Carburetor jet question
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Joined: Apr 2016
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From: az
Carburetor jet question
I have a question for my esteemed Evo peeps about a carb swap I want to do, actually exhaust also. I have a 1984 FXRDG that came with some shorty slash cut pipes that are loud, and kind of ugly. The bike also has an SU carb on it that I want to replace. So here is what I have: the PO gave me a box with a new exhaust system in it, forget the brand, but they look identical to the original ones minus the crossover. The carb is a Keihin CV carb and I have the manifold for it, an air cleaner and a bunch of hardware.
The carb has 170 main and 42 pilot in it now, and I also have an extra 190 main and 45 pilot. My question is, with a pretty close to a stock setup with the pipes, and the rest of the motor (as far as I know) what size jets do you think I should be using with this?
Thanks,
theDog
The carb has 170 main and 42 pilot in it now, and I also have an extra 190 main and 45 pilot. My question is, with a pretty close to a stock setup with the pipes, and the rest of the motor (as far as I know) what size jets do you think I should be using with this?
Thanks,
theDog
Grand HDF Member
Joined: Apr 2007
Posts: 3,724
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From: Brighton, MI
Pilot: 45 or 46 to start. May need to eventually go up to a 48. Main jet: start with the 170, but 180 is pretty common with some going as high as 190. It all depends on how the bike performs and the plugs read with carb and pipes.
To start, I would go 45 pilot and 180 main with new intake seals and carb to manifold seal. Make sure you give the carb a good cleaning and once over inspection before installing and tuning.
Pay attention to the diaphragm for the slide, the diaphragm for the accelerator pump, all passages should be clear, inspect float needle rubber tip, and make sure the needle jet is installed back in it's proper orientation. It is easily installed upside down and will cause problems if installed upside down. YD
To start, I would go 45 pilot and 180 main with new intake seals and carb to manifold seal. Make sure you give the carb a good cleaning and once over inspection before installing and tuning.
Pay attention to the diaphragm for the slide, the diaphragm for the accelerator pump, all passages should be clear, inspect float needle rubber tip, and make sure the needle jet is installed back in it's proper orientation. It is easily installed upside down and will cause problems if installed upside down. YD
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Joined: Jun 2007
Posts: 45,429
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From: Bedford UK
Two Dogs together!
Slashcuts are a pain to tune, so you are wise to replace them. The carb sounds more suitable and a good choice. Further to Yankee's suggestion you can buy an overhaul kit, which comes with all the perishable parts so you can strip, clean and rebuild your c/v carb with confidence.
Before installing it, check that the idle adjuster has been uncovered. When new it is hidden under a small diaphragm, which can be (v carefully!) drilled through and winkled out, to get access to the screwdriver slot underneath.
Slashcuts are a pain to tune, so you are wise to replace them. The carb sounds more suitable and a good choice. Further to Yankee's suggestion you can buy an overhaul kit, which comes with all the perishable parts so you can strip, clean and rebuild your c/v carb with confidence.
Before installing it, check that the idle adjuster has been uncovered. When new it is hidden under a small diaphragm, which can be (v carefully!) drilled through and winkled out, to get access to the screwdriver slot underneath.
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