Author Topic: IT125H Carburetor screws  (Read 397 times)

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Offline ksec

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IT125H Carburetor screws
« on: May 23, 2018, 11:26:51 PM »
Hey, So I got my bike started and it runs good, I adjusted the screw on the side of the carb that has the brass nut on it, and this changed the way it idled (Clockwise = higher rpm, CountClockwise = lower rpm). This was all well and good and I got it to idle decently and sound alright, but When I tried adjusting the other screw (the one that comes up at a 45degree angle on the opposite side) nothing really changed. I noticed some slight differences in the way the throttle responded etc. but I'm not really sure what the screw is for. Any knowledge would be appreciated, and please correct me if any of this info is incorrect. thanks.

Offline Devondan

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Re: IT125H Carburetor screws
« Reply #1 on: May 24, 2018, 01:47:45 AM »
Hi there, why not introduce yourself here: http://www.yamahait.com.au/forum/index.php/topic,1.0.html

But it sounds like you are going about things the wrong way? Get the bike properly warmed up then adJust the screw with no nut until the motor ticks over the fastest and most even, then turn the screw with the nut  in or out to set the idle speed. This screw is the one that just opens or closes the throttle a bit, the other is the pilot screw that affects mixture. Generally this screw should be about 1 1/2 to 2 1/2 turns out. Report back if it isn’t.

If you use the search function you’ll find loads of useful stuf about jetting and setting up carbs.

Dan
IT  400D - Trail riding
74 Montesa Cappra - Racing
YZ250 H - Racing
Norton ES2 500 trials
Norton 250 Jubilee - Road
Norton 350 Navigator (in boxes)
Norton 350 Single M50 (in boxes)

Offline ksec

  • Yama-Cheese
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Re: IT125H Carburetor screws
« Reply #2 on: May 24, 2018, 04:29:04 AM »
Alright thank you! I wasn't sure which screw was which. I'll try out your recommendation and let you know how it goes  :D

Offline Martin I Henry

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Re: IT125H Carburetor screws
« Reply #3 on: May 24, 2018, 05:58:47 AM »

Ideally, you need to get a Genuine Yamaha manual for your little IT.

In the past I've seen them on Canadian eBay for a good price when compared to the US and Europe.

Avoid the Clymer manual at all costs.

Cheers,

Dave R.

Offline ksec

  • Yama-Cheese
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Re: IT125H Carburetor screws
« Reply #4 on: May 24, 2018, 11:15:03 PM »
I'll keep a lookout for one, thanks for the replies!
-Kyle

Offline ksec

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Re: IT125H Carburetor screws
« Reply #5 on: June 23, 2018, 01:42:33 PM »
Here's a few photos of my IT125H (1981)

Offline Martin I Henry

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Re: IT125H Carburetor screws
« Reply #6 on: June 24, 2018, 02:08:45 AM »

Good to see an IT125 being used !

Cheers,

Dave R.