Suzuki 2 Strokes

Hello !
New to the Board ! Glad you guys are here. Love the vintage Suzukis
I just scored a very nice '72 GT550J. I've just about covered or uncovered most about the bike. Been through Carburetors ( found some main jets incorrect , but clean), Ignition and Timing. Injection and Crankcase oil changed Etc.
Now here's my question please: Any ideas are welcome
All carbs have 27.5 pilot jet and all passages clean,float level @ 24mm. But, Both outboard Carbs want the idle air screw out 2-1/2 turns! (leaner) , Middle cylinder likes it at only 3/4 turn.


Bike runs well. Starts good, cold or hot. Idles consistently @ 1400

Are the pilot jets new or re-purposed? The reason I ask is that old jets have often been cleaned out with wire and may be oversized. Cheap jet kit jets are not close to the right flow rates.

It is also possible that the bypass outlets may have been compromised but I would start with shiny new genuine Mikuni jets. If the jets are new, try one size smaller on the rich pair

I too have a 550 J. I replaced all my internal jets(Expensive but then so is a seizure!) My airscrews are out one turn only. I think that 2 1/2 is close to the maximum of 3. After that it has no effect at all on the airflow. Have you considered dropping your needle clips one groove to see if that has any effect?

Thanks Guys !!
Just what I needed to get some thoughts going. The jets are indeed the "old ones". I'll source some new pilots and mains. I'm at 900 feet above sea level, needle clips are on the middle groove all three carbs.

Thanks Again !!!

If you'd like a copy of the 1972 GT550 service manual, PM me your email address and I'll bung you a copy FOC.
It's a scan of the original book I had (and still have) from many years ago when I had a GT550J when they were new - and gives lots of useful stuff for all Suzuki models up to that date. Jets, ratios, electrics etc. etc.

Nice to hear of another GT550 coming back to life. Is it a Gold or Blue one?

Alan

I'm in Tulsa. I have a Suzuki service manual that covers the 550J ONLY No other bikes or models. It was published by Suzuki in 1973. 77 pages plus fold out wiring diagrams and exploded views. I don't need it as my 550 is a 76. You can have it for $10 plus postage. The book is a little rough around the edges but the pages are clean. No grease smudges. PM me if interested. This not a Clymer or a Haynes. Published by the mother ship and covers the 72 550 only.

There is almost enough of us to start an Oklahoma 2-stroke gang

Here's an update on my settings:
Points to 45* dwell
Timing each using dial indicator
Used Timing light to verify
Carefully removed each exhaust side pipe, added 1-1/4" metal freeze plug to L&R exhaust crossover.
Removed rubber airbox rubber inlet diffuser.
Rejetted to; 102.5 mains, 30 pilot center, 25 pilot L&R. All needles 4 from top.
She's Happy now !!

Hi
As I said in a previous post I have a 550 J which was a U.S. import. Mine came with the exhaust altered as you state and I actually wanted it to look original so at great cost I bought a replacement set. I could never understand why they had been altered. Can you tell me what the advantage is of blocking off the crossovers? Please keep it simple as I am a very low level mechanic! Thanks

GTandcbr wrote:Hi
As I said in a previous post I have a 550 J which was a U.S. import. Mine came with the exhaust altered as you state and I actually wanted it to look original so at great cost I bought a replacement set. I could never understand why they had been altered. Can you tell me what the advantage is of blocking off the crossovers? Please keep it simple as I am a very low level mechanic! Thanks

The crossovers in the exhaust smooth out the engine and allows for more low end power. However, it hurts high rpm power. Suzuki went this route to make it more of a cruiser than the Kawasaki H1 was. Removing the crossovers gives you more mid and high end power.

When you remove the crossovers, you MUST rejet all three carbs the same or you'll burn the center piston.

Jeff

Thanks for that i understand that now.