Dellorto Carburettors

Rick F · Post by **Rick F** » Thu Nov 02, 2006 3:19 pm

Hi Guys,

I have been putting a GT750 back together and have struck an interesting problem.
I fitted brand new 36mm Dellorto's back in 1986. The bike has sat around most of the time since then. Always tempted to sell it, but lucky I have hung on (against some stiff opposition from my wife)

I got some carbie kits & started to rebuild myself, but half of the bits seemed to missing or the wrong ones. i bit the bullet & took them off to a local guy here, who happened to be the guy that rebuilt the motor in 1986,
He had all the bits I needed but now has discovered that the tip of one of the mixture screws has broken off inside the carby! He can't seem to get at it & is unsure how he will get it out!
The suggestion of a new carby has come up-serious money I dont have at the moment-the new fibreglass tank sucked up all of the budget!

A real shame as the carbs had only done about 3000 k's- my own fault for letting them sit around I know (kids-mortgages etc etc) all the rubbers had perished inside and I spent hours cleaning out all the black goo.

Any suggestions on how to get the tip of the screw out would be most appreciated!

Rick F
Murwillumbah
NSW Australia

Craig in France · Post by **Craig in France** » Sun Nov 05, 2006 12:46 pm

Hi Rick

How frustrating! Some thoughts ...

As designed, the tip itself doesn't locate into anything - it simply juts into a small passageway within the carburettor body (screwing the screw in/out determines how much of this passageway is blocked/left open and therefore the amount of fuel-air mixture that gets fed into the engine at idle); so if it's stuck, it could be no more than fuel residue that's holding it in there. (And I understand yous guys in Oz suffer from particularly gummy fuel ...)

Possible solution: loads of carb cleaner, leave to soak, repeat etc ... and then a good blast with an air line to dislodge it.

Even a bit of heat might not go amiss. Me, I'd put the whole carb in an oven and heat it up slowly. The alloy body should expand more than the steel of the tip and let it go.

HTH

Craig in UK

Rick F · Post by **Rick F** » Wed Nov 08, 2006 2:34 pm

Hi Craig,
thanks for that- they are soaking at the moment- have been for several days
Will try that first before the oven. I was trying to think of some way to get some suction going.
It was going to be a couple of weeks clean up, & has turned into a year or more bare frame restoration with one problem after another!

I wont let it happen again, once it is going this time- I'll keep it going

Regards
Rick

Craig in France · Post by **Craig in France** » Thu Nov 09, 2006 1:26 pm

Hi Rick

I was trying to think of some way to get some suction going.

Borrow the vaccuum cleaner ? Just need to fashion up a little nozzle to fit on the end ...

Ciao

Craig

machten · Post by **machten** » Thu Nov 09, 2006 11:29 pm

You could also try an ultrasonic cleaning bath to dislodge it. This will also clean up the internal fuel paths at the same time, which is well worth doing if it has been sitting for an extended period.

Post by **BevHevSteve** » Fri Nov 10, 2006 8:22 am

+ 1 on the ultrasonic cleaner. I have one and use it after soaking the bodies in carb cleaner. I think the ultrasonic will disolve the gunk that is holding the piece in the hole, and, if you can have the body in the cleaner so the adjuster hole is down, it *might* even fall out since it vibrates etc....

machten · Post by **machten** » Sun Nov 12, 2006 6:12 am

Hi Rick,

Steve put it better than I could for the ultrasonic bath. The key question is "Why has the end broken off?". There are two reasons I can see: Either pure over tensioning ( so it may even have broken on the way in) or, oxidation of the brass through electrolysis between the brass and aluminum alloy over time (more likely). In both cases you probably have fuel "gunk" compounding the problem. The fuel gunk is why I'd use ultrasonic first and heat as a last resort. You could actually bake the gunk solid with a heat approach first. With ultrasonics, in theory, the brass tip will resonate at a different frequency to the host alloy, allowing a break of seal. The scenario Steve puts forward of it just dropping out is real. I'd go with a good carb cleaner soak, then an ultrasonic bath, assess results and go from there. This approach worked for my PHF-32's that sat neglected for 22 years.

Good luck!!

Regards,

Kevin

Rick F · Post by **Rick F** » Tue Feb 20, 2007 3:42 am

YeahGuys,
Thank for all the advice etc.
By the time I ran around, tried everything.... the ultrsonic cleaning bath did nada.........

So the good new is, guess what my wife got for our 8th wedding anniversary! A brand new pair of Dellorto PHF36 mm carbs from Bevel Heaven. She loves them, so she says!

The bike should have a Blue Slip for registration tomorrow!!

Thanks Steve

Rick F · Post by **Rick F** » Tue Feb 20, 2007 3:45 am

You Know what they say,

Long after the price is forgotten

The bevel lives on

machten · Post by **machten** » Tue Feb 20, 2007 4:10 am

Rick F,

Sorry the ultrasonic didn't work you as it worked for me. On a more important note, are you available for consulting services on buying PHF's for your wife on your anniversay? If you could publish that trick, it would raise the already high value of this forum to new level!!!

Kev

Rick F · Post by **Rick F** » Wed Feb 28, 2007 4:28 pm

Hi Kevin,

I not sure about the consulting, I will be paying for that one for years.

She will want to come for a ride on it now!

On another note, every thing was all set to go, Bike is running very well with the new carbs, we filled the Tank with fuel, (was less than half while tuning up the carbs) only to discover my new Fibreglass tank, from a very reputable organisation in Sydney (no names!), is leaking.

I only waited about 6 months for it! So it has gone back for repair.

One thing after another!

Cheers

Rick

machten · Post by **machten** » Fri Mar 02, 2007 3:22 am

Hi Rick,

Two steps forward, one step back! I remember my father often telling me "It is the anticipation of reward that makes life's labour sweet". It didn't do much for me at the time, but that first ride after restoration IS sweet.

Hang in there!

Kevin

Rick F · Post by **Rick F** » Tue Mar 20, 2007 5:43 pm

Bike works!

I rode it up and down our little country rode here a few times

Need to register it & paint the tank, but now it is up and running, I don't feel the urgency

I originally had the engine rebuilt in 1986 with sport pistons & valves,

with the new 36mm carbs it goes like a weapon

I have to get the speedo working to see how fast. Feels fast, but I am taking it really easy

Regards all
Rick

PS my wife loves it

<-=- Club Bevel Heaven -=->