Air Jet Mix-Up Problem

Note dated 11/17/2008: The folks at Clymer's are apparently not listening. Roger Gerson and Jim Morrison recently reported that their copies of Clymer's GL1000 Manual (Fifth edition, 23rd printing - July, 2004) still perpetuate this mistake. It's safe to assume that all versions up to this point have this error!

I mainly use the official Honda Workshop manual as my technical reference "Bible." I occasionally look at Clymer's or Haynes for cross-reference. Recently, I was reminded of a serious, long-standing problem with most (all?) Clymer GL1000 workshop manuals. This "typo" can cause serious distress if you rely on the misinformation when rebuilding your carbs.

For some reason, the Clymer manual reverses the correct sizes of the primary and secondary air jets in the "Fuel System Specification Chart" found on page 101 (my edition of the Clymer's manual is the fifth edition, 20th printing dated June, 2000…This problem may be fixed in later editions?). Figure 22 (on page 96 of my Clymer manual) correctly locates the primary air jet in the outboard position.

The air jets are the small jets located on the upper portion of each carb body. You access these by removing the carb tops. The air jets are found beneath the small kidney shaped cover plate retained by one screw. There is a small (important) gasket just beneath the plate.

Here's the correct size and orientation of these jets:

It easy to screw this up given that the jets will fit in either spot. Doesn't help much when you rely on a bogus manual (Clymer's) that has it backwards!

I've seen several bikes arrive at my shop with these jets reversed, so I know people are still relying on this bad information. A bike with reversed jets will typically have vague, sloppy carburetion issues across the rpm range and poor fuel mileage.

GL1000 carbs are a bit unusual in that there are two sets of "main" jets. There is an independent primary main (fuel) jet and a secondary main (fuel) jet which works in conjunction the CV throttle slide and its attached jet needle. The air jets under discussion above meter small air circuits to these two main fuel jets. The non-intuitive part of all this is that primary main fuel jet (#62 or #65 depending on year) has a smaller orifice than the secondary main fuel jet (#120 or #125 depending on year), yet it pairs with the larger of the two pilot air jets. The good news here is that it's impossible to mix up the primary and secondary main fuel jets...they have different external dimensions.

Not to confuse the issue any further, but there is also a pilot air jet in each carb which meters air for the idle portion of the carb circuits. These are located in the brass elbows where the vacuum tubes attach. See the "Off-Idle" Fix below.

Special thanks to Jerry Roebke of Colorado Springs for reminding me about this problem.