well I finally got my fcr 37. I instantly changed the leak jet to a 35 to help with the bog. The jets are a 160 main and 45 pilot. I threw it on and it feels lean for sure. the pilot seems ok but it has a bad dead spot when ya snap the throttle. I have the air box lid off so I put it back on and it ran better by far. I guess I will bump the main up first and get the wide open dialed in then see what I can do to help the bog. Do you guys think if I upped the pilot it would help with the hesitation? It's about 3 turns out on the pilot screw so I'm thinking I may be able to go up a little on the pilot.
anybody run an FCR37 on their warrior?
- Thread starter mvvette97
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cheese_05_70
Well-Known Member
Could someone explain what the benefits are when going to a fcr37 and 39 vs the btm36 mikuni. Just a bigger carb and more power for built motors?
What does it all take to bolt one on also. Raptor intake boot?
Thanks
What does it all take to bolt one on also. Raptor intake boot?
Thanks
Gen1Pat
Well-Known Member
Yeah I'd go up on the pilot by one. Perferably 2 turns out on the mixture screw is usual. Have you plug chopped it? Although the main plays a part in the mid-range, the needle is what controls it mainly. Sounds like you need to raise the needle a notch or two. Plug chopping and lots of jets is what ya need to do. I remember reading that the "dead spot" was part of the accel pump issue with the 37. Hard to tune it out, from what I've read anyway.
Bigger carb, more velocity, more air flow, modern design, TONS of tunablity, more powerfull accel pump... It CAN fit in the rappy boot, but is too tight IMO. I make my own manifolds.
I have a parts fcr 40 carb so I'm going to swap the blue spring in the 40 to my 37. There is a spring on the black plastic arm on the acc pump. After doing this it will be the same acc pump setup as my 40 that's on my kfx. I'm also going to jump up the pilot and main a bit and see what it does.
Just to let everybody know I got my fcr37 on and tuned for the most part. At first I had that bad acc pump bog that you guys were talking about with the 37mm. I got that all cured and am very impressed how the thing runs. I ended up using a 45 pilot at two turns out on the mixture screw and a 165 main. I may bump it up a little. To fix the bog I used the 35 leak jet in the bowl and larger starter jet beside the pilot. I think it was like a 72 or something. The part number for the starter is 09492-35G00. I set everything with the acc pump the same as my fcr40 on my kfx and it's amazing. So really to get the 37 to work with no bog you need the 35 leak and 72 starter. I'm gunna play with the main a bit more but I think I have it very close. Just thought I would share what I did to fix the acc pump issues with the 37.
duneracerweston
Well-Known Member
Interesting... I wonder which is the better mate for the350, the 37 or 39. I may haveto test a 37 out some day
Not really sure but I have a spare fcr40 I put on it lastnight just to try and I noticed that I lost alot of bottom end with no real topend gain compared to the 37. I think the 40 was a little large for it. If I had a 39 I would try it but I would guess it would be very close to the 40. But once I changed starter jet and leak jet it completely fixed the terrible bog it had. Oh and I tried a 50 pilot but I had to have the mixture screw all the way in and it still wasn't enough. Didn't want to idle. The 45 worked perfect for the best idle without having the mixture screw out too far.
Gen1Pat
Well-Known Member
Interesting. I noticed no bottom end loss with my bike. But, I am running a +4 stroker, and have more cylinder volume. It's interesting how the leak and starter jets played a part in jetting. Mine is burning fine, but, I wonder if changing the starter and leak jets, if I can back down the jetting...
duneracerweston
Well-Known Member
I run a 39 with no bottom end loss, granted mine is far from factory, I would still be interested to try it.
I'm not sure the function of the starter jet but the one that came in my 37 was a 42 or something and it was really lean. After putting the 72 or about that starter jet it totally fixed it. Usually the 35 leak jet will fix the bog but it didn't on mine. It was better than it was with the original leak jet but not good. After changing the starter jet it was a huge change.
duneracerweston
Well-Known Member
Starter jet is the one on the intake side of the carb correct? Its in the intake?
The starter jet is beside the main jet. It is pretty much between the main jet and the float needle. So if you were setting on the machine it would be the rear jet facing the back or air filter side of the carb. Kinda of like from rear of carb to front, starter jet.. main jet..pilot jet.
Venom
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sorry to be a grave digger but no point in opening a new thread
is this the one?
FCR 38mm MX
http://santamariadafeira.olx.pt/carburador-keihin-fcr-38mx-iid-436235314
is this the one?
FCR 38mm MX
http://santamariadafeira.olx.pt/carburador-keihin-fcr-38mx-iid-436235314
DeadLastRacing
Well-Known Member
they are using a 39mm off a YFZ.
Go to ebay and type in honda CRF 250R carb. Mine is off an 04. Just for some info for you guys I tried an FR39 the other day and it did run good but didn't have the low end torque that my 37 made. The top end seemed pretty much the same. I went back to the 37. It seems like a better carb for my setup. If I were going to run a big bore or stroker I would go with a 39 or 40 but for stock bore the 37 gave me the best power from the bottom end up to the top. The fix for the 37 fcr bog is a 35 leak jet and a 74 starter jet. As for the main jet I run a 170 and 45 pilot.
I have a high compression piston with alot of head porting and stage 1 hotcam and the full exhaust. The fcr37 was a VERY good upgrade. It gave it much better torque and at the same time let the engine rev to the high RPMs more like it should. In my opinion it's the perfect size carb for a stock bore.
Gen1Pat
Well-Known Member
I can go for that. My stroker has all the torque you need, and the carb works great with it. I've figure the 39 with stock stroker would be rpm happy.
