550/650 upgrade/conversion

[Guest]

Hey there everyone. I’m having a difficult time using the search feature to find a good thread with instructions to modify/upgrade/convert my ‘78 550 to a 650 top end.
I know there’s got to be something in this forum or out on the ol’ interwebs, but I cannot find anything really good.

Can anyone send me a link, please?

I need to know how to go about it. I’ve got my 550 engine completely split and tore down, so I figured since I’m rebuilding from scratch, I might as well upgrade to keep up with my buddies.

Thanks in advance!

[Nessism]

https://www.thegsresources.com/_forum/showthread.php?84029-Suzuki-GS-6-550-Yes-672-block-and-pistons-on-a-550-cases

https://www.thegsresources.com/_forum/showthread.php?201268-GS550-to-650-cylinders-questions-compression-heads-vm-vs-bs

An old member here named Suzuki_Don made an epic thread detailing his conversion. Unfortunately, I can't find it. If you did around in the archives long enough it should show up though.

[Nessism]

Ah, try searching on "Suzuki_Don". There are tons of hits specific to the 550/650 conversion.

Good luck

[Guest]

Awesome! Thanks guys!

[salty_monk]

Good luck! The 650 is supposed to be a great match of power & weight so I imagine it will only be better in the 550

[Guest]

So I searched for Suzuki_Don and it looks like he only has 1 post. Been a member since 2019. Is there another Suzuki_Don?

[Nessism]

Type "Suzuki_Don" in the search field and hit enter. His old login expired and the new user with the same name is not linked to his old account.

[salty_monk]

Yeah it's a bummer that the names time out here... I think that should just be taken permanently...

[xkaes]

This may or may not help.

In the 1978 version of the Clymer GS550 manual, Chapter 11 deals with Performance Improvement. It discusses, and shows, increasing the displacement to 590cc or 740cc.

I haven't gone down that road, but the chapter did help me improve my front shocks!

[Guest]

I've not long done mine, and it's all on my blog with pictures etc.

Here's a link to the first post where I strip it, there's a few posts related. Oh, and the difference is phenomenal. This bike is so torquey now and goes anywhere in top gear!

https://biketech7.blogspot.com/2020/06/suzuki-gs550e-673-conversion.html

[Guest]

What an amazing write-up! Thank you for taking the time to put this out there for peeps like us who are trying to do the same! I picked up a donor 650G, and just got it running. Want to make sure it’s a suitable donor before ripping it apart.
I’ll be referring to your blog regularly as I continue my journey through this project! Thanks!!

[Guest]

Thank you for the compliment!

[Chuck78]

Basically you just need a custom thicker base gasket or head 650 gasket,
Use only GS550 or GS650E cam sprockets, 650G cam sprockets are not compatible with the chain drive cranks,
& you need to clearance the cases for the 650 cylinder sleeves to fit.
I built one but the engine is sitting on the bench as the wife had 3 other bike projects she wanted done 1st, and the 550 is still 548cc...
550 carb jetting obviously is a bit off for what the 673cc GS650 top end needs

[Chuck78]

FYI look at the 650 frame (or 450, 750, 850, 1000, 1100) & weld on some frame spine bracing that those havebut the 400/425 & 550 are lacking, it'll make it handle way better. The braces behind the ignition coils.

[Chuck78]

Suzuki_Don's build thread is difficult to search for also because the title is not for a build thread themed topic, it's the troubleshooting/aftermath of his first 550/673 build attempt where he was trying to troubleshoot a knocking noise... That ended with the discovery that the deck heights were somehow slightly different, and the hybrid build required him to custom cut a base gasket out of thicker than stock gasket material in order to not have the pistons smacking lightly against the head...