---------------------------------------------------------- Kolb-List Digest Archive --- Total Messages Posted Sun 01/07/18: 9 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 12:07 AM - Re: best props (JC Gilpin) 2. 08:31 AM - Re: Re: best props (John Fitt) 3. 09:55 AM - Re: Re: best props (John Hauck) 4. 10:53 AM - Re: best props (Stuart Harner) 5. 11:11 AM - Re: best props (John Hauck) 6. 12:38 PM - Re: best props (Stuart Harner) 7. 01:00 PM - Re: best props (John Hauck) 8. 01:41 PM - Re: best props (Enrichers) (John Hauck) 9. 09:31 PM - Re: best props (Richard Pike) ________________________________ Message 1 _____________________________________ Time: 12:07:50 AM PST US From: JC Gilpin Subject: Kolb-List: Re: best props At what point are you measuring the pitch?? Some do it at the tip but tradition does it 24" out from the center. On a Warp drive I measured a difference of 7 degrees between 24" and the tip, less at the tip of course.... See http://www.stolspeed.com/id/62 for careful prop comparisons. The results are sobering..... ________________________________ Message 2 _____________________________________ Time: 08:31:18 AM PST US From: John Fitt Subject: Re: Kolb-List: Re: best props Warp drive recommends placing the protractor at the tip. Tried different met hods. Raised the tail to make the prop hub exactly plumb (0 deg. ) then adjusted e ach blade using a =9Ccrutch=9D that held the blade level. Maybe the mixture is too rich at full throttle giving lower EGT and loss of p ower, but the plugs look good to me...while experimenting with the main jets at the present pitch I saw the plugs going towards white with a slight decr ease in max attainable rpm. Sent from my iPhone > On Jan 7, 2018, at 12:07 AM, JC Gilpin wrote: > > At what point are you measuring the pitch?? > Some do it at the tip but tradition does it 24" out from the center. > On a Warp drive I measured a difference of 7 degrees between 24" and the t ip, less at the tip of course.... > > See http://www.stolspeed.com/id/62 for careful prop comparisons. > The results are sobering..... > > ________________________________ Message 3 _____________________________________ Time: 09:55:10 AM PST US From: "John Hauck" Subject: RE: Kolb-List: Re: best props Been a long time since my two stroke days, but I still remember a few of the procedures I used to stay alive. Initially, I chased EGTs, spark plugs, main jets, etc. Finally, I discovered that Rotax shipped their engines tuned for 0 to 1500 or it may have been 3000 feet MSL with a very wide OAT range. It was not necessary to try and do something the factory had already done. The primary problem with tuning, getting the EGT in the range called for by your Rotax manual, was prop loading. Discovered this while screwing around in the air with my Ultrastar and Cuyuna ULIII02. I noticed when at cruise RPM if I pushed the nose over the EGT increased. When I pulled the nose up the EGT decreased. I noticed the engine was very sensitive to prop loading. Changing pitch attitude is same as prop pitch change when loading and unloading the engine. >From then on I insured I pitched the prop correctly. Loading the engine so it would just bump the tach red line WOT (wide open throttle), straight and level flight. If I did this the EGTs would be right where they were supposed to be per the Rotax engine manual. At cruise RPM, which is much leaner than WOT RPM, I adjusted fuel needle height to get correct EGT. Static RPM should probably be 400 to 500 RPM (I no longer remember the difference between static and WOT, straight and level flight RPM). Minor adjustments of jets and needles may be necessary to tune the engine for OAT and altitude, but nothing major if the prop is pitched correctly. I think the OAT range was pretty wide. One of our Kolbers fabricated a laser for Warp Drive prop adjuster. He sent me one. I use the protractor to adjust one blade, then use the laser to adjust the other blades to be exactly the same pitch as the first. Having all blades exactly same pitch is important. I make sure the aircraft is secure. Make a dot on the laser point on a piece of wood on the floor with the first blade adjusted with the protractor. Then adjust the other blades to get that laser right on the dot. john h mkIII Titus, Alabama From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Fitt Sent: Sunday, January 07, 2018 10:31 AM Subject: Re: Kolb-List: Re: best props Warp drive recommends placing the protractor at the tip. Tried different methods. Raised the tail to make the prop hub exactly plumb (0 deg. ) then adjusted each blade using a =9Ccrutch=9D that held the blade level. Maybe the mixture is too rich at full throttle giving lower EGT and loss of power, but the plugs look good to me...while experimenting with the main jets at the present pitch I saw the plugs going towards white with a slight decrease in max attainable rpm. Sent from my iPhone On Jan 7, 2018, at 12:07 AM, JC Gilpin wrote: At what point are you measuring the pitch?? Some do it at the tip but tradition does it 24" out from the center. On a Warp drive I measured a difference of 7 degrees between 24" and the tip, less at the tip of course.... See http://www.stolspeed.com/id/62 for careful prop comparisons. The results are sobering..... ________________________________ Message 4 _____________________________________ Time: 10:53:52 AM PST US From: "Stuart Harner" Subject: RE: Kolb-List: best props EGT is pretty critical on a 2-stroke. Think blow torch on the exhaust port. EGT is determined by mixture and engine loading. Rotax (maybe all) engines with Bing (maybe all) carbs are known to run towards lean in the mid-range. So think of it this way. For max HP output you want the engine running near its red line but you don't want it to go over that and self-destruct. Setting the max full throttle RPM of 6300 (static) on the ground will give you a close to red line RPM when straight and level. Once you get that set you can go about checking the mixture (EGT and CHT temps) while running the engine static on the ground. Usually factory settings are sufficient to get you through the break in hour. Elevation and air temp will play some part in this too. Once you get airborne you will be able to start the fine tuning which is usually just moving the needle up or down a notch or two. Sometimes you have to change needles and or jets. That is a little far into the weeds for initial setup concerns. Or tweak the propeller pitch but usually if you get the static RPM right you won't have to unless it over revs in level flight at full throttle. In my case I had to raise the needle to get it to quit running lean on descent. I still have to watch it carefully if I am near 4000 RPM and push the nose over too far in descent. This "unloads" the prop meaning that the energy produced by burning fuel is not being converted to thrust but is dumping overboard through the exhaust. Changing throttle setting or adding a little "choke" helps cure that. I was admonished for doing the "choke" thing as if you forget it and have to jab the throttle you are asking for an engine out. So use this technique at your own risk. Reading the plugs is the best way to know if your mixture is right as temperature probes have been known to be less than accurate at times. The plugs never lie, or so I have been told. If you don't have them already, get the manual for the engine that will tell you the break in procedure and the operating temp limits. Then also get a carburetor manual as it will explain in detail how the carb works all through the operating range. It helped me figure out what was going on and what needed attention at each stage of the process. Firefly Rotax 447 B box 2.58:1 Warp Drive 60" 3 blade Stuart -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Fitt Sent: Saturday, January 06, 2018 5:56 PM Subject: Re: Kolb-List: best props Were the final pitch adjustments small compared to the first, did the engine really come on strong, with any EGT changes? Sent from my iPhone > On Jan 6, 2018, at 3:43 PM, Stuart Harner wrote: > > --> > > Same prop (60") and gear box here except on a 447. > > I started at 13 but had to back it down to about 8 to get in the > ball park. Had to fiddle with carb/pitch settings a little to get the > proper EGT's. I don't remember exactly but I think it is currently at > 7.5 > > LOTS of power for a Firefly and really smooth over 2200 RPM. > ________________________________ Message 5 _____________________________________ Time: 11:11:49 AM PST US From: "John Hauck" Subject: RE: Kolb-List: best props Bing carbs use an enricher, rather than a choke. There is an enricher well and enricher jet in the float bowl. Going full throttle with the enricher full on probably will not result in an engine out, at least for me. When the enricher is activated the fuel in the enricher well is dumped and additional fuel is pulled through the enricher jet. So...if I understand correctly, when the enricher is activated air flow is not reduced, but we are now running with a richer mixture which is not enough to kill the engine. A choke restricts airflow. BTW, your explanation of how to tune for prop and carb is much better than my previous feeble attempt. Respectfully, john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Stuart Harner Sent: Sunday, January 07, 2018 12:54 PM Subject: RE: Kolb-List: best props EGT is pretty critical on a 2-stroke. Think blow torch on the exhaust port. EGT is determined by mixture and engine loading. Rotax (maybe all) engines with Bing (maybe all) carbs are known to run towards lean in the mid-range. So think of it this way. For max HP output you want the engine running near its red line but you don't want it to go over that and self-destruct. Setting the max full throttle RPM of 6300 (static) on the ground will give you a close to red line RPM when straight and level. Once you get that set you can go about checking the mixture (EGT and CHT temps) while running the engine static on the ground. Usually factory settings are sufficient to get you through the break in hour. Elevation and air temp will play some part in this too. Once you get airborne you will be able to start the fine tuning which is usually just moving the needle up or down a notch or two. Sometimes you have to change needles and or jets. That is a little far into the weeds for initial setup concerns. Or tweak the propeller pitch but usually if you get the static RPM right you won't have to unless it over revs in level flight at full throttle. In my case I had to raise the needle to get it to quit running lean on descent. I still have to watch it carefully if I am near 4000 RPM and push the nose over too far in descent. This "unloads" the prop meaning that the energy produced by burning fuel is not being converted to thrust but is dumping overboard through the exhaust. Changing throttle setting or adding a little "choke" helps cure that. I was admonished for doing the "choke" thing as if you forget it and have to jab the throttle you are asking for an engine out. So use this technique at your own risk. Reading the plugs is the best way to know if your mixture is right as temperature probes have been known to be less than accurate at times. The plugs never lie, or so I have been told. If you don't have them already, get the manual for the engine that will tell you the break in procedure and the operating temp limits. Then also get a carburetor manual as it will explain in detail how the carb works all through the operating range. It helped me figure out what was going on and what needed attention at each stage of the process. Firefly Rotax 447 B box 2.58:1 Warp Drive 60" 3 blade Stuart -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Fitt Sent: Saturday, January 06, 2018 5:56 PM Subject: Re: Kolb-List: best props Were the final pitch adjustments small compared to the first, did the engine really come on strong, with any EGT changes? Sent from my iPhone > On Jan 6, 2018, at 3:43 PM, Stuart Harner wrote: > > --> > > Same prop (60") and gear box here except on a 447. > > I started at 13 but had to back it down to about 8 to get in the > ball park. Had to fiddle with carb/pitch settings a little to get the > proper EGT's. I don't remember exactly but I think it is currently at > 7.5 > > LOTS of power for a Firefly and really smooth over 2200 RPM. > ________________________________ Message 6 _____________________________________ Time: 12:38:49 PM PST US From: "Stuart Harner" Subject: RE: Kolb-List: best props Yup, that is why I put the quotes around "choke". I had an engine stoppage on roll out after landing when I forgot to turn off the enricher circuit. Flooded a warm engine, I did. (Yoda voice) If you use the enricher to control mixture on decent, it would be best to develop the habit of turning it off prior to any throttle changes. Something that only practice can provide. Then when you are distracted (or old and forgetful)..... John, you were the one that explained prop loading to me so that I could understand it back in my engine/prop setup days. So there! Stuart Do not archive -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Hauck Sent: Sunday, January 07, 2018 1:11 PM Subject: RE: Kolb-List: best props Bing carbs use an enricher, rather than a choke. There is an enricher well and enricher jet in the float bowl. Going full throttle with the enricher full on probably will not result in an engine out, at least for me. When the enricher is activated the fuel in the enricher well is dumped and additional fuel is pulled through the enricher jet. So...if I understand correctly, when the enricher is activated air flow is not reduced, but we are now running with a richer mixture which is not enough to kill the engine. A choke restricts airflow. BTW, your explanation of how to tune for prop and carb is much better than my previous feeble attempt. Respectfully, john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Stuart Harner Sent: Sunday, January 07, 2018 12:54 PM Subject: RE: Kolb-List: best props EGT is pretty critical on a 2-stroke. Think blow torch on the exhaust port. EGT is determined by mixture and engine loading. Rotax (maybe all) engines with Bing (maybe all) carbs are known to run towards lean in the mid-range. So think of it this way. For max HP output you want the engine running near its red line but you don't want it to go over that and self-destruct. Setting the max full throttle RPM of 6300 (static) on the ground will give you a close to red line RPM when straight and level. Once you get that set you can go about checking the mixture (EGT and CHT temps) while running the engine static on the ground. Usually factory settings are sufficient to get you through the break in hour. Elevation and air temp will play some part in this too. Once you get airborne you will be able to start the fine tuning which is usually just moving the needle up or down a notch or two. Sometimes you have to change needles and or jets. That is a little far into the weeds for initial setup concerns. Or tweak the propeller pitch but usually if you get the static RPM right you won't have to unless it over revs in level flight at full throttle. In my case I had to raise the needle to get it to quit running lean on descent. I still have to watch it carefully if I am near 4000 RPM and push the nose over too far in descent. This "unloads" the prop meaning that the energy produced by burning fuel is not being converted to thrust but is dumping overboard through the exhaust. Changing throttle setting or adding a little "choke" helps cure that. I was admonished for doing the "choke" thing as if you forget it and have to jab the throttle you are asking for an engine out. So use this technique at your own risk. Reading the plugs is the best way to know if your mixture is right as temperature probes have been known to be less than accurate at times. The plugs never lie, or so I have been told. If you don't have them already, get the manual for the engine that will tell you the break in procedure and the operating temp limits. Then also get a carburetor manual as it will explain in detail how the carb works all through the operating range. It helped me figure out what was going on and what needed attention at each stage of the process. Firefly Rotax 447 B box 2.58:1 Warp Drive 60" 3 blade Stuart -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Fitt Sent: Saturday, January 06, 2018 5:56 PM Subject: Re: Kolb-List: best props Were the final pitch adjustments small compared to the first, did the engine really come on strong, with any EGT changes? Sent from my iPhone > On Jan 6, 2018, at 3:43 PM, Stuart Harner wrote: > > --> > > Same prop (60") and gear box here except on a 447. > > I started at 13 but had to back it down to about 8 to get in the > ball park. Had to fiddle with carb/pitch settings a little to get the > proper EGT's. I don't remember exactly but I think it is currently at > 7.5 > > LOTS of power for a Firefly and really smooth over 2200 RPM. > ________________________________ Message 7 _____________________________________ Time: 01:00:11 PM PST US From: "John Hauck" Subject: RE: Kolb-List: best props Reckon you are a better explainer than I am. ;-) I ended up with about 1200 hours on my two strokes before I graduated to a 912. Never used the enricher during descents, or got an indication that I needed to richen things up a bit. I normally shot landings at engine idle, and was probably too excited making wild ass descents with power on back in those golden days of utralighting. john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Stuart Harner Sent: Sunday, January 07, 2018 2:37 PM Subject: RE: Kolb-List: best props Yup, that is why I put the quotes around "choke". I had an engine stoppage on roll out after landing when I forgot to turn off the enricher circuit. Flooded a warm engine, I did. (Yoda voice) If you use the enricher to control mixture on decent, it would be best to develop the habit of turning it off prior to any throttle changes. Something that only practice can provide. Then when you are distracted (or old and forgetful)..... John, you were the one that explained prop loading to me so that I could understand it back in my engine/prop setup days. So there! Stuart Do not archive -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Hauck Sent: Sunday, January 07, 2018 1:11 PM Subject: RE: Kolb-List: best props Bing carbs use an enricher, rather than a choke. There is an enricher well and enricher jet in the float bowl. Going full throttle with the enricher full on probably will not result in an engine out, at least for me. When the enricher is activated the fuel in the enricher well is dumped and additional fuel is pulled through the enricher jet. So...if I understand correctly, when the enricher is activated air flow is not reduced, but we are now running with a richer mixture which is not enough to kill the engine. A choke restricts airflow. BTW, your explanation of how to tune for prop and carb is much better than my previous feeble attempt. Respectfully, john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Stuart Harner Sent: Sunday, January 07, 2018 12:54 PM Subject: RE: Kolb-List: best props EGT is pretty critical on a 2-stroke. Think blow torch on the exhaust port. EGT is determined by mixture and engine loading. Rotax (maybe all) engines with Bing (maybe all) carbs are known to run towards lean in the mid-range. So think of it this way. For max HP output you want the engine running near its red line but you don't want it to go over that and self-destruct. Setting the max full throttle RPM of 6300 (static) on the ground will give you a close to red line RPM when straight and level. Once you get that set you can go about checking the mixture (EGT and CHT temps) while running the engine static on the ground. Usually factory settings are sufficient to get you through the break in hour. Elevation and air temp will play some part in this too. Once you get airborne you will be able to start the fine tuning which is usually just moving the needle up or down a notch or two. Sometimes you have to change needles and or jets. That is a little far into the weeds for initial setup concerns. Or tweak the propeller pitch but usually if you get the static RPM right you won't have to unless it over revs in level flight at full throttle. In my case I had to raise the needle to get it to quit running lean on descent. I still have to watch it carefully if I am near 4000 RPM and push the nose over too far in descent. This "unloads" the prop meaning that the energy produced by burning fuel is not being converted to thrust but is dumping overboard through the exhaust. Changing throttle setting or adding a little "choke" helps cure that. I was admonished for doing the "choke" thing as if you forget it and have to jab the throttle you are asking for an engine out. So use this technique at your own risk. Reading the plugs is the best way to know if your mixture is right as temperature probes have been known to be less than accurate at times. The plugs never lie, or so I have been told. If you don't have them already, get the manual for the engine that will tell you the break in procedure and the operating temp limits. Then also get a carburetor manual as it will explain in detail how the carb works all through the operating range. It helped me figure out what was going on and what needed attention at each stage of the process. Firefly Rotax 447 B box 2.58:1 Warp Drive 60" 3 blade Stuart -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Fitt Sent: Saturday, January 06, 2018 5:56 PM Subject: Re: Kolb-List: best props Were the final pitch adjustments small compared to the first, did the engine really come on strong, with any EGT changes? Sent from my iPhone > On Jan 6, 2018, at 3:43 PM, Stuart Harner wrote: > > --> > > Same prop (60") and gear box here except on a 447. > > I started at 13 but had to back it down to about 8 to get in the > ball park. Had to fiddle with carb/pitch settings a little to get the > proper EGT's. I don't remember exactly but I think it is currently at > 7.5 > > LOTS of power for a Firefly and really smooth over 2200 RPM. > ________________________________ Message 8 _____________________________________ Time: 01:41:49 PM PST US From: "John Hauck" Subject: RE: Kolb-List: best props (Enrichers) I do remember one time the enricher saved me from an engine out. I was flying the FS 447 from Bert Howland's airstrip in Maryland, NY, to Monterey, NY, and the Ultralight Flight Farm, owned by Bill and Barbara Locke. Stopped at Norwich, NY, for fuel. My routine was estimate how much fuel and oil I would need, dump the oil in the tank, rock the airplane to mix up the oil and gas, then top off the tank. I took on quite a bit of fuel after I made my estimate and poured the oil in the tank. On takeoff I got about 100 feet above the ground and started losing power. When I twisted my head around to see about making it back to the airport I saw a big trail of blue smoke. Light bulb went on really quick. Forgot to mix the oil and gas. I pulled the enricher full on, kept the engine running until I got on the ground, all the while trailing big clouds of blue smoke. Pulled the fuel bowl off the carb. It was full of dark blue oil. I had gotten distracted while answering questions during refueling. BTW: That was 1989. I was on my way to Oshkosh via Homer Kolb's, all the New England States, the flight farm, over Niagara Falls, up to Sault St Marie, MI, back down the north and west shore of Lake Michigan, and finally Oshkosh. Those were fun, exciting days. john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Hauck Sent: Sunday, January 07, 2018 3:00 PM Subject: RE: Kolb-List: best props Reckon you are a better explainer than I am. ;-) I ended up with about 1200 hours on my two strokes before I graduated to a 912. Never used the enricher during descents, or got an indication that I needed to richen things up a bit. I normally shot landings at engine idle, and was probably too excited making wild ass descents with power on back in those golden days of utralighting. john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Stuart Harner Sent: Sunday, January 07, 2018 2:37 PM Subject: RE: Kolb-List: best props Yup, that is why I put the quotes around "choke". I had an engine stoppage on roll out after landing when I forgot to turn off the enricher circuit. Flooded a warm engine, I did. (Yoda voice) If you use the enricher to control mixture on decent, it would be best to develop the habit of turning it off prior to any throttle changes. Something that only practice can provide. Then when you are distracted (or old and forgetful)..... John, you were the one that explained prop loading to me so that I could understand it back in my engine/prop setup days. So there! Stuart Do not archive -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Hauck Sent: Sunday, January 07, 2018 1:11 PM Subject: RE: Kolb-List: best props Bing carbs use an enricher, rather than a choke. There is an enricher well and enricher jet in the float bowl. Going full throttle with the enricher full on probably will not result in an engine out, at least for me. When the enricher is activated the fuel in the enricher well is dumped and additional fuel is pulled through the enricher jet. So...if I understand correctly, when the enricher is activated air flow is not reduced, but we are now running with a richer mixture which is not enough to kill the engine. A choke restricts airflow. BTW, your explanation of how to tune for prop and carb is much better than my previous feeble attempt. Respectfully, john h mkIII Titus, Alabama -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Stuart Harner Sent: Sunday, January 07, 2018 12:54 PM Subject: RE: Kolb-List: best props EGT is pretty critical on a 2-stroke. Think blow torch on the exhaust port. EGT is determined by mixture and engine loading. Rotax (maybe all) engines with Bing (maybe all) carbs are known to run towards lean in the mid-range. So think of it this way. For max HP output you want the engine running near its red line but you don't want it to go over that and self-destruct. Setting the max full throttle RPM of 6300 (static) on the ground will give you a close to red line RPM when straight and level. Once you get that set you can go about checking the mixture (EGT and CHT temps) while running the engine static on the ground. Usually factory settings are sufficient to get you through the break in hour. Elevation and air temp will play some part in this too. Once you get airborne you will be able to start the fine tuning which is usually just moving the needle up or down a notch or two. Sometimes you have to change needles and or jets. That is a little far into the weeds for initial setup concerns. Or tweak the propeller pitch but usually if you get the static RPM right you won't have to unless it over revs in level flight at full throttle. In my case I had to raise the needle to get it to quit running lean on descent. I still have to watch it carefully if I am near 4000 RPM and push the nose over too far in descent. This "unloads" the prop meaning that the energy produced by burning fuel is not being converted to thrust but is dumping overboard through the exhaust. Changing throttle setting or adding a little "choke" helps cure that. I was admonished for doing the "choke" thing as if you forget it and have to jab the throttle you are asking for an engine out. So use this technique at your own risk. Reading the plugs is the best way to know if your mixture is right as temperature probes have been known to be less than accurate at times. The plugs never lie, or so I have been told. If you don't have them already, get the manual for the engine that will tell you the break in procedure and the operating temp limits. Then also get a carburetor manual as it will explain in detail how the carb works all through the operating range. It helped me figure out what was going on and what needed attention at each stage of the process. Firefly Rotax 447 B box 2.58:1 Warp Drive 60" 3 blade Stuart -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of John Fitt Sent: Saturday, January 06, 2018 5:56 PM Subject: Re: Kolb-List: best props Were the final pitch adjustments small compared to the first, did the engine really come on strong, with any EGT changes? Sent from my iPhone > On Jan 6, 2018, at 3:43 PM, Stuart Harner wrote: > > --> > > Same prop (60") and gear box here except on a 447. > > I started at 13 but had to back it down to about 8 to get in the > ball park. Had to fiddle with carb/pitch settings a little to get the > proper EGT's. I don't remember exactly but I think it is currently at > 7.5 > > LOTS of power for a Firefly and really smooth over 2200 RPM. > ________________________________ Message 9 _____________________________________ Time: 09:31:07 PM PST US Subject: Kolb-List: Re: best props From: "Richard Pike" What John said. Prop loading is what determines EGT's on 2 strokes. One of the things I like about the IVO is that once you get the jetting where it ought to be (by jetting it like Rotax says) is that you can adjust your EGT's by adding or taking away pitch. More pitch=lower EGT's. Less pitch=higher EGT's. With the IVO, you loosen the big nut and turn the hub bolt 1/2 turn coarser for winter. Lock the big nut down. When warmer weather comes, loosen the big nut, turn the big bolt 1/2 turn finer. Lock the big nut down. Go fly. Worse case scenario? You have to raise or lower the jet needle in the clip one notch from winter to summer if modding the prop pitch does not do quite enough. Big deal. Here is why it works that way: http://oh2fly.net/oldpoops/pg11.htm -------- Richard Pike Kolb MKIII N420P (420ldPoops) Kingsport, TN 3TN0 Forgiving is tough, being forgiven is wonderful, and Grace really is amazing. 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