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This is continued from the "Theory" thread - read it first!
2 - Jetting size chart
All measurements refer to mainjet size and are approximate, as no two bikes are exactly the same and thus the sizing will vary. 'OR' means 'instead of', or 'not in conjunction with'. 'AND' means 'as well as' or 'in addition to'.
+1 - Slipon system OR unpacking/debaffling OR high-flow air filter OR modified airbox
+2 - Pods OR full system exhaust OR modified airbox AND high-flow air filter
+3 - Velocity stacks OR pods AND slipon OR unpacking/debaffling
+4 - Pods AND full system exhaust OR velocity stacks AND slipon OR unpacking/debaffling
+5 - Velocity stacks AND full-system exhaust
Remember, all references given are approximate, and I would use them as starting points for additional tuning only.
3 - Plug chopping
This is how you find out if your engine is running rich or lean. Aside from the more obvious symptoms like a lean engine cracking and popping when you wind on thr throttle, or a rich engine bogging down when you wind it on, in which case you will need to adjust the jets accordingly either way as you see fit. After some experimentation you will soon know what is lean and what is rich, and can go from there with the rest of your future tuning.
A plug chop gives you a snapshot of the condition of the spark plug at the moment in time when you perform it, and is a very useful tuning tool. It is performed by simultaneously itting your kill switch and pulling in your clutch, then rolling to a rest and pulling your plugs on the side of the road. Black or sooty is too rich, and will cause plug fouling and loss of economy and power. White is too lean, and will cause overheating and loss of power. A biscuit brown colour is what you are chasing, indicating a good fuel to air ratio for your engine.
You can perform a plug chop at any speed and engine revolution, but there is not sense in changing the pilot jets while your mainjet is still stock - you need to work from the top down to acheive results. Thus, once you get the jetting close enough in your garage, you need to throw some tools in your backpack and then take the bike for a spin to warm it up. This is critical, a warm engine runs leaner than a cold one and vice versa. Once you've warmed it up (15min good riding) then find a deserted bit of road and run max rpm in whatever gear you feel comfortable with. Hold for a few seconds, then perform a plug chop. This will give you engine conditions at maximum rpm, and you can adjust your mainjets accordingly.
4 - Changing jets
Your carburettor is the heart of your engine, metering fuel into the incoming airflow so your engine can combust it and produce power. It is essential to know which parts perform each function before you start tuning, or you won't know what action provides which results...or why! Another must is only changing one carburettor setting/part at a time, or you will not know which setting or part yeilded the result. Capiche? Right, onto business.
You will need to tune your carburettor(s) from the 'top down', starting with your mainjet which controls fueling up to maximum engine revolutions. Once this is set via experimentation in the garage, then plug chopping to fine-tune, you can move onto every other part. The midrange is governed by your needle, moving it upwards in the carburettor body will let more fuel flow for a given throttle setting. Low range is governed by your pilot jet, and this is the jet often responsible for lacklustre off-the line performance or bad idling. A single size up at a time should tell you whether you are going in the right direction, after you've set your mains and needle, of course. Acceptance of throttle from low rpms is your float height. Lower the float height if you are not running rich, but continually bogging down. You should be able to give the engine full throttle from 2~3,000rpm and have the engine slowly pick up, not stutter and bog.
Perfecting your carburettor tuning is not an easy task, but it need not be tiresome. Simply take a few tools and jets with you on an afternoon ride, and do what you need to on the side of the road. It may also help you to keep a log of what mdifications you have made, along with their results. This will save you time and money in the long run.
Cheers - boingk
2 - Jetting size chart
All measurements refer to mainjet size and are approximate, as no two bikes are exactly the same and thus the sizing will vary. 'OR' means 'instead of', or 'not in conjunction with'. 'AND' means 'as well as' or 'in addition to'.
+1 - Slipon system OR unpacking/debaffling OR high-flow air filter OR modified airbox
+2 - Pods OR full system exhaust OR modified airbox AND high-flow air filter
+3 - Velocity stacks OR pods AND slipon OR unpacking/debaffling
+4 - Pods AND full system exhaust OR velocity stacks AND slipon OR unpacking/debaffling
+5 - Velocity stacks AND full-system exhaust
Remember, all references given are approximate, and I would use them as starting points for additional tuning only.
3 - Plug chopping
This is how you find out if your engine is running rich or lean. Aside from the more obvious symptoms like a lean engine cracking and popping when you wind on thr throttle, or a rich engine bogging down when you wind it on, in which case you will need to adjust the jets accordingly either way as you see fit. After some experimentation you will soon know what is lean and what is rich, and can go from there with the rest of your future tuning.
A plug chop gives you a snapshot of the condition of the spark plug at the moment in time when you perform it, and is a very useful tuning tool. It is performed by simultaneously itting your kill switch and pulling in your clutch, then rolling to a rest and pulling your plugs on the side of the road. Black or sooty is too rich, and will cause plug fouling and loss of economy and power. White is too lean, and will cause overheating and loss of power. A biscuit brown colour is what you are chasing, indicating a good fuel to air ratio for your engine.
You can perform a plug chop at any speed and engine revolution, but there is not sense in changing the pilot jets while your mainjet is still stock - you need to work from the top down to acheive results. Thus, once you get the jetting close enough in your garage, you need to throw some tools in your backpack and then take the bike for a spin to warm it up. This is critical, a warm engine runs leaner than a cold one and vice versa. Once you've warmed it up (15min good riding) then find a deserted bit of road and run max rpm in whatever gear you feel comfortable with. Hold for a few seconds, then perform a plug chop. This will give you engine conditions at maximum rpm, and you can adjust your mainjets accordingly.
4 - Changing jets
Your carburettor is the heart of your engine, metering fuel into the incoming airflow so your engine can combust it and produce power. It is essential to know which parts perform each function before you start tuning, or you won't know what action provides which results...or why! Another must is only changing one carburettor setting/part at a time, or you will not know which setting or part yeilded the result. Capiche? Right, onto business.
You will need to tune your carburettor(s) from the 'top down', starting with your mainjet which controls fueling up to maximum engine revolutions. Once this is set via experimentation in the garage, then plug chopping to fine-tune, you can move onto every other part. The midrange is governed by your needle, moving it upwards in the carburettor body will let more fuel flow for a given throttle setting. Low range is governed by your pilot jet, and this is the jet often responsible for lacklustre off-the line performance or bad idling. A single size up at a time should tell you whether you are going in the right direction, after you've set your mains and needle, of course. Acceptance of throttle from low rpms is your float height. Lower the float height if you are not running rich, but continually bogging down. You should be able to give the engine full throttle from 2~3,000rpm and have the engine slowly pick up, not stutter and bog.
Perfecting your carburettor tuning is not an easy task, but it need not be tiresome. Simply take a few tools and jets with you on an afternoon ride, and do what you need to on the side of the road. It may also help you to keep a log of what mdifications you have made, along with their results. This will save you time and money in the long run.
Cheers - boingk
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