Internally Collapsed Header on Honda GL1000?

Internally Collapsed Header on Honda GL1000?

Collapsed GL1000 Header

Example courtesy of Steve Seamans of NGWClub Forum

This is a fairly rare defect on GL1000s, but I have seen a few cases. The GL1000 header above is 90% blocked in the area marked by red paint!  There is no distortion on the outside of the header. I’ve only seen this on GL1000s, but it could probably happen on other models as well.

Symptom: Low power output on a GL1000 with verified correct compression, ignition and carburetion. Usually, the bike will start and idle fine and respond as expected to carb synch.

Explanation: these headers are “doubled-walled.” Apparently a manufacturing defect can allow distortion of the inner wall … virtually blocking that cylinder’s exhaust header.  

I’ve seen this on both low mileage and high mileage bikes. Unfortunately, the only way to diagnose this issue with certainty is to remove the header for a visual inspection.

My advice: whenever you remove the header for any reason, take a moment to check for this defect.

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