GT550A carburettor setup

Johninreading
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Re: GT550A carburettor setup

Post by Johninreading »

OK read through the setup again. Set up is either done on the bench or on the bike. So I did it on the bench. I’m sure everything is correct. Any suggestions most welcome.
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Harrymail
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Re: GT550A carburettor setup

Post by Harrymail »

It is well worth checking that the slides are synchronised on the bike, using an air flow meter. Can make a big difference to tickover.
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barney01
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Re: GT550A carburettor setup

Post by barney01 »

I understand the best method to manually set up the carbs is on the bench. But as I said before the airflow meter is by far the most accurate so you can physically see that the carbs are sucking air the same.watch here.
https://youtu.be/9G5Hsenlv1g
The meter is about £30 and every time I have the airbox off it takes 2 mins to check and synch the carbs. Worth every penny IMHO
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Johninreading
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Re: GT550A carburettor setup

Post by Johninreading »

I have a set of 4 vacuum gauges. The two outside carbs each have a small dome cross-headed screw that can accept the gauge pipes. Question is where do I connect the gauge for the centre carb. Also there are two air pipes connecting the three carbs and these incorporate a plastic take off nipple. What are these for and should they remain open to the atmosphere or be sealed with a cover?
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mizzytheman
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Re: GT550A carburettor setup

Post by mizzytheman »

Not sure where you would connect the vacuum gauges on the 550 carbs as I’ve never worked on those carbs. However, standard vacuum gauges may not be able to read the low vacuum created by a 2 stroke unless you you have a set of these.

http://www.carbtune.co.uk/inst.html

Worth a read through their website as it offers some good advice
barney01
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Re: GT550A carburettor setup

Post by barney01 »

Firstly the other tubes you refer to are air vents open to the atmosphere.
With reference to the carb balancer. I have no experience of using one of those but I have read they are too inaccurate on 2 strokes because the air is too disturbed .
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Johninreading
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Re: GT550A carburettor setup

Post by Johninreading »

OK, so better to use an airflow meter shoved into the carb inlet. I capped these air vents off (mistake?)
barney01
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Re: GT550A carburettor setup

Post by barney01 »

Yes vents need to be open to allow air to escape
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teazer
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Re: GT550A carburettor setup

Post by teazer »

That technique with disconnecting plugs and then adjusting idle speed after that is a load of cods wallop IMHO.

I bench synch the carbs first by getting fuel levels etc identical across all three carbs. Then adjust the slides so that they all start to lift at exactly the same time. I do that with three pieces of steel rod - all the same length. Insert one in each carb until it hits the front edge of the slide. Then crack open the throttle and all 3 should tilt at exactly the same time/rate.

If they start off at different angles, the throttle stops need to be adjusted to get them level.

That's a good place to start. Then remove the rods and fire up the bike and use an airflow meter and tweak the air/fuel screws to get flows the same in each carb.
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slosher
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Re: GT550A carburettor setup

Post by slosher »

teazer wrote:Then crack open the throttle and all 3 should tilt at exactly the same time/rate.

Then what do you start adjusting to balance them assuming they are the block type please tell because the book doh :)
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