Moto Guzzi t3 - Out with the Mikunis and back to Dellorto - Thoughts?

[across]

I am slowly bringing a 1977 Moto Guzzi - T-3 back to a more "Slightly Stock" or atleast Italian component bike.  Quick History it had some heavy mods done in the 1990s with Rennsport stuff,  kinda looked like a transformer 90s sic fi bike
-complete exhaust kit, large Mikuni 36mm flat slide TM carbs, The VHB manifolds have been replaced with the non clamp style with the rubber attachment like the newer PHF Dellorto carb. engine also had the big bore done to 1000cc. with a dual plug head and deep sump oil pan etc.  The bike runs well and is a peach on the highway at 85mph.  I removed the rennsport exhaust because it actually sat right below the oil pan and oil changes requires the pipe removal, so that was the first to go.  Now I am thinking about  the carbs.  I have received many comments on "if it ain't broke don't fix it" from my friends at home (solid advice yes) which I have learned the hard way many times, however I would really like to put the dellortos on the bike to return to a more "stock " approach. My experience is only with older brit bikes so I know how this can go with carbs, down a very dark long road so maybe some of you out there may weigh in on this from experience. What I have been thinking so far is to
1.Replace the Mikuni Tms with New Dellorto PHF 36mm and buy a few different size main jets above and below the stock size and tune from there

2.the other option which was suggested to mefrom some guzzi folks here at home  was to find a good used set of the stock VHBs and rebuild them and also replace the stock manifolds etc. and go back to the actual stock carb. with a change in jets etc. to accommodate the big bore etc.

I am a little hesitant to try option 2 as I do worry about buying good "used carbs" and the rebuild etc and worn parts. 
Anyway - anybody out there who cares to share their knowledges would be great. Cheers and happy Sunday

[mach1mustang351]

Funny, im working on the opposite. Im putting Mikuni carbs on my 1000SP. I was torn the same way you are. I really wanted the Dellortos to work, but after 6+ rebuilds and tons of work on them the bike still wont fuel at idle. I decided that it running is more important than being original. Maybe one day it will go back. Good luck with it.

[across]

yeah I have had a few people remark that the mikunis are there for a reason and I should not fight gravity on this one, I had tried to switch to mikunis in the past from Amal on british bikes  but always went back to the simple Amal which seemed to work best.

[Aaron D.]

Do you know what mods were done? I sort of understand your thinking but I bet the Mikunis work a lot better.

[across]

 Everything that was done to this bike is hand written on notebook paper from the 90s and it's kinda vague, apparently the rennsport company folded and left town so it's hard even here in Southern California where they are actually from to get much history or insight. the mods that I know about to the motor are the 2 plug heads and the big bore kit to 1000cc. and a deep sump for the oil pan.  The carb manifolds are the later Dellorto type to accommodate the later style rubber mounts which the mikunis are attached to, the carbs are a huge 36mm size.  Another reason I want to switch to the dellortos as they seem to be a bit simpler to work on as well.  These mikunis are pretty elaborate with a ton of parts.  The Dellorto PHF seems similar in sense as a Amal concentric and parts for them through MG cycle are available.  These Mikuni TMs it seems are hard to source parts for too.  Again this is all a learning experience for me so anyone with some insight on this is great.  I know that it's hard to really predict but maybe some of you have dealt with this dilemma before and could shed some light - Cheers

[jabberwocky]

You should know that switching back to dellortos will give you a very heavy throttle spring. I am On my T3, I use the throttle binder screw, so my hands don't go numb, but it's kind of annoying. I'd love to have Mikunis on my bike, I'm just afraid I'd be chasing the jetting for a whole summer.

[Arizona Wayne]

Yes, the Dellortos have strong throttle springs, even on my 30mm PHFs.  I use a Throttlerocker to deal with that.  If the bike runs good I'd leave the carbs alone.  The 1000cc Guzzi motors came with either 36 or 40 mm Dellortos.  My CX100(SP) has smaller valves and has the 30mm carbs instead.  If it ain't broke don't `fix' it.     In 50+ years of riding I rarely have any carb issues.  Don't understand why others do unless they can't keep their hands off them. 

[guzzista]

Before you actually change anything enjoy riding the bike as it works well, then I would read the Guzziology chapter on carburetors,  sizes,  jetting options and so forth.  That might either help you on your direction or convince  you to ride the bike as is. Either way you cant go wrong, save the effort required to get the Dellos dialed in. As per stiff throttle complaints, if set up well the PHFS( or VHB's) should be pretty easy to live with. I have 2 bikes with 36's and one with VHB's.  The throttle effort is not bad even if not as  light as my EFI bike.

[Antietam Classic Cycle]

You should know that switching back to dellortos will give you a very heavy throttle spring. I am On my T3, I use the throttle binder screw, so my hands don't go numb, but it's kind of annoying. I'd love to have Mikunis on my bike, I'm just afraid I'd be chasing the jetting for a whole summer.

Lighter springs are available...

[huub]

i just changed the carbs on my lario from dellorto to mikuni , in my opinion the mikunis are a better option.
so first try to ride the bike , and try a dellorto equipped bike.

if you decide you really want dellorto's , i've got a nice set of 36 mm dellorto's i could swap for your mikuni's.
36 mm carbs on a tuned guzzi 1000 is not too big, all the 850 le mans models came with 36 mm carbs.
you might check the valve sizes, if the heads are done to le mans specification a smaller carb will reduce the top end power ,

[jabberwocky]

Lighter springs are available...

Really!? I clipped a coil out of my springs, helped a tiny bit. I realize that this reduces preload, but actually raises the spring rate. Are you talking of something I have to hope I can find at a hardware store, or something I can order that is proven and intended to fit. I'd really like to get a set.

[Antietam Classic Cycle]

Really!? I clipped a coil out of my springs, helped a tiny bit. I realize that this reduces preload, but actually raises the spring rate. Are you talking of something I have to hope I can find at a hardware store, or something I can order that is proven and intended to fit. I'd really like to get a set.

http://www.mgcycle.com/index.php?main_page=product_info&cPath=62&products_id=2110

Dellorto's lightest throttle slide return spring for PHF and PHM series carburetors. This spring is rated at 0.7kg@70mm. Suitable replacement for all PHF and PHM round slide carbs as found on 850, 1000, and 1100cc Guzzis.

[jabberwocky]

Do  you know if they work on VHB's? That's what I'm dealing with.

[keuka4884]

My 1978 T3 has VHB's. The stock return springs have a 2 kg pull. Not enjoyable. MG cycle has 1.1 kg springs for the VHB's. That should solve your problem.

[Antietam Classic Cycle]

Do  you know if they work on VHB's? That's what I'm dealing with.

Different springs for VHBs: http://www.mgcycle.com/index.php?main_page=product_info&cPath=62&products_id=4661

[jabberwocky]

Well shucks, thanks for that. That got me perusing the MGcycle site, and I found some other things that will go on my next purchase.