UK Karting - Notice Board (2-Stroke Karting) : Odd behaviour of Pre-EVO Rotax carb

Notice Board (2-Stroke Karting)

Odd behaviour of Pre-EVO Rotax carb
Posted by 'JamesHughes' on 27 Jun 2020 @ 12:19

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JamesHughesJoined: December 2008
Total Posts: 45
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Hello all,

this one is a bit confusing.

Engine on the whole runs well, but was hesitating and bogging a bit at about 12500, and not going much higher. Tied jet changes, needle placement etc.

The only thing that has changed it is removing the breather pipe - the one that loops between the two carb breathers and has a slot in to actually breath.

I'm trying to figure out why that makes so much difference - revs to 14k, no hesitation etc. The breather is not blocked in any way.

Idea 1. The pipe was routed in front on the carb. At speed air is being forced in the cutout, pressurising the carb and preventing fuel getting in. Removing the breather means this doesn't happen

Idea 2. fuel in the bowl is going up the breather, then dropping back in, so too much fuel is in the carb. Removing breather means fuel is discarded rather than dropping back in the bowl.

For 1 I can reroute the breather to back of carb.
For 2 I can add a small catch tank and see if anything comes out.

I need to check the float level as well. Not sure what weight floats I am using so also need to check that.

Anyone have any other thoughts?

Message Thread:

Odd behaviour of Pre-EVO Rotax carb by 'JamesHughes' << You are here!

Re: Odd behaviour of Pre-EVO Rotax carb by 'BrianP' (29 Jun 2020 @ 9:16)

Re: Odd behaviour of Pre-EVO Rotax carb by 'JamesHughes' (29 Jun 2020 @ 15:06)

Re: Odd behaviour of Pre-EVO Rotax carb by 'BrianP' (30 Jun 2020 @ 9:34)

Re: Odd behaviour of Pre-EVO Rotax carb by 'JamesHughes' (01 Jul 2020 @ 19:56)

Re: Odd behaviour of Pre-EVO Rotax carb by 'BrianP' (01 Jul 2020 @ 20:40)

Re: Odd behaviour of Pre-EVO Rotax carb by 'Mark 71' (03 Jul 2020 @ 12:30)

Re: Odd behaviour of Pre-EVO Rotax carb by 'JamesHughes' (03 Jul 2020 @ 23:19)

Re: Odd behaviour of Pre-EVO Rotax carb by 'JamesHughes' (12 Jul 2020 @ 20:58)

Re: Odd behaviour of Pre-EVO Rotax carb by 'JamesHughes' (02 Aug 2020 @ 23:47)

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