Day One - New Project

[hodakamax]

Hey Rich, Thanks for the info. Nothing is "set in stone" on this project. I will take a look at Bill's repro 93 pipe. Actually it's a 94A Wombat pipe 949171 whereas the Squirt pipe is 969161 if that makes a difference. The engine will be reeded but not radical with a 24mm carb. Fun so far!

Maxie

[hodakamax]

OK, the mock up is a little crude, but this is kinda what I have in mind. This appears to be able to add 4-8 + inches for a little more low end.

Maxie

[racerclam]

The Rat pipe actually makes good bottom end with a silencer clamped on , without its not as good but too loud any way. Maybe you could take the bike to Midas 8o)

Rich

[hodakamax]

Rich, what's the Midas 80?

[racerclam]

this is my smiley 8o) Not an 80 its just sideways and with a nose

Rich

[Charlie R]

Max, what about something like this?

[hodakamax]

Charlie, I really like that set up. Rick Mott also has a cool trials exhaust that I like. It appears no one likes my kinky mock-up. It's just four 90 degree bends. Can you bend that tight? (humor me!)

Max

And Rich, got it finally, a little slow on my part. DUH

[RichardMott]

My exhaust is an Ace header with a Fantic exhaust welded to it. The heat shield is an Ace. I had a butchered Ace exhaust system from Ebay. To attach the shield, I ground off the nut plates and had the welder re-attach them to the Fantic chamber. The tip has a piece of rubber radiator hose clamped to it. It is fairly quiet.

[hodakamax]

Ah, thanks Rick, I've been trying to find a picture of that.

Max

[RichardMott]

Here is a more up to date photo at a different perspective.

[racerclam]

This is the trials bike I had built as well as the pipe
Rich

[racerclam]

sorry the pic isnt a close up of the pipe though

Rich

[racerclam]

I experimented wit it a bit , first with just a straight pipe then I added a slight bulge to it after the head pipe which worked good then I added a Taylor tit to it that is the same diameter as the rest of the pipe about 5 inches long and it goes under the carb that too was a plus

Rich

[hodakamax]

Lots of innovations on that machine--I'm liken' it!

Max

[Charlie R]

Max, I use 180 degree U bends then cut and weld them together. So the long answer is yes What head pipe diameter are you using? And for the record, I have no idea what the pipe I pictured fits. It does however bolt on directly to the 100 by way of an exhaust nut, just like the Ace 100 pipe. Easy Peasy! Anybody familiar with this pipe?

[hodakamax]

Charlie, the 939192 exhaust nut is on a 93 cylinder and has the dimensions of 1.520" ID and the inner collar is 1.375" OD. It looks like 1.5" pipe coming out of the nut. Where it would graft into the 94A pipe is about 1.55" OD. I must admit I have no knowledge of pipe sizes or wall thicknesses available. Is this making any sense?

Max

[Charlie R]

Absolutely Max, perfect sense. I'll check my U bend stock and see if I have any 1 1/2". I wish I knew what that pipe came off of, I'm gonna try it and see how it works and report back.

A quick tutorial for anyone who cares...... Tube is measured by OD. Pipe is measured by ID.

Also if you could post a side view of your mock up pipe that would help me with reference.

[Zyx]

Is there a reason why no one simply designs an expansion system for their trials bikes? The math isn't all that hard. Cutting and pasting shows that the engines are fairly tolerant of design differences, but rather than guess at the result, just make one that works for your displacement and power band.

[hodakamax]

Good question AZ, I too have thought about that. Maybe it's because expansion chambers aren't very effective at low RPMs. Certainly something to consider. You are retired and clever, can you draw us up a prototype to at see what it might look like? Might be interesting. My assignment for the day is to paint the deck or I'd help.

Maxie

[hodakamax]

Charlie, here's a few more shots. It's flexible (so to speak) as long as we can get it all in there.

Max

PS-- the first bend down from the muffler is a 90 even though it doesn't look to be. A little flexing and the're all four 90s. The shot on the earlier post shows it a little better.

[JayLael]

The idea of an expansion chamber on a trials bike is not new. Beta produced these bikes in 1984, and was considered , "way ahead of it's time". Now in present day the idea seems to have been mostly scrapped. Most modern bikes use a two or three stage glass pack. Power band hits are not conducive to good smooth trials riding. I think the Wombat pipe will work great with that header on it. Otherwise buy a center section for a Montesa cota 348, or Bultaco sherpa t/alpina, repack it, and build your trials exhaust based on the glass pack design. They work way better than an expansion chamber ever will, (unless you are planning to race your trials bike). BTW 1 1/2 inch header pipe is the correct size for a 125 for sure. 100s and 90s are smaller.

[racerclam]

Harry Taylor was in favor if an expansion chamber in a trials bike but obviously it mut be desighned correctly.Im no trials expert but the pipe I built on mine with three steps each time I added volume by the bulge on the head pipe ot the Taylor tit made a better working pipe , the volume change was minimal and provided for some expansion of exaust . It definatly did not make pipey just torquey

Rich

[BrianZ]

Max, I use 180 degree U bends then cut and weld them together. So the long answer is yes What head pipe diameter are you using? And for the record, I have no idea what the pipe I pictured fits. It does however bolt on directly to the 100 by way of an exhaust nut, just like the Ace 100 pipe. Easy Peasy! Anybody familiar with this pipe?

I think the pipe in the picture is from a Chaparral.



Chaparral used Fuji motors, so the pipe flange would have been similar, if not identical.

Brian

[hodakamax]

OK Charlie, I had to get my wife to shoot this--not enough hands. This is a much better shot.

Max

[hodakamax]

My wife Eweleen is quite a fab person. I asked her about an hour ago if she could shorten this pipe. "Sure," she said. Check it out!

Maxie

PS--Actually she has taken out about the same amount as I have added to the header pipe, about 8 inches for a same overall length--Whatever that's worth.