hodaka ace 100 build (new to building hodakas)

lukenessmonster · Post by **lukenessmonster** » Thu Nov 26, 2015 7:26 am

I aquired a 1968 (i think) hodaka ace 100 frame and parts about a year ago. everything but the engine. I just bought an ace 100 mx B engine on ebay. from what I can find while researching, the mx motors are from super rats which they built in 69. am I correct? I believe the super rat engines are the same as the ace engines. Am i correct? will this engine and frame be compatible?
I have built many bikes but I'm new to the Hodaka world. Any help would be greatly appreciated. Thanks.

Oh and can someone explain the "B" designation in ace 100 MX B.

hodakamax · Post by **hodakamax** » Thu Nov 26, 2015 9:30 am

A lot of your questions can be answered on the Strictly Hodaka web site under FAQ. Also by looking at the schematics you can tell the differences between the two engines. They are interchangeable in the frames as far as bolting the engine in. E-bay listings are definitely not the place for correct information. Check it to see what you really have by serial numbers on the frame and engine. Lots of old engines can be a hybrid of interchangeable parts from other models or even aftermarket parts.

Happy Thanksgiving,

Max

PS--Love your username.

bchappy · Post by **bchappy** » Thu Nov 26, 2015 12:06 pm

From the Strictly Hodaka web site go the "FAQ" tab at top right and then chose "How to Identify Your Hodaka". There is a chart in that section that shows what year each model was made. As Max said, the number on the right front of the engine will tell you what it was, but as cylinders and most everything else will interchange there is no telling what you have.

If it is a Super Rat engine throughout you have a nice engine.

Have fun and the forum is here if you need it.

Zyx · Post by **Zyx** » Thu Nov 26, 2015 4:46 pm

lukenessmonster wrote:I aquired a 1968 (i think) hodaka ace 100 frame and parts about a year ago. everything but the engine. I just bought an ace 100 mx B engine on ebay. from what I can find while researching, the mx motors are from super rats which they built in 69. am I correct? I believe the super rat engines are the same as the ace engines. Am i correct? will this engine and frame be compatible?
I have built many bikes but I'm new to the Hodaka world. Any help would be greatly appreciated. Thanks.

Oh and can someone explain the "B" designation in ace 100 MX B.

To address your questions, yes, the engine will fit. While the Super Rat and Ace 100 are not the same engine, the differences are invisible for the most part. The Super Rats had straight cut gears (spur) instead of helical, different gear ratios, larger carb, tuned pipe, more aggressive porting. That sort of thing. Ace 100 engines are marked with a P engine number, the Super Rat has an M number. The model B was made in 1969. You can pretty much mix and match parts between these engines and build what you want, and most folks have done so over the years, so just because it says Super Rat on the sales slip doesn't guarantee what's inside the motor. A year ago I bought a Super Combat 125 engine on eBay, only to find that the gear set was from a model B 100cc engine, and the clutch was cobbled up from various machines. You may want to go through it and verify what's inside. I mounted my "new" 125 engine in my old Ace 100B frame. Dropped right in.

Someone else will have to answer the question of why Hodaka named models as they did.

Hodaka is an easy machine to work on. Get a manual for the torque specs and oddball stuff, but very straight forward.

lukenessmonster · Post by **lukenessmonster** » Thu Nov 26, 2015 5:34 pm

Thanks for the advice. I get my engine in a week and I'll check the numbers then start breaking it down

lukenessmonster · Post by **lukenessmonster** » Fri Nov 27, 2015 7:06 am

I have the original carb off of the old ace 100 motor that was originally I the bike. Will that carb work on this new motor if it is intact a super rat?

dirty_rat · Post by **dirty_rat** » Fri Nov 27, 2015 7:22 am

The carbs are not a BOLT ON change. The Ace carb was a 20mm carb and the mounting manifold only had two mounting holes where it attached to the Ace cylinder (the Ace cylinder only had two studs to mount the manifold/carb). The Super Rat had a 24mm carb and it's manifold had four holes for mounting to the Super Rat cylinder (the Super Rat cylinder had a larger mounting area and had four studs to mount the manifold/carb). So, in a nutshell, the manifolds were different and won't bolt up from one to the other (although with some work, they can be mounted up). The carbs also had a different spacing on their mounting holes and the two don't match/line up, so you can't mount the 20mm carb on a Super Rat manifold and visa versa. Hope that helps.

Zyx · Post by **Zyx** » Fri Nov 27, 2015 7:56 am

There is no reason to mount the original 20mm carb unless you are just trying to get it running. It will work, but the Ace 100 carb is tiny by most any measure. I did a reed conversion way back in my be 1972, and went to the Super Rat carb at 24mm. Much better. I even used that same reed/carb assembly when I converted the rat cylinder to a Webco 125 unit, and although a bit small for a 125, the 24mm worked well in the woods. With reeds you could even try a 26 or 28mm carb, which I eventually did with the Webco.

Bigger isn't always better in itself, but being able to upgrade opens opportunities for improvement. Scout around. Someone is going to have an old GEM reed assembly that will make big improvements.

For what it is worth, my old 24 Mikuni had a slotted two bolt flange that allowed for a range of two bolt spacing. I believe the 20 did not, making it much easier to mount the 24 to whatever was likely to fit, while the 20 required the original manifold or original bolt spacing to mount.

lukenessmonster · Post by **lukenessmonster** » Fri Nov 27, 2015 10:45 am

My carb off of the original ace is slotted. Maybe it's already an upgrade.

Zyx · Post by **Zyx** » Fri Nov 27, 2015 11:42 am

Measure the Venturi at the back to the nearest mm. I checked the parts list for the Ace 100 series and it appears they all used the same 20mm non-slotted carb. Yours could be from a Rat, or someone could have slotted the flange, which would likely show as a home brew thing just by looking.

lukenessmonster · Post by **lukenessmonster** » Fri Nov 27, 2015 12:45 pm

One hole is slotted. It measures 22.37mm does that sound like a super rat carb?

Zyx · Post by **Zyx** » Fri Nov 27, 2015 12:57 pm

Mine measures 24.40mm and has two slots.

: 24 Mikuni - Super Rat (93)

I have no idea what might have used a 22mm carb but the one slot sounds like someone's solution to a carb that didn't fit because the holes were too close together. Someone else might have an idea here.

Zyx · Post by **Zyx** » Fri Nov 27, 2015 1:05 pm

I can't find a Hodaka that used a 22mm. It appears that some of the Honda industrial engines did. It could have come from anywhere, but that makes it suspect for use unless you are good at jetting. Are you sure it is 22mm? I don't have an original 20mm Mikuni to measure, but I doubt it measure much over 20mm.

lukenessmonster · Post by **lukenessmonster** » Fri Nov 27, 2015 2:55 pm

How do I post a picture in my comment. I'll post a pic of my carb

Zyx · Post by **Zyx** » Fri Nov 27, 2015 3:07 pm

When writing a response, spool down the page. You will see the tabs for attachments. Follow the prompts.

lukenessmonster · Post by **lukenessmonster** » Fri Nov 27, 2015 3:24 pm

Yep I'm a little slow on the uptake. Here's my carb

Zyx · Post by **Zyx** » Fri Nov 27, 2015 8:01 pm

That does look like a 20mm due to the throttle adjuster on top of the slide. Might measure again.

The slot could have been someone's idea of making it easier to remove from the bike. Look at the slot. Does it look like a factory job? If it does it might just be good workmanship but I don't think they came that way.

Looking at your photo the o-ring looks shot. Also, does anyone know whether the 20mm Mikuni flared from Venturi to flange mount surface? I usually measure at the flange because it's easier than measuring the Venturi at the slide. Is it possible the throttle bore opens two millimeters post-Venturi?

Bullfrog · Post by **Bullfrog** » Fri Nov 27, 2015 8:27 pm

Every flange mount Mikuni I've seen has a slight flare between the slide and the flange - but I don't have any reliable information regarding how much flare.

Ed
PS: I don't remember the visuals of the early small carbs well enough to be of any assistance in identifying the carb in the photo.

Zyx · Post by **Zyx** » Sat Nov 28, 2015 7:17 am

Ed, I don't remember specifically, either, what the 20mm looks like. Just going from the schematics, the 20mm had two holes, no slots, but it did have the throttle adjustment on the top of the slide instead of through the Venturi body. I have always assumed there is a bit of a flare, but would not have thought there would be 2mm worth. Could be though.

Likewise, photos on the Internet for vintage and modern Mikuni carbs show either holes, slots, or spigot mount, but I have seen none with one hole, one slot. Someone may have done the slot to mix and match parts. It should hurt nothing as far as usability.

The old 20mm served well for many years, and can be used on a Super Rat I suppose. It would probably take away a lot of snap from the 93 cylinder, but might also make it more tractable off road. Blending parts is a Hodaka tradition.

BrianZ · Post by **BrianZ** » Sat Nov 28, 2015 7:48 am

The carb in the photo looks like the standard 20mm Mikuni used on the Ace 100. Every one I have seen is slotted on one side. I measured a couple of mine and they were all about 21.5 mm at the manifold end.

Hope that helps.

Brian

taber hodaka · Post by **taber hodaka** » Sat Nov 28, 2015 9:42 am

Just for info all 90 or 100cc ace engines had one side hole and one side slot. The carb in the picture is stock early 90 or 100 cc. I believe that there was a 22 mm made for the 90cc race engine. -----------Clarence

lukenessmonster · Post by **lukenessmonster** » Sun Nov 29, 2015 1:06 pm

Cool. Thanks for all the help. I'm just waiting for the new now. Then I'll see exactly what it is

lukenessmonster · Post by **lukenessmonster** » Tue Dec 01, 2015 1:58 pm

Got my motor. The number is p50519. On the chart do I use the frame # column to figure out the year and model? If that's the case this shows to be and ace 100b. Not mx. Is there any differences between an ace 100 and ace 100b. Or is it just accessories on the frame?

Zyx · Post by **Zyx** » Tue Dec 01, 2015 4:11 pm

Engine numbers and frame numbers were not the same number. "P" engine numbers were used from the Ace 90 through the 80 Dirt Squirt. No "P" engines were used in Super Rats as built by the factory. The numeric sequence of the frame will tell you when the frame was made. Hopefully. The chart on Strictly Hodaka used to show engine start numbers, but no longer. To find the year yours was made, use the frame number.

There were differences between Ace 100 and Ace 100B not attributable to accessories alone. Compare the spec sheets for the Ace 100 and 100B. On the other hand, they were probably more alike than they were different.

Given the number on your engine, it would have been relatively late production Ace 100B, either very late 1970 or early 1971. It is definitely not an MX engine case. Until you take it apart, you won't know what parts it is built from. The number alone does not answer the question, but to represent a "P" engine as a Super Rat is typical eBay stuff.

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