Ace 90 radial head

[jakecb420]

So, i picked up another ace 90 a few weeks ago that has a high compression head on it that I was wondering if anyone could shed any light on. There is an H stamped on the bottom of it. Also, there was an aluminum spacer that looks like it should go under the cylinder(but I'm not really sure) that was not installed in the engine that came in the box of parts with the bike. The spaced is about 8mm thick(guess). I can take a pic of the spacer tomorrow if anyone would like to see it too but I figured I would post some pics of the head tonite.

[Bullfrog]

That looks like an after-market accessory made by DG. I had a DG radial head on a Wombat 03 ISDT Qualifier machine back in the day. The DG head an aluminum extrusion which was machined to fit any number of machines in the mid 1970's.

Does the cylinder stud pattern on that head match the ACE 90?
Ed

[jakecb420]

Yes Ed, it does match the ace 90 bolt pattern. I actually checked compression before I took it off the motor and it was about 200 psi. I ended up robbing the motor for the counter shaft to get my regular use ace 90 fixed up.

[Bullfrog]

I was under the impression that this particular head came about when someone noticed a large aluminum extrusion which was being used as a heat sink/cooling device on some sort of electrical equipment and decided that it could be machined into custom motorcycle engine heads. All this happened in the mid 1970's. Of course there may be earlier parts of the history of which I am not aware. It is surprising to me that in the mid 1970's someone would put so much time/effort/money into a head like this for a 90! But there it is. Wouldn't it be neat to know, " . . . the rest of the story"?
Ed
PS: It would also be nifty to have the rest of the story on the 8mm deck spacer.

[jakecb420]

I will try to contact the guy I bought it from. I actually seen it on the forum marketplace here. There are still pics of the whole bike on the website still. The fellow said he bought it off a neighbor in 1965, the title was actually in his wife's name. Anyway, I'll see if he can give us more info.

I took a couple pics of the spacer. It is actually 6.11 mm. There is a gasket only on one side.

[jakecb420]

Sorry, I didn't attach the photos.

[racerclam]

That spacer would be a bad thing since it would raise all the ports 6mm. the only purpose I can think of is if someone had a rod 6mm longer like is being done on some other bikes like Yamaha where ther is not the correct rods available anymore . The linger rod will also affect power band , the engine would favor higher rpm , also cylinder wear would be lessened due to less side loading from better rod angle

Rich

[jakecb420]

I received a message back from the previous owner about the head, here is what he said.... "about the head, it was in the early '70s when i got a little serious about trials with it. we did not have internet so i'm guessing it was in a motorcycle parts catalog. DG had advertised a similar head around the same time period. i am pretty sure the spacer was from an attempt to install a yamaha 125cc piston in a bored hodaka cylinder. this did run for a while till the cylinder wore thru the ports. sorry i don't have any more info for you,"

Some interesting stuff I would say.

[gregg_floren]

I have a a head that I think is the same. I heard the same story that Ed related about the aluminum electrical heat sink. I showed it to Harry and I think he told me the gentleman that made them was named Manny Herriman. I'm not sure on the spelling. Maybe someone can correct that if it's wrong?

It definitely has fewer CCs machined out of the head than stock. In fact Harry felt it would raise the compression way too high.