Basic terminology used :
carburetor : Basic functionality of the carburetor is to mix fuel with air in proper ratio and then feed it in the engine.
Lean Mixture : If Air-fuel mixture supplied by the carburetor has less amount of fuel than required it is said to be lean condition.
Rich Mixture : If Air-fuel mixture supplied by the carburetor has more amount of fuel than required it is said to be rich condition.
Tools : Only one screwdriver will be enough for the job.
Pre-requisites to the tuning : Take your bike for a short ride of 3 to 5 kilometers so that engine can warm up a little.
carburetor : Basic functionality of the carburetor is to mix fuel with air in proper ratio and then feed it in the engine.
Lean Mixture : If Air-fuel mixture supplied by the carburetor has less amount of fuel than required it is said to be lean condition.
Rich Mixture : If Air-fuel mixture supplied by the carburetor has more amount of fuel than required it is said to be rich condition.
Tools : Only one screwdriver will be enough for the job.
Pre-requisites to the tuning : Take your bike for a short ride of 3 to 5 kilometers so that engine can warm up a little.
Warning/Disclaimer : Work with soft hands,Do not over tight any screw otherwise you may damage the threads. I have taken full care while writing but I will not be responsible for any damage to your bike done during the steps. Follow at your own risk.
Locating the carburetor on bike , I have marked in red color in the image below.
Understanding the different screws on the carburetor :
There are three main screws in the carburetor (explained from left to right in image below):
1. Mixture adjustment screw : This is the main screw for adjustment of Air-Fuel ratio.
2. Idle adjustment screw: This is to control the engine RPM at idle condition.
3. Auxiliary Air screw: this is part of emission controlling unit, to my greatest surprise most of the mechanics keep it close always.
Click on the image above to see the exact location of screws.
Effect of these screws on Air-Fuel ratio and engine RPM.
Effect of these screws on Air-Fuel ratio and engine RPM.
1. Mixture adjustment screw : Rotating this screw clockwise makes Air-Fuel mixture leaner and rotating it anti-clockwise makes Air-Fuel mixture Rich.
2. Idle adjustment screw: Rotating this screw clockwise increases the engine RPM and rotating it anti-clockwise decreases the Engine RPM.
3. Auxiliary Air screw: Rotating this screw anti-clockwise increases the engine RPM.
There are two methods for tuning :
1. With no role of auxiliary air screw [Followed by me and most mechanics also]
2. With auxiliary air screw [as per book ]
1. Tuning with no role of auxiliary screw :
Step 1 : Start the bike and let it idle for some time (~40 seconds) to warm up .
Step 2 : Tighten the auxiliary air screw fully clockwise.
Step 3: Increase the engine idle RPM by 20 to 30 % of normal idling. Say around 1500 RPM. This can be achieved by slowly rotating idle screw clockwise i.e. closing it.Here you will have to use your senses like ears and feel the vibrations of bike since this particular method does not have tachometer.
Step 4 : Fully tight the mixture adjustment screw clockwise. It will make the mixture leanest possible and decrease the engine RPM to the lowest level. You will feel that bike vibrations are also decreasing.
Step 5: Slowly start rotating mixture adjustment screw anti-clockwise (1/8 turn at a time) . This will keep on increasing the engine RPM’s slowly and steadily , keep it opening until a point where engine RPM will become constant. Stop at this point , this is the idle mixture point. The bike is vibrating and humming well.
Hint : In my case this is between 1.5 turn to 2 turn.
[You have reached the optimum mixture of Air-fuel, if you will keep it rotating anticlockwise then it will make mixture richer and richer , and after 4 ,5 rotations you will find the RPM decreasing.]
Step 6 : Making the bike idle normal, rotate the idle adjustment screw anticlockwise slowly until bike RPM becomes normal say 1000 RPM.
Your tuning is complete. Test the throttle response now, it will be better. If you still feel some hesitation then repeat steps 1-6 again.
2. Tuning with role of auxiliary screw [as per royal enfield electra 5s service manual]:
Although I don’t use this method by one can follow and share the feedback with me.
In this method step 1 to 6 are same as explained above. Only following 2 are additional steps :
Step 7 : Loosen the auxiliary screw by 1/2 turn (anticlockwise) , it will increase the RPM .
Step 8 : Loosen the idle adjustment screw to make RPM back to normal 1000 RPM.
keep on doing this exercise (step 7 and 8) until turning out auxiliary screw does not increase the engine RPM.
Identifying the optimum mixture by reading the spark plug insulator color.
1. This is how a new spark plug looks like :
2. spark plug color with optimum mixture : [Light brown to chocolate brown] , both are OK. First one is little bit lean.
3. spark plug color with rich mixture : [Black with lot of carbon deposit]
4. Following is the image from internet in case of lean mixture :[metallic white with metallic particles deposits ]
Hidden secret : Although everyone calls it tuning. If we speak technically then it is called setting up engine idling. Tuning is bit complicated process which involves upgrading jets . watch this space for more ....
Good job dude... very well written!
ReplyDeleteThanks chief , I will keep on adding the DIY jobs in future as well.
ReplyDeleteVery well written, Thanks for sharing.
Deletethanks buddy it help alot
Deletegood info bro... worth for carb bulls.
ReplyDeleteThanks for the appreciations.
ReplyDeleteMy electra 5s was not going compresed and regular misfiring ...plz any body help me
ReplyDeleteMy electra 5s is returning 30kmpl, it has a good pickup and easily ruins other bikes on highway...but it kills my pocket too. Please let me know if it is the fuel mixture or some other issue, it has done only 4000km. Engine sounds are smooth and there are no funny emissions from the exhaust
ReplyDelete@Ravil Thakur : 30kmpl is good for CI Electra models. If this is UCE model then it is on lower side , it should be ~ 40.
ReplyDeleteTake him to your mechanic.
I have been getting 50kmpl milege on bullet 350cc 1998 model ...by turning mixture screw in anticlockwise direction say( 6 turns), may it leads to any engine problems???you mentioned above was to get good milege when turning mixture screw in clockwise direction....must reply
ReplyDelete@farhan Lean mixture will lead to serious damage to engine. It may burn engine valves and hole in cylinder block in long run.
ReplyDeleteAs farhan said when he turned the screw anti clockwise it increased the mileage which means lean mixture. But you said clockwise will make mixture lean. First confirm yourself
DeleteTry to understand tge air fuel mixture screw oii s not an ordinary screw. Its an valve which controls the fuel going in the carb. So turning clock wise will close it so less fuel is going. And turning anticlockwise will open it out or screw it out. So more fuel goes. The concept has to be clear that tuning is not done for mileage. It is done for optimum performance of your engine. Perfect tuning will give you the best mileage and best performance from your engine.
DeleteLike if a person gets less food he will starve. And if he gets more it will be waste so you should get just the sufficient amount of food. Same with engine. Fuel is the food for an engine
What a fantastic article. I have been encountering hell lot of problems with my CI Electra. Have to take to the mech almost monthly. Everytime he lowers the RPM, i get problems starting the bike. I take it to him again and he simply increases it, resulting in excessive fuel consumption. I will try to do it myself this time.
ReplyDeleteSecondly, if you are from delhi, please help locate me a good mechanic.
Aalam bhai dda flat kalkagi very famaous mac once you reach you can ask anybodh
DeleteHey bro thanx for your beautiful article....i have some query in my mind which i wanna clear....so bro please help me out.
ReplyDeleteIn your step 4 you have mentioned "Fully tight the miture adjustment screw clockwise." (is it the clockwise direction for making the mixture leanest or is it the anti-clockwise direction)
And you have also written that "It will make the mixture leanest possible and decrease the engine RPM to the lowest level."(so bro after making the mixture leanest possible...do we have to decrease the RPM to the lowest level by the idle RPM setting screw or the mixture screw will itself decrease the RPM at lowest.
Regards,
Bhaskar Singh
Turning clockwise will make the mixture lean. Turning anticlockwise will open the screw so thus making the mixture rich..
DeleteReduce the idle rpm once done with carb tuning.
If you have any issue since there is no tachometer its very tough to perfectly tune it. its prefered to get it done at a authorised service centre bt from an experienced mechanic as the have some meter to read the engine rpm
Because air fuel mixture plays a very vital role in combustion which takes place in a engine.
And amardeep very well written bro.. being an marine engineer i love machines and fault finding and problem solving is my hobby.
2012 Electra 5S (4500 KM only) which starts to sputter and jump.just like reserve symptoms
ReplyDeleterotate the knobe in reserve for few second and return back it works fine.i also checked this in full tank.
pls help
thanks a lot :):)
ReplyDelete@ smart teleservices
ReplyDeleteI also have the dame problem in my electra (2005 Model), so if you come up with a solution plz share it.
I have '75 Royal Enfield STD 350. It have idling issues. Not that it will die at every stop but sometimes it does when I am changing to low gear while turning a bend. This is a very abrupt case and I used to think it was my driving fault but this not the case. I have even cleaned the air filter and tried "tuning" using your points also. These by the way are absolutely marvelous points and nicely written. Please advise.
ReplyDeletei hope ur bike is having wiring issue. i had almost same problem before. My IG key wiring was short circuit that time. after replacing IG switch my problem solved. so kindly carefully inspect the wiring system totally for any where short circuited. ( wiring somewhere getting short circuit to body while turning curves ) Thanks
DeleteTry draining all fuel from fuel tank and removing any water present.
DeleteCan you help me in sharing the electra 5s cast iron bike service manual. Your help will be much appreciated. email to simonserao@gmail.com
ReplyDeletevery gud explaination with pictures, really makes it easy to do things. We never looked at spark plug of our bullet but after reading your blog and applying i, we could easily see the difference and also now starting the bullet is very smooth and mileage as also increase. really appreciate your article. Thanks a ton.
ReplyDeleteVeere
ReplyDeleteCha gae
Keep doing this great job
Can we use this technic on 29mm vc carbs?
ReplyDeletei mean on c350 2014 models?
What a great job by posting this info with pics!!!! Appreciate all your efforts and work for this.. you rocks..
ReplyDeletemy STD bullet 350 (1982) doesn't start in one kick in morning so what should be its setting lean or rich? to what should I set so that It would start in one kick? Please advise...
ReplyDeleteHI
ReplyDeleteThanks for the great info and pics.. I also own a Electra 2009 model.
Can you tell me how do we know if the Bull is running lean or Rich?
Regards
I meant to say how can you know the bull is running lean or rich while riding..?
ReplyDelete@Ajjaykumar, while riding you won't know if its running lean or rich.. you need to plug out the spark pulg, if it's too dark then its running rich and if light brown then its lean. It should be dark brownish when its tuned to optimum. Hope this helps.
ReplyDeleteAfter getting the optimal adjustments for engine idling (method 1), do you revert the auxiliary air screw to it's original position?
ReplyDeleteDear Mr.Amerdeep,
ReplyDeleteYou have made it crystal clear, fine great job. keep on posting. i once again thank you thanks alot. Jagan Tamilnadu. thilakerjagan@gmail.com
Hi Amardeep,
ReplyDeleteI own an Electra 5s, 2006 model. It has been used for barely 5200 km and was lying dead in my uncles house for 2 years. I had got the bike serviced, fixed and everything for normal riding has even done. I could manage to tackle all problems except mileage. It delivers a mileage of merely 17 kmpl. I just don't understand what the problem is with the bike. I got the carburettor changed to a brand new carb and got this done from the genuine royal enfield service center but to no help. My bikes average is yet very pathetic and even though the spark plug is white, the bike does not provide proper mileage. Please help me.
@Aditya, I faced the same problem. No need to worry, you just need to take ur bull to proper mechanic to tune the new carb. I did too and now its returning 30+km.lit. I doubt your bull is not tuned correct as u mentioned white car. After tunning my car is dark brown. pls note its not black but its dark brown.
ReplyDeleteThey say the flota bowl will become chilled and you'll see water in the exhaust if carb setting is optimum. It's that so?
ReplyDeleteI see some smoke from the exhaust can't really figure out its black or white. My bull used to run rich, now it's running lean.. Its a 95" sad. Suggest how should I proceed with diagnosis and treatment.
This comment has been removed by the author.
ReplyDeleteHi Amardeep,
ReplyDeleteThanks a ton for the illustrated guide to idle setting. I’ve a new Electra 350 Twinspark of 2014, done less than 400 km till now. Does this method also work for my model? There’s no auxiliary air screw in this it seems. Or is there? Can you please explain? I drive more than 80 km per day and want to keep my fuel bills in control. Awaiting your reply please.
Hi Prasenjit,
ReplyDeleteI guess electra 350 , 2014 model has vacuum carb so I don't think u l have the aux screw there..
@Tajindarpal
ReplyDeleteYou can google for engine detail.. you will find tons of links
Hi,
ReplyDeleteI am Electra 350UCE 2012 Model, done 43000KM. Early I was getting the mileage of around 30-33KMPL, Suddenly it got decrease to 28-30KMPL.. Daily I will ride of about 60 - 65KMs, Suggest what needs to be done.
I need to get mileage around 38-40KMPL. So that I can have some money in month end...
Regards
Chandrakanth.PG
Great job Amar, professional explanation. One info, any idea where to get high pressure oil pump for bullet.
ReplyDeleteThis comment has been removed by the author.
ReplyDeleteHi Amardeep,
ReplyDeleteI own a Bullet Electra 5s 2014, during cold starts, the engine shuts off immediately. To keep the engine on, I need to hold the throttle on. I am facing this issue from day 1.How to tune my bike? Is therr any issue?pls help
@amrut, just increase RPM of ur bull and ur problem will be solved.
ReplyDeleteHi Amar,
ReplyDeletevery well narrated and explained with pics, although I feel that there is small correction required for tuning of pilot screw. As checked with Electra 5s CI(2008) Model, turning clockwise(tighten) will make the mixture RICHER(More petrol and less air) and visa versa.
Thanks..
TUNING AND USING BULLET MIKCARB CARBURETTORS
ReplyDelete• Adjust the throttle stop screw so the engine runs at a fast tick-over, say about 20%
above the idle speed you wish to achieve
• Unscrew the pilot air screw to increase the engine speed to its fastest possible
• Gradually unscrew the throttle stop screw to reduce engine speed to the target idle
speed
• Again unscrew the pilot air screw to increase engine to the highest tick-over possible
• Finally, gradually unscrew the throttle stop screw to reduce engine speed to the correct
idle speed. (Usually this process carried out twice – as described – will be sufficient to
achieve a correct tick-over.)
NB – sequence: pilot air screw out = fast; throttle stop screw out = slow
What a great job by posting this info with pics!!!! Appreciate all your efforts and work for this.. you rocks.. " Royal Enfield "
ReplyDeleteThanks for sharing your ideas and thoughts, i like your blog and bookmark this blog for further use thanks again… Royal Enfield
ReplyDeleteHi,
ReplyDeleteIs there a different carburettor on Electras that were built prior to the Twinspark version?
The carb is different with the three screws positioned differently. The middle screw is positioned at the bottom vertically
DeleteThis comment has been removed by the author.
ReplyDeleteHi Amardeep
ReplyDeleteI have standard model bullet 2012.i want to decrease the rpm bcoz as u know new model bullets runs fast than old ones.i want better stocks nd slow speed like dugg dugg..is it any solution to ride the bike slow like old
I'm using classic350 UCE..the carb was on 4 turn...after weeks the popping from exhaust occurrs while decelerating...then i set carb to 6 turn..then the sound disappeared for some weeks. Again the popping sound from exhaust occurring.what is the problem? I can't figure out.please help.
ReplyDeleteUseful information. Thanks for posting it. It really helped me.
ReplyDeleteVery useful article.
ReplyDeleteGreat job.
Haven't found this much properly explained article on any other website.
Thanks
But according to pete snidal. When the pilot screw is IN it is rich and out means its lean.
ReplyDeleteHi, when I tightened it rpm increased
ReplyDeleteAnd on loosing rpm decrease till death
It's 1996 model 350
From what I understand what you're referring to as the 'mixture screw' on the VM 24 Micarb is an air screw. Tightening it fully makes the mixture 'rich' which is defined as more petrol and less air, while opening it takes the mixture to optimal and then to 'lean' which is more air and less petrol. Also, as a standard procedure, all skilled Enfield mechanics will turn the air screw counterclockwise quickly and not slowly to determine the change in idling while they'll turn the idling screw clockwise slowly to decrease it. Just my two bit.
ReplyDeleteIn my machismo 350 1999 with micarb the mechanics say if air screw is turned clockwise then more petrol goes in & turning anticlockwise makes it lean,tuning done with idle speed increased,
ReplyDeleteEngine not stalling wen i close the mixer screw fully clockwise. Wat may be the cause. My bullet is Electra 5s 2009 model
ReplyDeleteमेरे पास 2008 इलेक्ट्रा 5s मॉडल है मैं यह जानना चाहता हूं कि उसके कार्बोरेटर में कितना तेल रहता है
ReplyDeleteHelo sir i have a 2005 electra running good but i want to know if air screw is turn clock wise that mean my bull take lean petrol or rich fuel ,bcoz i have take long drive in highway my top picup 80km last not getting 100 km whats a problem help me to
ReplyDeleteAmazing information source great!!!!
ReplyDeletemust visit this sites blogs
http://blog.garslubricants.com/