Jetting Made Simple
#1
11-18-2003, 02:36 AM
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Jetting Made Simple
Every day I see on the forum, " What jets do I run? What goes where? What jet should I use?.......so on, and so on. Here is an easy way to find out exactly what is needed, and I mean exactly. Recently I have purchased a Digatron tach one that shows the temperature of the exhaust it has been invaluable in determining the exact jet to use in the front and rear. By trade I am a Machinist/Pressure Welder I use on a constant basis a simple thing to determine heat and it is relatively simple. It is the best thing, it is precise as it gets except for a $1000 dollar infrared heat detection gun. This I am talking about is a Temperature Stick. It consists of basically a wax that melts at predetermined temperatures. You can buy these from a Welding supply store for a couple of bucks and will do you for years. At a temperature you buy the stick for it will melt at that temperature.
Optimal temperature exiting your exhaust from the engine should be no higher than 1200*F at 2 inches from the head on a 4 stroke. I have numerous temp sticks mostly from heat treating metals the ones to use on your exhaust will be a 1200* and a 1300*. Run your quad at 1/2 to 3/4 throttle for 2 minutes immediately come to a stop get off your machine touch the exhaust with the exposed end of the temp stick at 2 inches from the head. If the 1200* melts easily on initial touch then your temperature of exhaust is to high then you must jet up to cool your exhaust down. You will have to do this for the rear exhaust pipe as well so you may have to previously remove your seat to gain access quickly the exhaust pipe cools at fast rate. If the 1200 melts slowly and the 1300 does not melt then you are in the ball park. If the 1200 does not melt at all then you are to rich and must go down in jet size to gain more internal heat.
1300*F and above for sustainable runs will cause a melt down in your machine. This is something to try jetting is a finicky business it is trial and error. I have seen it many times where your buddy has the identical modds to your machine, you jet yours like his/hers and it doesn't run right. Every motor is different this is a better way to produce a more precise jetting change for your own situation. Don't rely on what works for your buddy because I almost guarantee yours will be different than his.
Optimal temperature exiting your exhaust from the engine should be no higher than 1200*F at 2 inches from the head on a 4 stroke. I have numerous temp sticks mostly from heat treating metals the ones to use on your exhaust will be a 1200* and a 1300*. Run your quad at 1/2 to 3/4 throttle for 2 minutes immediately come to a stop get off your machine touch the exhaust with the exposed end of the temp stick at 2 inches from the head. If the 1200* melts easily on initial touch then your temperature of exhaust is to high then you must jet up to cool your exhaust down. You will have to do this for the rear exhaust pipe as well so you may have to previously remove your seat to gain access quickly the exhaust pipe cools at fast rate. If the 1200 melts slowly and the 1300 does not melt then you are in the ball park. If the 1200 does not melt at all then you are to rich and must go down in jet size to gain more internal heat.
1300*F and above for sustainable runs will cause a melt down in your machine. This is something to try jetting is a finicky business it is trial and error. I have seen it many times where your buddy has the identical modds to your machine, you jet yours like his/hers and it doesn't run right. Every motor is different this is a better way to produce a more precise jetting change for your own situation. Don't rely on what works for your buddy because I almost guarantee yours will be different than his.
#3
11-18-2003, 08:28 AM
#5
11-18-2003, 09:25 AM
Jetting Made Simple
I second that motion to induct this into the “tech tip website”. Thanks alltoys
I just come upon an old RTD Thermometer in my box toys and it looks like it can read up to 1800 F just need to order a surface probe.
Alltoys please tell us more about your “Digatron tach” sounds cool.
Ride on…
RJ
I just come upon an old RTD Thermometer in my box toys and it looks like it can read up to 1800 F just need to order a surface probe.
Alltoys please tell us more about your “Digatron tach” sounds cool.
Ride on…
RJ
#6
11-18-2003, 10:40 AM
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Jetting Made Simple
Mudfoot, Fireman650, Kawy,
I Think OldKaw would dump this on his site this is an easy affordable way to find out your jetting circumstances.
RocketJoe,
The Digatron tach is a DT-50k it was designed for kart racing but will work excellent on the Kawi or any machine for that matter. There is another version for 2 strokes as well plus there are a number of varieties with different price tags as well. This one sells for 350 US a little pricey but how much is a motor worth.....!!!!! It has 2 exhaust temperature monitors that can be set to warn of impending meltdown a set of lights flash when it gets to hot. It has play back where it registers hi and low runs plus a play back where it shows exhaust temperature and rpm at a one second play back interval.........real time play back. Basicly for every second that you have gone it shows a temperature reading and exhaust reading excellent for any type of racing or just messing around. I think it is worth while ivestment with regards to the price of a motor plus you can adapt it for a multitude of applications. Shotgun uses one for his pulls to see where to manipulate his clutch and so on. Have a good one hope these little hints helps you out.
I Think OldKaw would dump this on his site this is an easy affordable way to find out your jetting circumstances.
RocketJoe,
The Digatron tach is a DT-50k it was designed for kart racing but will work excellent on the Kawi or any machine for that matter. There is another version for 2 strokes as well plus there are a number of varieties with different price tags as well. This one sells for 350 US a little pricey but how much is a motor worth.....!!!!! It has 2 exhaust temperature monitors that can be set to warn of impending meltdown a set of lights flash when it gets to hot. It has play back where it registers hi and low runs plus a play back where it shows exhaust temperature and rpm at a one second play back interval.........real time play back. Basicly for every second that you have gone it shows a temperature reading and exhaust reading excellent for any type of racing or just messing around. I think it is worth while ivestment with regards to the price of a motor plus you can adapt it for a multitude of applications. Shotgun uses one for his pulls to see where to manipulate his clutch and so on. Have a good one hope these little hints helps you out.
#7
11-18-2003, 11:36 AM
Jetting Made Simple
Alltoys,
I will put a Digatron tach on my Christmas list. A new surface probe for my old RTD Thermometer is over $125.00 so I just ordered a new RTD from http://www.toolsource.com its manufacturer by Tif Instruments: Thermometer, Digital with 3 Probes, -40° to 1999°F ToolSource part#: 54469 Price: $169.99.
Ride on...
RJ
I will put a Digatron tach on my Christmas list. A new surface probe for my old RTD Thermometer is over $125.00 so I just ordered a new RTD from http://www.toolsource.com its manufacturer by Tif Instruments: Thermometer, Digital with 3 Probes, -40° to 1999°F ToolSource part#: 54469 Price: $169.99.
Ride on...
RJ
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#8
11-18-2003, 11:58 AM
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Jetting Made Simple
RocketJoe,
That is an excellent price for the monitor I wonder if the electrode has to be inside the pipe to register or if the probe can be attached to the outside of the pipe. I would rather the probe be on the outside to reduce exhaust restriction if it is possible. Definately a respectable price to help with the nasty jetting issues.
That is an excellent price for the monitor I wonder if the electrode has to be inside the pipe to register or if the probe can be attached to the outside of the pipe. I would rather the probe be on the outside to reduce exhaust restriction if it is possible. Definately a respectable price to help with the nasty jetting issues.
#9
11-18-2003, 12:05 PM
#10
11-18-2003, 05:53 PM
Jetting Made Simple
Originally posted by: alltoys
Every day I see on the forum, " What jets do I run? What goes where? What jet should I use?.......so on, and so on. Here is an easy way to find out exactly what is needed, and I mean exactly. Recently I have purchased a Digatron tach one that shows the temperature of the exhaust it has been invaluable in determining the exact jet to use in the front and rear.
Optimal temperature exiting your exhaust from the engine should be no higher than 1200*F at 2 inches from the head on a 4 stroke. If the 1200 does not melt at all then you are to rich and must go down in jet size to gain more internal heat.
1300*F and above for sustainable runs will cause a melt down in your machine.
Every motor is different this is a better way to produce a more precise jetting change for your own situation. Don't rely on what works for your buddy because I almost guarantee yours will be different than his.
Every day I see on the forum, " What jets do I run? What goes where? What jet should I use?.......so on, and so on. Here is an easy way to find out exactly what is needed, and I mean exactly. Recently I have purchased a Digatron tach one that shows the temperature of the exhaust it has been invaluable in determining the exact jet to use in the front and rear.
Optimal temperature exiting your exhaust from the engine should be no higher than 1200*F at 2 inches from the head on a 4 stroke. If the 1200 does not melt at all then you are to rich and must go down in jet size to gain more internal heat.
1300*F and above for sustainable runs will cause a melt down in your machine.
Every motor is different this is a better way to produce a more precise jetting change for your own situation. Don't rely on what works for your buddy because I almost guarantee yours will be different than his.
Using a EGT themocouple for determining Air/Fuel ratio is dangerous at best. I've used EGT gauges on my race engines for ~10 years; it is only good if you have a solid reference..... if you are trying out new mods, then the reference changes. I tend to use the Exhaust gas temp as an indication of combustion efficiency rather than purely AFR.....you can easily have high EGT readings and be rich as a pig. It's not a good practice, IMO.
1300*F? How did you derive this info? I've run my cast-piston 425hp Subaru Boxer engines (also a four stroke) at 1550*F for the last two years. I believe each engine (Kawasaki or whatever) will have a different EGT profile, based on camshaft design, ignition timing, and static compression ratio. Stating that "1200*F is optimal on a four stroke" is misleading.
My advice: 1) establish a EGT baseline on your particular bike. 2) Find out what type of pistons are in your engine (cast or forged) 3) If cast, try to keep within 200-250*F of your baseline temp...if forged, stay under 1550*F and use 93 octane. Don't use EGT for jetting; unless you know your engine like your wife, it will mislead you.
Steve