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

[boris.h]

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...

[Brendan W]

Hi Boris.
I am looking forward to reading about the progress of this project. Good luck with it.

[boris.h]

hi, thanks. I'll try to send few pics for every modification, even for the head port....

[tatu]

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

I like this!

[boris.h]

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)

[boris.h]

Here are the first pic's (last Week end)

[boris.h]

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.

[Brendan W]

What do you think was happening around the cam chain tunnel ? It looks like there was some extra sealer put on the headgasket.

[boris.h]

don't know, Maybe the old headgasket which burned...

[mattfeet]

O? habitez-vous en France? Nous avons de la famille ? Amboise.

[boris.h]

j'habite dans le sud de la France, ? c?t? du mont ventoux (carpentras, 84)

[mattfeet]

Tres bien. Je ne parles pas bien le Francais mais je jouis d'essayer. Mon femme et je voudrais visiter la prochaine.

[boris.h]

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

[Big T]

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.

[boris.h]

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