GS650/GS550 conversion questions

[prichmon]

Hello all;

I am starting the process of my 550/650 build. I have a few questions which I was not positive the answer from my search.

1978 GS550 wire wheel.
1981 GS650E

Can I run the VM22s from the 550?
Will the CVs bolt to the airbox of the 550?
What is the suggested starting point for the jetting with the 650 and VM22?
Compression is 150-160psi. What is the stock compression?
If I bought the 740 kit what is the starting point for jetting with the vm22s?
Would larger VMs work from a 750 or larger?

Could someone confirm I can run either of the head pipes and cans?
Does the final drive need changed to better suit the bike?
What are thoughts on doing a smaller more modern chain for efficiency?
What are the advantages of the aluminum 1100 swingarm? Weight saving only?

Can someone verify the intake 650 cam is the better of the 2 cams?

Could a set of 750/850 cams work in the 650 head?

I scalped the front end, dual disc setup from the 650E
The foot pegs look like they would bolt up but the pegs would be at the wrong angle. Any idea on rubber mounted pegs which will bolt up?

I'm sure Ill have more questions.

Thanks for the help.

Rich

[Poldark]

Welcome aboard,

Please slow down a bit.  Maybe quick introduction about yourself and your background with Suzuki motorcycles.  Start with brief overview of what the vision is for your project. ( I want this engine in that frame with those wheels and suspension).  After that, your many questions can be addressed.  But the first thing is to read the rules, the moderators take them seriously in order to keep the forum focused.

 

[Swiss Toni]

Welcome, Rich. Would it not be a lot easier just to go straight for a complete 750 motor? There was best part of an Aircooled one going free on here, not so long ago! Why stick to Aircooled? B6, Teapot 6/750/1100, most oil oilers will fit! Make your mind up, and get some pictures up, because ... 

Edited September 10, 2019 by Swiss Toni

[Blubber]

Hi,

Welcome,

We love pictures,

Introduction in the general section, please 

[Poldark]

2 hours ago, Swiss Toni said:

Welcome, Rich. Would it not be a lot easier just to go straight for a complete 750 motor? There was best part of an Aircooled one going free on here, not so long ago! Why stick to Aircooled? B6, Teapot 6/750/1100, most oil oilers will fit! Make your mind up, and get some pictures up, because ... 

I don't think a gs750 engine will fit into a gs550 or gs650e frame.  His location is Ohio, "free" is not free if you have to pay shipping cost across the ocean.  Oil cooled 600's are cheap and plentiful here in the US.  The larger ones less common and more expensive.  Some people don't like the look of a radiator or large oil cooler on the front of their bike.  He can either build an air cooled 740 or install an oil cooled 750 with similar end results.  One route requires engine work (internal) to be done, the other requires fabrication (external) such as engine mounts, cooler brackets, and wiring modification. 

[prichmon]

The scope of work is as follows:

Make a budget friendly sporty GS. I wish to clean and touch up rather than restore to keep the crusty character of the old girl. I need a reliable daily of the girl.

Gs550l wire wheel $300

Gs650e parts bike $300

The 550 just don't have enough power and buzzes way too much.

I am attempting to get max bang with minimal change. 

I'm a big guy and know the limitations of the 550 engine. It need more torque and hp.

I wish to keep as many 550 parts as possible to simplify install, unless there is more performance to be had for cheap.

I have been robbing 650e parts and buying reliability parts to upgrade the 550. Complete front forks, dual discs, dyna ignition system, cleaned and rejetted carbs, coil relay mod, sonic springs, all new fluids and preload set to my size.

So I have been running through mod paths.

1... put 650 topend on 550 bottom. Keep the 6th gear, 25 pounds lighter.

2... install complete 650e engine. Simpler. No gaskets or other costs

I am looking at the following for power and ease of install:

which exhaust would be best?

Which cams? 650 intake, 550 exhaust?

What final drive? 650 for lower rpm or 550 for more torque?

Which carbs? Do the CVs really gain that much? Do I need more carb if running stock airbox? Should I snag a set of 26s for a 750 and install on 550 racks?

 

Thanks 

Rich

 

 

 

 

[Customgs]

I would think swapping the complete 650 would be the easiest.  But if you do decide to use the 550 bottom end and the 650 top end, use the 650 cams. When using the 650 cams you will need to switch the timing gears off the 550 cams to get it to work.

I believe mac 4 Into 1 exhaust is all they sell anymore for the 550/650.  

Also the CV carbs are more difficult to tune, but are tunable. I tuned my 550 with cv's and velocity stacks, and it ran rather well after playing with some different jet sizes.  

Edited September 11, 2019 by Customgs
Typo

[Poldark]

The requirement not to use the 650 camshaft sprockets, applies when using engine parts from a shaft drive 650.  You should be fine with the engine from a chain drive bike, but of course you should count sprocket teeth to be sure.  You could just transfer the whole 650e engine into the 550 frame (my first Suzuki was such a combination) but you loose 6th gear.  Exhaust ports are different sizes between 550 and 650.  For $120 you can get a set of oversize pistons to take the 650 to 700 or 740.  Depending on what year 550 engine, it may need the upper case relieved to accept the 650 cylinder block. 

[prichmon]

Thanks for the replies guys.

Where are you finding a 740 piston kit for 120? I'm very interested.

So the vm22s will work so I will keep those and the stock airbox and such.

I'll swap in the whole engine. 

Is the OEM 550 and 650 "e" pipes the same? My 550 is a little rougher than the 650.

Is the 550 exhaust cam better than the 650? I plan to open the 650 to do valve clearance check.

Someone cut the stator wires off the 650 so I'm going to swap the stator from the 550.

Has anyone seen an article on painting the engine? The cases has some corrosion.

Thank you

Rich

 

 

[richyrich]

Why not put an oil cooled , running,  engine in it while you have the 550 on the bench to big bore it .  

[Poldark]

Cruizin Image has the piston kits; can be ordered directly from them or on E--ay.  The 740 kit requires a larger bore head gasket, which is supplied making the kit $170.