FCR Questions

BelgiqueBasterd · Jul 12, 2009

Took apart my FCR carb and came across a couple of strange things.

First off all, the pilot fuel screw on the parst diagram it shows that on the pilot fuel screw there is a spring, a small washer and a small O ring. On mine the O ring was missing does anyone know wich size this o ring is? The parts manual doesn't mention it.

Second, there is no main air jet in the carb it's just a hole, if I look into the small hole I can't see any threads so I presume that this is a carb where the carb body is drilled to a certain size instead of removable jets. The carb came out of a Honda CRF 450, anyone happen to know wich size the hole is drilled to?

And last, the starter jet is a 68, in the husaberg manual it says that it should be 85, will this make a big difference in starting or is this just details?

DaleEO · Jul 12, 2009

BelgiqueBasterd said:
Took apart my FCR carb and came across a couple of strange things.

First off all, the pilot fuel screw on the parst diagram it shows that on the pilot fuel screw there is a spring, a small washer and a small O ring. On mine the O ring was missing does anyone know wich size this o ring is? The parts manual doesn't mention it.

Second, there is no main air jet in the carb it's just a hole, if I look into the small hole I can't see any threads so I presume that this is a carb where the carb body is drilled to a certain size instead of removable jets. The carb came out of a Honda CRF 450, anyone happen to know wich size the hole is drilled to?

And last, the starter jet is a 68, in the husaberg manual it says that it should be 85, will this make a big difference in starting or is this just details?

Belgique,

I don't know what size that little O ring is, but, be sure you have a really careful look up inside that hole to make sure it's not stuck up there. If it's there and you put on another and seat the fuel screw you'll shove the existing O ring into the orifice and have fits trying to figure out what's going on.

I have not heard a FCR MX carb like yours without a Main air. It should be a 200 on the Main air jet, and a 100 on the pilot air jet. At least that is what is stock. I am guessing the threads are there, unless someone drilled it out. This could explain why your dyno guy ended up with such a huge main jet.

The start jet. Yes this can make a big difference, but, that carb was for a 450. And since you have a 650 the intake impulse is much stronger so the jets typically need to be smaller. If it is starting okay with the 68 then it's working and doesn't need to be fixed.
Taffy has a great explanation on start jet sizes in the doc.

Hope this helps.,

Dale

BelgiqueBasterd · Jul 12, 2009

Did some digging on the TT forum and found the answer, apparantly there are FCR carbs with a fixed orifice .200 so that's one thing solved.

Now all I need is a new starter jet and an o ring for the fuel screw.

Husaden · Sep 4, 2009

I've got one of the FCR's with no main air jet as well.

http://husaberg.org/index.php?name=PNph ... 5027#95027

But how do you know what it is drilled to ??

No threads in there for sure, but I am planning to screw in a 200 anyway.

Anders, DK

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