Spark plug reading

I think this is too lean, but would like a second opinion before I start drilling out jets or whatever it is I have to do.





Its a 76 750 Twin. Pod filters, 2 in to ! with a glasspack. I was hoping maybe I could get away without rejetting as I live at 5300 feet, but I dont think I got that lucky.

in the top picture it looks like it might be between ok and a tad lean. In the bottom picture I see you have B8ES plugs and I think that something like a B6 or B7 is recommended. However, I dont have a twin and dont have experience with twins so dont do anything until a twin owner comes along. How is the bike running currently ?

It is hard to explain. It runs great for a while, and then randomly will start running terrible to the point that it wont accelerate, and then wont idle, and then wont run at all. Let it sit a few hours, and bam it runs fine again.

and I got the b8es from my service manual, maybe the 4 is different.

Using the Gas/Alcohol mix most of us are? The fuel will absorb water, making your bike's engine give unusual plug readings.

What I see from Kawasaki is the B1-2 takes the 8's. Then the B3-4 takes the 6's. Why they needed to go 2 heat ranges hotter, I don't know. If anything the later bikes would be leaner, which would be hotter combustion. My head hurts.

the left one looks ok, the right one looks lean, turn fuel mixture screw in a little on that one a recheck

xbmxxx wrote: It is hard to explain. It runs great for a while, and then randomly will start running terrible to the point that it wont accelerate, and then wont idle, and then wont run at all. Let it sit a few hours, and bam it runs fine again.

A classic symptom of too tight valve clearances.

Good Fortune!

They read B8ES, probably says NGK on them on the other side.

yes they do say NGK, the comparable ,Autolite, Champion ,etc have diff numbers,
if ur manual says 8's go with it, I've seen people experiment a little with diff numbers but something like a 4 would way off

Yeah I'd say a bit of air screw fiddling and moving your needle up a shade would do the trick. Like Patton says look at your valve clearances too.

jonnybravo wrote: yes they do say NGK, the comparable ,Autolite, Champion ,etc have diff numbers,
if ur manual says 8's go with it, I've seen people experiment a little with diff numbers but something like a 4 would way off

I think he was referring to the 4's as the 4 cylinder models, his is a twin of course, not a 4 heat range plug.