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PHBH30mm carbs - T3 manifolds

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Gfiver View Drop Down
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    Posted: 02 Mar 2019 at 20:12
There may be many who have done this, but here's my take on it.
    I was interested in fitting 32mm Mikuni carbs, but decided on the PHBH 30mm Dellortos, partly because of Stein Dinse's amazingly good value deal on a pair of new carbs with rubbers & hose clips for just over £200.
   My reason for takling this job is that my G5 came to me with 36mm PHF carbs fitted. A size of carb wasted on the small valve "big block" heads, and also a problem in "space for air filter" stakes. I had cutaway side panels etc, but as they're the wrong carbs, why continue the struggle?
   The carbs took only 4 days to arrive from Germany. They seem to be as specified for V65s, but come with a pair of 125 main jets which should be close to what's needed.
   I chose to use original T3/MkI Spada style inlet manifolds rather than the plastic manifolds that are available, as those have the same shallow bend as the LeMans, that lead to air filter clearance problems, or so it seems to me.
    Availability problems of the cast ally inlet manifolds led me to a s/h set from TLM in Neimegen, only to find a set on UK Ebay the day after I placed my order but the ones from TLM were a reasonable price.
Not wanting to pull the old carbs off the bike befor I was sure I had everything I needed, this morning I made a simple wooden jig with the manifolds bolted their correct distance apart, and with the L/H set back as they would be on the bike, to check for cable runs and air filter options.
    This worked well with the jig at an easy bench top height., and I was able to measure up for everything.
    One significant point is, that the VHB carbs fit directly onto the stubs with a nylon sleeve, but with the PBHB type, the necessary carb rubber would push the carbs closer together under the tank.
    Measuring carefully I cut 8mm off each stub,  leaving just enough machined area for the rubber to sit on. Another point is the lack of a groove for the bead inside the rubber sleeve to locate in. One could just shove the rubber on and squish it down with the hose clip, but I wanted to do better than that. Again measuring carefully, scribling a line around the stub, I started with a shallow  hacksaw cut as a guide for the 4mm round file that I used to put the groove in the right spot.
     Care is needed because the inside diametr of the stub is not concentric with its outside, so the wall thickness varies from 4mm- 3mm.
    With the stubs modified so far, the rubbers sat firmly in place, even without the hose clips tightened, and looked good as well, as there was no longer a bare section of machined stub between the rubber and the rest of the stub.
    However, glancing inside the rubber, a non concentric step was visable where the rubber's narrow centre section meets the stub.
    While I'm not interested in sqeezing every ounce of power from my G5, principals of gas flow also make for smooth running and best fuel consumption, and so half an hour with a small half round file and some wet and dry eased the edge of the step.
    I was now ready to trial fit the carbs on the jig and it was clear that they now point so much inwards that the space for air filter problem is still present. Measuring between the thottle cable exit points give 225mm which seemed to be just right for cables to clear frame tubes etc.
     You might wonder whether I tried the Guzzi specific 1 into 2 K&N air filter. I did and it wouldn't fit. The sleeves are too small I.D. for the PHBH carbs and the angle the sleeves leave the body of the filter seemed wrong also.
     Gutsibits list a pancake style filter which should do but its on back order so I looked at the S&Bs that had been on the PHF carbs. Nice to find that they are a better fit on the PBHB than on the PHF, and on the jig, there is just room for them both. The chrome caps just/almost touch with maybe a paper thickness clearance. If I hadn't shortened the manifold stubs, there would not have been enough room. However I realise that some small discrepency on the jigs measurements could mean that the clearance is not there when the set up is on the bike, but on the other hand, the clearance might actually turn out to be greater. We shall see
    I was now at a point where I could think about actually trying the new carbs, stubs & filters on the bike. As I had, had to measure up for new throttle & choke cables, and everywhere being closed on Saturday I felt that there was time to try the new carbs on, and if something wasn't right, refit the old ones.
    On the first side all went well, carb & filter off and then the LeMans type manifold. The stepped studs were difficult to get out, but they came. The new carb, stub & filter went on nicely on the off side, with the float bowl just touching one of the gearbox bellhousing nuts if the carb was dead upright, but just one degree or so of tilt and all was Ok.
    On the second side one stud came out but the other two would not. I tried eveyting I knew but having only a 6mm thread to hold while you try to unwind a stuck 8mm thread is always going to be difficult.
    Even two nuts locked together would not hold and welding a nut on the 6mm stud, held, but the stud sheared. B****R! Can't go forward and can't go back and put the old carbs back on either. The only good thing is that I have a pair of spare heads waiting to be picked up from having new guides fitted, but that place is closed on Saturday as well, and anyway I haven't got a spare head gasket.
   So time to chill out. Order gasket along with throttle and choke cables on Monday, and tomorrow, just whip the head with the knackerd studs off, ready for the spare one also on Monday.
I realise a few pics would have helped a lot, but I have no idea how to put them in.
If somebody else is willing, could they put them in if I email the pics to them ?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2019 at 09:43
Progress this morning.
Before removing the head with the broken carb stubs, I checked that nearside carb for clearance, and as on the offside, the floatbowljust  kisses the bellhousing nut. But a hand made 8mm thick "Tufnol" heat resisting spacer between head and manifold will push each carb back just enough to clear. I may even be able,using a hole saw to create an "O"ring groove on each side of the spacer to make sealant unnecessary.  My existing S&B oval tapered filters, though a bit ratty will clear each other and be Ok to be going on with.
That accomplished, an hours work had the offending head off and stripped ready to take to Hamlin's in Bridgwater tomorrow to get the stud remains removed, when i go to pick up my other 2 heads, one of which will go back on the bike and the carb conversion can proceed from there.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote chilly Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2019 at 09:50
Interesting write up for folks looking to go this way with Carbs, shame it all went wrong in the final stages, hopefully it will all be worth it.
I fitted 30mm PHFs to my T3 with the slow bend plastic type manifolds, this kicked up a lot more problems than I envisaged, but in the end i'm pleased with the result.
 
Good luck with your endeavours .
 
Cheers
Chilly
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2019 at 10:30
Yes its a shame about the studs, but the silver lining is that I'm now taking time to make the manifold spacers. They'll be 10mm Tufnol as that's what I have, but that extra 2mm will keep the floatbowls nicely clear of the bellhousing nuts.
And it looks like the holesaw tecnique of "machining" an O ring groove will work Ok. I've just tried it out on a bit of wood and there is just room, between the studs and the central hole, for a 2mm wide O ring.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldrat Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2019 at 14:48
Good write up, it’s always useful to see what ingenious things others get up to.


Did you ever think about using straight inlets?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Mike H Quote  Post ReplyReply Direct Link To This Post Posted: 03 Mar 2019 at 19:14
Originally posted by Gfiver Gfiver wrote:

just  kisses the bellhousing nut. But a hand made 8mm thick "Tufnol" heat resisting spacer between head and manifold will push each carb back just enough to clear.


Those 30mm carb elbowed inlet stubs should have the two thick gaskets each, as normal, the length of the fixing screws that attach them to the heads have a specific length to suit, so that if just one thick gasket is missing they will bottom out in the head and the stub won't tighten up. This is an indicator that something is wrong (i.e. not enough or wrong thickness gaskets). I think the total thickness is 6 mm or somesuch. I'm sure more can be added if extra thickness is needed.





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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2019 at 15:46
Well no worries about total thickness of gaskets (if that's the minimum of insulation needed).
Having got both sides tightened up and everything sitting as it should, with the 10mm spacers, plus a few more spacers, it takes 18mm total thickness for the PBHB float chambers to clear the bellhousing nuts, so just to be sure the final version will be a 20mm thick Tufnol spacer on each side, and I'll fit fiber washers under the Allen bolt heads just to make sure, and Allen bolt lengths adjusted to suit.

Correction on distance between throttle cables as they exit the carb tops. Its 210mm not 225mm

I got my other heads back (and left the one with broken studs) today but I'm still waiting for the necessary gaskets to pop a head back on.
But with the head sitting in place and carbs on both sides, its looking good. Plenty of space for the solenoid cover, and a chance discovery that the chrome end caps are entirely decorative rather than strucural, whe one just fell off as I handled it !
This gives a couple of mm of clearance with a daylight gap between the filter ends where before they just touched. And if anything shifts, it will be a rubber to rubber contact rather than metal to metal.
Just finished fiddling with fuel pipes, getting them sitting nicely with the new set up but its all I can do right now. Hopefully the necessary gasket, cables and other bits will arrive and at the end of the week or at the weekend, I should be able to try it out.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2019 at 15:50
Regarding straight inlets:
This is on a G5 and side panels would need major modification and I don't think I,d like the look, or the probable interferance of boot top with carbs. I'm sure that on your Zagato cafe racer, they look dead right.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Oldrat Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2019 at 17:29
Thanks. Would love to see some pics when you have time, as I said, I love different approaches.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote red leader one Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2019 at 19:52
Have you tried Tram Drivers gloves with a Fireman's helmet and one foot in a bucket?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 04 Mar 2019 at 22:45
No.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 06 Mar 2019 at 15:58
The 20mm spacers have worked out nicely. Proper clearance for the float bowls. (they must be a wee bit bulkier than on the old VHB carbs).

Throttle and choke cables arrived toay and fit perfectly. Gutsibits "throttle cables CAA28500" have just the right free length to fit with the Tomaselli twin pull twistgrip on pretty high bars.
And choke cables are for V65s "CAA19134 & CAA19133" using the original rocker cover mounted lever.
Both choke and throttle cables fitted with a 90 degree cable entry, which helps to give the cables easy runs.

No further progress until the L/H head comes back from having the broken studs renewed.
(I have 2 spare heads , but the ones on the bike are a better set)
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Post Options Post Options   Thanks (0) Thanks(0)   Quote chilly Quote  Post ReplyReply Direct Link To This Post Posted: 07 Mar 2019 at 08:54
Makes a nice change that cables fit straight out the packet Thumbs Up 
 
Onwards and upwards.
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Post Options Post Options   Thanks (1) Thanks(1)   Quote Gfiver Quote  Post ReplyReply Direct Link To This Post Posted: 07 Mar 2019 at 09:56
For the V65 choke cables, yes.
The throttle cable was a case of very carefully measuring of inner and outer lengths, and then on Gutsibits site, trawling through all the different throttle cables they list not only with which model, but with "outer length" & "Free length" (meaning, the extra length of the inner cable.
But yes, nice that those also came exactly to those listed measurements.
It enabled me to get the cables much quicker than if I had to order them one off from such as Venhill.


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Post Options Post Options   Thanks (0) Thanks(0)   Quote chilly Quote  Post ReplyReply Direct Link To This Post Posted: 07 Mar 2019 at 19:15
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