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New UK member looking for your help - GS750

  • Thread starter Thread starter PS26GS
  • Start date Start date
P

PS26GS

Guest
Hi All,

Recently joined this forum after using lots of the great materials to help restore my 1977 Suzuki GS750DB, UK model, with double front disks. Quite pleased with the results, see attached photo, although I can't get the bike to run properly, and am not sure where to go next!

When I bought the bike, the engine ran OK, although I could not run it on the road to test it for any length of time. The engine has had the following done to it:-
- rebored, new pistons and rings, so compression OK
- carbs cleaned and restored by local bike restoration company
- fitted Dyna electronic ignition
- running standard airbox and filter, standard exhausts
- using original coils and leads, as seem in good condition
- fitted new genuine Suzuki fuel petcock

Once reassembled, the bike started easily and ran OK, if a little lumpy. I have since:-
- static timed the ignition (yet to do this with a timing light)
- adjusted float heights and checked jets (fuel was overflowing)
- fitted two sets of B8ES plugs
- checked for spark. Is good on all cylinders when tested with new plugs
- set pilot air screws to 1 turn out

But the engine won't run properly!
- When plugs are new, it starts on choke OK, and comes off choke after about 1 minute.
- With a new set of plugs, it seemed to run and idle quite sweetly for a short while.
- Plugs seem to get fouled after a while (black carbon, not wet fuel) and bike starts to misfire
- Get's so bad, bike won't run properly, or start properly. Have done about 3-4 miles on the road with new plugs before the symptoms become too bad to ride.
- It doesn't appear to affect specific cylinders, they are all much the same

It seems like the bike is running rich, but not sure why. Was thinking of trying it withour air filter element, and also stripping carbs to adjust pilot fuel jets. Don't think it's running suffering any air leaks, but hard to prove that. But not sure what else it could be....:confused:
 
No, I don't. But looking at the insides of the carbs, I'd say that none of the jets have been replaced. The float valves are new, as are the gaskets etc, but I don't think the jets are.
 
Best to know main jet size (and needle position)- you never know who did what and why! Sure sounds like a rich condition
 
Your air screws should be 2x the turns of your fuel screws. Fuel screws are usually about 7/8 to 1 turn out, so having the air screws only one turn out is probably not enough.

Try backing those air screws out another turn, and then do the highest idle adjustment to fine tune them.
 
It's your carbs right enough. Nothing too difficult to sort. Were the carbs fully stripped down - to the last bit I mean? Or were they just tossed in an ultrasonic cleaner? The former takes time and latter won't work. If you need a hand give me a ring on 01428 713982. I'm only just up the road.

Oh, and air screws on a DB are set to 1 1/4 or 1 3/4 turns out as standard (depends on your engine number) so you are in the right ball park there. Don't run it without the air filter - you'll only be masking a problem if it runs ok (which it more than likely won't).

And one other thing (and call me Mr Picky but if you're interested...). A DB had spoked wheels. If yours is an early 77 somebody has put on the later wheels. If it's a later 77 it's an EC (1978 model year). Nice looking bike - very nice.
 
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Greetings and Salutations!!

Greetings and Salutations!!

Hi Mr. PS26GS,

Everything starts with a proper cleaning of the carbs. You'll find guides on my little website. Adjusting the jetting for the pod filters is critical. More in the links below.

Let me dump a TON of information on you and share some GS lovin'. :D

I just stopped by to welcome you to the forum in my own, special way.
big_hi.gif


If there's anything you'd like to know about the Suzuki GS model bikes, and most others actually, you've come to the right place. There's a lot of knowledge and experience here in the community. Come on in and let me say "HOoooowwwDY!"....
hat1.gif


Here is your very own magical, mystical, mythical, mind-expanding "mega-welcome". Please take notice of the "Top 10 Common Issues", "Top 15 Tips For GS Happiness", the Carb Cleanup Series, and the Stator Papers. All of these tasks must be addressed in order to have a safe, reliable machine. This is what NOT to do: Top 10 Newbie Mistakes. Now let me roll out the welcome mat for you...

carpet.jpg


Please click here for your mega-welcome, chock full of tips, suggestions, links to vendors, and other information. Then feel free to visit my little BikeCliff website where I've been collecting the wisdom of this generous community. Don't forget, we like pictures! Not you, your bike! :D

Thanks for joining us. Keep us informed.

Thank you for your indulgence,

BassCliff
 
Hi babes. Nice bike.
Carbs flooding..... Stuck needle valves...?
Give the carbs a sharp tap with a hammer on the float bowls... See if that helps...

Popping and banging.... Difficult to start...
Running too lean. Adjust the fuel flow screw on the top ov the carbs by the inlet manifolds (cv carbs.); dont know where they are with slides...

Good luck. Your not far from getting it humming...

Oh i just thought... Have you relined the petrol tank as the same thing happened to me and it was the rubbish (cheap) tank sealent being disolved by the new ethinol enriched petrol!!!
Look for sticky goo in the carbs and inlet rubbers.....)

Seana
Xxx

Hello from Brighton.
 
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Thanks for the ideas. I think I'll delve once more into the carbs. They were properly dismantled and cleaned, but perhaps not well enough.

Hampshirehog, you are picky...and right! I have the wire wheels in the garage, just chose to fit some alloys I got off eBay for ?10 rather than spend a fortune on refurbishing the wire wheels. Will do that when I have a bit more cash....and it's running right!
 
Worth checking that the choke plungers are shutting off nice and smoothly and that the rubbers on the plungers haven't cracked or gone rock hard. Plus check that the link arms are the right way up - you can get 3 of them upside down and it looks like they are working but they're not.
 
Quick update on progress. Carbs and jets all clean (main jets 100). Found pilot fuel screw settings around 2 turns out, so have reset these to 1 turn out and pilot air screws to 1.5 turns out for now. Adjusted float heights to 26mm as specified in the Suzuki workshop manual. Found also one o-ring on the carb mounts was pinched and therefore damaged. Waiting for parts to arrive before I can reassemble and test again. Fitted third set of new plugs too.

Hopefully, this time, things will be better....
 
Received and fitted new O-rings. Those originally fitted obviously came with a gasket set and were too big in every dimension! Also cleaned excess oil from filter element. Refitted everything and it works! Just completed a 20 mile shakedown, and seems to be running pretty fine.

Will need to tune up air screws, stobe ignition timing and vacuum balance the carbs and it should be as good a new! Lots of great advice and materials here and used the VM Carb Rebuild from Paul Musser as a guide. Thanks. :lol:
 
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