I have seen a few posts but nothing was too definitive so I thought it was finally
time to post.

I have an 85 GSL. No mods. I haven't done anything to it for about a month. The weather has been up and down and hasn't been a factor so far. It has been running like a champ. Now, completely out of the blue, when I am getting on it
when I shift into 3rd around 4,000 RPM it starts to surge heavily. I am at a loss.

This is my second 7. The first (85GS owned for a year and half) was taken out by a blind old man and totalled earlier this year. I found the GSL in need of alot of work and the GS has surrendered many parts to it's replacement.

This site has been invaluable to me since I bought my first and this is my first post
because I have usually been able to dig through the archives to find my answers.
Thanks for all those posts and any help I can get now.

 

Start with testing the shutter valve. Procedure is here.

http://www.mazdatrix.com/faq/shutter.htm

It's a valve that controls a butterfly inside the FB intake manifolds. When it goes bad it can cut off flow and cause a chugging type of symptom.


Also in addition to this check your secondary linkage (search forum for it). It's a on passenger side and there is a line and hook and the anchor tends to pop of the hook. That's just a tip the first one was probably more of the problem.

edit: Ah I think I am wrong sorry maybe it could be Anti Afterburn Valve. Check both above anyway.