Topic: Speed Pony - 550 race bike recreation

[Tintop]

  That swingarm is interesting.  So it links up to the shock behind the steering head?  Don't think I've ever seen that before.

The single long laydown shock design came from Yamaha's motocross bikes, and was transplanted to the TZ 250/350.  Later it was part of the 700 / 750 design.  You can see the big motocross reservoir at the back (just behind tank) in one of the pictures.  Although Speed Pony's frame was built in 73 (with this one), it was assembled in 78, and used a TZ750 shock.

[fastbroshi]

I wouldn't exactly call it 'concourse' condition.  It does look as bit worse than it probably is.  Seems they decided to clean it up for the pictures, and power washed it with a steam genny.  Clean it up alright, peeled off most of the paint, and then it flash rusted.

I'm seeing a vision - another niche of bike.  Broken spokes, number plaques, crap paint, crap slicks, a hacked off ducktail 750 seat....it's a Rat Racer.  Getting lapped is cool.   

[bwaller]

I wouldn't exactly call it 'concourse' condition.  It does look as bit worse than it probably is.  Seems they decided to clean it up for the pictures, and power washed it with a steam genny.  Clean it up alright, peeled off most of the paint, and then it flash rusted.

I'm seeing a vision - another niche of bike.  Broken spokes, number plaques, crap paint, crap slicks, a hacked off ducktail 750 seat....it's a Rat Racer.  Getting lapped is cool.   

 

[fastbroshi]

I kid, I kid!!  I know he's going to totally redo it, but it's comical thinking of racing it like it is.

[bwaller]

I quess I'm a little tired. 

[Ecosse]

I kid, I kid!!  I know he's going to totally redo it, but it's comical thinking of racing it like it is.

i really would not be surprised if 'rat racer' became the next fad. maybe it is already... i'm so un-hip.

 

[Syscrush]

What's the status, man?

[Tintop]

What's the status, man?

Unfortunately it looks like the owner wants to put an H2 in the Mieklejohn frame.   Hasn't actually said no, but....

So this weekend I plan to strip the 750.  This is what Denis used, when he built the 1st one.  When he will be able to fit it into his build schedule I not sure, but think mine should be done by Xmas.  I'm going to be getting a really big stocking.

[Syscrush]

I can't believe I'm just noticing this now, but that frame seems to have a TON of rake!  I am surprised to see geometry that conservative on a purpose-built race frame.

[Tintop]

I can't believe I'm just noticing this now, but that frame seems to have a TON of rake!  I am surprised to see geometry that conservative on a purpose-built race frame.

Actually it is slightly steeper than a 750.  Head is @ 25 degrees (750 is 26 I think), and used a 750 based front end, with an WM3 18" rim.

[Syscrush]

Actually it is slightly steeper than a 750.  Head is @ 25 degrees (750 is 26 I think), and used a 750 based front end, with an WM3 18" rim.

25?  Wow, it looked like more than that to me.  Trick of the eye, I guess.

I don't know, I just did a really ghetto geometric analysis in MS Paint, and to me it looks like it's at 25 degrees as it sits with the rear on a stand.  It looks like the rear wheel is at least 1.5" in the air, which would suggest that when it's on level ground that bike would have almost 27 degrees of rake.

Is it just the angle of the photo?  Or is the bike set up with a lot more sag on the front than the rear so it settles into a more nose-down position?

[Tintop]

Got down to the shop this weekend, and started stripping down the 73 750.  Just need to remove the rear wheel, and the oil filter to get the engine out.  I'm thinking of calling this version a 'Woodie Hard Tail'.



We put the empty 750 engine on a table with a TZ750 frame.  Looks like it only needs to be about 1 to 2 inches deeper, and with slightly steeper down tubes for the engine to go in.   However, I want to make sure there is enough room to remove the top end, without removing the engine.




Next step is to get the 73 frame de-greased, and then put it on the frame table to locate pickup points, and swing arm pivot.

By the way, in the background of the 2nd photo, is a KR/H2R frame kit headed to OZ.  Those are original rims on it.   Same guy is also getting a TZ750 kit.

[Retro Rocket]

Hi Mate, in the second photo with the TZ frame, why not keep it compact and use no bottom frame rails.? Make the engine a stressed member of the frame, then it is easy to drop the engine for work and even lighter.....

Mick

[bwaller]

Now the fun part huh T-top?

Make sure there is room for the phantom filter box. 

I like the engine out the bottom idea too rr.

[Retro Rocket]

Now the fun part huh T-top?

Make sure there is room for the phantom filter box. 

I like the engine out the bottom idea too rr.

Yep, looking at that pic again, i think it would highly possible to build a very compact little bike......

Mick

[Tintop]

Hi Mate, in the second photo with the TZ frame, why not keep it compact and use no bottom frame rails.? Make the engine a stressed member of the frame, then it is easy to drop the engine for work and even lighter.....
Mick

Now the fun part huh T-top?
Make sure there is room for the phantom filter box. 
I like the engine out the bottom idea too rr.

Funny you both should say that.  When I was speaking with Denis this weekend, one of the subjects was the Foale frames.  His main criticism was that he had persisted in using engines as stressed members that were never designed for the loads.  There was supposedly enough room in the Mieklejohn frame to remove the head.  I would imagine though that removal of the laydown shock would be required 1st.

[Retro Rocket]

In Mec's thread about his egli replica race bike, it has the engine as a stressed member and it works just fine, he undoes the front mounts and the engine swings down and forward for ease of maintenance....Scroll down and have a look at the egli frame pic......

http://forums.sohc4.net/index.php?topic=44736.0

This link shows the engine swung down for maintenence....

http://forums.sohc4.net/index.php?topic=44736.175

Mick

[Tintop]

In Mec's thread about his egli replica race bike, it has the engine as a stressed member and it works just fine, he undoes the front mounts and the engine swings down and forward for ease of maintenance....Scroll down and have a look at the egli frame pic......
http://forums.sohc4.net/index.php?topic=44736.0
This link shows the engine swung down for maintenence....
http://forums.sohc4.net/index.php?topic=44736.175
Mick

This has all the makings of a 'stressed / unstressed' version of an oil thread Mick.   It's not relevant to the project, as it is a replica that used a full loop.  But if you want to start a new thread.

That said, I would think being able to sevice the top end in the frame is a better 'race track' solution than having to drop it, before you start work.  Also the benefits of the additional ~3' of 1 1/8" CroMo to frame rigidity & handling, out way any very small weight penalty.

[Syscrush]

This has all the makings of a 'stressed / unstressed' version of an oil thread Mick.   It's not relevant to the project, as it is a replica that used a full loop.  But if you want to start a new thread.

That said, I would think being able to sevice the top end in the frame is a better 'race track' solution than having to drop it, before you start work.  Also the benefits of the additional ~3' of 1 1/8" CroMo to frame rigidity & handling, out way any very small weight penalty.

I'm sure that everyone in this thread has bought something cool or built something custom and had to respond to the wannabes saying stuff like "An SV, eh?  If I got a bike, I'd go for a 'Busa!", or "Looks great, but why'd you put that weird tail on there?", or "that points cover clashes with that remote filter mount."

My standard response is along the lines of "Well, when you build a bike you can do whatever you want with it." 

[Retro Rocket]

This has all the makings of a 'stressed / unstressed' version of an oil thread Mick. Wink Smiley

Not at all bud, just saying that there were a pile of frame manufacturers including Egli that successfully raced these bikes with no bottom tubes all using 750/4 engines, it was relevant to the discussion an in no way argumentative. I liked the compact nature of that TZ frame...

Mick

[Tintop]

The Egli and its kin are designs from the 50's, this frame is early 70's (with some improvements).  If running the 750 as a stressed frame member was problem free, do you not think Honda, in all the years they raced it, wouldn't have made at least one. You always hear about the success's, not the failures.

I think a 550 might just slide right into that TZ750 frame though Mick.

[Retro Rocket]

The Egli and its kin are designs from the 50's, this frame is early 70's (with some improvements).  If running the 750 as a stressed frame member was problem free, do you not think Honda, in all the years they raced it, wouldn't have made at least one. You always hear about the success's, not the failures.

I think a 550 might just slide right into that TZ750 frame though Mick.

Sorry mate but i have to solidly disagree with you on that, there have been and still are lots of frames that support the 750 as a stressed member and i assumed with the knowledge you are gathering about after market frames for the Honda's that you would know this. Don't let the fellow that told you that it "can't" support a 750 engine, influence what is being said here. Seriously mate i have known about these stressed member frames for 30 years + in a racing environment and have read thousands of articles on them and not once have i ever heard of a structural engine failure for this type of frame. There are a lot of titles and races won by bikes in this format as well. I am not trying to argue with you mate but currently there are a couple of our Euro members successful racing these as well and they are NOT 50's technology, like anything they have evolved. Mec's frame was completely made by himself and it is a 1000cc masterpiece.
You can go back and tell your mate that he is completely wrong with his assumption and should maybe look into something and not simply assume that because the engine is sitting in a cradle that it can't be used otherwise. Keep an open mind mate, thats how we get progresses in technology, not by being dismissive.   Now back to the frames you have.....You lucky bastard....

Mick

[Tintop]

Just to set the record straight Mick.   I used the word 'design', not 'technology', they are not the same thing.  The Egli frame was designed in the 50's.  There have been many recreations / replicas / variations in the 50 years since.  Each one without doubt, incorporated the most current 'technology' available at the time.  MEC's frame is no different in that respect.  I'm also sure we both wish we had his skills, and shop.

Re my builder having 'assumptions'.  It's not like using the engine as a stressed member is something he can't, or won't do.  Probably his best known one is Jay Leno's Vincent Spl., built in the 70's.  There are 2 Vincent Specials being built now, with mono shock suspensions. A Martin (I think, but will check for you ) just came in to be reproduced.  If I want to build a Martin 750 replica next, well I do have an extra engine, and Denis is right next door.

...Now back to the frames you have.....You lucky bastard....
Mick

After that brief, interlude I will continue with a description of the changes to the TZ frame to create Speed Pony's frame.

The engine will have to drop slightly ( to allow for cam cover & carb clearence, to the mono shock.  This should also create most of the space needed for 750 head work.  At the same time the swing arm pivot will be lower, and the front tubes move forward.  As you can see in one of the Speed Pony photo's the down tubes have a bend to clear the exhaust ports.  Next up getting the 73 750 frame on the table, and establishing the major points.

[Syscrush]

and Denis is right next door.

On one hand I wanna come hang out with you & D sometime and buy you guys some beers.

On the other hand, I'd never escape without putting down a fat deposit on a nice custom frame!  Think Denis wants the distinction of having a hand in the world's lightest street-legal a/o-cooled Suzuki I4 bike? 

[Tintop]

and Denis is right next door.

On one hand I wanna come hang out with you & D sometime and buy you guys some beers.

On the other hand, I'd never escape without putting down a fat deposit on a nice custom frame!  Think Denis wants the distinction of having a hand in the world's lightest street-legal a/o-cooled Suzuki I4 bike? 

How about a TZ750 style frame with a Water Buffalo, there are 3 engines sitting there.