Keihin CDK 2 - Reverse Jetting?

[Miguelxj]

Is this possible?

I have a 750sp on a X2 hull and trying to figure out if this can be done on a set of triple jet CDK2 40?

I managed to get it running OK with the following specs:

Main 140
Pilot 80
Middle 45
1.6 ns
18 psi popoff

PROK flame arrestors (low restriction)
650 Coffmans pipe


My other X2 (650 with Sbn44) is setup with reverse jetting and it runs so nice, very snappy throttle!

Any input or a starting point?

Thanks in advance!
MR


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[JonnyX2]

Miguel PM user WMAZZ, he is very keen on reverse jetting and those Keihin carbs

[Miguelxj]

Tried to a month ago but nothing..


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[Miguelxj]

Just looking for some opinions...

What effect would a different ( bigger) needle and seat have on this setup?

Is it true that on these carbs, the NS are part of the aluminum body?


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[waterhappy]

I'll ask Wmazz later this week. With a mid range jet I do not believe it is possible though.

[Miguelxj]

Thanks man!

I got it running good with the following specs:

140 main
80 and 55 pilots

12 psi popoff

I have idle now and its snappy. Only thing bothering me is the bogging down in the first 4 or 5 seconds after shuting the engine down...


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[waterhappy]

Bill said he'd check this afternoon. Couple things, are the low speed bypass homes drilled out (larger then 24 thousandths) sounds like the spring was cut to have the pop off that low. The pilots sound s little large. Do you have a restrictor on the fuel return?

[bandit88]

That popoff is really low, probably contributing to the bog.

[Miguelxj]

Waterhappy: stock unmolested carbs out of a 1994 750 XI supersport.... Only messed with jets and spring.

Recomended popoff for these carbs range from 10 to 24 psi. With higher popoffs the engine would run lean on low rpms, had to pinch it.

Bandit: agreed. But as stated, I could not run it on low rpms without low popoff :/


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[wmazz]

I have a 750sp on a X2 hull and trying to figure out if this can be done on a set of triple jet CDK2 40?

You can not reverse jet a set of Keihins, But you have one of the better sets of
Keihin cabs. Drilling the small hole under the mid-range check valve to 1mm will
give you excellent throttle response. Better than many Mikuni's.

James (WaterHappy) has a pair of Keihin's from a Polaris 1050 on his 800cc PJS
Super Cylinder engine, and they have many advantages over a set of Mikuni's.
His set has (2) 1mm holes.

Is this possible?

I have a 750sp on a X2 hull and trying to figure out if this can be done on a set of triple jet CDK2 40?

I managed to get it running OK with the following specs:

Main 140
Pilot 80
Middle 45
1.6 ns
was ->18 psi popoff
now ->12psi pop-off
PROK flame arrestors (low restriction)
650 Coffmans pipe

My other X2 (650 with Sbn44) is setup with reverse jetting and it runs so nice, very snappy throttle!

Any input or a starting point?

Thanks in advance!
MR

First off, what is the reason or problem that led you to such rich jetting.

What was the original problem?
What is the low speed (pilot) screws turned out too?
""Important"" What impeller and nozzle are you using?
Is the Coffman pipe dried out?

The stock flame arrestor is very free flowing, and there is no reason to
lower the pop-off when you made the change.

What type of gaskets are you using on the carb base? and have you
recently rebuilt the carbs?


Bill M.