Difference in fuel mixture screw settings front/rear

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macca__macca
Posts: 56
Joined: Mon Mar 31, 2014 4:21 am

Difference in fuel mixture screw settings front/rear

Post by macca__macca »

Hi all,

I recently removed and thoroughly cleaned my carbs.

During this time I took it upon myself to also go down in size on my main jets - the previous owner had installed jets that were too large imo.

I am now running 185f/190r mains from a DynoJet kit.

Question: My fuel mixture seems to be right at 1.5 turns out for front, 2.5 turns out for rear. This seems like a large delta considering most people only have .25 turns difference between front and rear. What could cause this and is it indicative of a broader issue? I'd always thought there was something wrong with the mixture on my rear as the spark plug indicated too rich (the front was fine) - the rear plug's insulator was completely clean/white which is odd.

Details about my bike:
K&N air filter
DynoJet kit: 185f/190r
Stock 45 pilots

Freeflowing slipons - D&D pipes (LOUD doesn't begin to describe them!)

The DynoJet kit recommends starting at 2.5 turns out front and rear when setting mixture after jetkit installation.

When i did the fuel mixture setting procedure I also noticed that when adjusting the mixture for the rear cylinder i didn't notice much difference (if any) when screwing it in or out, whereas when setting the front there was a noticeable sweet spot where the idle increased.

I'd appreciate your thoughts on the above.

Thanks all,
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lloydie
Posts: 20921
Joined: Mon Jan 17, 2011 11:16 pm
Location: In the garage somewhere in Coventry

Re: Difference in fuel mixture screw settings front/rear

Post by lloydie »

1/4-1/3 is the normal difference between the two .
I always set the rear mixture first as it runs hotter than the front .
Also having your carbs in balance makes a big difference when setting the mixtures I've found .
NZSpokes
Posts: 643
Joined: Sat May 31, 2014 10:50 am
Location: Auckland, New Zealand

Re: Difference in fuel mixture screw settings front/rear

Post by NZSpokes »

Hard to compare the 2 when they run different emulsion tubes, deal with different heat stresses etc.
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