Reed Valve vs Piston Port Ace 100b+

[JackM]

The Ace 100 I got a while back came with what i think is an 01 Dirt Squirt cylinder with a reed valve intake. He included the proper cylinder and a brand new SR Wiseco piston kit with the sale. Its a reed valve piston, so can it still be used in the original cylinder? I don't know what the po's original plans were, but apparently he quit the project some years ago. The cylinder that was on it had been bored nearly to the max, and he told me there was low compression. Here's some pics of the new cylinder and piston.

[Hydraulic Jack]

If your question is whether the reed valve modified piston can be used in a standard 100B piston port cylinder, or an original non-reed Dirt Squirt cylinder without adding reeds to either one, the answer is no. Without reeds to stop the back flow of pressure through the holes in the piston, the bike would not run. You will need to decide which way you want to go. Reeds or no reeds. Once modified for reeds, a piston can only be used in a reed valve motor.

Personally, I would modify any piston port Hodaka to reeds given the choice, with the exception of showroom resto efforts or vintage class limitations dictating using the piston port. Better power, better economy, whatever. Reeds show superior performance everywhere except WOT, and there I think it is a even match.

[JackM]

Jack, the cylinder that was on it was the 01 dirt squirt, but I don't want to use that cylinder. I'm just fixing this bike up to putt around on trails, and really not interested in modifying the new cylinder to accommodate the new reed-type piston. Your answer cleared things up for me. I figured the new piston wouldn't work, but wanted to make sure. Maybe Strictly Hodaka would want to trade me the one I have for a new standard (or maybe one over, not positive yet) piston port piston. Its still NIB. Thanks for your reply.
JackM

[Hydraulic Jack]

You can always ask Paul. Or, someone here on the forum might want to swap with you.

[DG29]

Pm sent on piston.

[jakecb420]

I see that dg29 already sent a message about the piston, let me know if it doesn't work out for some reason. I would love to have a crack at buying it.......

[racerclam]

LIke Jack said , reeds are the way to go , Especially for trail rideing , lug ability Is waaaay better and easier to ride ,

Rich

[JackM]

Here are some pics of the two cylinders side by side. The one on the left was on the bike along with the piston shown. I now don't believe that it was an 01 dirt squirt cylinder, but really don't know what it was off of. The only difference I can see is the bottom fin is solid on the old one and indented on the new on (rt side). Also, it looks like someone did a poor job of enlarging the port holes. Jack, Rich, you guys make a strong point of using a reed valve set-up, so what would you recommend to do going forward? I already have the correct manifold for a piston port motor. Thanks
JackM

[Hydraulic Jack]

Neither cylinder is from an 01 Dirt Squirt for sure. Both have screw in exhaust nut and two stud intake. The 01 was reed valve from the factory, three bolt exhaust flange and four bolt intake.

Personally, I don't know which of the early 100's had a solid bottom fin as shown. Measuring port heights on the modified cylinder would, at this point, be a waste of time because they are almost certainly no longer stock height. You could measure port height on the other cylinder, however. There was little variation between ports on the 100cc trail bikes, but at least it would be a place to start in finding which is which. Measure from top edge of the cylinder down to the highest point on each port, in millimeters, and record your measurements. This might tell whether it is an Ace cylinder or Super Rat at least.

The piston is curiously modified. I suppose the concentric rings were supposed to be an anti-seize feature. I doubt it adds much in reality. I have never seen one like it, but someone was trying to be cutting edge I suppose. Whoever ported the intake needs to be spanked. Weld one end of the cylinder shut and use it for growing strawberries.

Seems to me that both cylinders have the same intake stud placement, so if you have a reed intake that fits one, it should fit both. After that you really only need to have a modified piston. There are other things you can do to maximize reed installation but they are not strictly necessary. Victory ports, boost ports, or whatever are nice but not required to work. Holes in the back of the piston are not required, either, but are easy to do, do not permanently change the engine, and do increase low to mid throttle power. If you have (dare I say it) a Dremel, you can mod a piston. Unless you are experienced, don't port the cylinder. You can use either a one ring or two ring style piston with reeds.

I don't know if your Wiseco is an old style or new style Wiseco. There were issues with early Wiseco/Hodaka pistons but I don't remember what the issues were. Wiseco pistons need a bit more skirt clearance than cast ART Hodaka pistons to avoid seizures because Wiseco pistons are forged and respond differently to heat than do lighter, less dense cast pistons. But they do work. They just need to be set up correctly.

Here's another question for someone expert in Wiseco pistons. In the photos above, the Wiseco label shows clearance at .002" which I would think just a smidge tight for a Wiseco, and a "type 2 dome." There is a compatibility question as to dome style and cylinder head configuration. Anyone who knows these things might advise on compatibility.

[racerclam]

First we know its not a super rat cylinder since it has a 2 bolt intake the rat has 4. Then also that piston shown is of later design and material which is good. The old wiseco pistons were different in that more clearance was required and many people didn't know that . The new ones have a high silica content which is much harder and grows much less so the clearance need not be much more than stock cast pistons. The high dome piston works with a low compression ace head and the flatter dome works with the super rat head. if your interested in properly porting your cylinder give me a call 702-858-9177 . Also for your small reeds I have carbon fiber pedals for that , 2 large pedals that replace the 4 small , I also remove the divider in the cage to make better use of them.

Rich

[JackM]

So, if the good cylinder is properly ported, the new piston shown should work. Is that correct? If so, I'll have to think about what I want to do. This piston came from Strictly Hodaka, but i don't know how long ago. Thanks, JackM

[racerclam]

That is not an old school piston , its a high silica piston

Rich

[JackM]

Rich, I appreciate your help but you're beating around the bush. All I'm trying to do here is find out what will work. If this one won't work, then I'll sell it and find something that will. If porting the cylinder proves too costly, then I'll stick with plan A and use a piston port piston. Thanks, JackM

[DG29]

So you would like to use the (top) new Weisco reed piston with one of your standard Ace 100 (two bolt intake) cylinders? If so, can you post a photo of the reed intake manifold and carburetor intake boot that you have.

[Hydraulic Jack]

I don't think Rich is trying to be vague. The piston you have is usable in the new (or unpainted anyway) cylinder. Assuming you have a reed setup that fits the two bolt intake, you have all parts needed. Does the Wiseco fit the bore in that new cylinder? If so, you have what you need. What Rich is suggesting is that if you want to improve your cylinder to maximize reeds, he can do that for a fee, and has better reed petals as well.

[Al Harpster]

I tried to add my two cents worth last night, but must not have clicked "send".

I've used Rich's modified reed intake with his two reed system. It definitely works and is worth what he charged for it.

I've also had Rich do porting work on my Ace cylinder(s). The work is a good value. My Ace is now faster than I'm willing to go.

I found the 'standard' Ace cylinder with the "Reed Carefully" modifications OK, but wanted more performance.

Rich provided the more performance.

If you get your's going in a "standard" configuration and find you want "more", Rich can help.

If you have not seen the "Reed Carefully" instructions for the Ace 100 engine they can be found on Strictly Hodaka's website or on Hodaka-parts.com website. It makes for good reading & I found it helpful.

[JackM]

Thanks for that info, Otilla, I'll check it out. I've read of Rich's work, and appreciate his expertise, but I was just looking for a simple yes or no answer on whether the piston would work or not on the stock cylinder. I'll have to give him a call. Here's a pic of everything lined up (cylinder, reed intake and carb) lined up. The carb is the standard 20mm Mikuni. Also, pic of the bike so far,after painting the frame, headlight bucket, etc. Thanks, JackM

[Al Harpster]

I think hydraulic jack is correct when he says if the piston fits you should be fine. Put the piston in and try to slide feeler gauges between piston skirt and cylinder wall.

Less than, say, .003 is likely too tight.

I don't know about a maximum, but I'd guess .006 or .007 might be a bit much. It depends on how much piston slap noise you can live with.

If the reeds look good and the carb is setup to recommended specs you ought to be OK.

I think that's probably a 24 mm carb you have. Maybe wrong, but the vm20 I had on my ace would NOT fit the reed manifold.

I set my 24mm up to the iron cylinder Super Rat specs. That's worked well for me.

[Hydraulic Jack]

Looks like a 24mm Super Rat carb. The 20mm was two holes but not slotted, just two holes. The 24 was slotted. Measure the engine side of the carb throat and see. A 24 will work just fine for a reeded 100.

[JackM]

You guys are right. It's a 24mm carb alright. I read the article "reed carefully" and really don't want to go that route. A little too much modifying to suit me. Would a k&n filter fit if I decided to go with the reed set-up? I know I'm asking a lot of questions here, but sooner or later I'm going to have to decide which way to go with this project. So far, I have the correct cylinder, wrong piston, wrong carb, both type intake manifolds (so I'm covered there - yay) and no air filter set-up, all for a '71 Ace 100B+. If I sell the NIB piston and 24mm carb, it will help offset the cost of buying a new piston and carb if I can find them. I'll have to think this one over. Thanks, guys. JackM

[Hydraulic Jack]

Not sure why you would sell the 24mm Mikuni. It is a very good carburetor and easy to tune, plus it will give you more power all around on a reed valved engine. It isn't necessary to do port modifications to use reeds, it is only necessary to have a modified piston, which you have. As long as it fits.

Not sure the question has been answered directly, or I missed it. Does the Wiseco piston fit either bore without having to have a cylinder bored out to match? Hidden in the question is one you might not know the answer to, which is whether the bare metal cylinder has been bored to match the Wiseco piston? If it fits, it probably has been. If it hasn't yet been bored to match and the piston is too large at the moment (0.020" over??) then the cylinder can be matched to the piston and you are good.

The carb and manifold shown in the first of three of the last photos posted is shown on a black cylinder. May we assume this is the "original" cylinder with the wild porting job, that you don't intend to use because it is already bored out to the max? If so, doesn't the entire carb and manifold swap directly to the other cylinder? If it does, then you are already half way home to a reed valve top end. If the Wiseco piston fits the other cylinder, the unported one without paint, then you are already in possession of the parts you need.......as long as the piston fits.

I raced a 24mm Mikuni on a Webco 125 conversion 100B bike a half a lifetime ago, and it was more than enough to get me around in the woods. I still have the trophies. So that 24 is a great start on a healthy engine. The reeds are a Super idea. If the Wiseco piston either matches or can be made to match the spare cylinder, I wouldn't sell anything. I would build it.

[Al Harpster]

I don't think you'll have much luck finding a 20mm mikuni. If you happen to find a good one it's going to be expensive.
You might work a partial trade for your 24mm if it's in top condition.

I believe you CAN use the reed intake, the drilled piston and the stock non-boost ported cylinder. There's an old article called The Reed Valve that talks about just that.

The article shows that adding the drilled piston and reed valve does almost zero for performance. No better, no worse.

Then dyno tests are done with the boost ports added to the cylinder.

Conclusion: reed intake does zip by itself. Reed intake allows boost ports to be added. Boost ports give horsepower.

Bottom line still is..... if the piston fits you can make it work.

I'll try to find the article and post it. Cycle Magazine, 1970 I think.

[taber hodaka]

I have a 20 carburetor and whatever you may need. If you get rid of the reed intake, I could use it. I would also like to see your ported cylinder. I applaud those that attempt to port themselves and if you don't feel comfortable porting ,there are those that are masters at it. I like the reed setup myself. -------Clarence

[racerclam]

I can add the boost ports in that cylinder for the reed if you just want to do the minium for $100 . And I would not recommend a K&N filter if your going any where near dirt , Go with oiled foam such as a UNI filter.

Rich

[racerclam]

I can add the boost ports to your cylinder if you want to do the bare minium for $100. And I don't recommend a K&N filter if you going any where near dirt go with a oiled foam like UNI

Rich