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.

Comments

  1. A real head scratcher getting the mate’s 1975 Goldie going after 30 odd years gathering dust in the garage. Same front header pipe on the left side and you can’t believe how it has almost fully blocked the pipe. The Japs worked out from the Poms that single chrome exhausts went blue and discoloured quickly and sometimes cracked and hence the multiple walled tubing at the headers. The mate knew his Goldie was running fine when it was laid up but 30+ years later there would have been rust between the tubing walls trying to push them apart. Firing it up again if the outer tube was strong enough not to burst then the thinner inner one had only one place to expand if it was the weaker tube and welcome to running on 3 cylinders.

  2. I just ran into this myself while replacing head gaskets. Not sure if this caused the head gasket to fail, or was somehow the result due to overheating? Regardless, looks like I’ll be picking up a set of Delkevics that I’ve been swooning over.

  3. Ken A Smith says:

    I removed my exhaust headers and found this on the right-hand side and wondered what the issue was. Now I know. I guess the only thing I can do now is to search for a replacement right-hand side header!

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