Who wants good head

[waxhead]

Ok well i used that title to get you but now you are here have a look whats up on the wax bench
We’re currently developing new dome shapes for our upcoming range, and I’ve never quite understood the logic behind a straight squish band on a round-top piston. Our new designs are built for the unleaded fuel era — with improved cooling and properly shaped squish bands for better performance.
The current domes on the market have up to 11 mm of material at their thinnest point, creating an unnecessarily long heat path between the combustion chamber and the water jacket. This excessive thickness causes heat retention, which can actually promote detonation under sustained load. We've addressed this by reducing the wall thickness to 8 mm minimum. While 5 mm is often regarded as the ideal balance between heat transfer and structural strength, we've chosen 8 mm to ensure long-term reliability. The last thing anyone wants is a cracked dome — even years down the track.

Let us know what combustion chamber volumes you’d like to see in the lineup. Keep in mind: when a dome is properly designed, you can safely run higher static compression without detonation

 

[WFO Speedracer]

is this a trick question ?

 

[Storbeck]

Correct me if I'm wrong on this, but a good combustion chamber can avoid detonation at a higher compression ratio, but it also will have faster combustion and thus need less ignition advance at peak.

Great if you have a programable ignition (zeel).

Not so great if you have a stock ignition or an msd enhancer with ~22 degrees of advance or if you advanced the stator a little and have more like 25 degrees.

I fear you'll have trouble with people running way too much ignition advance.

I run 91 octane (that's what you can get at the pump around here) and zeel in pretty much everything so a dome that works well with that at about an 84-86mm bore on a stock cylinder is what I'd love to see.

 

[waxhead]

Correct me if I'm wrong on this, but a good combustion chamber can avoid detonation at a higher compression ratio, but it also will have faster combustion and thus need less ignition advance at peak.

Great if you have a programable ignition (zeel).

Not so great if you have a stock ignition or an msd enhancer with ~22 degrees of advance or if you advanced the stator a little and have more like 25 degrees.

I fear you'll have trouble with people running way too much ignition advance.

I run 91 octane (that's what you can get at the pump around here) and zeel in pretty much everything so a dome that works well with that at about an 84-86mm bore on a stock cylinder is what I'd love to see.

You're absolutely right that a well-designed combustion chamber can tolerate higher compression without detonation — but it's also true that a more efficient chamber burns faster, which means you need less ignition advance, especially at higher RPM.

Our new toroidal domes are a good example of this. They don't just burn faster — they also improve cooling and reduce detonation risk thanks to a correct squish angle. When the squish matches the piston shape, you get better mixture movement, cooling across the piston crown, and you avoid trapping hot unburned gases at the edges — a common issue with flat squish bands over domed pistons. That trapped gas is a major cause of deto pitting around the outside of the piston, something many riders have likely seen without realizing why.

The stock Yamaha heads actually have a mild toroidal shape from factory and hold up decently even with MSD enhancers — often pushing 22° of timing — but they’re far from optimal. If you're moving to a more efficient dome design, especially one that increases static compression and improves burn speed, then tuning becomes much more critical.

If you’re running a fixed or semi-fixed ignition like an MSD enhancer, you're not really chasing peak combustion efficiency — you're just pushing timing and hoping for gains. That can work with stock heads, but with a performance dome, it’s risky. You’re more likely to hit detonation because you’re not adjusting for the faster burn.

Thanks for bringing this up — it’s an important point, and we’ll make sure to include it in the documentation when the domes go live. For reference, the Wax V3 ignition curve we use is built with this in mind — it only runs 17–18 degrees at high RPM, which is exactly where these domes shine.

Edit. Thanks for bringing this up.

 

[Half flip95]

I want a dome that runs on 91 pump gas on a 760 ported with your 196* template with a wetpipe and oem cylinder deck height

 

[waxhead]

Yup and that's what we are working on right now, my desk is covered in 3d printed domes trying to get the perfect shape to not only optimizes power but to push away from the detonation threshold