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The First Pics Of The New Project


jaylael
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Is that a cardboard gas tank? Don't think it will hold up too long. HAHAHHAHAHAHAHAHAH

That exhaust looks very well done. But somewhat curious why you chose to go to the opposite side and then back over the top of the engine. To protect the header maybe?

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I routed the exhaust that way to get longer header pipe, which ought to improve the low end. Otherwise it would be allot shorter. I have no data to back it up, but the old story goes that more header pipe volume improves low end. Truth be told I think it just looks more trialsy, and it helps to fill in some of the visual voids in the front. Yes the cardboard tank should be all the rage next season. :banana2:

The front fender just touches the subframe on full compression. I have allready pushed the forks down in the clamps to flush, and ground the front corners off the alloy subframe and it still just touches the fender. I have decided to lower the front fender about 1/2 inch closer to the front tire, which is just enough to get it to stop contacting alltogether. Since the engine is just plain longer than the original one, this is a minor problem which is not easy to resolve any other way.

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  • 2 weeks later...

From one old mech. to another ; I think it's beutiful !!!! And if your interested my brother out in Baker City , OR. still has the beta zero that was given to me , might make a interesting project , or scrap metal.!!! you should contact him ,he's got a late model gasgas and is Quite the gifted custom painter .(when he's in the mood ...)(he was also the kid in cycleworld mag , fullpage colorshot of the world round in rhode island ,back in ?76? I think . And he can probly still ride better than me !)

And Jay I have to ask , as I'm a 33 yrs exp. ASE dual master w/a masters in mech.eng. toboot ; and I currently twist a wrench at a saturn dealer . How do you put up with the very young , gravy only parts changers ?????????? It hurts me sometimes to think that our trade is becoming a lost art ... (and I always heard that a small long intake helps low end too , till you start to loose throttle response !)

Glenn :mellow:

And the cardboard ROCKS !!!!

Edited by axulsuv
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Glenn: Send me your cousins contact info. I'm a fool for old trials bikes, but a bit on the poor side these days.

Rhode island world round was in 1975. He rode in it? I'd love to see that picture! How'd he do? I rode the one in 1977 at Port Huron Michigan, and attended the one in 1976 at Goldbar, washington. I was so impressed with Martin Lampkin. He stood out as a solid rider and a standup guy. Still is I'm certain. He was so personable and friendly. Acted as though we were old friends from the start. And man he could ride.

I hope to use a shorter inlet tract between the carb and reed, and reed to cyl. should be short as possible. The long intake is supposed to increase top end. Should be going forward with the job this weekend. Took time out to go ride in a trials at the weekend last sunday. Managed to squeak past our lad Ishy which is a rare and wonderful thing for me.

As far as the auto repair business I find that really good techs who truly understand how things work are hard to find. As automobile technology becomes increasingly complex, the challenges we face become greater every year. The guys I work with benefit from my insight regularly. I try to "teach a man to fish" rather than "give a man a fish" but they just want the fish, over and over again. I never refuse, but it hurts my heart to see it.

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Jay ; your right , the intake thing works on small bore 4t's , not reedvalved 2t's !... And it's my big brother , not my cousin and if I remember correctly? , he missed the same section on every loop , but other than that did quite well for a 15 or 16 yearold kid ! I'll check if he still has the zero sitting in his garage , I still owe him gas money for going to pick it up ... (I'll cover that ). But if I remember again , it's missing some crucial cooling components ? (radiator) but I was told it ran when parked ... And if you want it just head out that way and get it . I'll pm you with the details . I just can't bear to see a sport changing bike go comepletly to waste... and the zero was a turning point for trials bikes (I THINK). And one last note , have you contacted B&J racing for hopup parts for your hodie engine ? (flywheel weights , etc.) great guys and better service! And there always waiting to be fed ! never mind going out and catching it !!!

Glenn

Edited by axulsuv
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Guest majestyman340
Some purists might be outraged by such a project. Normally I too find engine swaps to be a distasteful subject, but... after several years trying to keep from doing this, I just came home from work one day and started in on it. I guess the winter weather has effected my judgement.

The front subframe has been welded together out of alloy strap material from the hardware store, and short chunks of renthall handlebar. It's very satisfying to be able to make something like that, finally having a tig welder to play with.

The project has a long way to go, but should prove to be a fun ride and a great conversation starter. Also perhaps a handy excuse for lackluster finishes in modern events. :rotfl:

Looks an interesting project, and I wonder if the original motor meant the s/a spindle mounted through the back of the engine cases?

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Yes. The original engine has a cast lug for the swingarm bolt to pass through. At one point I had envisioned just building a mount/adapter to theHodaka engine which did the same thing, but Idecided I could achieve more strength and rigidity with the mount welded solid to the frame like a Hodaka. I suppose this thing is strong enough the front downtube arrangement could be taken off without any ill effects. Tempting, but then it weighs almost nothing, and adds that extra assurance the frame is not going to bend upward.

Glenn, The 1990 Beta Zero is a ground breaking bike for sure. I liked my 1991 Zero very much back in 1994.

Bob Ginder is a really neat guy and his products and service are first rate, but... I am involved with the development, manufacture and sale of Hodaka related trials parts in my own right. Our flywheel weights are available at www.hodaka-parts.com

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Guest majestyman340
Yes. The original engine has a cast lug for the swingarm bolt to pass through. At one point I had envisioned just building a mount/adapter to theHodaka engine which did the same thing, but Idecided I could achieve more strength and rigidity with the mount welded solid to the frame like a Hodaka. I suppose this thing is strong enough the front downtube arrangement could be taken off without any ill effects. Tempting, but then it weighs almost nothing, and adds that extra assurance the frame is not going to bend upward.

Glenn, The 1990 Beta Zero is a ground breaking bike for sure. I liked my 1991 Zero very much back in 1994.

Bob Ginder is a really neat guy and his products and service are first rate, but... I am involved with the development, manufacture and sale of Hodaka related trials parts in my own right. Our flywheel weights are available at www.hodaka-parts.com

Worth making sure your gearbox sprocket is as close to s/a pivot point as possible, as the further it is away the more difference suspension movement is going to have on chain tension, which in turn is going to alter how well the finished bike is likely to grip in slippery conditions.

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"I have no data to back it up, but the old story goes that more header pipe volume improves low end. "

"I hope to use a shorter inlet tract between the carb and reed, and reed to cyl. should be short as possible. The long intake is supposed to increase top end. "

I've usually found that a slightly smaller diameter initial headpipe (less volume but different pressure/pulse/velocity pattern) tends to help bottom end, but this is a one-off project and as mentioned before, theory can be displaced by reality. The computer programs I use for exhaust development are only a tool that incorporates a baseline theory to get one "in the ballpark" and helps with the math, but a good ole cheap stopwatch is the final answer to if it really works or not.

I wouldn't worry too much about the carb mount at this time. The intake tract on a Trials two stroke is a balancing act in a way in that a relative slightly longer tract will tend to help bottom end but a smaller volume in the crank area (which in a non-reed valve engine includes the whole intake tract) tends to also help bottom end by raising the "primary compression ratio" (ratio of the crankcase volume to swept displacement, which affects pumping pressures through the intake ports). The ratio of the combustion chamber volume at TDC to swept displacement (generally "corrected" by measurement from the top of the exhaust port) is actually the "secondary" compression ratio in a two-stroke.

I think what all my psuedo-intellectual blah-blah means is that on a one-off project you need to essentially design and fabricate to fit and it can always be "adjusted" later if need be, as it usually does. I love to see people do projects like this, it's kinda like "rolling art" in a way and it's always interesting to see how they've solved the problems that normally come up in a frame/engine swap. I'll be following it's progress and very interested to see how the test rides turn out!

Cheers

Jon

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Thanks for the positive feedback. It is appreciated.

I have built and ridden three similar vintage machines previously which have given me a fair bit of good test data as far as engine performance. As time goes on I intend to play around with different pipe and carb configurations some more. The Sherdaka is going to get a dellorto 26mm carb for example. You are right about smaller diameter header pipe improving low speed resonse. (I think that's what you said) as the reality of prior tests have bourne this out as fact. I refer to the difference between response at near tickover, and "low end" which is really an innaccurate term, very hard to quantify. I'm not sure I even know what that means in reality.

I have tested several different cyl. heads, and cylinders over time and definitely feel as if I am getting the best combinations narrowed down. I have been very pleased with the iron model 94 wombat cyl and the amal mk 2 carb with the old Gem reed valve, and an O3 cylinder head with no head gasket and anaerobic sealer used in place of a head gasket, applied sparingly. The silver paint thing did not work well for me, developing a combustion leak over time. (Yes the surfaces were flat lapped and torqued to 18 ft lbs.) With this combination the orange and green "Tree-Frog" runs really good and the compromise is just about right. It has schnurle loop scavenging accomplished by ports hand cut by me in the cyl running up from the intake passages to the transfer port height so they all pop open at the same time.

The Green bike with the black frame is Tree-Frog type 2. It uses an aluminum cyl and head directly off an O3 Wombat with no significant mods. This also runs just amazingly well as it is. This is the same basic engine which will be used in the Type 4 or "Sherdaka".

In case anyone is not familiar with them I shall post photos of these prior efforts. I can allready hear Andy thinking, "Dear God, No!" :rotfl:

Anyway I had a brain fart ewhen I ordered inch and three quarter exhaust tube which was technically the wrong size. Once it was bought and paid for I decided to go ahead and use it. You will note there has been in prior efforts, a two inch, two 1 1/2" and now two header pipes made from 1 3/4" tube. The smaller diameter ones seem to be snappier off the bottom and really work nice at tickover roll on. Seem as if bigger carb and bigger pipe both give it more top end at the expense of this sweet chugging torque at slightly off idle. The bigger ones will cause a bog or flame out on snap throttle under load. Any road I guess I've rambled on enough for now.

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Edited by JayLael
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Worth making sure your gearbox sprocket is as close to s/a pivot point as possible, as the further it is away the more difference suspension movement is going to have on chain tension, which in turn is going to alter how well the finished bike is likely to grip in slippery conditions.

I agree. Good advice for sure. The engine is jacked back as far as it can go.

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