Misc: Carburettors VM34 pilot jets

Bill Cannon

Bill Cannon

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I've recently purchased a pair of Chinese copy Mikuni VM34 carbs. I've stripped and checked them and all seems well.
The 1200 Egli starts well with them on using the chokes. problem is the air screws need to be all the way in for a clean idle. This means I need larger idle jets but sadly the existing jets are not numbered, so I don't know which size i need.
Also most of the jets I am seeing online are 14mm long but the fitted ones are 16mm long, is this a problem?

As best as I can measure with vernier, they seem to be 1.1mm diameter.

Any advice, other than buying genuine ones, greatly appreciated!

Cheers
Bill
 
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Trickymicky

Trickymicky

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I'd suggest a full set, which are not unduly expensive (covering the approximate size you already have). Then use them as a plug gauge to determine the exact size of yours. From there, increase the size of the jet by the next available drill.
 
brian gains

brian gains

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As a starting point, on an 1100 cc it has #30 pilot fitted, starts after prime kicks with one or two prod's , invariably needs enricher though, idles when warm.
 
N

Nigel Spaxman

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I found that my Rapide with 34mm VMs,needed rather large pilot jets so that it wouldn't pop when going down hills on closed throttle. I ordered some #55s but I never put them in because before those arrived I drilled out the ones I had, It worked so well I never put the proper ones in.
 
Bill Cannon

Bill Cannon

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Confession time!
Being impatient I remembered my "dremel" kit came with some tiny drill bits so I found the smallest which measured 0.85mm, it would not go through the jet which I measured at 1.1mm. So I realised that the jet is "waisted" down to a smaller size.
What I should have done was wait until the drills I ordered arrived but I decided to drill them anyway. I had to do it with the dremel as the chuck of my pillar drill wouldn't go that small. The drilling went OK.
I refitted the jets after a good blow through and gave it a try.
Of course you have guessed! The bike started fine but even with the screws all the way out it is now way too rich.
The bike is probably rideable now but I'll now have to order some new jets.
Funny old life isn't it?
 
vibrac

vibrac

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Bit late to the party but in the racing comics I note there is a company a mile or so from Vincent Spares who make jets in UK for Mikuni Keihin Dellorto etc

KMT Products - Home

KMT Products - Home
www.kmtproducts.co.uk
 
Bill Cannon

Bill Cannon

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Thanks Tim. I have already got replacement 40 and 45 idle jets but now the float chamber gaskets have given up, I don't think they are ethanol proof. I have just received some gasket paper, as the replacements from Mikuni are actually different. Just waiting for a craft knife to arrive to finish them and fingers crossed we'll be in business again. I'm begining to understand why these carbs are so cheap!
 
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