (an old performance trick). If your fins are cast into the flywheel, don't do it. If you have a Honda, clone or other engine with plastic fins, go for it.
11.) Handle with care. Once you have the flywheel off, don't drop it...
So--Armed with the above information, go ahead and make an informed decision. This guide arms you with what you need to know, to decide whether removing your governor is a feasible idea and how to handle things if you do. And remember (for all the "Armageddon-is-coming-prepare-to-meet-thy-maker-in-a-sintered-metal-flywheel-induced-world-war-3-esque-everybody's-gonna-die-including-the-cockroaches-in-the-cupboard"-nervous-nellies out there): Sh*t Happens. On the one hand, your stock flywheel will very likely be fine. On the other hand, even a performance part could fail. Sh*t Happens.
One last point here: For those that may not yet be ready to dive into their engine and come out with a handful of governor parts, some engines (most notably Hondas and clones) have a VERY user-friendly means of governor adjustment. This adjustment is designed to fine-tune the governed speed to a different specification, but makes it super easy to gain a few hundred RPM. You can usually bring your GOVERNED MAX to 4000-4200 RPM with the turn of a screw. Your governor will still do its job, but you'll run a little faster. Locate the manual throttle control on your engine, it's the little lever you would slide to increase or decrease RPM if you didn't have a remote throttle (gas pedal). Behind that lever is a screw with a spring wrapped around it. Notice how the throttle rests against the tip of that screw when you move the lever to the "fastest" position? Great. Remove that screw. Presto--instant maximum RPM increase, no fuss, no muss.
It is also worth noting that these engines were designed to run at 3600 RPM, day in and day out. If you do run faster, the engine will wear faster. Fact of life. Treat it well, maintain it well, and you'll never notice the potentially shorter lifespan.
