Pilot adjuster screws, final verdict
Posted: Tue Apr 15, 2014 10:50 am
Dont want to start an argument, i want this to be a rational debate.
As part of the general cleanup of the site i want to lay this confusion to bed as i will be making a general fuelling FAQ in the near future.
I have always been led to believe that the CVK-D32 carbs have a fuel mixture screw, every pair of carbs that i have seen that have a screw in the same place is a mixture screw. When i took the bike to Jordans Dyno in Leeds they told me it was a mixture screw, James Brennan a former racer who owns the DIY garage in coventry has told me that its a mixture screw, and today i recieved this from Kawasaki UK:-
"Dear John,
Thank you for contacting Kawasaki Motors UK.
There is no specific mention in the workshop manual regarding if the pilot screw adjusts the air or fuel amounts, however as a general rule, if the pilot screw is located near the engine side of the carburettor then it adjusts the amount of fuel ie screw it out adds more fuel (richens mixture), screw it in reduces fuel amount (leans mixture). If the pilot screw is located near the air box side of the carburettor then it adjusts the amount or air ie screw it out adds more air (leans mixture), screw it in reduces air amount (richens mixture).
Looking at the workshop manual the pilot screws are located engine side of the carburettor, so screwing the pilots screw in would make the bike run leaner. The standard pilot screw setting is 1 and a half turns out.
I hope this information is of assistance to you.
Kind Regards,
Matthew Callaway
Technical & Customer Services Group
Kawasaki Motors UK
1 Dukes Meadow | Millboard Road | Bourne End | SL8 5XF
T +44 (0)1682 856750 | F +44 (0)1628 856798
customerservice@kawasaki.co.uk | http://www.kawasaki.co.uk"
After replacing my head gasket i tinkered with my bike, screwing the pilot adjusters clockwise inwards until they seated i backed them off to 1 turn out, the bike required some choke to start (i.e. its lean), after screwing them out to 2.5 turns out the bike didnt require choke (i.e. mixture was good to possibly rich).
Other than the online kawasaki parts diagram stating "Screw - Pilot Air", no other place refers to it as an Air screw, we have all come across inaccuracies in manuals before, i believe that this is innacurate as the workshop manual just refers to is a "Pilot Screw". And if Kawasaki UK and a respected Dynojet Operator say its a mixture screw, then until other evidence comes to light we will be calling it a mixture screw - any by evidence i mean a dyno trace before/after touching only the mixture screw.
To repeat: Until other information comes to light, you screw the pilot adjusters OUT for richer, and IN for leaner.
I have sent an email back to Kawasaki UK:
"Thank you Matthew, just for my own piece of mind, are there any carbs fitted to kawasaki motorcycles that have an air mixture screw located on the engine side of the carb? Its just that the http://www.kawasakioriginalparts.com/ website lists the UK zxr 400 L4 pilot screw as "screw - pilot air" which makes it seem like it regulates air as opposed to mixture...i think this is where my confusion is coming from. Any information you could shed on this would be greatly appreciated.
Thank you
John"
Also, for the record, im a scientist, i dont mind being wrong, but where i see 2 competing theories i would like the issue of which one is correct to be resolved, and resolved with evidence as opposed to "i said so". If you wish to discuss this in a reasonable manner please reply below.
As part of the general cleanup of the site i want to lay this confusion to bed as i will be making a general fuelling FAQ in the near future.
I have always been led to believe that the CVK-D32 carbs have a fuel mixture screw, every pair of carbs that i have seen that have a screw in the same place is a mixture screw. When i took the bike to Jordans Dyno in Leeds they told me it was a mixture screw, James Brennan a former racer who owns the DIY garage in coventry has told me that its a mixture screw, and today i recieved this from Kawasaki UK:-
"Dear John,
Thank you for contacting Kawasaki Motors UK.
There is no specific mention in the workshop manual regarding if the pilot screw adjusts the air or fuel amounts, however as a general rule, if the pilot screw is located near the engine side of the carburettor then it adjusts the amount of fuel ie screw it out adds more fuel (richens mixture), screw it in reduces fuel amount (leans mixture). If the pilot screw is located near the air box side of the carburettor then it adjusts the amount or air ie screw it out adds more air (leans mixture), screw it in reduces air amount (richens mixture).
Looking at the workshop manual the pilot screws are located engine side of the carburettor, so screwing the pilots screw in would make the bike run leaner. The standard pilot screw setting is 1 and a half turns out.
I hope this information is of assistance to you.
Kind Regards,
Matthew Callaway
Technical & Customer Services Group
Kawasaki Motors UK
1 Dukes Meadow | Millboard Road | Bourne End | SL8 5XF
T +44 (0)1682 856750 | F +44 (0)1628 856798
customerservice@kawasaki.co.uk | http://www.kawasaki.co.uk"
After replacing my head gasket i tinkered with my bike, screwing the pilot adjusters clockwise inwards until they seated i backed them off to 1 turn out, the bike required some choke to start (i.e. its lean), after screwing them out to 2.5 turns out the bike didnt require choke (i.e. mixture was good to possibly rich).
Other than the online kawasaki parts diagram stating "Screw - Pilot Air", no other place refers to it as an Air screw, we have all come across inaccuracies in manuals before, i believe that this is innacurate as the workshop manual just refers to is a "Pilot Screw". And if Kawasaki UK and a respected Dynojet Operator say its a mixture screw, then until other evidence comes to light we will be calling it a mixture screw - any by evidence i mean a dyno trace before/after touching only the mixture screw.
To repeat: Until other information comes to light, you screw the pilot adjusters OUT for richer, and IN for leaner.
I have sent an email back to Kawasaki UK:
"Thank you Matthew, just for my own piece of mind, are there any carbs fitted to kawasaki motorcycles that have an air mixture screw located on the engine side of the carb? Its just that the http://www.kawasakioriginalparts.com/ website lists the UK zxr 400 L4 pilot screw as "screw - pilot air" which makes it seem like it regulates air as opposed to mixture...i think this is where my confusion is coming from. Any information you could shed on this would be greatly appreciated.
Thank you
John"
Also, for the record, im a scientist, i dont mind being wrong, but where i see 2 competing theories i would like the issue of which one is correct to be resolved, and resolved with evidence as opposed to "i said so". If you wish to discuss this in a reasonable manner please reply below.