This. Compatibility is going to mean compromise of some undesirable flavor, it seems, so skip compatibility, IMHO.
Billet Head
- Thread starter waxhead
- Start date
waxhead
wannabe backflipper
- Location
- gold coast
That's the best reason I have heard so far.
The main reason we are doing this is so we can catch some of the people with ada heads as well. you have to understand this is not a big market and it costs a fair bit to enter it. We want the domes sales as well as the head shell sales to make it worth while.
Yes its surprising what a good dome shape can do to your engine
bored&stroked
Urban redneck
- Location
- AZ
Its interesting you say that, because I've been running modded stock heads forever, and everyone constantly tells me the squish is bad and the ADA head is SUCH a better design.
waxhead
wannabe backflipper
- Location
- gold coast
The stock head has some things better than an ada and the dome shape is a lot closer to what it should be. Imagine if you have both
- Location
- California
That is what happens when you listen to everyone, LOL. I would take a Group K modded stock head over an ADA for shape and sealing every time. The only drawback is the lack of a full girdle. Been using his stuff and machine work for over 30 years now and can't say Harry has ever been wrong.
waxhead
wannabe backflipper
- Location
- gold coast
The issue with machining heads is its hard to get the squish band to match the dome of the piston and this is what you have to do. ON a Kawasaki not so bad its a flat top the Yamaha not so much.
- Location
- Goodwood, ON
Group K did a great job. When I've done the solder check on the squish, it seems to be even across. I tore my engine down a couple days ago, so I had a good look at the dome shape. It's very close to what you seem to be after. Looking at pictures of ADA, I can see the issue. I still think you should do the full head and domes. You'll get a noticeable difference for much less money than most mods that you can actually feel, with the cheaper plugs and no compromising on design.
Please be quick. I'm planning to cut off the old pipe mounts and other parts of the head casting that I don't need before powder coating it. If I mess it up, I'm going to need a new head and I don't want to be forced to buy ADA when I know this gem is on its way.
Problem with kawasaki is the pistons are .050" or so down the hole, so with that and the thickness of the gasket no amount of machining on the stock head will get you nice tight squish clearance. Same problem on a yamaha if you use the stock head gasket because it's pretty thick. Could be fixed by milling top of cylinder.
I'm curious what you measure for squish clearance on the groupk head, and are you using stock head gasket?
I'm curious what you measure for squish clearance on the groupk head, and are you using stock head gasket?
waxhead
wannabe backflipper
- Location
- gold coast
IN the old limited days we used to machine around the chamber to drop it. I think TBM even made some drop domes
- Location
- Goodwood, ON
If I remember correctly, my squish is .050” with a stock gasket and there’s still room to take more off the head. I’ve used copper gaskets on older kawis and got the squish tight. I blew up a 550 because I forgot to check squish when I put on a westcoast head with the copper gasket.
- Location
- California
Yes, Group K accounts for this...
Group K "Head Gasket – All Group K kits are intended to be used with the stock .040″ head gasket. There are many aftermarket alternatives to this gasket, i.e. .020″ copper gaskets, and “O” ringed heads, etc. It has been our experience that the primary cause of most head gasket leaks is low spots on the cylinder deck surface. To address this problem, all Group K kits include cylinder decking to assure a totally flat deck. While all of the after market gasket replacements may be capable of maintaining a seal, none of them can resolve a leak caused by an irregular cylinder deck surface."
"Head Gasket Sealing – The stock sleeves of the Yamaha cylinders very often will drop .002”-.003” in the aluminum casting. This makes perfect head gasket sealing very difficult (if not impossible). To resolve this problem, our Cylinder Porting Modification includes cylinder top decking and lapping. This decking allows us to set up a more desirable squish clearance between the head domes and piston crowns. After this machine work, each cylinder top surface is “lapped” to assure the perfectly flat surface to maintain a lasting head gasket seal."
smokeysevin
one man with a couch
- Location
- Houston
Can you switch the o-ring from a piston-style where the o-ring groove is on the internal part to a cylinder mounted groove and use a thicker cross section ring to ensure you still get adequate squish while holding the ring in place? Cutting the groove in the head would be more expensive vs turning it but you might be able to tuck that section further down into the head vs having a nipple sticking up and shrouding he plug body.
Sean
Sean