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Re: Bonnie Carb Jetting help needed [Re: BrettF] #720104
12/27/17 4:30 am
12/27/17 4:30 am
Joined: Nov 2012
Posts: 291
Isle of Wight, UK
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koan58 Offline
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As long as the length from the grooves to the taper tip, and the taper itself, are the same, I doubt that any slight difference of point will matter.
The needle never fully pulls out of its jet, but once it is raised to a certain level, its orifice is opened such that the main jet becomes the governing factor.
Unless one of the needles is grossly out of spec, I think it is a red herring.
Have Burlen got back to you yet? Dave

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Re: Bonnie Carb Jetting help needed [Re: BrettF] #720705
01/01/18 8:59 am
01/01/18 8:59 am
Joined: Jan 2014
Posts: 318
Geneva, Switzerland
BrettF Online content OP
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Hi Folks, and a happy new year to all of you!

We had a nice 9 degree C day so did the final test of swapping the carbs around. The hypothesis was that after the swap the left would be very rich and right even more lean if the problem was with the bike, not the carbs. Remember that the plugs were very similar and just barely acceptable with a four size larger main on the right.

Well after the swap where I swapped everything, carb, slide, needle, filter etc. etc. and a good mile of WOT the plugs looked the same as before. Both borderline lean but fortunately no sign of detonation.

I've taken Burlen up on their kind offer to have a look over the carbs. This test was probably a wild goose chase as the excessively large main jets on both sides are already indicating that something is amiss.

Before sending them back I took as many comparative measurements as I could between the new and old carbs. One thing I noticed was that the throat of the old carbs seems marginally smaller than the new ones. I measured them in several places and while some were very close to 30mm others were closer to 29.7 or 29.8. But this might just be casting high spots.

Dave, from what I could measure it seems the needle clears the narrow "jet" portion of the needle jet by about 2mm when the needle is in its highest position. However, it seems it remains just in this "jet" section with the needle is in its lowest position. So I believe you are right and that this will not have any significant effect, especially considering I was running at the highest needle position. Note these measurements must be out a bit as Mr Healy indicates that the needle does exit the narrow portion of the needle jet in all settings.

One other difference I noted is the clearance between the bottom edge of the main jet and the bottom of the float bowl. In the new premier carbs the bowl seems a couple of mm shallower than my old original bowls. This means that the bottom of the main jet is closer to the float bowl base than before. On the old carb, the main jet sits about 2mm above the top surface of the drain screw whereas in the new carbs the main jet is level with, or even slightly submerged within the top surface of the drain screw (depending on the final thickness of the gasket). Could this have an effect, probably not considering the jet orifice vs the clearance around the main jet/drain plug internal cavity.

Over the winter I'll fettle the old carbs to get them straight again to ensure slides don't stick and if successful put them back on with new needles and needle jets, (old needle jets were worn to about one size larger based on my primitive "shade tree" measuring method) and probably 210 mains.

Will be interesting to see the result.


3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
Re: Bonnie Carb Jetting help needed [Re: BrettF] #720706
01/01/18 9:06 am
01/01/18 9:06 am
Joined: Jan 2014
Posts: 318
Geneva, Switzerland
BrettF Online content OP
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BrettF  Online Content OP
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Geneva, Switzerland
PS, does anyone know if one can obtain the carb mount tufnel spacers and the thicker carb mount o-rings anywhere in UK/ Europe. I've only found them in the US and shipping is prohibitive.

I've noticed that the Tufnel spacers seem to come in two flavours, a shiny one and a more matt looking one, is one preferable to the other?
thanks


3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
Re: Bonnie Carb Jetting help needed [Re: BrettF] #720708
01/01/18 9:48 am
01/01/18 9:48 am
Joined: Dec 2004
Posts: 9,063
Scotland
kommando Online content
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Re: Bonnie Carb Jetting help needed [Re: BrettF] #720723
01/01/18 12:40 pm
01/01/18 12:40 pm
Joined: Aug 2001
Posts: 7,026
scotland
triton thrasher Online content
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scotland
Halfway down.


http://www.hitchcocksmotorcycles.com/amal-carburettors-miscellaneous

Also try putting "tufnol" or “phenolic” in the search.


Amateur Loctite enthusiast.
Re: Bonnie Carb Jetting help needed [Re: BrettF] #720749
01/01/18 4:12 pm
01/01/18 4:12 pm
Joined: Dec 2006
Posts: 3,878
Massachusetts, U.S.A.
B
btour Online content
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Massachusetts, U.S.A.
Originally Posted by BrettF
Over the winter I'll fettle the old carbs to get them straight again to ensure slides don't stick and if successful put them back on with new needles and needle jets


Better to check now. Just how do you intend to fettle them?


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
Re: Bonnie Carb Jetting help needed [Re: BrettF] #721271
01/06/18 4:18 pm
01/06/18 4:18 pm
Joined: Jan 2014
Posts: 318
Geneva, Switzerland
BrettF Online content OP
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Geneva, Switzerland
Hi Folks,

I was digging around Burlens site and found that there are different types of bowls, this made me wonder about the clearances between the drain and main jet. Does anyone know what exactly is different between the different bowls (i.e. what the different given measurements mean?)?

Here is a capture from Burlens Site.

https://pin.it/dtdjhe5szbifq2



3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
Re: Bonnie Carb Jetting help needed [Re: BrettF] #721291
01/06/18 7:13 pm
01/06/18 7:13 pm
Joined: Aug 2001
Posts: 7,026
scotland
triton thrasher Online content
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Those differences are in the size of the hole in the needle valve which lets fuel into the bowl.


Amateur Loctite enthusiast.
Re: Bonnie Carb Jetting help needed [Re: BrettF] #721303
01/06/18 9:04 pm
01/06/18 9:04 pm
Joined: Nov 2012
Posts: 291
Isle of Wight, UK
K
koan58 Offline
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Brett,
TT is absolutely right. Most ordinary concs have 0.1" hole where the needle viton seals. The only question in that area was that skewed drilling on one of your carbs, which is probably unimportant, though not pretty.
Should you return them, I would ask for better, 'cos it's not good QC.

Maybe I've been lucky, but the usual bolting of a conc to a manifold has never given me air-leak, frothing or heat issues.
I've never done other than use the thickish waxy gasket with the std O ring.

If you must use the fat O ring, don't use a gasket. I think this is barking up a wrong tree, though won't do any harm.

Regarding the clearance between the main jet and it's available access for flow, forget it. Unless it caused a severe restriction, not worth thinking about.

Having said that, I've not observed these differences in bowl shape, apart from with and without drainplug. Any chance of a pic?

Dave

Re: Bonnie Carb Jetting help needed [Re: BrettF] #721712
01/11/18 9:52 am
01/11/18 9:52 am
Joined: Jan 2014
Posts: 318
Geneva, Switzerland
BrettF Online content OP
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Hi TT, Kommando and Dave, thanks for the info sanity check.

I've subsequently found that AMAL also sell the tufnol spacer as well as the other great sources (but not the larger o-ring), Dave, I've also have not had any problems previously with the "standard" fittings so they are not on top of my list of culprits

Out of interest, do the larger ID float seat holes use the same Float needle or are their specific needles for each hole size? I never thought about this and so never measured my valve seat hole (sounds obscene i know).

Dave, Sorry - sent the carbs back to AMAL for a once over - so cant take any pictures. Will keep you posted on the results though. I'll cry if they can not see anything as I have no more ideas. I can't even sell them on in good conscience.


3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
Re: Bonnie Carb Jetting help needed [Re: BrettF] #721717
01/11/18 10:39 am
01/11/18 10:39 am
Joined: Nov 2012
Posts: 291
Isle of Wight, UK
K
koan58 Offline
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K
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Isle of Wight, UK
Brett,
As far as I can see, the float needles are one size fits all.
There are brass and alloy versions of the viton tipped type, and an entirely alloy needle for alcohol use. Dave

Re: Bonnie Carb Jetting help needed [Re: BrettF] #721954
01/13/18 11:44 pm
01/13/18 11:44 pm
Joined: Aug 2012
Posts: 305
Hampshire, England
DoubleDiamond Offline
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Hampshire, England
There is a firm called Toolex here in the UK that sells Swiss made reamers that could be used as pin gauges as well as for taking the needle jets out to the next size. See here:- http://www.toolex.co.uk/

You could also buy a Mitutoyo bore measuring guage, type number 368-022.

Good luck


BSA: '71 B175; '68 B25; '71 A65; '71 A75
Triumph: '87 T140; '72 T150v
Re: Bonnie Carb Jetting help needed [Re: BrettF] #721956
01/14/18 12:00 am
01/14/18 12:00 am
Joined: Aug 2012
Posts: 305
Hampshire, England
DoubleDiamond Offline
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DoubleDiamond  Offline
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Posts: 305
Hampshire, England
The thick 'O' rings have dimensions of 34mm x 2.5mm

For a carb insulating washer, there is one on eBay - eBay item number:273019942044

HTH


BSA: '71 B175; '68 B25; '71 A65; '71 A75
Triumph: '87 T140; '72 T150v
Re: Bonnie Carb Jetting help needed [Re: BrettF] #722114
01/15/18 1:16 pm
01/15/18 1:16 pm
Joined: Jan 2014
Posts: 318
Geneva, Switzerland
BrettF Online content OP
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BrettF  Online Content OP
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Geneva, Switzerland
Thanks for all the input folks.

Got news back from AMAL and (unfortunately cry ) they see nothing wrong. cry

EDIT - Following a more detailed discussion with them, Burlen have indicated that they could also not get a fuel level within specifications. Whether this was due to an original problem, or me modifying the seat height in my attempts to achieve this as well as sanding the bowl flange flat to ensure no leaks there, they could not say. So they have replaced the float bowls and feel that it should work well now. Along with a suggestion of possibly using size 19 pilot jets. Not clear if the larger pilot jets are proposed as a general recommendation or due to the spitting when snapping the throttle open.

I look forward to testing them out.

Last edited by BrettF; 01/15/18 9:36 pm.

3D TV: A format that lost a format war without even having an opponent.
Bikes:
69 T120 on average (1967 rolling frame and 1971 Bonnie engine)
57 T110 on average (58 rolling frame - with 55 iron head engine)
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