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[boris.h]79 GS 550 / 673cc project

  • Thread starter Thread starter boris.h
  • Start date Start date
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boris.h

Guest
Hi everyone!
I'm boris, from France. I spent a lot of time watching the forum, without any presentation.

I started, doing some good jobs on my historical cars (1991 Renault clio 16v --> 200hp, and original 1984 mercedes 190 2.3L 16v --> 185cv).






I did a lot of job on che clio, all was made my myself, starting on mechanical stufs until the fenix 3 job (injection).

I fell into motorbikes passion, rebuilding on old '81 BMW R65 owned to my wife's father.


We started owning a suzuki 500 gse (for my wife) and my Suzuki gs 550 E.
I rode it a lot since last year, now I'm pretty sure I need more HP, even if I love the original base, behaviour, 6 speeds transmission, etc etc.
Loving doing original things, I'm starting to get some mechanical elements to do the "GS 650 top end transformation"
- gs 750 mikunis VM 26SS
- gs 650 head
- gs 650 top end with pistons
- gsxr 750 full exhaust.

I considered putting bigger valves on the head, but I affraid this job would not be a good improvement because the gs 750 vm26 would be restrictive... So I think I will just keep the standard valves, but porting the head (I do this on all the heads I work on)
About the 750 gsxr, I got it for few ?, stainless steel, brand new, and larger tubes diameter. I want a screamer! The aim of this project is something close to "plug and play", and a lot of more HP (I wish 70)
Here is the original base (I won't modify the frame into a "cafe racer")



For the instant, the gsxr header just fit without any modification in the gs 650 head. Nice point to start...
 
Last edited:
Hi Boris.
I am looking forward to reading about the progress of this project. Good luck with it.
 
hi, thanks. I'll try to send few pics for every modification, even for the head port....
 
thanks! 1800cc, 12,5/1, 200 hp / 995Kg --> lot of fun!
I just finished to spend my time making calculus, to validate GS 650 valves diameters....
So, I can confirm now this is a waste of time getting bigger valves on a gs 550 / 650 motor. OEM valves are very well sized. The result is that OEM valves are not restrictive until 11500 rpm with the new top end and head.... 11500 is a theorical value but I can trust in these results (already made on my cars).
This is a kind of "service" I can provide if someone is interested...

Other value that is good to know between intake and exhaust valves diameter: because of evacuation in pression, a same volume does not need the same valve diameter because it's hotter and the piston "pushes" the gaz away... so a good figure to know is intake valve diameter = 1.2 x exhaust valve diameter....
If the figures are good (found on internet), gs 550 = 30mm diameter for exhaust, intake --> 36mm..... 30 x 1.2 = 36.... ok for that!
Moreover, a last quick calculus is that I really need VM26 carbs... (intake venturi = 26mm to be not restrictive for the motor) :)
 
Some news :)
The head is totally naked and is in the "bath". I wish I get it that night, totally cleaned =)
I saw inside that there is some work to do on the valve guides...

About the crap: I received yesterday, the GS 750 boots. I wanted to put VM 26 on my motor so I bought GS 750 boots. Unfortunately, even if this is the good inside diameter, the mounting holes are at the wrong place... (distance between M8 holes on my head = 62.5mm, the same distance on the boots is 10mm lower --> fail). I think I have to find some KZ 650 or GS 650 boots, to be able to put VM26 carbs.
 
j'habite dans le sud de la France, ? c?t? du mont ventoux (carpentras, 84)
 
Tres bien. Je ne parles pas bien le Francais mais je jouis d'essayer. Mon femme et je voudrais visiter la prochaine.
 
Oh, don't hesitate to come over me to visit south of France (provence, marseille, le pont du gard, etc). I also try to speak english, sorry for the mistakes...

If you want to planify smtg, My wife and I would be glad to meet you (evec sharing homes!) we can continue using PM's :)
 
Boris,

I was wondering how you were going to manage the VM 26 carbs onto that head. I was sure the port spacing was different

Why not use the 650 carbs? I believe that's what most members who have done that conversion have done.

Looks like a good project. That head looks abused, some burned valves there

And, your English is a lot better than some of the Americans here.
 
I could use the gs 650 carbs. The main issue is that I want a minimal "throat" diameter to 26mm.... To start I wanted to keep the original look (VM carbs), but I think that VM28 carbs are hard to find and very expensive, even for the VM29'
thanks a lot for your last answer :)
 
I'm pretty sure that the VM 28 and VM 29 will have the same spacing issue as the VM 26s, and ,yes they're both more expensive

I think the KZ 650 has 24 mm, but I'm not sure of the spacing
 
Yes, I think also that VM24 has the same spacing. If not, it's always possible to change the carbs frame and to put new carbs body on a frame, shaped to have the same space between them..
So, I have the choice between:
- VM22 SS (already on my gs 550) --> too small for the gs 650 /550 configuration
- VM24 SS (It may be possible) --> want to find VM26 / 28 / 29 before choosing them, so not the real good choice
- VM26 SS --> 26mm is the minimal diameter that I want to put on my new configuration. If they fit, it would be the better choice
- VM28 SS --> hard to get (and about the price)
- VM29 SS --> harder to get and to buy than the 28, than the 26....

Moreover, I like VM carbs, because they don't need a dynojet kit to tune. Needles are directly adjustables, main jets, pilot jets... and I already have a lot of VM parts (main jets, etc)
 
Just started today to port my 650 head... a lot of aluminium removed... pictures coming soon..
 
Hi everyone
just recveived today...a beautiful stainless steel 600 gsxr exhaust, that fits perfectly in the 650 head :) I'll weld wideband threads on each tube...
just also bought mikuni carbs....
inside diameter = 34mm
total lengh = 125mm
outside diameter, airbox side = 50mm....
 
boris.h said:
Hi everyone
just recveived today...a beautiful stainless steel 600 gsxr exhaust, that fits perfectly in the 650 head :) I'll weld wideband threads on each tube...
just also bought mikuni carbs....
inside diameter = 34mm
total lengh = 125mm
outside diameter, airbox side = 50mm....
Click to expand...

What year gsxr?
 
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