The stock exhaust system has rusted out on the inside so I have bought a Black Widow replacement. All is well except the rear cylinder is on the lean side, not excessively, but the insulator on the BP7ES plug remains perfectly white with no sign of blistering. Although I was able to dial in the front cylinder using the pilot screw this approach is insufficient for the rear cylinder.
My Virago (1988 SE model) has two Hitachi HSC40 carburetors and they have been thoroughly cleaned in the ultra-sound and all jets blown clean. The bike is currently working and pulls well without any popping on deceleration.
The Hitachi HSC40s I have were their latest models prior to the change over to Mukini. Due to EPA requirements these carburetors have limitations as to which jets can be replaced/fiddled with. The idle circuit has an air jet which is pressed in and sealed away plus a fixed 0.41mm fuel jet. The 0.41mm fuel jet is pressed in and not easily removed. There is also a main air jet pressed in and not easily accessed and the main fuel jet which is easily accessed like on the BS34s. The needle can also be shimmed if needed.
Regarding the 0.41mm idle circuit fuel jet, I have found that Joe Minton had recommended drilling this out to 0.5mm. But on the Virago forums it is not recommended to do this because it makes the mixture too rich and this cannot be corrected with the pilot screw.
What might be a simple solution?
Thank you Guys.
Note: All my riding is down at small throttle openings so increasing the main jet or shimming the needle may not have much effect??
My Virago (1988 SE model) has two Hitachi HSC40 carburetors and they have been thoroughly cleaned in the ultra-sound and all jets blown clean. The bike is currently working and pulls well without any popping on deceleration.
The Hitachi HSC40s I have were their latest models prior to the change over to Mukini. Due to EPA requirements these carburetors have limitations as to which jets can be replaced/fiddled with. The idle circuit has an air jet which is pressed in and sealed away plus a fixed 0.41mm fuel jet. The 0.41mm fuel jet is pressed in and not easily removed. There is also a main air jet pressed in and not easily accessed and the main fuel jet which is easily accessed like on the BS34s. The needle can also be shimmed if needed.
Regarding the 0.41mm idle circuit fuel jet, I have found that Joe Minton had recommended drilling this out to 0.5mm. But on the Virago forums it is not recommended to do this because it makes the mixture too rich and this cannot be corrected with the pilot screw.
What might be a simple solution?
- I could just change my rear plug to a BP8ES or BP9ES to avoid over heating the electrode.
- Increase the size of the main jet.
- Shim the needle a little.
- Do a Minton mod and only drill out the 0.41mm jet to 0.45mm
Thank you Guys.
Note: All my riding is down at small throttle openings so increasing the main jet or shimming the needle may not have much effect??