Knock sensors

[squishycans]

Hello,

I have a 1978 GS750E that I'm rebuilding. I decided to go with the Wiseco 850cc pistons. They have 10.25:1 compression, but I only have 91 octane available to me. Wiseco said 10.25 isn't that aggressive and 91 octane would be fine.

But I feel concerned now. The service manual says to use 89 octane at 8.7:1 stock compression. So I'm not sure 91 octane would be enough of an increase?
So it looks like I have some options.
*Double up the cylinder gasket, losing a lot of compression (I would imagine) and losing some of the benefit of the pistons.
*Use octane booster with 91 octane and assume that's not going to detonate.
*Just use 91 and hope for the best
*Get a knock sensor, try 91 in summer and see if any knock, then use octane booster.

That said, is there a universal knock sensor that could be tapped into the cylinder head somewhere? I was thinking I could just add a gauge to the bike and monitor or log it on a heavy max rpm pull. Anyone done this?



*P.S. If anyone can tell, I'm paranoid about knock since I destroyed a high boost Honda motor with a failing fuel injector.

 

[Nessism]

My memory is a little foggy since the last discussion on this but I think octane rating listed in the manual is different from what's commonly on the pump in the US. This thread goes into more details...https://www.thegsresources.com/_for...ing-87-octane-in-these-bikes&highlight=octane

 

[squishycans]

Ahh okay. I had no idea that research method was different than the (R+M)/2 pump. Okay awesome, so these should be fine. THANK YOU!

 

[Steve]

And, ... even if you <did> install a knock sensor, what would it do? :-k

All the knock sensors I know of are connected to computers that will back off the timing or richen up the mixture a bit.
Last time I looked, a '78 750E did not have much of a computer on-board.

.

 

[Guest]

In my experience the wiseco's will prob give you a true 9.5:1 when installed on a 2v gs750.