Need help with GSX400 cam timing

[xxenzor]

Hey guys, I’m working on checking the timing on my 1980 GSX400E and could use some advice.

The manual says that at TDC, the inlet camshaft “3” arrow is supposed to be angled, and the exhaust camshaft “2” arrow should be vertical. On mine, both arrows are vertical. There are exactly 20 pins between the two arrows on the timing chain, so that part seems right.

The cam lobes are pointing away from each other like they should, but the notches on the ends of the camshafts are facing each other—not perfectly parallel to the gasket surface

Is it a problem that the “3” arrow is vertical instead of angled, or does it sound like everything’s okay? Just want to make sure I’m not missing something here.

[Nessism]

Photos needed: show crank aligned to 1-4T position, show exhaust cam, with --1 mark aligned level with gasket surface. Then count links between marks on intake and exhaust cam. I hope you have the factory manual for your bike, not a Clymers or Haynes.

[Rich82GS750TZ]

Pins between 2 and 3 or start counting with the pin over #2 as Pin #1 and the pin over #3 as pin # 20? It matters. Make sure to read manual and count as described. This is a constant and common source of misinterpretation.

[xxenzor]

Photos needed: show crank aligned to 1-4T position, show exhaust cam, with --1 mark aligned level with gasket surface. Then count links between marks on intake and exhaust cam. I hope you have the factory manual for your bike, not a Clymers or Haynes.

If I put the left cylinder on TDC the 2 points at the gasket on the exhaust and the 3 points at the gasket to the right on the intake

[xxenzor]

Pins between 2 and 3 or start counting with the pin over #2 as Pin #1 and the pin over #3 as pin # 20? It matters. Make sure to read manual and count as described. This is a constant and common source of misinterpretation.

the pin directly above the 2 and directly above the 3 is 20 pins

[xxenzor]

Photos needed: show crank aligned to 1-4T position, show exhaust cam, with --1 mark aligned level with gasket surface. Then count links between marks on intake and exhaust cam. I hope you have the factory manual for your bike, not a Clymers or Haynes.

If I’m TDC on the right cylinder the 2 and 3 are vertical with exactly 20 pins and the 1 on the exhaust is pointing at the gasket surface

[KiwiAlfa156]

This is the correct orientation of the cam sprocket arrows with the timing mark "T 1.4" aligned to the pointer. This from the 750 manual, but it should be the same. Notice that the slots in the cam ends are pointing at each other.

[Nessism]

Well, this bike seems to be a twin, so there is no 1.4 T mark. This photo shows a GS450 rotor, and the T mark. Same thing. TDC for the number 1 cylinder.

This is where it all starts. Set, then go to the exhaust cam next. The 1 mark may be a smig high, and that's okay because the cam chain may have elongated a little. The 1 mark should never point down, though.

Screenshot 2025-03-23 180351 by nessism, on Flickr

[KiwiAlfa156]

Oh it's a twin. My mis-read. We got the GSX400 four cylinder (Impulse) here in NZ (as well as the GSX400 TSCC twin, and the 2-valve GS450 Twin)