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Carb adjusts |
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Thetar 
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Joined: 10 Aug 2018 Location: Ireland Status: Offline Points: 39 |
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 Topic: Carb adjustsPosted: 21 Feb 2021 at 17:55 |
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Hello
I've done a search on the forum but can't find the definitive answer... On a v35 carb, what do the two screw adjustments do? What is the expected behaviour if I adjust them?
1. The one that sticks out and you can adjust by hand. 2. The one that is flush and you need a screw driver. Thanks :) Tar |
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Richard Hyatt
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Posted: 21 Feb 2021 at 18:00 |
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No 1 adjusts the tick over speed by pushing the slide up and down
No 2 varies the air fuel ratio at tickover
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Thetar
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Joined: 10 Aug 2018 Location: Ireland Status: Offline Points: 39 |
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Posted: 21 Feb 2021 at 18:03 |
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Thank you. If I tighten no.2 will that 'richen' the idle mix?
Edited by Thetar - 21 Feb 2021 at 18:31 |
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Thetar
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Posted: 21 Feb 2021 at 18:30 |
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I'm guessing that because no2 is an airscrew (not a fuel pilot screw) then opening it will make it leaner, closing richer. Correct?
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Dave P.
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Posted: 21 Feb 2021 at 18:41 |
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If this is a VHB carb the screw in question increases (Out) the amount of fuel/air mixture. The ratio's are determined within the carb drillings. Conversely screwing in reduces the supply.
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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.
1971 V7 Special. 1972 850GT. 1970 T120 Bonnie. 2009 500 Bullet. |
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Thetar
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Joined: 10 Aug 2018 Location: Ireland Status: Offline Points: 39 |
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Posted: 21 Feb 2021 at 19:23 |
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Got it, thank you.
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Mike H
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Posted: 21 Feb 2021 at 20:27 |
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It only controls mixture at idle speed, and up to about quarter throttle. The books all say, start at 1.5 turns out (from fully screwed in). Then screw out for maximum idle speed, or try it see if it does. Then screw it in until revs start to drop. Then back out again to restore the faster idle speed. THEN, adjust the throttle stop screw (the sticking out one) to get the idle speed you actually want. DO NOT mess this up for example having to have the throttle screw set higher otherwise it won't idle and stall, this isn't correct and can affect engine braking, as in, it doesn't, guess how I know!  Note also clogged up passages and jets will affect the behaviour of the idle screw; worst case is, twiddling it does nothing. |
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"Chicken nuggets don't dance on a Tuesday."
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Thetar
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Posted: 21 Feb 2021 at 21:32 |
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Brilliant thanks. I must have other issues. It's a bit reluctant to start but runs ok at first. Then after a few mins the idle speed falls and I need to keep tightening the idle speed screw to stop it from stalling. Until it will turn no more and it stalls. Oily plugs after all that. I'm thinking my valve guide seals are leaking or something up with the valves. Maybe worn rings. 40km on the clock. 35 yrs old.
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Ken-Guzzibear
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Posted: 21 Feb 2021 at 21:39 |
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look at the easy stuff first check fuel flow .... check carbs completely especially the chokes Had similar with a V50 gunge in fuel taps and carbs...inlet leak too
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The Older i Get, The Better I Was
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Brian UK
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Posted: 21 Feb 2021 at 21:40 |
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Brian.
Better 5 minutes late in this world than years early in the next. |
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c13pep
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Posted: 21 Feb 2021 at 22:19 |
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As Ken says do the easy stuff first plugs, points etc. but maybe a compression test on both cylinders should be the starting point
CHRIS
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you can`t have any fun in a straight line
Monza |
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Dave P.
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Posted: 21 Feb 2021 at 22:28 |
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It would do no harm to check that the valve clearances are correct too.
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TO LIVE OUTSIDE THE LAW YOU MUST BE HONEST.
1971 V7 Special. 1972 850GT. 1970 T120 Bonnie. 2009 500 Bullet. |
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yan1114
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Joined: 30 Jun 2020 Location: East Yorkshire Status: Offline Points: 55 |
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Posted: 22 Feb 2021 at 09:05 |
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My V35 had a very similar problem, turns out that the valve clearances were amended and mine was set to the earlier settings, it's only a small adjustment but cured my problem, cheap easy fix. From memory the early clearances were .04 & .06 the later ones .06 & .08
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johnno
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Posted: 22 Feb 2021 at 11:05 |
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1100 sport corsa , Yam R1, guzzi 650tt rider
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AdrianW
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Posted: Yesterday at 09:52 |
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My V35II had carb problems even though the bike was allegedly sorted and running well..! On inspection the slide needles on mine were corroded so I replaced them along with the corresponding atomisers. My bike (1982) has VHBZ carbs. If they have not been checked over it's worth having a good look inside to see what (if anything) needs replacing. A couple of gasket sets will help. When setting them up make sure the throttle slides hit the bottom of the carbs simultaneously, on my bike there are two separate cables and needed adjusting.. It's fiddly but worth it in the end. My tickover is still a little high but the plug colour is good so I'm leaving it... Good luck, Adrian Bristol UK
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Ken-Guzzibear wrote: