ET: Engine (Twin) Slide size 389 monobloc?

[Normski]

The owner previous to me fitted new 389/10 monoblocs, these new carbs have a /3 slide fitted. The old 389/10 monoblocs have 3 1/2 slides. I have found the bike runs better at normal road going throttle openings with the needles lowered one notch from middle, but am I changing the wrong thing? It seems a large step from the original fitting of /4 slides to /3.
Can people running monoblocs tell me which slides they are using please? My engine is Rapide with mk3 cams, Suzuki Pistons and is fitted with Club Spares foam filters, which are fairly free flowing.

 

[Brian Chapman]

hi
go towards 4s if not 4s ... over 50 years with monoblocs , series D outfit .
regards
brian.c

 

[John Cone]

Go by what the bible says

 

[John Cone]

I'm trying to decide whether to take the chance and buy a new set of Monoblocs, resleeve the old ones or go for consentrics

 

[vibrac]

Imho concentrics were a retrograde step from monoblocks but since fitting a Mikuni I feel it's an academic question anyway unless originality comes before effectiveness and suitability with the petrol composition expected in the future

 

[greg brillus]

Put new mono blocks on it, it will run fine, and look correct. Contact Burlen's you can buy direst from them, less expensive than 276/289 's.

 

[Normski]

I much prefer monoblocs to concentrics, if I had been buying the new carbs I would have bought the correct 276 1-1/16 size for a Rapide or Mikunis but I'll live with the 389's
Burlens recommend a 3-1/2 slide and someone else (Surrey Cycles?) recommend a 3 slide which is why I asked here about user experience. I doubt the people recommending the 3 slide can say on what experience that recommendation was based.

 

[greg brillus]

I supplied and installed a set of Mono blocks to an enclosed "D" about 18 months ago supplied and set up per stock from Burlen's, seemed to be just fine out of the box with minor adjustments.

 

[Normski]

I supplied and installed a set of Mono blocks to an enclosed "D" about 18 months ago supplied and set up per stock from Burlen's, seemed to be just fine out of the box with minor adjustments.

Which size carbs were these Greg? I am asking because I'm also interested about main jet sizes and Burlen recommend 280 for the 389 which is again richer than original.

 

[greg brillus]

389/10 One and one eighth bore. Same size as a Shadow. Put the info into their bike make/model selection listing and it will come up with the right ones.