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flumpy7
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PostPosted: 12:35 - 08 Jan 2011    Post subject: carb settings Reply with quote

Hi again

My wifes hartford vr125z (CG125 motor) has never idled consistently, jumping all over the place. Also, it has intermittent problems with starting that i am 100% are carb related. So anyhoo, ive taken the carb off and i think that basically someone has fecked the pilot screw settings up in the past. Mr Haynes isnt very helpful on this saying, set the screw as it was when you found it. Trouble is, it was fecked when i found it. How do i reset the pilot screw to make it run evenly and sweetly? Cheers
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hmmmnz
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PostPosted: 13:10 - 08 Jan 2011    Post subject: Reply with quote

the haynes manual i have say 1 3/8 turns out,
the xr125 which is very similar says 1.5 - 2 turns out

i would before you do that, is set the valve clearances, (don't under-estimate how often you have to do this on a push rod motor)

then with the bike warmed up, start with 1 turn out and turn the screw
until she starts gurgling then go back half a turn back in,
that should be it sorted.
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Ichy
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PostPosted: 13:24 - 08 Jan 2011    Post subject: Reply with quote

Easiest way by far is to use a gas analyser or, more realistically, a colourtune.

It is possible to set using your ear.

Wind the mixture screw all the way in counting the number of turns it takes to get there. This ensures that you can at least go back to those setting if you need to. Don't force the screw when winding it in, just let it seat lightly, its way to easy to damage the tip otherwise. Set the mixture screw to whatever the base settings are, if you don't know then between 1 to 1 1/2 turns out should be fine.

Get the bike nice and warm.

Set the idle speed to a level at which the bike continues to run, probably less than 2k is best.

Keep a count on how many turns you turn the screw, to the nearest 1/4 turn is fine.

Wind the screw in until it sounds like its starting to run worse.

Now wind the screw out until the engine sounds like its running fine.

Wind the screw out 1/2 a turn extra. If it starts to sound rough again then wind it back in a 1/4 turn.

Reset the idle speed to recommended (at a guess 1k is average)
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flumpy7
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PostPosted: 19:02 - 11 Jan 2011    Post subject: Reply with quote

Hi guys

Thanks for the info...very helpful. I have not yet got that far however, as when i started the bike after putting the carb back on i had a constant leak of petrol from the overflow pipe and from around the pilot screw. Any ideas what i have done?
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fiery tupp
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PostPosted: 19:34 - 11 Jan 2011    Post subject: Reply with quote

Another way you can check the idle mix , is to , while ticking over
Spray a little wd40 at the inlet , if the idle drops it is either ok or a little rich , if it goes up it is lean Neutral
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Odie
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PostPosted: 21:11 - 11 Jan 2011    Post subject: Reply with quote

flumpy7 wrote:
Hi guys

Thanks for the info...very helpful. I have not yet got that far however, as when i started the bike after putting the carb back on i had a constant leak of petrol from the overflow pipe and from around the pilot screw. Any ideas what i have done?


the needle valve (under the float) aint seating properly, probably a bit of crap under the needle or you aint fitted it back properly, will not help tick over and mixture.
easiest way to set the mixture on a single cylinder machine, warm it up and turn the mixture screw in 1/4 of a turn and see if the rpm goes up or down, if it goes up, turn it in another 1/4 of a turn, if it goes down turn the screw the other way.
The idea is that you find the highest tick-over position, then lower the tick-over and adjust it a little bit more till you have the thing at its best setting (highest tick-over, then set the tick-over speed to what you think is right, half a turn above stalling is normally good.
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flumpy7
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PostPosted: 15:44 - 13 Jan 2011    Post subject: Reply with quote

Man this is strartin to annoy me now. I cant actually get to the mixture screw when the carb is attached cause its tucked right underneath and there is so little room to get to it. Is this the same with the cg125 does any body know?
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Rogerborg
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PostPosted: 16:48 - 13 Jan 2011    Post subject: Reply with quote

What's the carb? Mikuni 26mm? Looks like this?

https://2.bp.blogspot.com/__DYtEEjm5wE/SdE2lp3cYgI/AAAAAAAAABo/92yQIiecTJM/s320/carb.jpg

You can use a teeny screwdriver (like from a glasses repair set), use the slight knurling to get purchase with the end a flat bladed screwdriver and 'push' the screw round, or if you know any men, you could ask them to just turn it using their strong manly-man fingers.

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