What affects what in the carb of the 1300 VTX
There are 3 things to deal with and each affects the other in some small way.
Selecting a proper main jet is sometimes hard for some so some tips for doing it properly. The first thing you need to do is give an educated guess or just toss a 215 in for trial, now you want the bike up to temp about an 8-10 mile ride then get the rpm up around 3500 you don't have a tach. so let's say 45 in second gear roll on the throttle and pay attention to how the rpm reacts it should be a good steady strong pull right up to the rev limiter if it is sluggish at the start and gets better as the rpm builds you have 1 size too large in and if it stops building good power before the limiter you may be 1 size too small.
The next step is the needle position if you are running an aftermarket needle it has grooves and your clip should start at the 3rd position from the blunt end if running the stock needle leave it as it is NO SHIMS yet. Now you take it out for the 8-10 mile warm up and now you want to be in 4th gear doing around 50 roll on the throttle hard if it bogs down then takes off and build good rpm your needle is too high if it hesitates (stutters) your needle is too low. If too low which will be 90% of the time add 1 shim this should be around .025 thickness give or take a little, now go and do the same test, and repeat till you have what you like, with after-market needle you would remove the shim and move the clip (the shim is about half a clip position).
Now on to the pilot jet, every VTX from the factory is very lean on the bottom end so you should start with the 58 if running a heavy breather you should have a 60.
the start point for the setting of the idle drop is
Now you get the bike up to full temp again then set the idle up to around 1000 and it is going to sound fast, you will now blip the throttle a little and it should return to 1000 without hanging or dropping from your 1000 initial setting, if it drops below you are rich if it hangs up you are lean.
Ok, now you have some base points to work from!
Review
Some of the main problems we face are lean surging at cruise this is due to the pilot jet is too small and at most cruise speeds 55-65 we are in the 2500 rpm range and what I see 90% of the time raises the needle or open the A/F neither will work 100% of the time and we end up chasing our tails.
When you open the A/F up above what it should be for the idle drop is run rich at idle then you hit around 1500 rpm and you are once again in the lean stage so what do you do well we raise the needle to compensate and this once again puts us back to a rich state till we get up to around 3000 rpm.
So in a sense, we just try to cover up and say all is right.
There are 3 things to deal with and each affects the other in some small way.
- main jet
- pilot jet
- needle position
Selecting a proper main jet is sometimes hard for some so some tips for doing it properly. The first thing you need to do is give an educated guess or just toss a 215 in for trial, now you want the bike up to temp about an 8-10 mile ride then get the rpm up around 3500 you don't have a tach. so let's say 45 in second gear roll on the throttle and pay attention to how the rpm reacts it should be a good steady strong pull right up to the rev limiter if it is sluggish at the start and gets better as the rpm builds you have 1 size too large in and if it stops building good power before the limiter you may be 1 size too small.
The next step is the needle position if you are running an aftermarket needle it has grooves and your clip should start at the 3rd position from the blunt end if running the stock needle leave it as it is NO SHIMS yet. Now you take it out for the 8-10 mile warm up and now you want to be in 4th gear doing around 50 roll on the throttle hard if it bogs down then takes off and build good rpm your needle is too high if it hesitates (stutters) your needle is too low. If too low which will be 90% of the time add 1 shim this should be around .025 thickness give or take a little, now go and do the same test, and repeat till you have what you like, with after-market needle you would remove the shim and move the clip (the shim is about half a clip position).
Now on to the pilot jet, every VTX from the factory is very lean on the bottom end so you should start with the 58 if running a heavy breather you should have a 60.
the start point for the setting of the idle drop is
- 55 jets should be around 2 1/2 (stock box)
- 58 jets should be around 2 (Spyker mod or decap with K&N)
- 60 jets should be around 1 3/4 (Hyper, BAK, Ashford, Doug's,.......) all heavy breathers
Now you get the bike up to full temp again then set the idle up to around 1000 and it is going to sound fast, you will now blip the throttle a little and it should return to 1000 without hanging or dropping from your 1000 initial setting, if it drops below you are rich if it hangs up you are lean.
Ok, now you have some base points to work from!
Review
- The main jet is from 3500 rpm up to the red line (Speed limiter)
- Needle position is from 2500 to 3500 rpm
- Pilot jet handles from 900 to 2500
Some of the main problems we face are lean surging at cruise this is due to the pilot jet is too small and at most cruise speeds 55-65 we are in the 2500 rpm range and what I see 90% of the time raises the needle or open the A/F neither will work 100% of the time and we end up chasing our tails.
When you open the A/F up above what it should be for the idle drop is run rich at idle then you hit around 1500 rpm and you are once again in the lean stage so what do you do well we raise the needle to compensate and this once again puts us back to a rich state till we get up to around 3000 rpm.
So in a sense, we just try to cover up and say all is right.
- If you want the best low-end torque for low speed you need the correct pilot jet
- If you want the cruise speed surging gone again the pilot jet
- If you want the best acceleration at cruise for passing you need the needle position correct
- And last if you like high-speed power to the top you need the best main jet.
