FCR help

[luvmyex]

I have a 162 main and a 52 pilot. K&N W/B e series slipon.and open air box.It seems to be loading up when i hit the throttle.After a hessiation it wil take off pretty good but still not real clean.Also seems like alot of back pressure when i let off the throttle.It dont backfire then but seems like its about to.Its also still rich.Black smoke.Should i drop down another jet?although it runs ok on top?Not sure what the needle setting is either i didnt even check that.Any help would be great.

[pnut420]

Im hoping thats a typo, try a 42 pilot and a 158 main.

[RytM1]

Hmmmm, I'm running a 170 main, and 52 pilot with my 416. What needle do you have in it?

[luvmyex]

Originally posted by pnut420
Im hoping thats a typo, try a 42 pilot and a 158 main.
No typo.its a 39fcr.
Im not sure what clip is in it.I bought it from BMW500hp.And havent even looked at the needle yet.It was jetted at 170 when i started.But its almost smooth on top end.Just when i first get on the gas it sputters.I did have to clean out the jets twice.I ran the old gas like a dummy.It had been sitting for about 3 months.I did drain the rest out and put new in.

[pnut420]

Take the pilot out, with your mods anything over a 42 is going to make it run real rich down low. If that doesnt do it, then turn the fuel screw in all the way, and then back it out 2-3 turns, that doesnt help try a 158 main.

My brother is running a sparks pipe, open air box and the FCR39 and we have a 158 main, 42 pilot 2 1/2 turns out on the screw, and it still has a little low end bog, but no black smoke thats for sure, with the 158/42, no matter what I did it didnt have blake smoke of the back, or foul the plug

[skemp]

You must have a stock motor..?
I can give you some advice after I know exactly what you have done to your quad. :)

[pnut420]

Originally posted by skemp
You must have a stock motor..?
I can give you some advice after I know exactly what you have done to your quad. :)

hehe, yeah you know your stuff :p . Im pretty sure its a stock bore, so thats why I was pointing towards the smaller pilot and main jets...

[lilpoppy]

First of all you need to find out which jet it is that is rich. Is it getting hesitation from no throttle to 1/4 throttle, 1/4 to 3/4 throttle or full throttle. If you are talking about full throttle then go down 1 size on your main jet and see if the hesitation goes away. Your pilot should be fine because i was running the same jetting on myne with no airbox lid and Spark's x-6 exhaust. If your hesitation is somewhere around half throttle try raising the clip on your needle one notch and see what it does. Most FCR's do have hesitation when you go from a stand still to full throttle and that is very hard to get rid of. You should be able to get it to where it runs good while you are riding though.

[JD400exrider]

I aggree with lilpoppy. I am running a 168 and a 52 pilot. I think I am going to go back down to a 165. Seems to not run as well. I was just afraid on running to lean. The hesitation is there when cracking the throttle but if you back that screw out between 2-3 turns the hesitation seemed to clear up where you could not tell when riding.

[pnut420]

Originally posted by lilpoppy
First of all you need to find out which jet it is that is rich. Is it getting hesitation from no throttle to 1/4 throttle, 1/4 to 3/4 throttle or full throttle. If you are talking about full throttle then go down 1 size on your main jet and see if the hesitation goes away. Your pilot should be fine because i was running the same jetting on myne with no airbox lid and Spark's x-6 exhaust. If your hesitation is somewhere around half throttle try raising the clip on your needle one notch and see what it does. Most FCR's do have hesitation when you go from a stand still to full throttle and that is very hard to get rid of. You should be able to get it to where it runs good while you are riding though.

I thought you were running a 42 pilot, Im pretty sure thats what my brother is running :confused:

[skemp]

I am running a 52 pilot OCEM-P needle, and 165 main in my 416 with all the bells and whistles. I have gotten rid of the hesitation to the point that is is unnoticeable while riding through adjusting the fuel screw and accelerator pump. Runs perfect and strong. On a stock motor, I would try a 155 or 158 main and a 45 pilot. I like to start out rich on the main and then work my way down until it runs good, and start a bit lean on the pilot and work my way up until it loads up and back off one size. Good luck.

[luvmyex]

Yes the motor is pretty much stock cept the pipe And carb and open box.The skipping is about 0-1/4 throttle.And when i let off the gas its like it wants to backfire(Kinda like the motor dies) but dont.Im gonna try a smaller pilot and see if that helps.

[pnut420]

Originally posted by luvmyex
Yes the motor is pretty much stock cept the pipe And carb and open box.The skipping is about 0-1/4 throttle.And when i let off the gas its like it wants to backfire(Kinda like the motor dies) but dont.Im gonna try a smaller pilot and see if that helps.

Yeah this is exactly what my brothers is doing, but at no point is their any black smoke. I think the FCR is going to have a little more backpressure than before but I kinda like it in a way, slows you down a little for the turns.

The only way to get it perfect is to adjust the fuel screw and I believe that 0-1/4 problem can be fixed with the accelerator pump, maybe skemp can help you dial it in a little more, shoot him a PM. Alot of people cant figure out how to fix the 0- 1/4 throttle sluggishness, but I came across an article a engine builder wrote about having to adjust the accelerator arm to get rid of it. Also colby at C&D is said he was looking into getting a new accelerator pump for the FCR, said it was supposed to fix it completely, if hes sells it, I will buy it for sure.

You might want to start with a smaller main jet.

[pnut420]

Originally posted by JD400exrider
I aggree with lilpoppy. I am running a 168 and a 52 pilot. I think I am going to go back down to a 165. Seems to not run as well. I was just afraid on running to lean. The hesitation is there when cracking the throttle but if you back that screw out between 2-3 turns the hesitation seemed to clear up where you could not tell when riding.

I was suprised how much better my brothers ran after I backed it out 3 1/4 turns instead of 2. I guess that made it run a little leaner. Not sure.

[JD400exrider]

Pnut What are you or your brother running for a main jet. We are basicly at the same elevation and motor. I am just down the road from you and lilpoppy. I think lilpoppy is running a 165 / 52 if he has not changed jetting.
norcalatver lives around the corner and he was running a 172 until he put it his on a dyno. On the Dyno machine with a sniffer (into the tail pipe) he had to go down to a 162 and he is still is a little fat on the main. He has a 493 stroker with bigger valves, more aggressive cam and the works. The guy with the dyno is gone for a month to the races around the country. I would like to get close on the jetting sooner than that.

[JD400exrider]

One other question.

What effect on jetting does bigger valves, higher compression bigger bore have on jetting ? makes it need more fuel ? Bigger main ?

[pnut420]

Originally posted by JD400exrider
Pnut What are you or your brother running for a main jet. We are basicly at the same elevation and motor. I am just down the road from you and lilpoppy. I think lilpoppy is running a 165 / 52 if he has not changed jetting.
norcalatver lives around the corner and he was running a 172 until he put it his on a dyno. On the Dyno machine with a sniffer (into the tail pipe) he had to go down to a 162 and he is still is a little fat on the main. He has a 493 stroker with bigger valves, more aggressive cam and the works. The guy with the dyno is gone for a month to the races around the country. I would like to get close on the jetting sooner than that.

I screwed up Im running a 52 pilot and a 158 main, It came with a 162 and it was to much for the stock bore, etc... After seeing people dyno their bikes, it seems most people are jetted on the main, tend to think the bigger, the better:ermm:

I also messed with the fuel screw today by backing it out almost a full turn more and it seemed to not load up as bad anymore, came back down to a smooth idle.

JD400, we will have to go riding pretty soon, I should have mine up and running in a month, so we will have 4 quads in our group and 1 dirtbike guy. I found a pretty cool track by Brentwood, its called Sand Hill Ranch, the track is pretty cool, but it cost $25 per quad.

[skemp]

Originally posted by JD400exrider
What effect on jetting does bigger valves, higher compression bigger bore have on jetting ? makes it need more fuel ? Bigger main ?

Actually, these things can create the need for a smaller jet, because more fuel is being pulled through the jet. It would have never occured to me until I was having big time trouble jetting a big bore motor and decided to go leaner on the main; it worked. I then figured it out in my head from there. :) It does make sense.

[JD400exrider]

Originally posted by skemp
Actually, these things can create the need for a smaller jet, because more fuel is being pulled through the jet. It would have never occured to me until I was having big time trouble jetting a big bore motor and decided to go leaner on the main; it worked. I then figured it out in my head from there. :) It does make sense.

That might explain why my budy with the 493, big valves and higher compression has a smaller jet.

More fuel being pulled through a smaller jet. Can you explain a little more skemp