GS550/673cc head swap newbie help

[Crissy]

Greetings from Denver,Colorado I just picked up a suzuki gs550 on Craigslist I don't know much about these engines but I come to find the bottom end is a 550 with a 673cc head swap. It did come with a new pair of aftermarket coils and electric timing plate. New stator. It does not have the carbs or boots so I want to know all the mods that I need to have for this bike to run efficiently. For example what exhaust will I need. What carbs, jet kit and boots will I need. I appreciate the help and advice in advance

 

[Steve]

Not much point in just swapping the head, you sure it doesn't have the complete cylinder and piston set, too? :-k

Easy way to tell would be by looking at the base of cylinder #1, where the displacement is cast.

Another clue would be the chrome caps on the ends of the cams. The 650 caps don't have visible screws, the 550 caps do.

.

 

[Crissy]

What I am saying is that everything is already pieced together I am not saying that I'm going to put the 673cc head on the 550 base. I am saying that has already been done obviously it has the pistons inside I got the engine as a whole complete do you understand?

 

[Buffalo Bill]

There were several conversion projects posted here. Soon one of those masters will chime in.
This thread must be the most complete, contact tkent for detailed answers
https://www.thegsresources.com/_for...-the-550-699-project&highlight=550+conversion

 

[Nessism]

For example what exhaust will I need. What carbs, jet kit and boots will I need. I appreciate the help and advice in advance

It's hard to provide a definitive answer since there is variation in the 550's through the years, but for the most part the the exhaust from most any 550 or 650 should fit the engine and clear the crankcase/frame down below. The bigger unknown is how the muffler hanger will align in the rear. For carbs, you need either 650 carbs or the CV type 550 carbs which entered service in the 1980 model year and continued into 1983. No idea about a jet kit, but Dynojet does make a kit for the 550 (not sure about the 650). I suspect some custom jetting will be needed one way or another.

 

[Crissy]

I appreciate the help, I've been reading a bit on here on the forums and seen that the CV carbs from a 650 are the way to go I have cv550 carbs but don't want to use them. If you guys know of anyone with cv650 carbs let me know. Keep the detailed responses coming.. the more I know the better. I have talked to tkent but that guy is a busy man rarely has time to reply to me.

 

[Buffalo Bill]

I tell you right off, we have more respect for people who contribute knowledge after their own trial, error and expense. Not much energy for newbees who want quick solutions to problems we spent the time and expense to resolve.
The answers to your questions are rather obvious: If it has a 650 head, than your should try the carbs, boots and exhaust that were designed for that head. Jetting you can begin with 650 spec jets. Dialing it all in will be your learning experience.
If you get detailed guidance, that will be at the pleasure of the contributors.

 

[Nessism]

Both the 550 and 650 use Mikuni BS32 carbs. Not much difference other than the jetting. If you already have 550 carbs I'd rebuild them and give them a go. Rebuild instructions on Basscliff's website and linked in my signature. You will have to rejet but that's a given unless you have the stock airbox and exhaust.

 

[Crissy]

Im going to give those carbs a go with 650 jet kit and buy the 650 boots. Buffalo bill I understand you all the way man, sharing your knowledge will be well payed off by the universe it's self. I don't see why anyone wouldn't want to share their knowledge I ain't not demanding quick solutions like you think I am. I am asking questions because that's what this forum is about ain't it?

 

[Buffalo Bill]

Right, and best of luck with your project. Sounds like you bought it half finished and raw.
I would use the carbs I had and conservative jetting, easier to start an engine that's a bit under jetted than over. I hope you have the OEM airbox too. It'll start, run and idle so much better with that in place. Struggling with pods defeats so many wannabee "cafe racers", that show up later on Crapp List.
After it's running, synced and tested evaluate what next.
Wow, maybe you don't even know if the cams were installed correctly? You better examine the cam timing, valve function and engine compression before you buy anything.