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AFR woes

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  • #1

    AFR woes

    I know that lean mixture cause engine to overheat and all the damage it causes.
    Can rotating the Volume Screw on the carburettor ever make the mixture so lean that the engine overheats?The engine in question is a P180UG3 running on stock air filter, jets,everything stock in this department.
    Tags: None
  • #2
    Query Approved.
    :)

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    • #3
      Originally posted by pavanchirmade View Post
      I know that lean mixture cause engine to overheat and all the damage it causes.
      Can rotating the Volume Screw on the carburettor ever make the mixture so lean that the engine overheats?The engine in question is a P180UG3 running on stock air filter, jets,everything stock in this department.

      How else do u think u would adjust the AFR ratio in a Carb'd bike?
      When everything comes ur way, u r in the wrong way ;)

      Comment

      • #4
        Buddy I know its the only way to.

        My question is, Can the turning of the VC make the mixture so lean that it causes engine overheat?The question to the extent to which the mixture can turn lean by just the use of the VC.
        Last edited by pavanchirmade; 06-18-2009, 10:29 AM.

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        • #5
          Yes man, u can tune it for a lean mixture as well.

          The Volume screw only is adjusted for a more richer mix,so that the extra air from free flow filter is compensated by the extra fuel from the richer AFR.

          It can be both extremes.Very lean or very rich.Either way it s not good.
          When everything comes ur way, u r in the wrong way ;)

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          • #6
            Maybe if you lean it out completely and ride from Bombay to Pune it might get hot enough to seize the top end. Why do you want to go lean anyway? Fuel economy?
            Even to get the miles out of a litre there is a limit you can lean it till, on my truck the gas mixer diaphragm is a bit too lean and it actually is thirstier because I need to put my foot down more often.

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            • #7
              Originally posted by insanebiker View Post
              It can be both extremes.Very lean or very rich.Either way it s not good.
              very lean, engine heats up more: understood... but what could possibly be a disadvantage by making it rich.???? (other than fuel consumption)

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              • #8
                ^ Imagine you try to eat a burger in one gulp !! you make it too reach the bike wont be able to rev higher in higher gears.. Fir instance i once used a 135 jet on my karizma it was so rich that the bike couldn't cross 6000rpm in 3rd gear..
                Dont wanna miss that look on your face when i blow past you.

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                • #9
                  Originally posted by undefineme3 View Post
                  very lean, engine heats up more: understood... but what could possibly be a disadvantage by making it rich.???? (other than fuel consumption)
                  the High amount of unburnt fuel will also cause Faster carbon deposition in the engine

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                  • #10
                    Originally posted by undefineme3 View Post
                    very lean, engine heats up more: understood... but what could possibly be a disadvantage by making it rich.???? (other than fuel consumption)
                    Increased carbon deposits inside cylinder, on Spark plugs, and most importantly bike wont perform well.
                    When everything comes ur way, u r in the wrong way ;)

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                    • #11
                      Originally posted by kushanth View Post
                      ^ Imagine you try to eat a burger in one gulp !! you make it too reach the bike wont be able to rev higher in higher gears.. Fir instance i once used a 135 jet on my karizma it was so rich that the bike couldn't cross 6000rpm in 3rd gear..
                      ahhh.... so this brings to my question.... any means by which we can find if the engine is running lean or rich...???
                      because i have heating issues(weather also to blame )... i have with me a 29mm carb... and its got a 125 jet in it... but i have a feeling that i'm running lean: revs above 9k rpm in final gear..... moreover running on stock airfilter as of now...

                      Originally posted by Puneet1 View Post
                      the High amount of unburnt fuel will also cause Faster carbon deposition in the engine
                      so all this extra petrol!!! it just stays inside the engine..??

                      Comment

                      • #12
                        ^^Revving beyond 9K is no way to measure lean/rich state. Even a lean engine will rev till 9K rpm. U have to feel the bike to understand that.

                        Very poor low-end/top-end, overheating, high mileage, oil-burning, flat-spots in the rev-range, too good a mileage are signs of running lean.

                        If the bike runs rich, the bike will not rev well to the top range, have excellent low-end but pathetic top-end, poor mileage, an idling that is very unsteady etc.

                        All that carbon not only stays in ur engine, it will stay thru-out the exhaust path. U can really see carbon powder on the exhaust ends!
                        Democracy is when 2 wolves and a sheep meet to decide who is for dinner. Liberty is when the sheep has a gun.

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                        • #13
                          ^^ so how does one make an engine rich....??? i've already changed to 125 size... i think it had a 110 in it.... and yes overheating and oil burning i've observed... but no other abnormalities....

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                          • #14
                            As stock for Indian bikes 125.5 jet of the ZMA is the max. But using a Keihin on a MIKUNI has its own disadvantages. For the record, I nearly experimented with jet-sizes from 117.5 to 137.5 before finalising on the 127.5 jet. That's what my bike was running on till the end. Try sources and get a 130 or so size and tune ur carb accordingly.
                            Democracy is when 2 wolves and a sheep meet to decide who is for dinner. Liberty is when the sheep has a gun.

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                            • #15
                              Please try and understand the basics first and then start worrying about oil burning or getting more power out of your bike.
                              For perfect combustion of air and petrol is 14.68 : 1 by mass. Any more air than that is lean and any more fuel than that is rich. Now even though we like it live in a perfect world and keep this constant to save the trees and what not, an engine is not a generator where it idles for days at the same RMP turning the same load. We do want economy on highways and the power when we put our foot down.
                              Even though we can tweak the FI system or carburettor to get more power or economy, there is a limit we can play in within the laws of chemistry. I like to think that you can’t go leaner than 15.5 : 1 and can’t go richer than 13 : 1 for a standard naturally aspirated engine.
                              Too lean and the engine makes soo little power, you have to gun it to move and eventually end up using more fuel and getting NO power – too rich and you have unburnt fumes pouring out of the exhaust, and because there isn’t enough oxygen to burn the fuel you end up getting less power.

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