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Old 24th April 2008, 11:39   #1
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Question Help Tuning the Micarb for a Yezdi Roadking

OK, so I've searched various places on the web, and I cant get any manual or non-technical guide to tuning the micarb for my roadking. My mechanic does it, but I cant understand which screw is which, which one is the main jet and where the jet needle is, etc.etc..

Can someone please help me out, maybe with a diagram pointing out which csrews will affect what, which way to tune for power and which way to tune for efficiency, what to do if the carb floods, etc...

Any help would be appreciated. Cheers..
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Old 24th April 2008, 15:28   #2
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Mickarb is a copy of Mikuni, so the Mikuni manuals you find on the web will help you get a broad idea.

The big screw that you can turn with your fingers is the idle screw, turning it clockwise will increase the idle rpm(it pushes the carb slide slightly upwards).

Another small screw you find towards the rear of the carb(which can only be turned by a screwdriver or long fingernails) is the air screw. It adjusts the air fuel mixture at idle. Tighten it fully(do not use too much force) and then unscrew 1.5 turns. Should be enuff for a roadking. If you feel idling is not smooth enough, you can try turning this screw quarter turns this way or that way, until you find your sweet spot. Does not make much difference in actual riding.

main jet and idle jet are inside the float bowl, better you don't mess with them.

further tuning tips are byond the scope of this post. Just get this in your mind that playing with the screws alone is not going to matter much, with power or mileage.
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Old 24th April 2008, 15:38   #3
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The actual process of finding the right idle rpm is as follows.

Start the bike. warm it up to actual riding temperatures(10 minutes at good clip round the block).

Come back, pick your screwdriver.

Turn the big screw(idle screw) clockwise, you can see the rpms rise. Turn it enough so that the bike will not shut off when you close the air screw(this comes with experience, if you close the air screw and the bike is shutting off, then you need to turn the idle screw further in).

With the bike idling away at a fairly high rpm(not screaming rpms, mind you), close the air screw(turn it fully shut by turning clockwise - if the bike shuts off, see above). Now start turning the airscrew slowly, listening to the bike. You can hear the revs gradually rise and will reach a crescendo and then taper off. Try to keep it at the crescendo(a tachometer helps to find the peak rpm, but then roadking does not come with one).

Then, turn the idle screw(BIG ONE) anticlockwise, slowly, very slowly, until the idle rpms come down and reach a point where the bike dies. If you want the bike to idle, you have to turn it a quarter clockwise, else leave it as it is. Some people prefer the bike not to idle.

You can now turn the air screw a quarter of a turn clockwise(for better idling when cold) or leave it as it is.

or even turn it a quarter anti clockwise, hoping for better mileage.

You may have to adjust the idle screw in the morning, if you want idling after an early morning start.
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Old 24th April 2008, 15:39   #4
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if the carb floods, get the float needle and seat replaced.
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Old 24th April 2008, 15:53   #5
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contact praveen.sathaye on gmail - he runs a pune yezdi club, owns two of them beasts. he's your man!
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Old 25th April 2008, 13:39   #6
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good explaination kuttapan.

I have a Mikuni carb on my bike(Kinetic GF170). I am facing a problem lately. I get a big jerk (as if fuel supply is stopped for a second) while revving hard. This happens while riding as well as if bike is in neutral.
While riding this happens if I rev hard in lower gears or if I apply full accelerator when in top gear or while climbing .

How can I solve this problem?
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Old 25th April 2008, 15:02   #7
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I am not really sure if the carb is at fault here. Have you cleaned your carb already, if not get it thoroughly cleaned...All the jets etc using pressurized air. If the jerk is not momentary - i.e bike loses power and you have to roll of throttle for a few second before it will accelerate again, check float height and the fuel tap for flow.

Get ur electricals checked as well. Spark plug(clean and adjust gap), HT wire etc.

Maybe the more knowledgeable fellas can help better.

Last edited by kuttapan : 25th April 2008 at 15:04.
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Old 28th April 2008, 23:46   #8
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Quote:
Originally Posted by kuttapan View Post
...If the jerk is not momentary - i.e bike loses power and you have to roll of throttle for a few second before it will accelerate again, check float height and the fuel tap for flow.

the jerk is not momentary, I have to reduce rpm either by changing to higher gear or by slowing before I get some power back.

I am planning to get fuel tank cleaned this weekend, lets see if anything changes after that.
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Old 28th April 2008, 23:51   #9
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Quote:
Originally Posted by vabs78 View Post
good explaination kuttapan.

I have a Mikuni carb on my bike(Kinetic GF170). I am facing a problem lately. I get a big jerk (as if fuel supply is stopped for a second) while revving hard. This happens while riding as well as if bike is in neutral.
While riding this happens if I rev hard in lower gears or if I apply full accelerator when in top gear or while climbing .

How can I solve this problem?
If there is an accelerator pump on the carb then the diaphragm might be torn or the passage clogged. Get the carb cleaned thoroughly.
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Old 29th April 2008, 11:55   #10
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IF it is a CV carb, you may need to get the diaphragm changed as well.
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Old 29th April 2008, 13:06   #11
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Thanks ananth and kuttapan.

Its a CV carb. I did get it cleaned but didn't ask specifically to check for diaphragm damage. Will get it checked again this weekend and update.
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Old 8th May 2008, 13:52   #12
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Thanks Kuttapan, phamilyguy... update is as follows;

I followed your idle adjustment technique, and it worked really good - the bike stopped giving the jerks and splutters it used to earlier when cold starting.
A short time later, however, the bike would not start using the kick-starter - I had to push it to start, which, aside from being a little embarrassing in front of all the neighbours on a monday morning, was getting quite tiring.

So I went and got the whole thingamalajig checked up at Abdul Razzaks garage, and now the bike runs really smoothly. Thanks for all the input though!

Cheers!
~
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Old 11th May 2008, 01:57   #13
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Quote:
Originally Posted by kuttapan View Post
The actual process of finding the right idle rpm is as follows.

Start the bike. warm it up to actual riding temperatures(10 minutes at good clip round the block)...............................
.................................................. .................................................. .....
..............................
You may have to adjust the idle screw in the morning, if you want idling after an early morning start.
Excellent explanation there Kuttapan.
I like the bike not to idle, we call it Dead Beat.
It has some other advantages too, the bike cant be started nor can it be driven around by anyone not used to the dead beat, I believe in One man machine, i.e. no borrowing or lending.


Quote:
Originally Posted by vabs78 View Post
I am facing a problem lately. I get a big jerk (as if fuel supply is stopped for a second) while revving hard. This happens while riding as well as if bike is in neutral.
A similar problem my activa was giving me since the 1st servicing, getting the carb bowl cleaned solved the problem.

Last edited by gendarmee : 11th May 2008 at 02:03. Reason: adding 2nd quote
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Old 15th May 2008, 21:45   #14
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[quote=aveek;822973]Thanks Kuttapan, phamilyguy... update is as follows;

I followed your idle adjustment technique, and it worked really good - the bike stopped giving the jerks and splutters it used to earlier when cold starting.
A short time later, however, the bike would not start using the kick-starter - I had to push it to start, which, aside from being a little embarrassing in front of all the neighbours on a monday morning, was getting quite tiring.
quote]

That's coz you are a novice, and could not figure out the ideal setting for a cold start. The mechs have been doing it for donkey's years, they know what setting will work. You should not have given up, as I said in my earlier post, cold starting requires minor tweaking of the ideal setting.
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