Recommended Headwork for Slightly Overbored GPZ110

I am pulling the trigger on buying the oversized pistons for my 1982 KZ1100 B2. I am going for either 74 or 75 mm 10.25:1 wiseco pistons. I am doing it more for the high comp than punching out the engine.

What I am wondering is can I get by with just leaving the stock size valves in place or am I wasting my money not upping the valve size at this time? I really would like this to be the last time I take the head of the bike.

My goal is a solid reliable running bike that is moderately quick, not going out to hustle sport bikes, just a nice sounding streetable cruiser, potentially teaching motorcycle safety classes with it.

In my ignorant, ameture opinion, with stock cams and a small displacement increase, there is no need to increase the size of the valves. I think the only time you would be loosing anything with the factory valves is very near redline, and I take from your comments that low and midrange will be much more important to you.

The cams will be updated someday but in reality, would be timing it with a couple degrees of advance for bottom end more than redlining it..

If I want to go 90 MPH for hours on end, I have the beemer for that. This is just going to be my around town bike.

Here is some reading on the matter.


www.kzrider.com/forum/2-engine/604013-flow-chart#744202

www.kzrider.com/forum/2-engine/602288-kz...hings-to-know#724118

I agree with Texas KZ. Just do a good valve job and the bigger piston kit and I believe you will be quite pleased with the outcome. Back in the 70,s I had a 76 900LTD that I put an MTD 1170 kit in with no head work and had a nice ridable street machine. Of course to go that big required boring out the cases. I also had the crank welded befor it went back together.
Jerry

Having the head flowed would be best to get the full advantage of the capacity increase.

For a nice around town/bar hopper motor I'd do the 74 mm pistons, a good valve job, stock cams
a 4-1 pipe and a good ign.

On my B2 I did a valve job, and it wasn't until I was forced to that I went with the '84 Head, which has bigger valves, and more flow, and it made a noticeable difference - especially from 6500 rpm's and up.

GPzEric wrote: On my B2 I did a valve job, and it wasn't until I was forced to that I went with the '84 Head, which has bigger valves, and more flow, and it made a noticeable difference - especially from 6500 rpm's and up.

+1 ... :woohoo:

Porting factory head a much better option than using 83 /84 GPZ head .

DFIGPZ wrote: Porting factory head a much better option than using 83 /84 GPZ head .

:blink: Please explain.

zed1015 wrote: Having the head flowed would be best to get the full advantage of the capacity increase.

BINGO, the single biggest performance increase for most old Japanese bikes is in cleaning up the ports, its amazing just how much power can be gained by well ported head..