Still battling tuning this FCR Carb, need some other folks knowledge - Honda TRX Forums: Honda TRX 450R Forum
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post #1 of 8 (permalink) Old 06-09-2019, 09:17 AM Thread Starter
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Still battling tuning this FCR Carb, need some other folks knowledge

Finally got to the track with the quad to really try and tune this thing and I am not sure if it’s jetting or if I am having other problems.

I will start with mods/build. 05 with fresh build. OEM crank, CP piston 13.5.1 compression and web cam (grind # 961-962). It has a 06+ FCR Carb. NCVQ needle with the clip set at 3rd notch down. 52 pilot jet, 160 main jet and 55 leak jet. Also has CRF ignition, flywheel and stator installed on it. The valves I am not sure as the work was already done when I bought it. It looks like it might have mild port work. I have attached a photo looking into the intake side of the head so you can see what you think in regards to port work.

So originally I was having a start issue. This has been corrected by cleaning the carb and installing all new gaskets in it.

Now, onto the current issues. Finally got to take it to the track and really run it. Several things I observed and/or happened.
First, it seemed to run pretty good other than sometimes it would bog for a quick second when I would get back on the throttle as I was getting ready to land from a jump. I thought maybe the pilot was too big so I dropped it down to a 48. After installing the 48 pilot it still was still doing the same thing but after a few laps it started bogging more and ended up shutting off on me. It took it a few minutes before I could get it to fire back up, when it did I just went back to my truck where my tools were.
I was revving it in neutral and listening to the exhaust. When I would really rev it, it was popping and would shoot out a flame on decel. So I thought maybe I needed to adjust my fuel screw. It was set at 2 turns out so I turned it out to 4 and slowly started going back in. I only went half a turn and the idle picked up. So I backed it off a 1/4 of a turn and did some revs in neutral again. This time no flames and it sounded a lot better. Since I was out beyond 3 turns on the fuel screw I thought well I need to bump up my pilot jet. So I put a 52 in it but then when I was doing the adjustment with the fuel screw I couldn’t find a spot where the idle would pick up. I started 4 turns out and slowly kept going in until it was the whole way in. So I set it at 2 turns out and figured I would give it a try. Went back out and still the same thing, intermittent bogging and it eventually shut off on me.

Next I tried bumping the main up to a 170 and I took it for a ride down the road on pavement so I could really just run it through the gears and rev it out. It accelerated great but when I would let off the throttle and start coasting it would pop real loud and carry on. Even shut off at times but if you pulled the clutch in and let it back out it would bump start right back up.

I have read the thread on the FCR carb and also the thread on jetting but I need some suggestions as I am really striking out.
Do you think that this is a jetting issue? Or do I maybe have a two things going on here, jetting and something electrical?

Any help is appreciated, sorry for the long post. Just trying to give you as much information as possible.
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post #2 of 8 (permalink) Old 06-09-2019, 10:57 AM
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She’s giving you more fits, then tit$ on sow!

The lean bog, back on throttle, could be the leak jet. Smaller orifice leak jet allows more fuel to the venturi. I’m pretty sure that’s how it hurts. Popping on decelerations are exhaust leak. Make sure your sealed. The pilot jet. The 52 should be large enough. I would rise the needle. Maybe 2 slots. See which way a big change will effect the situation. Your main seems a little small too. I believe it is a few adjustments away from ripping.
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post #3 of 8 (permalink) Old 06-09-2019, 02:51 PM
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Is the carb a stock bore ?? Those stock carbs are happy with 42 to 45 pilots usually, may have an air leak, check the vac plate seal, sometimes under vacuum they pull the seal and block the idle pass below the slide, saw that with airbox removed, usually this happens because of carb cleaner sprayed in the carb throat. Also some carbs are bricked because of the mid body gaskets completely melted and pull air in the idle circuit, I had one of those that ran E85

Some of the symptoms you are describing sounds like a stator issue like misfire popping

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post #4 of 8 (permalink) Old 06-10-2019, 11:01 AM
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I agree on the stator, esp the shutting off when hot and not wanting to restart. Plus the stator will make you chase your tail thinking you have a jetting issue. Is the stator new?

04 450r
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post #5 of 8 (permalink) Old 06-10-2019, 12:16 PM Thread Starter
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Thrown Stones - I am going to check the exhaust gasket but regardless probably will just order a new one. I mean all the more they are I might as well grab one. The needle is on the 3rd slot down starting from the top. I could try dropping it to the 5th slot and see if it helps or makes it worse.

Gboezio - The carb as far as I know is stock bore. The guy didn't say anything to me about it being bored. It is from an 06+ 450ER as it does not have the hot start on it. I will check the vac plate seal but it should be good as I just had the entire carb apart when I cleaned it and I replaced that rubber seal before putting it back together. As far as bricked, I am not quite sure what you mean. I did have the mid-body apart and replaced the gaskets in the mid-body.

Duke416ex - The stator I am not sure if it is new or not. All I know is it's suppose to have a CRF Stator, Flywheel & ignition. Which is feels like it does because it rev's quicker than my previous 450r. Only thing is I don't know what year CRF they are from. Anybody know is there only a certain year that the CRF stator & flywheel were compatible with the 450r? Or is there a way for me to find out what year is in mine by maybe a part # on the ignition box? The couple of times it shut off on me it was only on decel, it wouldn't do it if I was on the throttle. Would that still be possibly the stator? And is there a way I can test the stator before I would go purchasing a new one?

Thank you for all your replies and help. I really appreciate you taking the time to read my long-ass post and trying to help me out.
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post #6 of 8 (permalink) Old 06-10-2019, 03:20 PM Thread Starter
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I just pulled the plug and took some photos of it. This plug was brand new before I went riding this weekend and has a max of 2 hours on it. I have attached the photos. Thoughts?
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post #7 of 8 (permalink) Old 06-12-2019, 07:08 PM
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I could never get my FCR carb right no matter what I did, I bought and went through a 04-05 carb and never looked back! I raced XC and the carb would start half a kick every time!

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post #8 of 8 (permalink) Old 06-17-2019, 03:12 PM
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Do a search on here and there was some info in the engine section on the crf stator swap. I looked at it but I know you do loose some lugging power and bottom end in exchange for the fast revving. Plus the lighter fly wheel can cause some trouble on killing the engine when chopping the throttle or letting off quickly. Have you checked the mid gasket on the carb? If you can find the year and locate a manual for that year there will be specs on how to check the stator.

Just noticed gboezio mentioned the mid gasket. This is one often overlooked cause you have to completely separate the carb to do it and it isn't a standard part many people replace.

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