I have searched a lot of threads and have not found anyone running jets this large. Guess I will buy some smaller jets and see what I can do. I checked to make sure it is squirting fuel when the throttle is wicked on and it is, but it doesn't seem like much is coming out. Should it be a full on stream kind of like liquid being shot out of a syringe??? Mine creates a short weak shot of fuel.....


Thanks for looking everyone..

 

I would think your pilot is too big and you main might be big also. If you can't get to a dyno you will just need to play around with the jets. Just change one thing at a time so you know whats it doing. My jetting and mods are in my signature.

 

From the research I have done it seems my main jet should be in the 175-185 range and my pilot should be mid to upper 40's. I think I will start with a 175 main and a middle 40's pilot to see what happens. I have poked around on youtube and I am sure my accelerator pump is not squirting near enough fuel when the gas is stabbed. I will pull the cover off the side and see if it needs the zip tie mod or if something is stuck. Does the size of the leak jet determine how much fuel is coming through the accelerator pump???? I have not pulled the carb off to see what needle is in it either. I will probably do that before changing anything. Any suggestions would be greatly appreciated fellas, thanks!

 

Ok, I found the needle is an NDSR on the middle clip. This explains the larger jetting from what I understand. I have ordered the NCVQ and the NCVP needles to see if they help. Looks like I will be starting from square one on the jetting fml. Not sure where to start with the NCVQ so going with a 48 pilot and a 175 main with the needle on the 4th clip. I will give the NCVP needle a shot if I cannot get good results with the NCVQ. Thoughts or opinions on this???


Thanks guys......

 

Sounds like you have gotten on the right track, ill try and share some of my carb tuning experience from my stock 07 yfz. the previous owner had every setting messed up..

Id start with the "mother fcr tuning info thread" if you haven't already found it, I haven't posted enough to be allowed to share links.
Even if you already know what the carb jet components are, the thread explains exactly what each jet circuit controls and some symptoms to recognize when tuning.

Backfiring on decel, or backfiring in general is the easiest way to recognize either the pilot or needle is too lean. If it backfires on a gradual deceleration(not chopping the throttle) then richen the needle. If it backfires on chopped throttle then richen the pilot.
So if you decrease the pilot size from what you currently have, I would expect the backfiring to get worse and it might start having trouble idling. I'd buy the next three sizes up in pilots and start working my way up until the backfiring stops at chopped throttle. with a full pipe system and a built engine, she'll need a larger than average pilot.

Bog at WOT is a sign of being too rich as well, so I would start with that by decreasing the main jet like you mentioned. Buy the next 3 or 4 smaller sizes and start stepping it down until it starts pulling better (it may take smaller sizes than that).

As a side note that I wouldn't worry about until you have it nearly dialed in, there could be some extra power to be had with the perfect main jet setup. Even if your jets are close enough to allow the bike run smooth and pull hard, the main can be altered some to give a few more HP, nothing crazy, maybe 2-4 if you're lucky. when you find the sweet spot that gits rid of the bogging, go up and down a size and see if it pulls any harder at WOT. It's not guaranteed, but worth a shot, these fcr carbs can be picky.

My bike when I bought it looked flawless, but it couldn't idle, ran crappy at half throttle, backfired any time you let off, and had slight bog at WOT lol, I've had the carb off way too many times to count... but I've gotten it nearly dialed in.
Goood luck Man!

 

Thank you C10vortec, I have learned a lot the past few days lol. Anyway, I have a 50 pilot and a 185 main with the NCVQ needle on clip 4 and the quad rips! I get a little backfire on deceleration so I am going to go with a 190 main instead of raising the needle. If I still get it after I will raise the needle one clip. The quad is kind of hard to start so I think I will go up a size or two on the pilot as well. I have an old stock yfz carb and compared it to the carb that is on it and there is a considerable size difference. I will check them both with my digital caliper to see exactly how big it is.

 

Glad to hear it!

 

Backfire on decel has nothing to do with the main jet..... idle fuel screw or pilot needs to give more fuel...

It's possible that the idle fuel screw is missing the o ring that seals to keep air from entering through the screw...

 

Well, I swapped out the 50 pilot for the original 52 and the quad starts easier, but still get a little back fire after hard WOT deceleration. The quad wants to hang the idle a little bit too so I'll spray some starting fluid around the carb to see if I have a leak. If not, could I be too lean on the pilot still or need to adjust the fuel screw out some more? I am 2 turns out and it is not missing the O-ring. I took the quad for a 10 mile ride last night in the heat and the fan never kicked on but the quad was not overheating so I am still not sure if the fan works lol. It was just a casual country road ride with some occasional WOT blasts. I did rap it out in 5th gear til rev limiter and it pulled hard all the way up. I feel the main jetting is pretty close.

 

I'm running 42 pilots in all my quads. I've tried 48's & 50's but they become boogers to start after getting some heat in the motor.


When I dyno, I've checked the AFR at idle with 42 pilots in all my setups. Puts the AFR right at 11.9-12.0:1 which is a good place to be.

 

I heard these things were lean from the factory??? Do you run the stock carb on your quads? What type of intake? I am running a bored carb with FCI and no box lid. I feel like the pilot jetting is close or could be increased honestly. I have not pulled any practice laps with it yet, so not sure how well it will start once hot.

 

I am also 2-2.25 turns out on my fuel screw.....how many turns out can you go??? If I went down to a 45 pilot I would probably have it turned all the way out lol.

 

Try moving the clip down one setting at a time on the needle to richen it as well, you have a lot of engine mods.

If you want to check your fan pull, unplug the connector from the radiator temp sensor on the key side and wire the two contacts together. This is essentially how the temp sensor works when it gets hot enough. With it wired together, anytime the key is on the fan should come on. The temp sensor on the opposite side controls the temp light in the same manner.

 

I feel the needle and main are close. I don't want to mess with too many things at once. When I have the pilot situation figured out I will try to knock down the main jetting.
I will pull the connector tonight and see if I can activate the fan with a jumper. Thanks for the help EVERYONE!

 

Ok, I pulled the connector to the fan sensor and put a jumper wire in and the fan would kick on with the key on. It appears the circuit is in tact so I guess the next step is to buy a new sensor? I did not get to mess with the jetting, but will get to that tonight.


Thank everyone

 

Did you SPray starting fluid all around the carb? Especially around the intake side, it's too bad the plugs on these are so hard to get to. I always start with the main jet and work down. Good old school way to see where your main is , do a run at wide open throttle, and hit the kill switch still at wot, do a plug reading , this will show exactly how your main jet is running. Adjust until your at a light dry brown,

 

I tried the starting fluid trick and the idle remained steady so I do not feel I have an intake leak. I feel pretty good about the main jetting at this point, plug looks light brown. I STILL get backfiring on deceleration with the 45 pilot. I have had the fuel screw in nearly all the way and over 3.5 turns out with zero change. I could go to a 42 pilot, but the quad wants to overheat when riding slower in the lower gears which leads me to believe I need to jet up the pilot.


I still cannot get this fan to run unless it's wired directly to the battery. Can the switch be tested in boiling water with a multi-tester? Should I check for continuity or an ohm reading??? If I run a jumper wire in the plug in the fan will run. I need to check this sensor!!!

 

Ok, so I decided to run a toggle switch on this fan until I get this sorted out and fried my starter solenoid after one ride lol. Now the solenoid just clicks once and will not allow full voltage through. I have a new battery and it's putting out 12.5 volts. When I stab the start button I hear the click and only show 2-3 volts passing to the starter. Could it be coincidence or did rigging up the toggle switch cause this???? I used the wires leading to the coolant fan sensor for the toggle switch....

 

I replaced the starter solenoid with no luck.....not sure wtf is goin on. The battery will show 12 volts and drop down to anywhere between 10 and 2 volts once the key is turned on. I disconnected the fan toggle switch and same results. Any input on where i should start looking? Once it worked just fine, started up the quad and at idle i was getting 13 volt charge on the battery. I let it run a bit to warm up and stabbed the gas a few times then took another voltage check and it had dropped down to 10 while running. No headlights and fan was not running.....wtf is goin on with this thing???