31K bored at 66,25mm fuelmixture is too rich

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havlis
Beiträge: 8
Registriert: So 26. Jul 2009, 21:32
Wohnort: Liberec

31K bored at 66,25mm fuelmixture is too rich

Beitrag von havlis »

Hi i need help with jetting of mi 31K RDs.
31K cylinders bored at 66,25mm, carbon reed flanges on original reed houses, 31W carburetors (no power jet), air filter from Macro Boemer.

I try MJ 300 it was unbelievable rich it four stroking also at the half of the gas.

Then I try MJ 240 it is still too rich, but now at the 1/2 of the gas it run. At the idle it four stroking. Air screw must be opened (screwed out) cca 8 rounds (it seems crew fall out any second).

It seems I must use MJ 190-200. I have feeling something is not right )=>>.
Please can you help me?
(Choke is pushed)
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Holliheitzer
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Beitrag von Holliheitzer »

Hi Havlis,

What value has the idle jet? And are they installed??
Your feeling is true :wink:

Holli
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havlis
Beiträge: 8
Registriert: So 26. Jul 2009, 21:32
Wohnort: Liberec

Beitrag von havlis »

Holliheitzer,
Pilot Jet is 22,7 and they both are properly installed )=>>

I try one more time blow whole carburetor with air from compressor (5 Bar).
It seams it must leaking fuel out of Jets anywhere.

But question is where it can be?
schrauberlehrling2
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Registriert: Mo 5. Sep 2005, 01:00
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Beitrag von schrauberlehrling2 »

Might be a good idea not to just blow some Air through the carbs, better throw them into an ultrasonic cleaner.
Especialy the Needle Jets and their air supply needs to be perfectly clean, if not your mixture will be far of to the rich side.
A high flow Filter combined with smaller than Standart Jets does not Sound like a good idea.
Do you use Mikuni Jets? Mikuni sizes refer to flow, other Brands tell the bore diameter...

greets
Florian
havlis
Beiträge: 8
Registriert: So 26. Jul 2009, 21:32
Wohnort: Liberec

Beitrag von havlis »

I have original mikuni jets, flow measure. (price for one was 3,2E)
Is there any cheaper version ?
m.eckert77
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Registriert: Fr 30. Mai 2008, 11:59
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Switzerland

Beitrag von m.eckert77 »

Hi,

you can get after market jets for around 1.5-2 E per piece. I dont know the manufacturer but a local bike stuff dealer can help you for sure.
Ich danke allen die geschwiegen haben obwohl sie nichts zu sagen hatten.
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MK
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Registriert: Di 16. Okt 2001, 01:00
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Beitrag von MK »

Did you install the slides the right way ? The cutaway must be on the airfilter side, not on the engine side.
Ciao
Martin
---------------------------------
SSDD (Stephen King, Dreamcatcher)
havlis
Beiträge: 8
Registriert: So 26. Jul 2009, 21:32
Wohnort: Liberec

Beitrag von havlis »

MK - nice try )=>>

Vulnerability was found. It was on left pilot jet carb. Some mess was on the surface of contact. The gas was leaking around the jet, then mixture was too rich.

Now i have best feeling from MJ 300. (carb with no power jet)
Jet needle is at the second position from down. Fourth position from upper.

Now around 5000rpm with little gas it seems to be too rich.
At the what position do you recommend the Jet Needle?
havlis
Beiträge: 8
Registriert: So 26. Jul 2009, 21:32
Wohnort: Liberec

Beitrag von havlis »

Now I try MJ 270 it seem to be the best around 4500 - 6000 is much more power. Lower rpms with minimum gas is prety smooth.

But it seems the mixture from 8000+ is too lean and the motor subjektiv loos some power.

It seem that i should use MJ 290 and i send Jet needle one pin down.
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