“Insensitive” Idle Mixture Fuel Screws?

I often field this common complaint: 

“I’ve noticed that turning the idle mixture screws nets different results on each of the individual carbs on my Honda GL1000:

  • #1 will kill the motor if turned all the way in
  • #3 has NO EFFECT on engine speed regardless of where it is set
  • #2 has what might be considered a “normal” effect
  • #4 has only a very slight effect if any at all

What does this mean????? I’m a bit confused?  Help please!!!!”

GL1000 Idle Fuel Mixture Screws

GL1000 Idle Mixture Fuel Screw

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Early vs. Late Carb Mixing and Matching / Honda GL1100 Carbs on Honda GL1000? + Honda GL1000 Carb Specs

You might consider this item: Randakk’s GL1000 Carb Rebuild Video

GL1000 Carb Interchange Issues

JoukoCarbs3

Honda GL1000 Carbs Restored by Randakk Customer Jouko Tomminen of of Lahti, Finland

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Honda GL1000 Carb Code Location

This is covered in my GL1000 Carb Rebuild Video, but just in case you haven’t made that great investment…

Here’s a photo showing the location of the all-important GL1000 Carb Codes:

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Common Honda GL1000 Carburetor Rebuilding Mistakes

You might consider this item: Randakk’s GL1000 Carb Rebuild Video

Here’s a partial list of problems encountered by amateurs when rebuilding GL1000 carbs. Often, I’m called upon to resolve botched rebuilds by incompetent mechanics, current or previous owners, brothers-in-laws and neighbors. Avoid these mistakes if you tackle a rebuild yourself.

JoukoCarbs3

GL1000 Carbs Restored by Randakk Customer Jouko Tomminen of of Lahti, Finland

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Honda GL1000 Floats 101

Randakk now offers GL1000 and GL1100 Float Setting gauges. Details here

I show how to set floats in the video: Randakk’s GL1000 Carb Rebuild Video

Setting Float

Note: The procedure for setting the float levels on GL1100 carbs is essentially the same as the one for GL1000 carbs described below. The only difference is that the float level spec for the GL1100 is 15.5 mm instead of 21.0 mm.

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Honda GL1000 Carb Repair Kits Compared (Updated)

Note: an objective analysis of available Honda GL1000 carb kits was recently completed by Ron Carmichael.

Randakk's GL1000 Master Carb Kit

Randakk’s GL1000 Master Carb Kit

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Special Tuning Tips for ’77 GL1000s + Carb Top Service

You might consider this item: Randakk’s GL1000 Carb Rebuild Video

Honda made a number of jetting tweaks in ’76 (K1 and LTD) and again in ’77 (K2) for US-bound GL1000s to cope with tightening emissions regulations. Other markets were affected as well. Honda necessarily made the bikes progressively leaner through these model years. Social responsibility is a good thing for large corporations, but these were not great moves from the rider’s point of view. Riding a bike with overly lean carburetion may be “green,” but it certainly can be frustrating.

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Air Cutoff Valve Overhaul

You might consider this item: Randakk’s GL1000 Carb Rebuild Video

The air cutoff valve is a simple but vital component of the carburetor system on GL1000s. It’s function is to eliminate backfiring on hard deceleration (throttle fully closed). Hard deceleration creates a high vacuum signal in the intake tract which activates the valve. When activated, it restricts the flow of air to the external idle circuit air jets thereby richening the mixture. This slightly richer mixture is calibrated to eliminate backfiring in this operational mode.

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Problem with Aftermarket Jet Needles

You might consider this item: Randakk’s GL1000 Carb Rebuild Video

Recently, I’ve discovered some improperly sized jet needles that were provided with aftermarket carb rebuild kits. The needles looked identical to the original but did in fact have a significantly narrower cross section at the mid-point of the tapered section.

Effectively, this made the needles much richer. The brand in question is NAPCO and the kits were for a ’76 which happens to be one of my bikes. The result of these improper needles was the bike in question ran fine near sea level (although a plug check showed it was running slightly rich in the mid-range and the fuel mileage was terrible).

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Throttle Return Spring Details

You might consider this item: Randakk’s GL1000 Carb Rebuild Video

Recently, a GL1000 owner was in my shop with an odd complaint. He reported that very heavy pressure was required at the throttle twistgrip to increase or maintain engine speed. Suspecting that the throttle cables were worn or damaged, the owner had just replaced both throttle cables, but this offered no improvement.

My test ride verified that indeed there was something amiss. This bike ran great, but after just a few miles the effort required at the throttle made my right forearm ache!

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