Post by Norbo on Jun 14, 2010 8:02:47 GMT 1
If you would like to help this topic, then feel free to post the set up and speck of your bike.
The more people that post the carb set ups the better idea others will have on what they may need to do.
125,10W............................................... 125,12A
Main jet 155...............................................Main jet 195
Air jet 1.0 ................................................Air jet 2.5
Needle 5GN36.............................................Needle 5GN36
Clip from top 3............................................Clip from top 4
Pilot jet 20.................................................Pilot jet 20
Air screw 1.5 turns out.................................Air screw 1.5 turns out
flote hight 1.0mm........................................flote hight 1.0mm
250LC 4L1
Main jet 190
Air jet 1.0
Needle 4N10
Clip from top 4
Pilot jet 20
Air screw 1 and 1/8 turns out
flote hight 1.0mm
350LC 4L0 Later Type
Main jet 220
Air jet 0.8
Needle 5K1
Clip from top 3
Pilot jet 22.5
Air screw 1.5 turns out
flote hight 1.0mm
350LC Early type
Non-Modded - ID 4L0 00
Main 140 or 160 in some cases
Pilot 20 or 22.5 in some cases
Needle 4H16 Clip 3rd from top of needle
Air Screw 1 1/4 turns out
Float Height 21mm +/- 0.5mm
Air correction circuit open in bell mouth
Modded type - ID 4L0 00
Main 160 or 170 for high speed running
Pilot 25 or 27.5 depending upon location and climate
Needle 4H16 Clip 3rd from top of needle
Air screw 1 1/4 turns out (tends to work better with 0.5 to 1 turn out with 25 pilots fitted)
Float height 21mm +/- 0.5mm
Air correction circuit blocked off in bell mouth and 3mm drilling into air correction circuit completed
31K YPVS................................................1UA YPVS
Main jet 240...............................................Main jet 185
Air jet 0.7..................................................Air jet 0.8
Needle 5K1................................................Needle 5L20
Clip from top 4...........................................Clip from top 2
Pilot jet 22.5..............................................Pilot jet 27.5
Air screw 1.25 turns out..............................Air screw 1.5 turns out
flote hight 0.5mm........................................flote hight 0.5mm
...............................................................Power jet L/H 65
...............................................................Powerjet R/H 60
There is no %100 correct jet for any one bike. You can fit a jet in 1 bike and it runs perfect and put the same jet on a bike with the same set up and for some reason the bike needs the needle moving or an air box top mod.
But there are a few general start up rools I have found to work well. These are just a starting pint but may save you time when choosing jets and trying to set up the crabs.
There are based on standard 26mm carbs There jets apply to all models 125, 2/350LC and YPVS:
Allspeeds 1 size up on standard. But often don't need any up jet
Microns 2 sizes up on standard
Nickons, Swarbrix, and all other race pipes 2 or 3 sizes up,
lomas often need a 3 or 4 up jets they are very hart pipes to jet .
If your bike is Tuned 1 more size up.
If you are pri mix 1 size up to compensate for oil displacement
Some tuned bikes need more air, so Pod filters need to be fitted, Usually you will fined a further up jet is needed but this is not always the case but something to bare in mined.
I often take the Air filter out first to see if this will do the job or remove the intake snorkel from the top air box top first.
It is important after up jetting that you adjust the oil pump as well so you don’t run week. 1 360 turn up for each jet is a good starting point.
I would always leave the needle clip on its standard clip to start with.
If you feel the bike is chugging/ holding back and not revving you may need to up jet. Some times moving the needle up will fix this.
If on full throttle you feel its bogging down and holding back release the throttle just a touch and if it feels like the bike picked up a bit you are over jetted. Sometimes moving the needle down will fix this
Always do a plug chop after a jet change. No matter how you think it's running a plug chop is the truth.
Take a plug spanner out with you .Fined a nice long road and thrash the bike down get in to a top gear at full revs , hit the kill switch ; shut off the throttle pull the clutch in then pull over wip the plug out and have a look. That’s a plug chop it should be biscuit brown . I like tun my plugs dark I prefer to see them more black over oil a little is better then not enough and running week on a hot day if your thrashing.
Reading spark plugs
I'ts not too hard to do, but I've read various understandings of how to read spark plugs and it seems there's different schools of thought on this. I always use a lighted magnifying glass of 5X to 10X to better see the tiny deposits. When checking your spark plug, always use a good used spark plug, making sure it's not worn out. A worn out spark plug will have a worn or rounded center electrode and or side electrode. New spark plugs are hard to read accurately for mixture checks, but if you have to use a new spark plug, then make sure to put at least 15 to 20 hard minutes on it before attempting to get a reading. I do my spark plug readings from the base ring at the bottom of the threaded body. The 'L' shaped grounded side electrode that's welded to the base ring will clue you into the heat range as this is the closest part to the piston. The porcelain will clue you into timing and preignition/detonation issues while the base ring will clue you into the mixture. Many people I've talked to and some of the articles I've read simply look at the porcelain color and use that as their sole guide for a proper air/fuel mixture, but I don't agree with that all together and would not recommend basing your jetting decisions solely on the color of your spark plugs porcelain.
Center/Ground Electrode
You want to first carefully look at the grounded side electrode to determine if you've got the proper heat range for your spark plug and this is done by closely examining the color change of the side electrode. If the color of the electrode changes near its end where it sits over the center electrode, then the spark plug heat range is too cold and what you're seeing is the color changing due to the heat transferring too quickly. If the color of the side electrode changes color near where it's welded to the base ring, then your spark plug is too hot and what you're seeing is a slower heat transfer from the side electrode to the base ring, resulting in preignition/detonation issues and most of the deposits will be burned off. Ideally, you want the side electrode of your spark plug to change color at about the half way point, about where it makes it's 'L' shaped bend.
Base Ring
The second thing you want to check is your spark plugs base ring and this will clue you into how your bike is jetted. The color of the base ring itself is close in color to the crown of the piston and what you're looking for here is a nice light to medium brown color all the way around the base ring. If you're seeing a chalky whitish or light grayish color or the color doesn't uniformly go all the way around the ring, then you are running too lean. If the color does go all the way around the ring, but you see dark colored soft dry soot that's heavily spotted on top of the base ring color, then you're running too rich and or possibly have a spark plug with too cold of a heat range. The presence of wet oil or ash deposits is a tell tale sign of possible engine problems such as valve stem or valve guide wear or worn out piston rings, etc, so don't confuse this with a rich mixture that leaves your spark plug carbon fouled.
Porcelain Color
The third thing to check is the porcelain color and this will clue you into preignition/detonation issues. What you're looking for are tiny specs of aluminum on the porcelain, which can be either black or shiny. If the tip of the insulator appears melted, then this is yet another clue to a pre-ignition/detonation problem. The detonation is caused by the air/fuel mixture exploding instead of burning and you may hear the resulting knocking sound from this, particularly when the engine is under a load. The knocking sound heard is actually a shock wave that's disrupting the boundary layer of cooler gasses that cover the internal parts of the combustion chamber, resulting in incomplete combustion. This rapid rise in pressure and temperature exerts extreme force on engine components and can do very bad things such as crack your engines head, crack or put holes in your piston, blow head gaskets, break your connecting rod, damage bearings, seals, etc. This is why you should not base all your jetting decisions on just the porcelain color alone because the porcelain color doesn't tell the whole story. Although the porcelain and base ring colors are similar, the porcelain usually appears lighter in color when compared to the base ring.
(1)Porcelain Insulator
(2)Center Electrode
(3)Side Electrode
Final Thought
There's a lot more to jetting than just stuffing jets in holes and hoping the problem goes away. If you can understand what your engine is trying to tell you when it runs funny you will have a better chance or correcting the problem than someone who doesn't have a clue. When you rejet, go slowly and carefully until the problem is solved. As a final thought let me remind you that jetting is a lot like life, if you have a choice it's always better to be a little rich!
I hope there tips help you .
The more people that post the carb set ups the better idea others will have on what they may need to do.
125,10W............................................... 125,12A
Main jet 155...............................................Main jet 195
Air jet 1.0 ................................................Air jet 2.5
Needle 5GN36.............................................Needle 5GN36
Clip from top 3............................................Clip from top 4
Pilot jet 20.................................................Pilot jet 20
Air screw 1.5 turns out.................................Air screw 1.5 turns out
flote hight 1.0mm........................................flote hight 1.0mm
250LC 4L1
Main jet 190
Air jet 1.0
Needle 4N10
Clip from top 4
Pilot jet 20
Air screw 1 and 1/8 turns out
flote hight 1.0mm
350LC 4L0 Later Type
Main jet 220
Air jet 0.8
Needle 5K1
Clip from top 3
Pilot jet 22.5
Air screw 1.5 turns out
flote hight 1.0mm
350LC Early type
Non-Modded - ID 4L0 00
Main 140 or 160 in some cases
Pilot 20 or 22.5 in some cases
Needle 4H16 Clip 3rd from top of needle
Air Screw 1 1/4 turns out
Float Height 21mm +/- 0.5mm
Air correction circuit open in bell mouth
Modded type - ID 4L0 00
Main 160 or 170 for high speed running
Pilot 25 or 27.5 depending upon location and climate
Needle 4H16 Clip 3rd from top of needle
Air screw 1 1/4 turns out (tends to work better with 0.5 to 1 turn out with 25 pilots fitted)
Float height 21mm +/- 0.5mm
Air correction circuit blocked off in bell mouth and 3mm drilling into air correction circuit completed
31K YPVS................................................1UA YPVS
Main jet 240...............................................Main jet 185
Air jet 0.7..................................................Air jet 0.8
Needle 5K1................................................Needle 5L20
Clip from top 4...........................................Clip from top 2
Pilot jet 22.5..............................................Pilot jet 27.5
Air screw 1.25 turns out..............................Air screw 1.5 turns out
flote hight 0.5mm........................................flote hight 0.5mm
...............................................................Power jet L/H 65
...............................................................Powerjet R/H 60
There is no %100 correct jet for any one bike. You can fit a jet in 1 bike and it runs perfect and put the same jet on a bike with the same set up and for some reason the bike needs the needle moving or an air box top mod.
But there are a few general start up rools I have found to work well. These are just a starting pint but may save you time when choosing jets and trying to set up the crabs.
There are based on standard 26mm carbs There jets apply to all models 125, 2/350LC and YPVS:
Allspeeds 1 size up on standard. But often don't need any up jet
Microns 2 sizes up on standard
Nickons, Swarbrix, and all other race pipes 2 or 3 sizes up,
lomas often need a 3 or 4 up jets they are very hart pipes to jet .
If your bike is Tuned 1 more size up.
If you are pri mix 1 size up to compensate for oil displacement
Some tuned bikes need more air, so Pod filters need to be fitted, Usually you will fined a further up jet is needed but this is not always the case but something to bare in mined.
I often take the Air filter out first to see if this will do the job or remove the intake snorkel from the top air box top first.
It is important after up jetting that you adjust the oil pump as well so you don’t run week. 1 360 turn up for each jet is a good starting point.
I would always leave the needle clip on its standard clip to start with.
If you feel the bike is chugging/ holding back and not revving you may need to up jet. Some times moving the needle up will fix this.
If on full throttle you feel its bogging down and holding back release the throttle just a touch and if it feels like the bike picked up a bit you are over jetted. Sometimes moving the needle down will fix this
Always do a plug chop after a jet change. No matter how you think it's running a plug chop is the truth.
Take a plug spanner out with you .Fined a nice long road and thrash the bike down get in to a top gear at full revs , hit the kill switch ; shut off the throttle pull the clutch in then pull over wip the plug out and have a look. That’s a plug chop it should be biscuit brown . I like tun my plugs dark I prefer to see them more black over oil a little is better then not enough and running week on a hot day if your thrashing.
Reading spark plugs
I'ts not too hard to do, but I've read various understandings of how to read spark plugs and it seems there's different schools of thought on this. I always use a lighted magnifying glass of 5X to 10X to better see the tiny deposits. When checking your spark plug, always use a good used spark plug, making sure it's not worn out. A worn out spark plug will have a worn or rounded center electrode and or side electrode. New spark plugs are hard to read accurately for mixture checks, but if you have to use a new spark plug, then make sure to put at least 15 to 20 hard minutes on it before attempting to get a reading. I do my spark plug readings from the base ring at the bottom of the threaded body. The 'L' shaped grounded side electrode that's welded to the base ring will clue you into the heat range as this is the closest part to the piston. The porcelain will clue you into timing and preignition/detonation issues while the base ring will clue you into the mixture. Many people I've talked to and some of the articles I've read simply look at the porcelain color and use that as their sole guide for a proper air/fuel mixture, but I don't agree with that all together and would not recommend basing your jetting decisions solely on the color of your spark plugs porcelain.
Center/Ground Electrode
You want to first carefully look at the grounded side electrode to determine if you've got the proper heat range for your spark plug and this is done by closely examining the color change of the side electrode. If the color of the electrode changes near its end where it sits over the center electrode, then the spark plug heat range is too cold and what you're seeing is the color changing due to the heat transferring too quickly. If the color of the side electrode changes color near where it's welded to the base ring, then your spark plug is too hot and what you're seeing is a slower heat transfer from the side electrode to the base ring, resulting in preignition/detonation issues and most of the deposits will be burned off. Ideally, you want the side electrode of your spark plug to change color at about the half way point, about where it makes it's 'L' shaped bend.
Base Ring
The second thing you want to check is your spark plugs base ring and this will clue you into how your bike is jetted. The color of the base ring itself is close in color to the crown of the piston and what you're looking for here is a nice light to medium brown color all the way around the base ring. If you're seeing a chalky whitish or light grayish color or the color doesn't uniformly go all the way around the ring, then you are running too lean. If the color does go all the way around the ring, but you see dark colored soft dry soot that's heavily spotted on top of the base ring color, then you're running too rich and or possibly have a spark plug with too cold of a heat range. The presence of wet oil or ash deposits is a tell tale sign of possible engine problems such as valve stem or valve guide wear or worn out piston rings, etc, so don't confuse this with a rich mixture that leaves your spark plug carbon fouled.
Porcelain Color
The third thing to check is the porcelain color and this will clue you into preignition/detonation issues. What you're looking for are tiny specs of aluminum on the porcelain, which can be either black or shiny. If the tip of the insulator appears melted, then this is yet another clue to a pre-ignition/detonation problem. The detonation is caused by the air/fuel mixture exploding instead of burning and you may hear the resulting knocking sound from this, particularly when the engine is under a load. The knocking sound heard is actually a shock wave that's disrupting the boundary layer of cooler gasses that cover the internal parts of the combustion chamber, resulting in incomplete combustion. This rapid rise in pressure and temperature exerts extreme force on engine components and can do very bad things such as crack your engines head, crack or put holes in your piston, blow head gaskets, break your connecting rod, damage bearings, seals, etc. This is why you should not base all your jetting decisions on just the porcelain color alone because the porcelain color doesn't tell the whole story. Although the porcelain and base ring colors are similar, the porcelain usually appears lighter in color when compared to the base ring.
(1)Porcelain Insulator
(2)Center Electrode
(3)Side Electrode
Final Thought
There's a lot more to jetting than just stuffing jets in holes and hoping the problem goes away. If you can understand what your engine is trying to tell you when it runs funny you will have a better chance or correcting the problem than someone who doesn't have a clue. When you rejet, go slowly and carefully until the problem is solved. As a final thought let me remind you that jetting is a lot like life, if you have a choice it's always better to be a little rich!
I hope there tips help you .
