High Idle after Carb balance

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Suzuki416
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Joined: Fri Aug 26, 2016 10:17 am
Bike owned: 3 x NC35, 3x NC24, NC29, RC46
Location: London
Re: High Idle after Carb balance

Post by Suzuki416 » Wed Apr 08, 2020 7:54 pm

great news

Hubbskiboy
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Bike owned: GK76A 1993 and 1990
Location: West Midlands
Re: High Idle after Carb balance

Post by Hubbskiboy » Wed Apr 08, 2020 9:38 pm

I also bought a couple of inline fuel filters to stop any potential crap going into the ultra sensitive carbs, but you'll never find the space to fit them!
Once the fuel tank is back on, there literally is no room on these bikes to fit anything like that to the fuel lines.
So they're just sitting in a spare parts box somewhere.

moforockband
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Bike owned: GK73a SP CRM250 mk3
Re: High Idle after Carb balance

Post by moforockband » Thu Apr 09, 2020 12:58 pm

hutchy wrote:
Wed Apr 08, 2020 6:57 pm


A new fuel line and t piece allowed me to hook up to both fuel lines from the carbs. Larger screw shoved into carb #3s vacuum line and ready to go.

Time to fire her up.. it ran like sh*t.
On the older gk73a models, the mixture screw o rings give trouble, and give the symptoms you mentioned. The o rings have to be a tightish fit around the mixture screw body, otherwise they will let air into the pilot circuit. I'm assuming you changed these with the Lifetek kit?
What do you think cured it, as you said that even when you connected the 2 fuel supplies it still ran bad?

And I did not know that your bikes had 2 feeds, lol. Sounds like backwards development to me, I'll stick with the more improved older version ;)

hutchy
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Re: High Idle after Carb balance

Post by hutchy » Thu Apr 09, 2020 7:41 pm

Mofo,

Yes, the pilot screw oring and washer was replaced as this was included in the kit. Did a lot of reading and this is the one item that kept being mentioned for bad running.

I think in the end the things that made the difference were:
-Fuel feed to both carb fuel hoses (external fuel tank and split this with a T piece)
-Full set of Orings and Gaskets supplied by Litetek (Cheers Blair)
-Full carb clean and compressed air through all nooks and crannies of the carbs and jets
-Raised the needle 1 notch to account for my exhaust and air filter (for those not in the know, you lower the washer on the needle towards the point and this in turn raises the needle, allowing more fuel to enter the needle jet for mid range running.. this combats the extra air supplied by the air filter and exhaust)
-Air/fuel mixture screws.. revs were hanging which indicates a lean mixture. After double checking all diaphragms and spraying brake cleaner over the inlets to confirm no air leaks, this was the logical step.

Then it came down to trial and error.. for me, 1.75 turns out was the best option. In the future I will probably tune each carbs mixture screw as per Liteteks guide (basically, 1 carb at a time open and close the mixture screw, listening for when the revs drop- then set the screw in the middle, where the revs are the highest)

- Morgan Carbtune inverted. Once happy that the bike was idling a lot better, it was time to balance the carbs. 1+2, 3+4 then balance both sets.
I took it for a run today and it was great.. 1st time I’ve not had any form of bogging around the 4-6k RPM range.

Hope this helps someone else!


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