Thanks Brian, as obvious as it sounds, I hadn’t linked the size of the manifold exit to the size of the carb, Doh!!!It is 38 mm dia, so it is just as well you pointed that one out, I feel really stupid now.Does the breather box do anything other than route any collected oil to a receptacle? Breather pipes used to dangle out at the back didn’t they and now route to the intake?
AND! does it make any difference if the carb is off a two stroke?
The person to ask that one would be Ray Ex smoking biker BUT as far as I can remember the settings for 2T will be different to a 4 stroke bike.
But Ray is an avid 2T fan so would know more.
I am aware not all carbs suit a Vee Twin, delOrto work well on a Guzzi plenty of them available as well
i would use one of the delorto’s you already have, should be fine bar a needle or jet change once you have it running.
dont worry about the breather, its just for condensing oil vapour and getting it back to the sump. Universal tin style one from ebay or a high mounted mini k&n style one will be fineguzzi-t52013-05-20 21:48:36
One of the Dellortos you already have will work, probably with no change in terms of jetting, but with that manifold will produce a bias at tickover, making it impossible to get an even tickover. Guess how I discovered this.Not aware that a two stroke carb is any different in terms of the basic casting, but all the jets will need to be changed almost certainly. Things like the way the atomizer jet sits in the casting etc.
I’ll give one of mine a bash then
Sorry but I beg to be contrary, must be lots of topics on here now about oil breather problems. It’s not just “tubes hanging out the back” and “condensing oil mist”, the pistons work like a pump to try and blow out the crankcase contents, the crankcase can’t simply be sealed because that stresses the oil seals etc. so it will just come out somewhere else, in fact the one way ball valve contrives to maintain a slight vacuum in the crankcase (not a lot of people know this) this helps the seals keep the oil in plus scavenges oil away from the rocker boxes. So it needs something a bit more sophisticated! Balls it up and you risk dumping your sump contents with consequent risk of engine damage. I’ve actually had this happen to me (the big breather hose came off at 90 mph on the M6 because it had no jubilee clip [long story]). Ergo I recommend the Le Mans style, as you can’t the use original air filter which includes its own breather box. HTH
According to my Dellorto guide, yes it does, for 2 strokes it may have a taller needle jet, (“extended nozzle”) for 4 strokes “the atomizers … are manufactured with different types of side drillings because the positions of these holes affect acceleration response”. Fully open throttle position in both cases, but allow for ‘overlap’. HTH
I know all the theory re single carbs …heck the Brit bike industry often did both. BUT Guzzi work real well with the standard set up. Chatting to the guy that puts the virago stuff together it does , on them actually make the bike accelerate faster AND use more fuel !!!
I also understand the “need” to try to do something different. But I do often wonder WHY make things difficult?? Great if you have a good engineering background use of workshop facilities, but why upset a decent system that works? Make the system that is work at it’s best cos the 850-1000cc Guzzis work real well on the road , go well stop well handle well as standard IF everything IS set up correctly AND return 50 mpg
We just had a round trip to Somerset 2 up fully loaded running up the M5 at 80 the fuel worked out as near as I can calculate by miles covered and fuel used 48-52 MPG on a bike that IS 38 yrs old
Not being funny just …non-plussed at some of the “ideas”
The Guzzi breather system works, Guzziology goes into it and some alternatives BUT basically the system as is WORKS … Del-Orto Carbs work !!!
If I can get a Dellorto I will, If I can fit the breather box back in,I will. And I can fully understand anyone who wonders at the sense of me fiddling with a bike that works and that will quite possibly not when I have messed about with it, but I will not do anything to it that I can’t put back to standard. The plain fact is I enjoy tinkering and as long as I have one bike up and running I am happy. I haven’t got any great technical knowledge but I have been riding bikes for 43 years and have always fixed anything that has gone wrong and modified anything that took my fancy. My main problem is remembering stuff - give me a recipe book or a workshop manual and it’s a piece of pee. My often basic questions generally refer to stuff I have done before, but just can’t remember how, some things just don’t stick and as I have precious little time to play nowadays I am not doing these things often enough to drum them into my skull. Well anyway, it keeps me happy and maybe confuses others but hey, it takes all sorts and if I get it going I’ll be chuffed to bits.I’ll still need to tap your collective brains, mind.
OOOppps wasn’t “having a go” PLEASE don’t take my comments personal like… I sometimes …just “wonder” and yes indeed it takes all sorts, me i kinda do fettle and also enjoy it, especially when it WORKS
But i s’pose I also come into the if it ain’t broke mob…sorreee if I Pi***ed y off …didn’t mean owt by it …
My v50 did 10 years of riding mainly 2 up with a K&N breather mounted infront of the battery with no oil loss or problems and my t5 ws going just fine with the same setup untill i sorted the frame breather. The V Twin is just a standard 4-stroke engine, im sure different people with have different milage with breather solutions
guzzi-t52013-05-22 08:51:10
Not peed off, I just needed to explain that I have an uncontrollable need to fiddle and tinker with stuff.
Go for it, it’s your bike and your time. Thats part of the fun and exactly how I like to do things.My T5 will be going single carb when I have time to make a manifold up and see how it runs!Im deffinatly looking forward to progress reports 
I think it’s a good research project at the very least. All power to your elbow and all that.I tried it on the V50, and it worked apart from the bias on tickover, using just one of the original carbs. A different design of manifold with a longer stub for the carb might well have cured this, but I couldn’t see how to fit it in. Mike, “two strokes may need a taller needle jet” is what I was referring to when I mentioned the fit of the atomizer jet in the block.Dellorto call the needle jet an atomizer jet.Some of the carbs used on Guzzis in the States had additional protrusions on that jet, something to do with emmissions.
Have you got any details on the manifold you used Brian? I had hoped to make a adjustable section to hand tune the position of the carb then fabricate a proper one based on a bit of testing, not sure if you go for a simple ‘t’ joint and position equaly allowing for stepping in the cylinder or to make a simple plenium infront of the carb
guzzi-t52013-05-22 11:53:49
Making a manifold out of plumbing fittings as in Gambalunga is probably the most sane way to go and proven. I was seduced by sparkly stainless steel and will probably live to regret it! But you live and learn and then, in my case, forget!
Mine was just in copper, soldered T and 135 elbows. For a V50II only needed 24mm stuff.I have since wondered about reversing the direction of the Tee, so that the carb sits between the pots where the air box used to be. It would allow a longer intake stub. Very cramped going backwards as there is a battery in the way.I’ll try and get a photo up.
Brian UK2013-05-22 13:18:51
This from an old BSH mag. The builder used an 850T3 engine and fitted a twin choke Weber 40DCOE carb. I should imagine the manifolds were the least of the problems he had to overcome…
Looks like he mounted the motor along the frame, instead of across it, and driving though an old AMC gearbox. So at least he had room for the carb in that position! Astonishing!