Carb or hoover....

[Alex59]

Hello,

Today i set the synchronisation of the carbs on my triumph vitesse MKII. At the same flow rate (+/- 5kg/h) one of my carb is quiet and the other one make noise like an hoover.

Do you have any idea of what can cause this difference between the 2 carbs.

Thanks for your answer

Alex

[johny]

I take it both needle pistons are always in matching positions and perfectly free to move? Also was the synchronisation much out of adjustment?

Youve set the butterflies to give the same air flow but if one carbs piston sticks (usually its jet isnt centred correctly) then the sound could be changed and obviously fuel mixture would be incorrect at that point.

Another possibility is that a rubber diaphragm (Im assuming standard Strombergs here) is perforated so its piston wont rise the same as on the other carb.

Finally an air leak would also generate a different noise so have a look around the carb joint to the inlet manifold plus any pipes connected to the carb where air might be drawn in.

Of course in each case the running of the engine will be affected...

[Alex59]

Thanks Johny for your answer, i'll check for the movement of the piston. The synchronisation wasn't much out of adjustement.

The carb joint to the inlet manifold are new, i replaced it when i have to repair the inlet manifold (banjo break).

[johny]

Its worth checking things as think having different noises is strange however seeing how it drives will be the decider...

[PeteH]

It`s now 40 years since I had a Vittese. But I found that checking the mixture with (in my case) a Colourtune, was a good indication of carb; balance?. I had 2 of them so they went in #2 and 5 cylinders.

Pete

[NonMember]

11 hours ago, johny said:

Finally an air leak would also generate a different noise

This. Carbs should make a "shh" or "fff" noise, if you're getting a howl or a whine then it's probably a loose gasket causing an air leak.

[Pete Lewis]

do make sure the diaphragm location lugs are placed correctly  

with the top cover off a lookdown the piston the two holes in its base must be   engine facing  

i take these are CD/CDS  IE   no temperature compensators fitted 

and if its |CDS  on the front carb make sure the choke disc valve is clean not blocked or badly corroded

 

Pete 

[Iain T]

15 hours ago, Alex59 said:

one of my carb is quiet and the other one make noise like an hoover

I had the same after I fitted my reconditioned carbs. The front hissed. First I thought it was the manifold gasket but on closer inspection it was the front carb heat insulator and gasket. The ones fitted to my car had a slot/notch protruding out of the centre main hole. On my Cds150 carbs this notch is not required and in certain orientation it very slightly protruded out from the manifold and let air in. I bought two correct isolators with just the plain centre inlet hole which solved the problem. 

Iain 

[Alex59]

Thanks everyone for your answers.

I checked again the noise of the carbs and it's pretty close...next time i'll have to clean my hear.

But I think i will have to dismount the carbs and made a joints kit to refurbish the carbs (have some leaks too)

I have a 150CDS a the front, the second one, have no number but it's a CD one.

 

[Iain T]

Alex, my problem was at the carb to inlet manifold end the video shows carb to air cleaner. I agree best take the carbs off and take a look at all the joints. After fixing all my leaks tuning became a LOT easier!

Iain

[Pete Lewis]

the front will be CDS  the rear CD as there is only one with a starting valve(choke)  so your carb mis is correct the front choke feeds the rear carb witha short plastic tube 

Pete

[Iain T]

13 hours ago, Pete Lewis said:

front choke feeds the rear carb witha short plastic tube 

I think I saw that in the video? 

[Alex59]

Yes i have that tube from the front carb to the rear one