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GT550A carburettor setup

Posted: Thu Aug 01, 2019 1:46 pm
by Johninreading
I have rebuilt a set of old carbs: ultrasonic clean, new bellows, boots and fitted a carb refurb kit (gaskets , needles and jets). The main jets supplied are marked 98 but both my old carbs and the ones I bought to refurb we’re fitted with 102.5 so have rebuilt using these.

I’ve checked float height (24.5mm). Now I need to set slide heights and mixture screws. My Haynes manual only has instructions for old triple cable carbs. Anyone have a link to a setup guide for the later A/B throttle body model.

Thanks
John

Re: GT550A carburettor setup

Posted: Thu Aug 01, 2019 5:19 pm
by barney01

Re: GT550A carburettor setup

Posted: Thu Aug 01, 2019 11:39 pm
by teazer
Try not to use old jets unless you know their history. Too many people poke thinks into holes they were never meant to go into.

And if possible, set the FUEL level while the crabs are on the bench

Re: GT550A carburettor setup

Posted: Fri Aug 02, 2019 7:51 am
by mizzytheman
teazer wrote:Try not to use old jets unless you know their history. Too many people poke thinks into holes they were never meant to go into.

And if possible, set the FUEL level while the crabs are on the bench
It’s probably better to use another bench that doesn’t have crabs. :roll:

Re: GT550A carburettor setup

Posted: Fri Aug 02, 2019 8:51 am
by canaletto5
These are not to be confused with crabs on the beach. Beach crabs just nip your toes but bench crabs walk off with the components of your carburetor. The only way to stop them is to smear blue grease everywhere ;)

Re: GT550A carburettor setup

Posted: Fri Aug 02, 2019 11:53 am
by barney01
:P :P :P

Re: GT550A carburettor setup

Posted: Fri Aug 02, 2019 11:54 am
by wardy
canaletto5 wrote:These are not to be confused with crabs on the beach. Beach crabs just nip your toes but bench crabs walk off with the components of your carburetor. The only way to stop them is to smear blue grease everywhere ;)
Does this include all Shell fish that I may keep in my workshop or just crabs.
Presumably fresh water crabs behave in the same way as salt water ones.
I've had similar issues with whelks, mussels and shrimps so I now keep them away from my bench top and and motorcycle related items.
The two just don't mix... it's not worth it.

Re: GT550A carburettor setup

Posted: Fri Aug 02, 2019 11:40 pm
by mizzytheman
.....

Re: GT550A carburettor setup

Posted: Sun Aug 04, 2019 7:21 pm
by Johninreading
So, all back together with 102.5 main jets. Followed set up exactly as described in link (thanks for that). Good news, started on choke first prod and ticks over like a Swiss watch. Revs to about mid revs very well, but gets really lumpy above about 3000. Now the bad news, pulling away, engine is really lumpy and will not rev smoothly. I didn’t understand the synchronisation steps (the bit about disconnecting the plus one at time) but maybe Sync is the cause of my issue). Going to read through the instructions all over again. Question, to get at the throttle valve adjusters I’m gonna have to remove the tank and tune it with what’l fuel is in the float bowls. Is that the right way to do it?

Re: GT550A carburettor setup

Posted: Sun Aug 04, 2019 7:36 pm
by barney01
Best way to balance the carbs is with an airflow meter just need to take the airbox off