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GT550 Vacuum gauge use

Posted: Sat Jan 30, 2021 4:12 pm
by Hush
Can someone show me how the GT550 uses a vacuum gauge? I am used to removing small screws on multi carbs and fitting screw in tubes to use a carb balancer but obviously the 550 does not have these so I am thinking maybe you have to block off the entire carb intake somehow to use one.
A photo would be greatly appreciated. :D

Re: GT550 Vacuum gauge use

Posted: Sun Jan 31, 2021 2:56 am
by gammakeith
They are not used on a two stroke so they don't have the tappings. Balancing throttles slides by eye or with drill bits of the correct size is usually considered sufficient and will be specified in the manual. Even my RG500 doesn't have one. The idle mixture screw can then be tweaked to give a good tickover. The bonus of a two stroke with separate exhausts is that you can usually get a good tickover by "ear" by listening to the individual exhausts.

Keith

Re: GT550 Vacuum gauge use

Posted: Sun Jan 31, 2021 3:10 am
by GTandcbr
I once had a friend who drilled out the blank cast on the opposite side to the airscrew. Then threaded the hole and used a acrew in nipple to push the vacuum gauge hose. Then afterwards he just screwed in a bolt to block it off

Re: GT550 Vacuum gauge use

Posted: Sun Jan 31, 2021 3:13 am
by markush
See pics.
There are already "Phillips" screws at the outer carbs. For the middle use the vacuum hose to the fuel cock.

Pics show GT380, but the carbs are from 550. Wouldn't matter, the screws are at the 380 carbs, too.

The use of vacuum gauges with a two-stroke only works if they have a low measuring range, up to a maximum of -0.5 bar. Otherwise with a maximum value of -1 bar, as you often get, they hardly indicate anything useful.