Joe Hooper (Pit Stop Performance) recommendations for camshaft tuning.

If you have ping with high lift long duration cams fitting lower lift shorter duration cams may not cure the issue. Usually going back to stock cams in your situation would raise dynamic cylinder pressure and change the power characteristics.

 
 

Thanks for the clarification; that’s what I thought. That’s why I’m considering fitting the new DCR pistons to work with the stock GPZ1100-84 camshafts as well—just to build in some headroom. I ran a setup like that back in the day, but with a ported GPZ1100-84 cylinder head, oversized valves, and different pistons.

Back when I wanted to run injected alcohol I needed 16:1 or higher static to burn it efficiently. I used a off the shelf 13:1 MTC piston but found there was a lot of wasted room in the stock Kawi hemi head combustion chamber. I took Bondo casts and designed a better version of that piston then made a scraping tool that profiled the new piston crown shape by +1mm. I used the tool to scrape and remove material so the chamber just cleared the new piston achieving the higher ratio.

Custom scraping tool :

   

New piston 3D printed in corn starch next to old cut down 13:1 MTC :

 
 

That’s top-notch work! 👍🏻 So, how did things turn out with the alcohol-fueled engine? I’ve just started working on the pistons; I decided to first eliminate potential detonation hotspots. It’s going to be a street bike, so I need good torque at low to mid-range RPMs. I might mount a cooling fan on the cylinder head, triggered by a sensor installed in the head itself—set to kick in at 115°C. Though, I’m not sure if it’ll actually make a difference.

v.f. post=928318 userid=56273That’s top-notch work! 👍🏻 So, how did things turn out with the alcohol-fueled engine? I’ve just started working on the pistons; I decided to first eliminate potential detonation hotspots. It’s going to be a street bike, so I need good torque at low to mid-range RPMs. 

That all happened about 25 years ago and the alcohol bike ran pretty good for a lot of years. I recently took it apart as I am done drag racing (check my posts on here) and that engine is going back to running on the street, so I will be tearing it down and returning back to 10:1 compression. No doubt I will be cutting down the piston domes (pretty similar to your photo) and reworking the combustion chamber or running a 6061 base spacer. For sure I have some work ahead of me.

If that is the piston your running you need to flatten that sharp ridge on the top and put some radii on all those sharp edges.

That picture I posted of the piston is currently in my street bike.

How long did the engine run on alcohol? Is there any wear, or does anything need replacing? Yes, of course—I’m going to remove all sharp edges and might even polish the pistons. I’ll need to set the displacer volume to 13.5–14 cm³. But there is some good news: I’ve concluded from this that my engine doesn't want to run on 95-octane fuel with a dynamic compression ratio of 8.6.)))

v.f. wrote:

How long did the engine run on alcohol? Is there any wear, or does anything need replacing? Yes, of course—I’m going to remove all sharp edges and might even polish the pistons. I’ll need to set the displacer volume to 13.5–14 cm³. But there is some good news: I’ve concluded from this that my engine doesn't want to run on 95-octane fuel with a dynamic compression ratio of 8.6.)))

Every day is a school day sometimes the only way to know is to "give it a go"

But the way it drove on 100-octane fuel... )))

v.f. wrote:

How long did the engine run on alcohol? Is there any wear, or does anything need replacing? 

I raced that bike a few times a year from 1997 till 2012, so about 15 years but only ever had the top end apart. Maybe covered about 20 miles in all that time. The only wear I expect may be plain bearings, shift forks, maybe piston wall scratches.

Every time you start it you have to throw out the oil and clean out the tank and injector lines then run lube thru the whole system. Alcohol can only sit overnight at most, nitro is even shorter so it entails much more maintenance than running gasoline.

Even 20 miles under those conditions can cause significant wear to both the crankshaft and the transmission. I hope the wear won't be critical. Running on alcohol fuel is a whole different level—advanced territory—and I never quite reached that stage. Motorcycle drag racing isn't very popular here, and there are very few purpose-built tracks. By the way, it’s impossible to find a bike like a GPZ or KZ—regardless of the model year or engine displacement. You could order one from Japan or the US, but given current logistics issues, that’s extremely expensive. In reality, they simply aren't available here. There are a few KZ1000 Police models around, but they are scarce and pricey. The vast majority of bikes on the road are Japanese models from the 2000s or later.Not long ago, I wanted to buy a GPZ750 to build a replica of a 1983 superbike. But I couldn't find one...