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SB6r fuel pipes / carbs update

 
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Horseheed



Joined: 31 Aug 2018
Posts: 37
Location: Co Durham

PostPosted: Sun Sep 02, 2018 1:29 pm    Post subject: SB6r fuel pipes / carbs update Reply with quote

Hi, I've removed the carbs again and found one pilot jet blocked which I cleaned BUT I removed the card tops for the first time and found two diaphragms had been pinched quit a bit by the previous owner, no holes but both creased , will they regain there original shape or not ? Removed the fuel pump and now running gravity feed . Whent out for a ride ( about 20 miles ) and approx 1 gallon of petrol later returned home still running badly in third / fourth it won't Rev when I try it just splutters badly. Help much appreciated. Cheers
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brian



Joined: 22 Aug 2011
Posts: 3769
Location: Australia

PostPosted: Sun Sep 02, 2018 11:14 pm    Post subject: Reply with quote

If the diaphragms aren’t split or holed and the slides move freely then there shouldn’t be a problem.

It depends on where in the rev range it’s running poorly. usually...

Idle / low revs - pilot circuit
Midrange - needle jet circuit
Top end - main jets

Of course all of the circuits “overlap” to some degree which can make it tricky
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'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
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Horseheed



Joined: 31 Aug 2018
Posts: 37
Location: Co Durham

PostPosted: Mon Sep 03, 2018 5:02 am    Post subject: Reply with quote

brian wrote:
If the diaphragms aren’t split or holed and the slides move freely then there shouldn’t be a problem.

It depends on where in the rev range it’s running poorly. usually...

Idle / low revs - pilot circuit
Midrange - needle jet circuit
Top end - main jets

Of course all of the circuits “overlap” to some degree which can make it tricky
. Hi Brian , it's the midrange , I can't get it near top end and it's fine at idle. I've checked the diaphragms and they are have returned to the correct shape with no holes or splits. Cheers Nigel
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Jonny B Bad



Joined: 05 Dec 2009
Posts: 555
Location: NE London

PostPosted: Mon Sep 03, 2018 9:01 am    Post subject: SB6R Reply with quote

How many miles has it done? What notch are the needles on? What main jets has it got in? If your diaphragms are pinched, sounds like an HFO has been in there. So best to check the basic carb build.
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brian



Joined: 22 Aug 2011
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Location: Australia

PostPosted: Mon Sep 03, 2018 9:59 am    Post subject: Reply with quote

Check that the needles are sliding freely.

Check if the carbs have stock jetting / settings. I’m not sure what stock is though sorry
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'99 DB4 #104, '96 SB6 #1165, '94 DB2 J #652, '99 DB4 #088, '08 VTX1800, '93 ZXR750R M1, '95 ZXR750, '95 ZXR750 Race Bike, '94 CBR400rr NC29 Race Bike, '94 CB250, '49 BSA C10 250, '61 BSA A10 650, '89 ZXR750, '91 Ducati 851
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Horseheed



Joined: 31 Aug 2018
Posts: 37
Location: Co Durham

PostPosted: Mon Sep 03, 2018 10:13 am    Post subject: Re: SB6R Reply with quote

Jonny B Bad wrote:
How many miles has it done? What notch are the needles on? What main jets has it got in? If your diaphragms are pinched, sounds like an HFO has been in there. So best to check the basic carb build.
Hi, it’s got 7800 miles on it , needles on number one notch, 145 mains , diaphragms have gone back to original shape . Had a ride yesterday approx 18 / 20 miles and used a gallon of petrol NOT good. Cheers for the help. Nigel
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stockcar



Joined: 07 Apr 2011
Posts: 836
Location: in the shadow of the "angel"

PostPosted: Mon Sep 03, 2018 3:44 pm    Post subject: Reply with quote

bit confusing as you have 2x threads on the same subject..........

from the amount of fuel it has used it would appear to be running massively rich and this in itself would stop it revving as it is effectively drowning the motor

cant help with the exact cause but that is the line you need to follow
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Horseheed



Joined: 31 Aug 2018
Posts: 37
Location: Co Durham

PostPosted: Mon Sep 03, 2018 6:00 pm    Post subject: Reply with quote

stockcar wrote:
bit confusing as you have 2x threads on the same subject..........

from the amount of fuel it has used it would appear to be running massively rich and this in itself would stop it revving as it is effectively drowning the motor

cant help with the exact cause but that is the line you need to follow
Yes it is a bit confusing , it's the first time I've done anything like this and got in a bit of a knot but thanks for the help anyway. Cheers
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Jonny B Bad



Joined: 05 Dec 2009
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Location: NE London

PostPosted: Mon Sep 03, 2018 9:21 pm    Post subject: SB6R Reply with quote

Right, somebody has been in here trying to fix the havoc caused by the vacuum fuel pump. That has to go for a start. The standard mains are 150s - somebody’s tried to lean it off by putting 145s in. The needles need to be on notch 2 if not 3. At that mileage it may well have worn needle jets and needles - order a new set of each - the numbers are on them - and a set of 150 mains from Allen’s Carbs. Don’t get involved with Dynojet kits or any of that mumbojumbo. Once you’ve got that lot fitted, let us know how it’s running.
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Horseheed



Joined: 31 Aug 2018
Posts: 37
Location: Co Durham

PostPosted: Tue Sep 04, 2018 4:59 am    Post subject: Re: SB6R Reply with quote

Jonny B Bad wrote:
Right, somebody has been in here trying to fix the havoc caused by the vacuum fuel pump. That has to go for a start. The standard mains are 150s - somebody’s tried to lean it off by putting 145s in. The needles need to be on notch 2 if not 3. At that mileage it may well have worn needle jets and needles - order a new set of each - the numbers are on them - and a set of 150 mains from Allen’s Carbs. Don’t get involved with Dynojet kits or any of that mumbojumbo. Once you’ve got that lot fitted, let us know how it’s running.
. Many thanks for the info, as you've probably guessed I don't know a lot about them. Will order parts like you said and let you know Many thanks to everyone who's trying to sort it out Cheers
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