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PHBH30mm carbs - T3 manifolds

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Gfiver View Drop Down
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 16 Mar 2019 at 09:32
Some progress.
     I've had it running, but depite Steine Dinse's assurance that the carb's jets, needle'etc are correctly set up, its not right.Much better than the 36mm pumpers on upper throttle range. On the 30mm carbs it just zooms up through the gears like it never did on th bigger carb, but there's an awkward spot, just in the wrong place for pulling away from a stop without using extra revs.
     Looking for the cause has made me realise that with the std. T3 type manifolds, the left hand, marked "S" has a sharper bend, tucking the carb further in under the frame tube. This does make it difficult to get the carb top off and spring and slide out. Not impossible, but tricky enough to make loosing the carb top "O" ring far too easy.
     "If only the "S" elbow didn't turn in so much" I wondered, "Like the "D" one".
So I tried it. Swopped the "D" elbow onto the L/H head & carb, upside down, but that makes no difference, and Bingo! there's the new L/H carb sitting just as the R/H does but 18mm further back (because of the off set of the 2 cylinders) Space for air filters looks like it will be still more improved, but what about the bell housing nuts ?
     Acres of space between L/H carb and offending nut, so much that I removed the carefully crafted 20mm spacer and even with just the 2 std. insulating gaskets, nut and float bowl clear each other nicely.
    But what about the R/H side ? Swapping the "D" elbow back to the R/H carb, with just the 2 std. gaskets, the nut and float bowl do just touch but a slight tilt of the carb on its rubber, or maybe one extra gasket and it'll be Ok.
    All I need now is an extra "D" elbow, but Ebay will provide.

    If those not familiar with older big block Guzzies with these inlet manifolds wonder why on the standard set up, left & right hand elbows have this different bend, it would be so that left & right carbs line up with the original air filter housing, despite one cylinder being 18mm further back than the other.
    So if you are happier with separate K&N style air filters, why not fit a "D" type elbow to the L/H side and have much easier access to the carb, whether its square or round slide instrument?

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Chris A View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris A Quote  Post ReplyReply Direct Link To This Post Posted: 16 Mar 2019 at 12:03
Glad it's all "sort of " working out" . Perhaps a slide with a larger cutaway would improve things -apparently they tend to be a bit rich as standard and can be leaned out by carefully filing away the cutaway in 1 mm steps as per dellorto or lessif cautious.What will also matter is that both slides are identical.
  Alternatively, lifting up the needle a notch and going down a size in idle jet might work it out.You might need all these changes ....suck it and see by doing one step at a time- leaving the slide mod last.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 30 Mar 2019 at 17:15
Well its been a couple of weeks since I reported progress and much has happened.
     The right hand induction elbow fitted to the left hand head works a treat. With the tank chocked up its easy to get a ball ended Allen key to the 2 screws holding the carb top on, to get the slide out on both sides, without even having to loosen the hose clips and tilt the carb body.
    The air filter problem is solved. The existing S&B tapered oval air filters with 42mm I.D. inlet fit easily with enough space around them so that the oposite filter does not get in the way if removing a carb with filter still attached.
    Heat proof spacer beteen head and elbow: I ditched the "O" ring idea and settled for 2 std. insulating gaskets either side of an 8mm ally spacer giving a total thickness of about 14mm which is just enough to keep the off side float chamber away from the bell housing nut.
    As for the carb settings, above 1/4 throttle it felt good, below 1/8 throttle it was Ok, but between those two, no matter what I did with idle jets or the needle there was a rough area.
    In my own mind, refreshed by looking at throttle opening diagrams, it seemed highly probable that a different slide was needed. But the problem there, is that new Dellorto slides cost £30 each so that's an eye watering £60 just to try it, not certain that it will solve the problem.
    Rob at Eurocarb in Reading has been a great help and understood my desire to avoid new slides if possible. He suggested a 50 idle jet instead of th 38 that the carbs came with. Tried that but a 46 was better and bought the pilot screw into its working range at around one and a half turns out. But the roughness at 1/8-1/4 was still there.
    Next Rob mentioned various alternative needles, but suggested a larger 270 atomiser jet so I tried that. This sadly also did nothing to remove the rough spot, so "Hey-ho!" lets try a 50 throttle slide instead of the 45 that the carb came with.
     New 50 slides came today. a notable difference, rough spot moved up to 1/4 throttle, but was really bad. This was with the needles in lowest (weakest position) with their clips in the higest of 4 grooves. Successive runs on a suitable local road, raising the needle a notch at a time got rid of the rougfh spot and increasingly smoothed out the whole range, but with the needle at its highest position,(richest) a half throttle plug chop does look a little pale so I may now try a 280 atomiser jet.
As for the main jet. To be safe I have stuck a 130 in in place of the 125 supplied.
     But where, on todays roads, can you safely hold a big bike at full throttle even for half a mile, cut the engine and coast into a layby to check plug colour ? I could use a lower gear, but as I do not have a tacho fitted the risk of over reving is too great. I may find a suitable bit of the A303 in the early dawn, when its quiet enough, but I may just stick with the 130 jets. If they are a shade oversize it shouldn't matter much as I shan't often be holding the throttle hard open.
    I'm really glad to have now got the settings about right, particularly in the lower range as on Tuesday I have it booked in at Black Dragon Motorcycles to get tickover set right and carbs balanced. With that done a different atomiser jet or different needles should get the whole range spot on.
     My old Gunson's Colourtune set has been a great help, giving a clue to wether a rough patch is over weak or over rich.
     A week ago I was tareing my hair out. Now I'm thinking, what a wonderful bit of kit a carburettor is. Little screws adjusting one bit, bits of metal with really accurate holes controlling another, a big alluminim slide, like a gate controlling the draught throur the middle of it, and then choice of needles opperation in a jet also available in different sizes, and they all work together, so long as you get the right combination of them all !
     When I have got it thoroughly sorted, I'll make a new post, giving the full spec that I've arrived at. Different exhausts and air filter arrangements might require some changes, but it will be a great help to anybody else who wants to use these delightfully simple carbs of a "small valve" Tonti.


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Chris A View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris A Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr 2019 at 22:16
Great to read the progress...Well you now know that the slide cutaway was wrong from the box.You could do what I suggested in a previous post and file off another  1.5 mm from the original ones and turn them into a pair of 55's.My gut tells me that that will sort it out but I'm no guru....
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 02 Apr 2019 at 22:55
That's just what I've done and it is better.
And a 272 atomiser jet, only a wee bit bigger than the 270 which replaced the original 260 seems to have improved things above 1/4 throttle but that seems to be the biggest atomiser available for te PHBH carb. If I need to go any richer in that area there are richer needles that I can use.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris A Quote  Post ReplyReply Direct Link To This Post Posted: 03 Apr 2019 at 11:24
Yahoo ! It must be very fulfilling getting nearer to perfect running ...congratulations on your persistence !

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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 2019 at 10:45
At last ! Some significant progress. Smile
I had a dyno session booked at Somerton Classic Motorcycle Engineers, but when Chris tried to insert the probe up the end of the Keihan silencers, the baffle wouldn't let it in far enough which was a bit of a set back. But with it on the rolling road we at least established that the needle and atomiser jet combination was too rich.
So after some more swapping bits around, and more half throttle plug chops, this morning,
BISCUIT BROWN PLUG, from edge to edge Smile real rich tea bikky colour ! At last.
When I took it to the dyno, there was just a little hesitation, or stumble at low throttle which felt as if the engine was going to cut out, just as I turned a slow corner. We did notice that one choke cable did not have a good run and might have been just lifting the plunger slightly off its seat. I have rearranged that, and this morning its much better, a little attention to the slow running, now that choke is behaving, will hopefully smooth it all out.
Current settings are now:
58 idle jet
Mixture screw 1 & 1/2 turns out
60 slide
X8 needle with clip on 3rd groove from the top
130 main jet ( this large until dyno test can decide)

The solution to getting it fully sorted on the dyno, Chris suggests, is a cheap pair of silencers which the probe can slip inside for its whole length, and then adjust to suit the Keihan silencers.
Options are a cheap pair of dunstal megaphone type silencers that I could sell on afterwards, or has anybody got a gash pair of silencers to lend or sell ? They don't have to be smart or quiet, just have no obstructive baffles.

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Chris A View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris A Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 2019 at 22:17
Nice one! Sounds like your nearly there .I could lend you my " silencers" but the postage would be outrageous...hopefully someone based in the UK can do it. I'm thinking of going down the Dyno route with mine but the cost is a bit prohibitive and they won't like playing with an old bike either. There is an extremely competent and well known independent Guzzi and mainly Ducati tech near, but he has just been hired to st up and run the local Ducati concession so he possibly won't have time to do it now.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 2019 at 22:42
Thanks.
The great thing about the place in Somerton is that old bikes are what they specialise in and cost is £40, which can save on buying too many different jets, needles, slides etc.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Chris A Quote  Post ReplyReply Direct Link To This Post Posted: 18 Apr 2019 at 23:39
To me that's an absolute  steal Gfiver and like you say it makes tuning that much simpler. I've contemplated getting a wide band sensor with a dash readout but that's a couple of hundred.I'm pretty sure dyno time here is a lot more and I've heard that some operators won't put old bikes on theirs in case they blow up on a run !
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Post Options Post Options   Thanks (0) Thanks(0)   Quote cheefysteve Quote  Post ReplyReply Direct Link To This Post Posted: 05 Jun 2019 at 21:02
Been reading this with great interest as I bought a pair of said carbs myself a couple of years ago and am just considering fitting them to my t3 which i have just refurbished. 
I am looking forwartd to the next instalment
Did you get sorted with some silencers?

"When I got the time, I ain't got the money, when I got the money, ain't got the time"
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Post Options Post Options   Thanks (0) Thanks(0)   Quote dan_s Quote  Post ReplyReply Direct Link To This Post Posted: 17 Jun 2019 at 13:20
I know of three bikes on which the PHBH 30 carbs from stein dinse were mounted, all with the same jets. On one G5 it worked as it was, no problems. Another G5 and a california II ran bad with the new carbs no matter what fiddling was done with jets needles and  filters and the owners reverted back to the original.
Good luck
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