Topic: Mono Shock conversion mock-up

[TexasTwister250]

What do you think?  Should I remove or Move the down tubes from the old shock mounts? 

[babyfood1217]

I say leave it, looks good as is.  Perhaps move this to the project thread.  I'd indulge more with questions and comments, but I'm not sure this is the right thread...

[bluesmoke69]

Nice looking bike!!

[Terry in Australia]

Looks good mate, mono-shocking is a good mod, I presume you've worked out where you're going to re-locate the oil tank and electrics.

Just be careful using the stock triple trees with those shorter forks and smaller front wheel though, the guy who built my bike initially used the standard FZR1000 triples and the rake was so steep that the front end tended to "tuck under" in tight corners and tried to throw him off.

He fixed it by machining up new triples using the original CB750 rake and trail. Cheers, Terry.

 

   

[TexasTwister250]

Looks good mate, mono-shocking is a good mod, I presume you've worked out where you're going to re-locate the oil tank and electrics.

Just be careful using the stock triple trees with those shorter forks and smaller front wheel though, the guy who built my bike initially used the standard FZR1000 triples and the rake was so steep that the front end tended to "tuck under" in tight corners and tried to throw him off.

He fixed it by machining up new triples using the original CB750 rake and trail. Cheers, Terry.

 

   

Yes the rake is a bit steeper with the GSXR triples and forks.  If the steering is too quick I will have a set of custom triples built to change it but I'm hoping that it will be ok.  Since this is initially going to be a track bike the electrics should just be a small battery and the starter solenoid.  For the oil tank I'm thinking of using a small radiator as a large oil cooler with enough capacity to eliminate the oil tank.  I'm researching for the right size radiator/oil cooler.  Has anyone tried that before?

PS - Beautiful bike and seamless double disk conversion!

[babyfood1217]

Hey Twister,

After searching through a number of threads I think I realized why I really like your monoshock.  Modern bikes, have the monoshocks as part of the intended design, look great with all the open space between the rear wheel and frame.  hacking off the rear triangle and modding/fabbing a new one looks ok on these bikes if done right, but I think it is a bit harder.  They way you've done it keeps a lot of the classic lines of the complete frame.  That's why I like it (stayed up way to late last night searching this forum for all the box swingarm, monoshock, and frame-mod thread I could stand to look at... got my mind racing )

Also in the search, I happened to come across your initial build thread where it talked about the box swingarm and all the work you put into it.  Holy thought out batman!  That's a lot of work.  Looks great though.

In my quest for a monoshock, I came across this guys website.  I imagine he's on this forum somewhere, but anyhoo...

http://denoonsp.com/bimota-7.htm

At the bottom of his Bimota project page, he does side-by-side comparisons of a number swingarms.  I know your SA is already done, just wanted to share

[754]

 Cut it off at tank and by the swingarm, and build mounts to take subframe..
Now you have Huge choices with what you can do with the back part of the bike..

[TexasTwister250]

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Hey Twister,

After searching through a number of threads I think I realized why I really like your monoshock.  Modern bikes, have the monoshocks as part of the intended design, look great with all the open space between the rear wheel and frame.  hacking off the rear triangle and modding/fabbing a new one looks ok on these bikes if done right, but I think it is a bit harder.  They way you've done it keeps a lot of the classic lines of the complete frame.  That's why I like it (stayed up way to late last night searching this forum for all the box swingarm, monoshock, and frame-mod thread I could stand to look at... got my mind racing )

Also in the search, I happened to come across your initial build thread where it talked about the box swingarm and all the work you put into it.  Holy thought out batman!  That's a lot of work.  Looks great though.

In my quest for a monoshock, I came across this guys website.  I imagine he's on this forum somewhere, but anyhoo...

http://denoonsp.com/bimota-7.htm

At the bottom of his Bimota project page, he does side-by-side comparisons of a number swingarms.  I know your SA is already done, just wanted to share

.

Wow, he really put alot of work into his analysis.  Great website thanks for sharing.  I'm anxious to ride mine and find out how it handles.  I suspect I will have to strengthen the frame, I have some ideas on how to improve the torsional rigidity if needed, but wanted to ride it first to just see how it does.  I still have to sort out if I can use a small radiator in place of the oil tank.  Thanks for taking the time to give the great feedback.

[turboguzzi]

couldnt quite understand if you have a linkage there,

in case you do, this is the tool i used to modify the linkage in my GPZ750 race bike

http://www.idbcorp.com/jay/suspension/susprate.html

a bit tricky to set up/configure, but very accurate

that said, i am one of those who cant really understand the point of those suspensions mods in a vintage bike....

but here in hipo we accept all kind of weirdness with open arms

[TexasTwister250]

[quote ... i am one of those who cant really understand the point of those suspensions mods in a vintage bike....

but here in hipo we accept all kind of weirdness with open arms

[/quote]

I can definitely understand preferring restoration instead of modification.  My only goal is to give the CB750 modern handling and feel, my secret hope is that when I use it for trackdays that I can compete with modern 600's in the intermediate class.  But that may not be possible with the frame limitations of these old bikes.  If nothing else in the end it will be a cool looking old air cooled cafe racer that reflects my personalty and taste.

[turboguzzi]

mine is hardly restored, we're in hipo after all ....all racing oriented mods, just done in the spirit of the period.

I think its the wrong approach to try going against modern 600's,

 in our last race we had a modern 600 race inserted in the program and they were running 1:16's compared to 1:24's for the top vintage 750's, 1:20's for the top vintage 1100 open classers, (without modern suspension mods like yours). dont think that your mods will buy you those 8-4 seconds. 

regardless of what i think, enjoy what you are doing, there are good skills behind those mods


 

 

[TexasTwister250]

Finally got the bike running after 2 years...

[FrankenFrankenstuff]

I.love.that.bike. Please make a video.

[BLUE71TURBO]

  It need's a turbocharger !        Yes it's a great looking motorcycle.   

[FrankenFrankenstuff]

Only thing that bike needs is my butt firmly planted at the controls.

[Sam Green Racing]

What do you think?  Should I remove or Move the down tubes from the old shock mounts? 

I think you only left it on to have an excuse to post a picture so we could all say WOW

WOW....WOW....WOW... and for the last picture... DOUBLE WOW,  he's got a pair.

Sam.

[Retro Rocket]

Whilst i like what you are doing here your bike will never handle like a modern bike. Lots of differences, for a start, the position of the steering head in relation to the swingarm pivot is a critical measurement in modern motorcycle geometry, for 2, you look like you are using the triple clamps that came with the forks, less offset = more trail, slowing down steering and can induce a feeling like the front is trying to tuck under, you also have a longer swingarm which will also slow down steering so as it sits, it will be more stable in a straight line but harder to throw into corners....  Looks cool though....

[TexasTwister250]

Wrong, wrong, and wrong.  Thanks for not giving anymore advice.

[ivanhoew]

lovely bike and conversion , does it keep up with the 600's now TT ?

[Retro Rocket]

Wrong, wrong, and wrong.  Thanks for not giving anymore advice.

Why so rude, might i remind you that you are in the High Performance section of the forum, so expect technical advice....

I would love to hear your explanation with some relevant information..?

Everything i said is correct,  smaller offset on the triple clamps {GSXR =35mm, stock K model 750 = 60mm} gives you more trail which slows steering input and can make the bike feel like its falling or tucking under going into a corner, lengthening the swingarm  slows down the way the bike steers into the corner,  some racers add about an inch to the rear as the arm is a bit short  but any more and it is detrimental to good handling. The correlation between the steering head and swing arm pivot is critical for a good handling bike, just compare the measurements of the stock Honda to any newer sport bike and you'll see what i am saying straight away, very different. Terry already touched on the triple clamp problems, i'm just adding detail. Remember, you are the one that wanted "modern handling". This subject has been gone over dozens of times on this forum before yours, so i suspect other will chime in with similar information. By the way, I have 3 750 bikes, two K's, one F, two with GSXR 1100K 43mm  forks, one with period correct Cerianni's {when Terry sends them back  } and one with a GSXR1100J swingarm, modified to suit { twin shock}, I am having 55mm offset triple clamps custom made to keep my trail exactly where i want it, {slighty more than stock}  do you think i just made all that up ?

There are some great books on frame geometry and suspension set up, look up Tony Faole and have a read..

http://www.tonyfoale.com/

[FrankenFrankenstuff]

[Terry in Australia]

Pass that popcorn Joe, or I'll punch you in the dickhole!