A Curious Ace 90 engine.

[rlkarren]

Picked up a couple Ace 90 engines yesterday. One of them is a bit different but sports an early Ace90 serial: P1213. It has the Ace 90 Shifter Cover but no Ignition/flywheel.

Note the absence of an oil vent in top, but it's inside the stator cavity instead via a small vent tube near the ignition cutout near the top. Also the rubberized bushings for motor mounts. Not sure about the glob of orange silicon near the bottom of the stator cavity. I may split it later today just to see what's inside.

It is a 4 speed. Piston bore measures ~48mm. The rod has what appears to be the Hodaka triangle on it and the numbers 880.

Any ideas? Thanks in advance.

Roger

[thrownchain]

That orange rtv is more than likely hiding a crack or a chip.

[hodakamax]

Hmm, interesting Roger, I've not seen one like that before. No clues here to what's going on. Keep us posted!

Max

[rlkarren]

It gets even more interesting...

Turns out it's a 5 speed. I should have clued in to the c-clip securing the drive sprocket. The orange silicon blob is sealing a vent that exists into a cavity between the lower engine mounts. That's good news...

I have to go out for the evening, but I think I'll start comparing parts with other Ace 90 motors I have when we return. In the meantime, if anyone has specs for the Ace 90 5 speed transmission, that would be helpful.

[hodakamax]

Wow, It's probably a close ratio 5-speed conversion with that clip. The mystery deepens! The individual close ratio gears on the countershaft should all be stamped 91. I also have one of the CR sets if you need a gear count. Also the mainshaft is splined.

Max

[taber hodaka]

Yes early Hodaka engines were rubber mounted. Vent tube came through the case and lubed the chain. The really early ace engine did not have ACE 90 or Hodaka stamped on the cases. They also had several different heads. The very first ones were just like the Yamaguchi engine "spelling"??------Clarence

[taber hodaka]

If you tear it down throw nothing away and keep parts separate as the seal for the sprocket is uniquely different. ect -------Clarence

[rlkarren]

If you tear it down throw nothing away and keep parts separate as the seal for the sprocket is uniquely different. ect -------Clarence

Good advise Clarence. And thanks for confirming the rubber mounts. I was really wondering about them. Also the other thing I noticed was the Sprocket collar and forgot to mention. Very different.

So I had some more time to really look into the internals. This is what I found:

Gears
All but 5th gear stamped "92". The Main Shaft is one piece.

Shift Cover
Ace 90 5-Speed on the Left. 1-up 4-down

Right case half
Ace 90 5-Speed on the Left. Normal Ace 90 on the right. You can see the machining on the left. Looks like not more than maybe 2mm taken off. There was no other evidence of machining that I could find, (so far).

This is certainly a treat. I've heard and seen many comments about a 5 speed conversion and always wanted to see one. I don't believe this is a close ratio conversion though. It looks like a standard Ace 100 Transmission, but that doesn't explain the counter shaft and sprocket collar. The Counter shaft has the ring cut out for the C-Clip and the sprocket collar is much larger with an O-ring mounted so that it seals against the counter shaft and Sprocket. The shifter is probably just Ace 100 parts, i.e. Chrome Tank Super Rat was also 1up 4 down,(at least the two I had were).

This is certainly causing me to reconsider my plans for my Ace 90/125 project. I think it might have just become two projects... Would like to know more about where this conversion may have come from. Home brew? or was it an "off the shelf"/"mail order item".

Roger

[hodakamax]

The 5-speed kit for the 90 came out as a racing close-ratio with 91 numbers. When the Ace 100s came out you could also get the wide-ratio kit for 90s as I recall. (Or a close-ratio for your 100). On the Ace 100 schematic it still shows both countershaft seals. The 90 close-ratio kit came with instructions on machining inside the cases for the extra gear and some slight grinding on the shifter case to allow a bit more travel for the ratchet arm going both up and down as shown above the red oval in the on the left side of the picture. The rod on the 90 had bushing on the upper end and the rod could be replaced with the racing 91 rod which carried over to the Super Rat 93s with needle bearings on both ends.

Strange that it has a 91 countershaft and 92 gears. I wonder if it was converted early and they didn't like the close-ratio (or it broke) and replaced it with wide-ratio gears from the new 100s? Does it have a bushing rod? Mystery!

Max

[rlkarren]

After some sleuthing, I think I'm able to identify what this is. Max piqued my curiosity so I did find information on a "wide ratio" 5 speed transmission available for the Ace 90. The gearing being the same as an Ace 100. This looks to be what I have with the exception of the main shaft which appears to be a standard Ace100 shaft. I think I'll re-assemble to make sure clearances are correct. In the meantime this is the casting on the connecting rod:

If the Main shaft actually fits OK, I just might have to build another bike around this motor!

Roger

[hodakamax]

Hmm, it looks like the rod is marked B80 with a B. It also appears to have a bushing upper end. I wonder if the early 90 used an 80 rod? Just asking questions, this is all before my time of selling the first Ace 90s.

Max

[admin]

Yes the very first Ace 90's used the Yamaguchi Ace 80 rods.

[taber hodaka]

It has the Hodaka H inside a triangle when did the Hodaka name first surface? I will have to look at the crank in engine 32. Clarence

[michael_perrett]

My 1965 Ace 90 has a B80 rod.

Mike Perrett

[Dale]

It has the Hodaka H inside a triangle when did the Hodaka name first surface? I will have to look at the crank in engine 32. Clarence

Since Hodaka was providing some of the motors for Yamaguchi, I would think that the Hodaka triangle would have shown up pretty early on.

[taber hodaka]

I have a engraved shift cover HODAKA. Like the early Ace 90 engraved handle bar plate.