OK not necessarily a new topic. I know this has been hashed over a lot - I just can only remember so much. What I remember was a discussion about how good the Hodaka stock pipes were vs aftermarket pipes or something like that anyway. I also remember - I think it was Capt Ed saying that Harry Taylor thought at least some of the stock pipes were pretty good but that maybe that was before the 01/02 Dirt Squirt/Toad pipes. Possibly the stock squirt pipe is a pretty good stock pipe???
Here's what I'm looking at - I have a 75 100cc Dirt Squirt with the stock exhaust and I'm wondering if any of the stock Hodaka pipes 100CC or 125CC are a lot better breathing then what I have. I'm not talking peak HP or even racing but trail riding and I like torque. I'm putting a set of road toad wheels on it 18"/21" to make it more road toad or 100cc Wombat like. I'm thinking I'll change the sprockets and chain to 14T/58 or maybe 15/60 which are pretty close to each other or maybe a bit lower with 14/60.
I know expansion chambers are the way to go but I'm spending a lot of blood ($$) on every thing else and want to hold off on hi dollar pipes even if they are better.
On multiple occasions Harry was asked (by me) for advice on how to make the Combat Wombat engine be all it could be without changing it into something else. Meaning, what could be done to make it run better without changing it from a satisfying piston-port engine with a pretty wide power band for use on the trails . . . and on the track. The exhaust system was always a part of the discussion, and Harry said (several times) something like, "Well, you know, the Combat pipe IS a pretty good pipe." And then I did a BUNCH of testing of AHRMA Classic Class legal aftermarket pipes . . . and found only ONE pipe which was as good as a Combat Wombat pipe with a modern spark arrestor/silencer in place of the stock silencer.
Harry and I didn't talk much about the high, right side street/trail exhausts on Ace 100's, Wombats, Squirts and Toads other than to sort of agree that they pretty much met the requirement of channeling the exhaust products to the rear of the machine in a reasonably attractive and unobtrusive way. Translation? Those are NOT performance pipes. Sure, they will work fine anywhere you ride . . . but if you are seriously looking for more performance, retaining those pipes will hold you back.
IF you decide to go with an expansion chamber for improved performance, which is a pretty good "bang-for-the-buck" decision, please, please, please install a good spark arrestor/silencer. Excessively noisy motorcycles have been the bane of our existence since the at least the middle of the past century.
Thanks ED appreciate the info. I didn't remember or possibly even realize it was the Combat Wombat pipe that was the "good" one and the others were just good "serviceable pipes. Reading into that a stock 100cc Super Rat pipe practically speaking probably isn't much different then a stock 100cc Dirt Squirt or Road Toad pipe and if I want "more" I need to go to an actual expansion chamber.
The "serviceable" pipes are the high, right side, STREET/TRAIL pipes . . . a statement which purposefully does not include the Super Rat pipes (any model) or Combat or Super Combat pipes.
Ed
OK - I had to go back to the schematics to figure it out. I had a Super Rat in the early 70's which had a high right pipe. I didn't know the numerical designation at that time - it was just a Super Rat. It was the 93B model since it had a spark arrestor and silencer and I did end up running it on the street with a light kit & license - easy at that time in California. So if I did happen to find a 93B pipe it probably works better then a stock high right side pipe and might even be called a simi expansion chamber - correct???
The chrome tank Rat pipe isn't a semi-expansion chamber . . . it is clearly a "for real" expansion chamber which happened to have a factory spark arrestor silencer. And yes, it would be better performing pipe than the stock Toad "street/trail" pipe on your Road Toad.
Thanks Ed, Got it - find a model 93B pipe in good shape that still has the spark arrestor baffle in it or a model 93 pipe and get a good after market silencer/spark arrestor and mount it on the 93 pipe.
One last question(?) I suspect adding an after market silencer/arrestor to the end of the model 93 pipe would have the effect of lengthening the stinger so it might be a good idea to cut the stinger back leaving maybe 2" or so to mount the newer silencer/arrestor to. It would still be a some what longer "stinger" but might work better?? Or does it make much difference??
Try the 93B expansion chamber first, if you like it leave it as is. The smaller the stinger the pipeier it is also the longer the stinger the pipe'ier that is what I remember. Others would know. Tuning (jetting ) and the chamber make a big difference, then there is porting, reed valves, racing pistons and the carburetor . Only my thoughts. -------Clarence
RE: a Wombat 94. I'm presuming that the better and later "93b" pipes will fit this frame/engine. Providing that the exhaust port/pipe fitting is compatible. Can the screw-flange fitting of the earlier type be adapted to the later slip-fit/springs type or would a new cylinder be needed?
Just planning for future upgrades. Not planning to make a super-bike but an improved exhaust is always a "freebie" power upgrade.
Bill2001 wrote:RE: a Wombat 94. I'm presuming that the better and later "93b" pipes will fit this frame/engine. Providing that the exhaust port/pipe fitting is compatible. Can the screw-flange fitting of the earlier type be adapted to the later slip-fit/springs type or would a new cylinder be needed?
Just planning for future upgrades. Not planning to make a super-bike but an improved exhaust is always a "freebie" power upgrade.
The header pipe diameter for a 93B pipe is smaller than the 94/94A pipe header. Which also means that the exhaust port is smaller for the 93B vs the 94/94A. So the 93B pipe will not fit to a 94/94A cylinder, (read: 94A slip fit nut), although it will fit the frame.
The 94A used the slip-fit exhaust nut with springs; the 94 did not. The 94 cylinder would need the holes drilled into the cylinder fins for the springs, but the 94A slip-fit nut is the same as the nut on the 94 pipe. You can make a 94 pipe fit the 94A slip-fit nut if you cut off the flange on the 94 pipe.
If you wanted the 93B pipe to fit, you would need to replace the header pipe. Unless you had a 93B pipe with a destroyed header that needed to be replaced anyway, I think you would be better off with a custom pipe.
I thought we were talking about putting the 93 series Rat pipe on a painted tank Dirt Squirt (though I mentioned a Toad earlier . . . which is OK cuz they have the same engine and frame). Enneywayeeee, the Rat pipe will require modification to fit up to the slip fit exhaust manifold on the alloy cylinder 100's, but the head pipe itself is the proper diameter to go on a 100. Hey, wait a second, the Rat pipe is slip fit model . . . and may actually fit up to the 99/01/02 exhaust manifold - you'll have to check it out. I'm not absolutely certain that a model 93 pipe will "bolt on" to the Dirt Squirt 01 chassis - but it likely will be pretty easy to mount it up.
For the intended use, I'd say functionality issues of mounting the pipe and a modern spark arrestor/silencer outweigh concerns about stinger length. Mount the spark arrestor/silencer where it is not in the rider's way and where there are "hard points" for a good sturdy mount . . . and don't worry about stinger length. Stinger length won't be out of the "reasonable" ballpark if you do that. According to Harry, 19mm was the target stinger ID for my Combat Wombat . . . and he told me what I'm telling you about the stinger length. Proper stinger diameter for a 100 is probably a teensy bit smaller . . . but I don't have a number for you. Um, take a look at the stingers on the HT-1, HT-2 and HT-3 pipes for information . . . and note how long they are! I probably missed something in my discussions with HT, but I'm under the impression that with the "proper" stinger diameter(whatever that means) - stinger length is more a function of what is needed to get to the silencer than it is a "tuning" specification.
Ed
Thanks ED - this is what I was looking for. I just had a thought that if I couldn't find a 93B pipe with the spark arrestor/silencer already on it and I found a 93 pipe with just a stinger on it - that hanging a silencer off the end would be ungainly and have some effect on stinger length - making it much longer. But I could move the silencer on back aways, trim off some of the existing stinger leaving enough to get a good clamp on or a good mount point and it would work OK. I would think I could find a correct diameter silencer/arrestor - same as the existing stinger so there shouldn't be too much of a difference in performance gain or loss from just the stinger length.
OK - Thanks. Still trying to understand a little bit more. Is this because there isn't much of a stinger lengthening effect with a silencer because once the exhaust pulse exits the stinger and expands into the sliencer the power is already made?? And the back pressure of he spark arrestor screen isn't much. Or something like that?
The stinger length with the silencer as well as diameter ( definitely affects ) tuning . I'm not a pipe expert but have played a bit with it. Example ! My HT 3 pipe I modified per Harry Taylors recommendation by fabricating my own stinger and silencer, I divided the stinger length into 3 sections and enlarged it by 2mm at each section , the difference was very noticeable at every throttle position, I have also played with The Taylor TIT . Going back to the late 90s I was the reason the Taylor pipes came into existence when I asked Harry if he could build me a High pipe for my super combat , he said sure but he hadn't had a Hodaka for 20 years so he had nothing to proto type a pipe on , then one day he called me and said Hey I just bought a super combat so I can now build you a pipe . So the very first pipe was on the bike the he built for him self then mine was next then Paul . This was when Harry got re involved with Hodakas again. Good memories.
I found this on Wikipedia and it was a good read! Also presents some formulas for stinger size va head pipe size based on diameter. Just thought I would share it! ; D Victor
An earlier reply from rlkarren about model 94 pipes and part of the answer was the header pipe wouldn't hook up because it was too big around and fit to the wombats larger ports.
I'm wondering how the larger 125cc expansion chamber would work with the 100cc models if the header was modified to the correct size to fit the 100cc cyl. Either by replacing the entire header to the 100cc size or just by replacing the 94 connection with a smaller short model 93 piece? Given that the pipe would fit the frame and then hook up to the 100cc barrel???
