Carb issues

[Pappy]

ok, someone has to know the answer to why the carb on the 450R loves to stumble around. it seems as when im hitting ruff trail, or even landing some jumps the carb will stumble and even flutter when im back on the gas.


is there a fix or is a new carb required?

[ZRider400]

mine does the same when landing off jumps.... still havnt figured it out yet, but someone replied in my other thread saying to adjust the air screw

[Pappy]

ive tried different settings with the air screw and it hasnt taken all the stumble out of it. it stalled on me yesterday after hitting a large rock face at the top of a decent hill, which led me backwards....allowing the quad to run me over :p

ive had it with this carb:grr:

[ZRider400]

Originally posted by Pappy
ive tried different settings with the air screw and it hasnt taken all the stumble out of it. it stalled on me yesterday after hitting a large rock face at the top of a decent hill, which led me backwards....allowing the quad to run me over :p

ive had it with this carb:grr:

time for a CRF450 carb:p

[PBSPERFORMANCE]

Hey Pappy heres my two cents on the Honda carb. I bought a 450R new as soon as it hit the dealers floor in February. It ran 45 minutes and then quit. After trouble shooting this thing for several hours I determined that the carb was defective. How did I determine this. Put a Lectron on it and it started 1st kick. Put an FCR on it off my CRF bike and it started first kick. After arguing with the dealer regarding this they agreed to look at it. Three weeks later they still had the quad and said they couldn't get it running. I contacted Honda customer service who basically told me they would do nothing as the long as the dealer was making an effert to fix it. As race season was approaching I had no choice but to buy a carb out of my pocket and put it on. I picked the quad up from the dealer. (Honestly I don't think they had a clue where to start) and put a new FCR on it. It started 2nd kick and has ran flawless ever since. I'm using the stock carb as a paperweight right now as a reminder as to how poorly I was treated by Honda. Pat WWW.PBSPERFORMANCE.COM

[Pappy]

well my quad starts extremly well, infact even with my old bones doing the starting i am not scared to go up against any electric start quad in a dead engine start:devil:

my b!tch is the stumbling part of this friggon thing. im used to it, but it will seem like the damn thing is missing when it occurs:grr:

what all is needed to make the FCR swap?

[ex kid]

have you checked the float level or needle? i had my needle too rich once before and it ran like crap when you hit the rough stuff but when you ran it down the street it was fine. sounds a little rich to me. just my thoughts.

[Pappy]

its all stock:confused:

any ideas are mucho aprreciated:D

[CTmxyfz]

go buy a crf 42mm carb.

[MY450R]

do you have stock jetting?
id check it
mine did the same thing but i just needed to rejet it

[CdaleXtreme]

I got an FCR and a TC Billet adapter for $475 off of ebay. I imagine it will cost a little more than that from retailers. But you will need The Adapter, availbe from a few different place, I think Exodous cvcles has them, TC racing, and Baldwin Motorsports. Balwdin sells a kit ready to bolt on for like $875 !!!

But There isnt much modding needed. The TPS is the main problem. the plug will not plug into the TRX wiring harness. I was gonna splice my TRX plug onto the CRF TPS but I took off both TPS's and they both look Identical aside from the TRX TPS has two mounting holes. But when mounted this shouldnt make a big difference. So basically Put your TRX TPS onto your FCR Carb, to make it compatible. I havent ran it yet so im not 100% sure it works but I have no reason to suspect it wont work......Boy that was alot of 3 letter abbreviations:eek2:

Also you will need Star bits, One standard star bit not sure which size, + a star bit with a dimple for the FCR!! :grr: I mean come on woudlnt a phillps or a 7mm do! But you may need to buy those tools if you dont have them to switch the TPS.

The stock carb is most likely putting too much fuel into the engine when you go from no throttle to full throttle. This stumble occurs because the accelerator pump is squirting too much fuel into the engine. You need to modify your stock accelerator pump arm to correct this. On the TPS switch for the FCR conversion you need to set the TPS with an Ohm meter for resistance. You do this by hooking it to the leads on the TPS and turning it clockwise or counterclockwise until you have the right resistance and locking the bolts in place. I purchased the special tools needed in a tamper proof set from ACE Hardware for around $10. You may need to also modify the CRF FCR accelerator pump also. Before you put it on the bike put some fuel in the carb and pump the lever quickly and hold it wide open. Use a stop watch and see how long it squirts for. I've modified my FCR39 for my 400ex and the throttle response is much improved w/ no dead spot now. Before I did the mod it was pumping for 2-3 seconds and now I have it down to about .35 seconds. You can also do this test on the stock carb and see how long it is squirting and maybe not have to spend $500 on a new carb. Although, the FCR is a way better carb.

[86atc250r]

I never had any trouble out of my stock carb - A friend did and found a tiny black shaving stuck in the mainjet --- probably from the tank.

Caused sporatic stalling and sputtering issues.

FCR conversion = very easy.

You'll need an adapter from Noss Machine
You'll need an FCR from a CRF, I used a 2003 model.

My total conversion was in the low $400's

Stock throttle cable and hot start will work. Hot start requires some mixing of parts from the FCR and your stock setup - pretty easy to figure out though.

TPS requires rewiring or switching between carbs - be sure to adjust the closed throttle resistance or your timing curve will be off.

Do not expect more overall acceleration -- in fact, I lost a little acceleration on mine (as shown by numerous 300' drag times, down about a MPH or two and almost a tenth). Throttle response seems a little better.

Starting is as easy as stock and jetting was very close for my HRC setup, right out of the box. The FCR seems to jet a little smaller than the stock carb, at least on the main, I haven't messed with the pilot yet.

Accelerator pump is dead on (at least for the CRF version of the FCR)

Only problem I've had with the FCR is likely a lean pilot, idle can be a touch erratic at times & it will stall every once in a while when it settles in... As I said above, I haven't touched the pilot yet & probably need to - in fact, I'm not even sure what it has in it.

[Pappy]

gabe, i did find junk in the carb that we talked about last week. i drained the tank and re filled it and no more cutting out under WOT. i was going to pull the part that is bolted to the tank to check the screen for debris, however it seems if honda has used a 1 way nut and its not removable as the 400ex is:confused:


im not certain a carb swap is the #1 answer. the 450R acted totally different when an aftermarket pipe was installed as it did not stumble and carry on as it does with the stock pipe. ive riden other 450Rs and noticed the same type of condition under the same riding conditions.

maybe one of you techheads will figure this puppy out:p

[Hammer trx450r]

why do you say stock jetting with a new exhaust?

[cinigen9]

I experienced a similar problem when I first purchased mine. I sought help from anyone that would listen including dealers. It became quite dangerous and I worked on it for around 3 weeks trouble shooting everything - yes, I mean everything on the bike.

Ended up going through the carb one last time and finally found a small bit of plastic lodged sideways in the mainjet - looked like a shaving from a screw. It was moon shaped, and under a load over rough ground it would rotate around and block off fuel and the bike would literally shut off. Then the bike would be fine once you slowed down. It was almost impossible to recreate the problem.

About 3 weeks ago at a race it started to miss on top again - popped off the bottom of the carb and found another small piece. This one was much smaller, but I am going to go through everything again and make sure no internal pieces were damaged during installation, and are slowly breaking apart. There is quite a bit of plastic on the inside of these carbs.

Just about everyone seems to think that this is something that I put into the bike. My opinion - not a chance. The first time this happened I had put maybe 4 tanks of fuel through it and if you have had one of the tank filters off you know that they work excellent at keeping debris out of the carb. I stand firm that this was debris from assembly.

Good luck,
Carson

[cinigen9]

Originally posted by Pappy
i was going to pull the part that is bolted to the tank to check the screen for debris, however it seems if honda has used a 1 way nut and its not removable as the 400ex is:confused:


might give it another shot. The petcock on mine unbolted and the filter pulled right out.

Carson

so you run a fuel filter now??? dont these gast tanks have a little filter or screen inside them already....???

[markeg192]

I've read about plastic shavings in the E-Ton quads. It seems the hole has to be drilled for gasflow. ............

[REDARMYRACER]

well what jets are you using. i agree with the debris blocking the main jet but if youre running a jet to fat the bike will sputter on landings and ruff terrain. i had the same problem and once i rejetted correctly( a good days effort of trials) the bike peforms flawlessly.

A new flat slide carb like the dirt bike has is better than the butterfly that comes on it stock but simply buying a new $450 carb is not the ansewer.

I am still going to get a new fcr, but anyones machine should run well with what is on it.

[cinigen9]

Originally posted by REDARMYRACER
well what jets are you using.

100% stock on mine.

[BSTURDIVANT]

The stock carb has 2 vent lines that turn down behind the carb- these let debris into the bowl- especially during washing on end!
Either extend the tubes into the front of the air box or install small filters on them to stop dirt and water. Take the bowl plug out and check before racing. (Never wash on end- even with fuel off- soaks air filter with fuel) Solved all our problems!

[cinigen9]

Originally posted by BSTURDIVANT
The stock carb has 2 vent lines that turn down behind the carb- these let debris into the bowl- especially during washing on end!
Either extend the tubes into the front of the air box or install small filters on them to stop dirt and water. Take the bowl plug out and check before racing. (Never wash on end- even with fuel off- soaks air filter with fuel) Solved all our problems!

Bsturdivant,

Where you experiencing the same types of problems listed above?

On the two solutions you threw out:

1) are you just running extended tubes into the top of the airbox with some holes?

2) what type of filter are you using on these lines?

thanks
Carson

[BSTURDIVANT]

Experiencing same problems- ended up being water and dirt in the bowl- the dirt would bounce up into the main jet and lean way out. A friend of ours extended his down the intake tube.
most auto parts stores sell small inline gas filters 1/4 " line that work good-just stick in the end (small plastic gas filter for Briggs and Stratton work good) NAPA keep in stock!

[cinigen9]

great information - thanks.

Are you guys running the hrc lid?

Carson

[Pappy]

Thanks Brent ill give that a try!