FREQUENTLY ASKED QUESTIONS
CARBS
Q. How should I maintain my Jettco 85.2 CVR Carbs?
A. If your carbs are off the motor, always keep the fuel inlet plugged - it only takes the slightest obstruction to unseat a float valve and have them flood.
Before you connect the fuel line to the carbs, turn the pump on and run some fuel into a container, if there’s any debris in the lines it will end up in the container and not the carbs.
If you're running our "85.18 or 2" carbs with between 4 and 6 PSI fuel pressure on your gauge and you don’t normally have flooding issues but your carbs have fuel dribbling or running out the clear plastic overflows (that's what flooding is) your motor won't idle or run right, especially at low RPM and low throttle. You must pull the bowls off, remove the float valves, blow the seats out in both directions, assemble them and try again, don't continue to try and run it when it's flooding, you'll just get grumpy..
When you first turn your pump on, flick it off and on for a few short bursts until the fuel pressure is up, this can help free up stuck float valves, If you turn the pump on and your carbs flood, turn the pump off and fire the motor straight away, let it run until it starts to starve for fuel, then flick the pump off and on and again and see if that shifts the obstruction or frees the stuck valve, in some cases it will.
If your carbs are marked "Jettco 55.23" or 24 or "Jettco 65.23" or 24 then 2.5 to 3 PSI fuel pressure is plenty.
If your carbs are marked "Jettco 85.18" or 2 then 4.5 to 5.5 PSI fuel pressure is plenty.
If your carbs are marked "JCO 85.XX" the above fuel pressure above still stands - however it means those carbs were originally converted by somebody else and have been sent to us to try and sort out. In a lot of cases we get them going fine. However some have been modified in a way that really compromises them. They're really parts only lemons and were sent back to their owners with some big question marks hanging over them at best... JCO marked carbs are not original Jettco carbs, don't get caught buying someones else's lemons!
The only reason we have the need for fuel "pressure" is to move fuel from the back of the car up to the carbs, once it's past the float valve and in the bowl the pressure in the line has NOTHING to do with how your motor runs unless you have way too much, in that case it floods and won't idle or you have not enough. In that case you can't move enough fuel from the tank to the carbs to keep your bowls full and so your bowls run out of fuel, normally at the end of the straights and it wont run right. This is not a jetting issue, it's a fuel delivery issue.
It's a good idea to run some unleaded petrol through them after racing, I use a plastic squeezy bottle full of petrol (gas for our USA buddies) and a short fuel line to fill the carbs. Start by draining the methanol from your bowls and blowing compressed air into fuel inlet to push the last of the methanol out, then do the drain bungs back up and fill them with the petrol from the squeezy bottle. Then start the motor, they don’t run really flash on petrol but it doesn’t have to run for long, then turn it off, drain the bowls, blow the excess out again and put them away. If you do this properly every time you use the car, there should be no reason for you to have to drop the bowls off at all.
NEVER tighten anything on your carbs more than a bit over finger tight and always keep the threads oiled and clean. I bet for every fastener that has dropped from the carbs because it was to loose, there’s been 500 drop out because they’ve been over tightened and stripped!
Always turn your fuel pump off first, BEFORE you turn the motor off. This will make sure that you don’t have any pressure left in the fuel lines. Having an almost vertical inlet port - any residual pressure will see fuel bleed past the float valve over time, flood the carb and then run down the intake port and fill the cylinder with fuel….this is not good. Try to always turn the pump off BEFORE you leave the track and head back into the pits
Methanol can dry out the lube between the throttle shafts and the bush. It's a good idea to spray some silicone spray around the bush both inside and out every now and again to help stop the butterflies sticking.
If you don’t maintain your air filter properly, your carbs wont run consistently. The grit will get in and stick the slides or at least make them not operate consistently. Apart from that it's also really hard on the valve seats.
It’s a really good idea to use some sort of additive to limit the corrosion damage caused by the methanol. We have been using a Lucas Fuel Treatment part #10576, that helps a lot with both gumming and corrosion both in the carb and the pump.
We now also recommend you fit a Ryco 373 fuel filter. These are a great little part and work fine with methanol, just make sure you put them in before your bypass valve or regulator and only take the pressure reading for your gauge after the filter. We need to know the fuel pressure at the carbs...not before the filter.
CARBS
Q. How should I maintain my Jettco 85.2 CVR Carbs?
A. If your carbs are off the motor, always keep the fuel inlet plugged - it only takes the slightest obstruction to unseat a float valve and have them flood.
Before you connect the fuel line to the carbs, turn the pump on and run some fuel into a container, if there’s any debris in the lines it will end up in the container and not the carbs.
If you're running our "85.18 or 2" carbs with between 4 and 6 PSI fuel pressure on your gauge and you don’t normally have flooding issues but your carbs have fuel dribbling or running out the clear plastic overflows (that's what flooding is) your motor won't idle or run right, especially at low RPM and low throttle. You must pull the bowls off, remove the float valves, blow the seats out in both directions, assemble them and try again, don't continue to try and run it when it's flooding, you'll just get grumpy..
When you first turn your pump on, flick it off and on for a few short bursts until the fuel pressure is up, this can help free up stuck float valves, If you turn the pump on and your carbs flood, turn the pump off and fire the motor straight away, let it run until it starts to starve for fuel, then flick the pump off and on and again and see if that shifts the obstruction or frees the stuck valve, in some cases it will.
If your carbs are marked "Jettco 55.23" or 24 or "Jettco 65.23" or 24 then 2.5 to 3 PSI fuel pressure is plenty.
If your carbs are marked "Jettco 85.18" or 2 then 4.5 to 5.5 PSI fuel pressure is plenty.
If your carbs are marked "JCO 85.XX" the above fuel pressure above still stands - however it means those carbs were originally converted by somebody else and have been sent to us to try and sort out. In a lot of cases we get them going fine. However some have been modified in a way that really compromises them. They're really parts only lemons and were sent back to their owners with some big question marks hanging over them at best... JCO marked carbs are not original Jettco carbs, don't get caught buying someones else's lemons!
The only reason we have the need for fuel "pressure" is to move fuel from the back of the car up to the carbs, once it's past the float valve and in the bowl the pressure in the line has NOTHING to do with how your motor runs unless you have way too much, in that case it floods and won't idle or you have not enough. In that case you can't move enough fuel from the tank to the carbs to keep your bowls full and so your bowls run out of fuel, normally at the end of the straights and it wont run right. This is not a jetting issue, it's a fuel delivery issue.
It's a good idea to run some unleaded petrol through them after racing, I use a plastic squeezy bottle full of petrol (gas for our USA buddies) and a short fuel line to fill the carbs. Start by draining the methanol from your bowls and blowing compressed air into fuel inlet to push the last of the methanol out, then do the drain bungs back up and fill them with the petrol from the squeezy bottle. Then start the motor, they don’t run really flash on petrol but it doesn’t have to run for long, then turn it off, drain the bowls, blow the excess out again and put them away. If you do this properly every time you use the car, there should be no reason for you to have to drop the bowls off at all.
NEVER tighten anything on your carbs more than a bit over finger tight and always keep the threads oiled and clean. I bet for every fastener that has dropped from the carbs because it was to loose, there’s been 500 drop out because they’ve been over tightened and stripped!
Always turn your fuel pump off first, BEFORE you turn the motor off. This will make sure that you don’t have any pressure left in the fuel lines. Having an almost vertical inlet port - any residual pressure will see fuel bleed past the float valve over time, flood the carb and then run down the intake port and fill the cylinder with fuel….this is not good. Try to always turn the pump off BEFORE you leave the track and head back into the pits
Methanol can dry out the lube between the throttle shafts and the bush. It's a good idea to spray some silicone spray around the bush both inside and out every now and again to help stop the butterflies sticking.
If you don’t maintain your air filter properly, your carbs wont run consistently. The grit will get in and stick the slides or at least make them not operate consistently. Apart from that it's also really hard on the valve seats.
It’s a really good idea to use some sort of additive to limit the corrosion damage caused by the methanol. We have been using a Lucas Fuel Treatment part #10576, that helps a lot with both gumming and corrosion both in the carb and the pump.
We now also recommend you fit a Ryco 373 fuel filter. These are a great little part and work fine with methanol, just make sure you put them in before your bypass valve or regulator and only take the pressure reading for your gauge after the filter. We need to know the fuel pressure at the carbs...not before the filter.