Bloody Moto Guzzi's - Help!!

[Rob Farmer]

One for the closet Guzzi owners on the site

I spent more than a few hours yesterday trying to sort the jetting on a Guzzi T5 850. The bikes an ex Italian Police machine thats been fitted with new 36mm Dell Orto pumpers instead of the standard 30mm carbs.

The carbs were fitted with K&N filters put was completely flat above 4k. The K&N's were removed and Le Mans velocity stacks fitted, this let the bike rev but it was running very weak. The main jets were changed to 135 and the needles lifted one notch at a time until the bike actually started to go a bit. Jetting this way is costly and time consuming so I was hopeing somebody would have an idea of the jet sizes to get about right.

The ideal would be to have some sort of filter in place, I think the K&N, they are new, will not allow sufficient airflow.

Main Jets an 18, slide is a 60/3.

 

[cookie]

i had a dig around in guzziology for you. i was really hoping for something more promising

he goes on to recommend the dellorto tuning guide that i have found here

on the plus side, he does think big carbs on the small valve heads are a good idea.

best of luck

 

[Rob Farmer]

"and spending months experimenting" - Bugger!!







Thanks Cookie. I knew I could rely on you - Thanks for the link

 

[Hew]

Yes, there is a definite need for a Guzzi partition in the Other Bikes section.
Good Luck Rob

 

[Keith Chapman]

Rob,
according to Mick Walkers Moto Guzzi Twins book the PHF 36BS/BD carb is set up thus.

850 lemans 1 & 2:- 140 main 60 pilot 603slide K5 needle on 2nd groove 265AB needle jet

lemmans3 115 main (could be a typo) 50 pilot 603 slide K18 needle 3rd groove 265AB needle jet.

If I can find my Dellorto books I might get more details.

There used to be a Dellorto dealer in Reading, dont know if he is still there, might be worth a Google.

Good luck

 

[Deleted account 211025001]

Blimey, talk about a can of worms

Here's some more:

My last Guzzi, T3 950cc high comp, 36mm pumps, foam filters (can't remember what make), oversize valves in LeMans heads and P3 cam (not sure that makes any difference ) was running 165/170 IIRC.

Andres

 

[(RIP) Proff]

Dell Orto man

The man from Dell Orto>>>>
http://www.jrs.uk.com/
He's well renowned on all things Dell Orto

did a Beautiful job on my R90s ones.

 

[Keith Chapman]

Try here too,
also gives some tech stuff on the site
www.dellorto.co.uk

 

[Rob Farmer]

Cheers Proff. I'll give him a call. Fourtunatly it's a mates bike, if the going gets tough I'll leave him to it

 

[cookie]

Cheers Proff. I'll give him a call. Fourtunatly it's a mates bike, if the going gets tough I'll leave him to it

that's the spirit

 

[Straypuss]

So what manifolds are used to fit the carbs? I have a set of 36 pumpers and have read up in the bible of the need for stepped studs to fit 36 compatible manifolds to wee valve heads also that Guzzi fitted two fibre washers to the mounting bolts to prevent air entering and weakening the mixture.
Where did you get your Guzziology Cookie? My sis went to his shop in Seattle, where she now lives, for mine and met his shop partner at a party.

 

[(RIP) Kaister]

Rob - it needs bigger mains - i'd go a 150.
If you want to use K&Ns then adjust the jets with the filter in place.
They are no different old/new

.....by lifting the needle on the smaller jets youre just letting more fuel through earlier which points to you needing the bigger main.

put a bigger main in and drop the needles to middle. Then when you think the main is right - plug chop it to confirm.

only when its right on full throttle / mains can you start messing with needle position otherwise you'll go round in circles and mask the problem.

 

[Rob Farmer]

Phil,

The K&N's were just killing the bike as the revs came up. I expected the bellmouths to make it run alot weaker but the bike to rev better but was obviously still running weak. The bottom and midrange seem fine but it starts to gasp around the 1/2 to 3/4 throttle, thats why I lifted the needles. I couldn't get a clear run at the top end.

Sraypus,

The bike came from a guy who builds some pretty trick Enfields. He's got a decent workshop and modified the manifolds himself.

 

[(RIP) Kaister]

The K&N's were just killing the bike as the revs came up. ............ The bottom and midrange seem fine but it starts to gasp around the 1/2 to 3/4 throttle, thats why I lifted the needles. I couldn't get a clear run at the top end.

all points to a much too small main jet

it CANNOT be the K&N - unless the design is wrong - they offer no flow restriction

Get the mains on a use or return basis - if you buy 3 or 4 sets a decent shop should let you return the others

 

[Rob Farmer]

Cheers Phil. I'll get him to order some 150 mains