Carb help/info?


17 replies to this topic
  • xr650r_Maine

Posted July 18, 2006 - 05:47 PM

#1

Hi, :thumbsup:
I just uncorked my 650r and drilled out the exhaust, I installed 175 main jet,68s pilot jet,B53E needle(3rd clip),and new HRC boot the one that goes between the carb and head, xr only filter backing(support) and Uni filter. I turned the air screw 1 1/2 turns out from seated, I think it should be 2 1/2 turns out not sure thou. The problem I am having is when I started it today w/choke it ran a little high on the rpm`s, about 2000/2500 I turned the idle down to a reasonable rpm, When I turned off the choke completly it ran bad,stalls,rough idle,won`t run past 1/4-1/2 throttle with out coughing and stalling.. What do I do from here? it`s a new BRP 2 miles on my sow. even going down the road I can`t run past 1/4-1/2 throttle falls on it face....I am at sea level.

next question If I can`t get this stock carb the work what other carn is better Edelbrock or a FCR 39MM or the 41MM carb? I see Barnumspro has the Edelbrock carb if I chose his carb would I still have to play with jetting? Thanks.

  • xr650r_Maine

Posted July 18, 2006 - 09:01 PM

#2

When you apply the choke, it's supposed to idle high.
Turn your idle back up to where it was. After you start it up cold with the choke on, wait till the engine's completely warm, turn the choke off and ride it for a bit- THEN adjust your idle..


I done that. Even after it`s warm/hot if I shut of the choke it`s worse.will barley run even adjusted the idle reasonable level, still no go :thumbsup:

  • J_T

Posted July 18, 2006 - 09:07 PM

#3

Make sure the plastic inserts are removed from the airbox, also I'd play with the air fuel mixture...it sounds like it is starving...
My stock carb also had the float out of adjustment when I first got it so the valve would close off with very little fuel and it would use it quick enough that it'd starve...but that was usualy on a minor incline. You have the parts right...double check it.

I wish I could help more.

JT

  • snaggleXR650

Posted July 19, 2006 - 04:02 AM

#4

They are correct, the bike should rev high with the choke on.

Set the fuel screw at 2.5 - 3 turns out from fully closed. Adjust your idle with the choke OFF, or all the way down. After you get it running with the choke off, you need to tune the fuel screw;

Turn it a 1/2 turn at a time CW or righty tighty, waiting and listening to the motor after each turn. When the bike starts to misfire/try to die, stop and note the fuel screw position. Now open the fuel screw back up, 1/2 turn at a time and note when the bike runs bad when turning CCW or lefty loosy. Your 'perfect' fuel screw setting should be right in between these two postions.

Put in a simpler way, set your fuel screw to the position that gives you the fastest idle. Then readjust the idle back down, stock is 1500RPM +/- 100RPM.

Also note, those jetting specs will probably be on the rich side, that's not really that bad, but your gas mileage will suck. Run the 68s for a bit, and pay special attention to how the bike starts after it's been ridden for a while. If the bike starts easier cold than when it's hot, you should go back down to the 65s pilot jet.

Just in case you didn't know, to access the carb jets/needle, simply remove the seat and and gas tank. Loosen the carb boot clamps and rotate the carb in place so that you can get the screws on the bowl. Remove and rejet as needed. You can also access the top of the carb this way to get to the needle...

Good luck.

  • xr650r_Maine

Posted July 19, 2006 - 11:37 AM

#5

Make sure the plastic inserts are removed from the airbox, also I'd play with the air fuel mixture...it sounds like it is starving...
My stock carb also had the float out of adjustment when I first got it so the valve would close off with very little fuel and it would use it quick enough that it'd starve...but that was usualy on a minor incline. You have the parts right...double check it.

I wish I could help more.

JT


Yes I have removed them(plastic inserts). :thumbsup: Maybe that it, my float. so how do I go about adjusting my float level.any pic`s info?. Thanks :ride:

  • xr650r_Maine

Posted July 19, 2006 - 12:04 PM

#6

They are correct, the bike should rev high with the choke on.

Set the fuel screw at 2.5 - 3 turns out from fully closed. Adjust your idle with the choke OFF, or all the way down. After you get it running with the choke off, you need to tune the fuel screw;

Turn it a 1/2 turn at a time CW or righty tighty, waiting and listening to the motor after each turn. When the bike starts to misfire/try to die, stop and note the fuel screw position. Now open the fuel screw back up, 1/2 turn at a time and note when the bike runs bad when turning CCW or lefty loosy. Your 'perfect' fuel screw setting should be right in between these two postions.

Put in a simpler way, set your fuel screw to the position that gives you the fastest idle. Then readjust the idle back down, stock is 1500RPM +/- 100RPM.

Also note, those jetting specs will probably be on the rich side, that's not really that bad, but your gas mileage will suck. Run the 68s for a bit, and pay special attention to how the bike starts after it's been ridden for a while. If the bike starts easier cold than when it's hot, you should go back down to the 65s pilot jet.

Just in case you didn't know, to access the carb jets/needle, simply remove the seat and and gas tank. Loosen the carb boot clamps and rotate the carb in place so that you can get the screws on the bowl. Remove and rejet as needed. You can also access the top of the carb this way to get to the needle...

Good luck.


That fuel screw you talking about is it the little screw on the right side just above the carb bowl on the carb body, If it`s the one u talking about I just set it at 2 1/2 turns out,cool thanks,But I will still have to adjust it a little better, I`ll try what you said thou. with that set I think it could be my float level is off or sticking hmm, How do I go about adjusting the float level, what happens is when I turn off the choke it will idle but if I give any more gas above 1/4 throttle it stumbles and if I go anymore than that it just dies. :thumbsup:

  • oldoutdoorsman

Posted July 19, 2006 - 12:28 PM

#7

ITs Probably not the float level, but maybe the float valve sticking.

As far as your jet sizes etc...they sound like it ought to be running much better than it is...even if rich.

If It was mine;
-I'd be inclined to take the carb apart, double check all your jetting and make sure they are the correct sizes (numbers on the jets match what you thought you were installing incase a wrong size put in wrong package)

- Make sure the fragile Brass jets aren't too tight,

- Get some carb cleaner and make sure all the passages are clean and free. AND NO DEBRIS in the jets

- BUT MAKE SURE THE Float Valve is moving freely and not binding. I have heard of some taking an emery board or very very very fine file to make sure no burrs on it b/c it was catching on some...

- Look at the service manual and make sure everything is where its supposed to be when you put it back together

- Do as Snaggle said about adjusting it properly!

- If All else fails you will have to go back to stock jets and see how it runs then and if it fixes the 1/4-1/2 throttle stuff just less power you will have to try just one part at a time.

AS far as float level since you were wondering. There are specs for the height in the service manual which says 16mm.
Float level isnt' hard...you just adjust the tab of the float that presses your float valve in the carb so it is closed when the float is in the proper position. If the float rises too far w/out closing the valve it will flood out. The other extreme is it will use the fuel in the bowl faster than it can refill. Try to do it with the float on the carb instead of removing it. As Snaggle said you can rotate the carb in the boots to get at the bottom of it but if you are going to dismantle it to check everything make it easy on your self and get a cookie sheet and sit at a table with the manual and some carb cleaner and a small brush!

  • snaggleXR650

Posted July 19, 2006 - 12:29 PM

#8

Hmmm. Ok, first of all make sure that you have the choke lever in the lowest position (OFF). Middle position is half choke, all the way up is full choke. I bought my bike used and the guy had this mixed up and he had the idle set so that it would run on full choke. I took off down the road and it would do what you are describing. I did some looking and found the choke on, when I turned it off it died. I adjusted the idle and then it ran sweet with the choke off.

Otherwise, go back and make sure that there are no rags, plastic bags etc... caught up in the airbox, intake boot, carb or intake manifold to the cyclinder head. After that, check to make sure exhaust is flowing out of the pipe.

When you accelerate, you need AIR and FUEL to sustain higher RPM's. All your jets and stuff are new so clogged/dirty jets seems to be out. My only other guess is that you have a MAJOR air restriction somewhere, such that only enough air can pass when at idle, but not nearly enough when you gas it.

Float level seems unlikely. To adjust the float level you simply bend a little metal tab that actuates a small valve. Look in your owners manual...

Let us know what you find...

  • xr650r_Maine

Posted July 19, 2006 - 12:45 PM

#9

Hmmm. Ok, first of all make sure that you have the choke lever in the lowest position (OFF). Middle position is half choke, all the way up is full choke. I bought my bike used and the guy had this mixed up and he had the idle set so that it would run on full choke. I took off down the road and it would do what you are describing. I did some looking and found the choke on, when I turned it off it died. I adjusted the idle and then it ran sweet with the choke off.

Otherwise, go back and make sure that there are no rags, plastic bags etc... caught up in the airbox, intake boot, carb or intake manifold to the cyclinder head. After that, check to make sure exhaust is flowing out of the pipe.

When you accelerate, you need AIR and FUEL to sustain higher RPM's. All your jets and stuff are new so clogged/dirty jets seems to be out. My only other guess is that you have a MAJOR air restriction somewhere, such that only enough air can pass when at idle, but not nearly enough when you gas it.

Float level seems unlikely. To adjust the float level you simply bend a little metal tab that actuates a small valve. Look in your owners manual...

Let us know what you find...


I have double checked everything as for parts rags etc. It will idle fine(choke off) but as soon as I try and give more than 1/4 or a little more throttle it stumbles and at 1/2 throttle it just wants to die,if I let off it will idle good.I can drive it with the choke in middle setting but it will caugh/stumble when I give it say 1/2 throttle or more. I`ll play with it and post my findings, Thanks Bud

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  • Mudshark

Posted July 19, 2006 - 04:34 PM

#10

Also... at sea level in your climate, I wouldn't run anything over a 170 main jet. go here for a good guide: http://www.xr650r.us/jetting/
Running too rich will reduce the effectiveness of the protective oil layer
on the cylinder walls and reduce engine life. A fraction lean in better than
running too rich.
It is strange that it runs better with the choke on though.... sorry, but I've
got to ask... the choke is off when the lever is pushed all the way back
toward the air-box (facing down), right?
I've had a Friend that got confused and was thinking it's off when it was all
the way on.... very rich mixture, no air, bad ....
Your new pig will idle like crap for the first 800 miles or so, it'll hang onto
high rpm and drop to idle slowly, this is "normal". I think, due to tight
intake valve clearance. After I set mine this stopped happening and it idles fine
now.

but just check that you've got the choke off correctly first.

  • snaggleXR650

Posted July 19, 2006 - 06:35 PM

#11

Hey,
It still sounds like you may be mixed up on the choke. When you go full choke, a butterfly valve in the mouth of the carb blocks the air intake. The vacuum from the cylinder and lack of air causes an extra rich fuel mixture into the cylinder. If the choke is left on, the bike will stumble/die at higher than idle throttle opening because there is no way for air to pass from the airbox. Half choke, the valve is like 1/2 open, and choke off it is fully open. So, having the choke on will definitely do what you are describing.

If you say you've got the choke right, then I'll take your word on it. That leaves a problem in your needle jet and needle circuit which takes over at around 1/8-1/4 throttle up through ~3/4 throttle position. The needle jet is the 'tube' that the needle moves in and out of. If there is trash in the needle jet or main jet that attatches to the end of the needle jet, the bike will choke off of fuel at lower to middle throttle positions. You didn't mention changing the needle jet, so this would be a good thing to check.

The needle jet is #21 in this exploded view;

http://www.serviceho...frames page.htm

  • HawkGT

Posted July 19, 2006 - 09:49 PM

#12

...Running too rich will reduce the effectiveness of the protective oil layer on the cylinder walls and reduce engine life. A fraction lean in better than running too rich...


Not sure I agree with that.

I'm familiar with cylinder wall washing due to overly rich mixtures but it generally takes a grossly rich mixture for that to occur at any significant level. The far greater danger is running too lean. Too lean errodes the protective boundry layer of gases that cling to most every surface in the combustion chamber. This boundry layer prevents the super-hot combustion gases from actually touching the chamber (cylinder, head, piston, etc). The boundry layer is like insulation that seperates the hot combustion gases from the metal surfaces. Lean mixtures are also more prone to detonating.

  • xr650r_Maine

Posted July 20, 2006 - 03:48 AM

#13

Hey,
It still sounds like you may be mixed up on the choke. When you go full choke, a butterfly valve in the mouth of the carb blocks the air intake. The vacuum from the cylinder and lack of air causes an extra rich fuel mixture into the cylinder. If the choke is left on, the bike will stumble/die at higher than idle throttle opening because there is no way for air to pass from the airbox. Half choke, the valve is like 1/2 open, and choke off it is fully open. So, having the choke on will definitely do what you are describing.

If you say you've got the choke right, then I'll take your word on it. That leaves a problem in your needle jet and needle circuit which takes over at around 1/8-1/4 throttle up through ~3/4 throttle position. The needle jet is the 'tube' that the needle moves in and out of. If there is trash in the needle jet or main jet that attatches to the end of the needle jet, the bike will choke off of fuel at lower to middle throttle positions. You didn't mention changing the needle jet, so this would be a good thing to check.

The needle jet is #21 in this exploded view;

http://www.serviceho...frames page.htm


Yes I changed the needle jet to a 68s. I think its my float level cause when I got everything back together I had to tap the float bowl a little cause it was not getting any fuel but as soon as I taped on the bowl it got some fuel and started. I`ll dig into it Friday my day off and report back.oh and the choke was all the way back(off position). :thumbsup:

  • snaggleXR650

Posted July 20, 2006 - 06:51 AM

#14

The 68s is the pilot jet, responsible for idle up to about 1/8 throttle or less and is installed to the side of the main/needle jet assembly. Your bike runs fine here, so that's not the issue. The needle jet, is rarely talked about, but it is a critical part of the fuel mixture up to about 1/4 throttle. As the needle is pulled out of the needle jet up through ~3/4 thottle, the needle taper diameter relative to the size of the needle jet is responsible for metering full. Only after ~3/4 throttle does the main jet (mounted to the end of the needle jet) start metering fuel. IF there is trash stuck in the main or needle jet orifice, then you bike will get choked off of fuel as you give throttle beyond idle.

If you have already had trouble with your float, then that could also be it if it's not letting enough fuel into the bowl. However, I would get some carb cleaner and squirt it real good up into the valve and linkage that the float operates, as well as through the pilot and main jet. Do this BEFORE trying to adjust your float level, as it could just be a small particle gumming up the works.

  • xr650r_Maine

Posted July 20, 2006 - 11:57 AM

#15

The 68s is the pilot jet, responsible for idle up to about 1/8 throttle or less and is installed to the side of the main/needle jet assembly. Your bike runs fine here, so that's not the issue. The needle jet, is rarely talked about, but it is a critical part of the fuel mixture up to about 1/4 throttle. As the needle is pulled out of the needle jet up through ~3/4 thottle, the needle taper diameter relative to the size of the needle jet is responsible for metering full. Only after ~3/4 throttle does the main jet (mounted to the end of the needle jet) start metering fuel. IF there is trash stuck in the main or needle jet orifice, then you bike will get choked off of fuel as you give throttle beyond idle.

If you have already had trouble with your float, then that could also be it if it's not letting enough fuel into the bowl. However, I would get some carb cleaner and squirt it real good up into the valve and linkage that the float operates, as well as through the pilot and main jet. Do this BEFORE trying to adjust your float level, as it could just be a small particle gumming up the works.


Yeah thats what I will try first, taking it apart and cleaning all the jets with carb cleaner and have them blown out, It ran so good before I uncorked it,even thou everything is new there could be a small piece of junk in there.

  • xr650r_Maine

Posted July 23, 2006 - 12:56 AM

#16

:thumbsup: :ride: Thanks to all that posted and helped :cry:

I found the problem,well 2 that is, the pin that the float rides on was half out and the float was stuck alittle and I also found a piece of red plastic in 68s jet. I thought I cleaned the new Clark 4.3 tank good enough with soap and water and let dry but I guess not...my bad, Live and learn....Now it starts first kick :ride:

  • LesJive

Posted July 23, 2006 - 03:39 AM

#17

Do you have a fuel filter inside the tank? The stock Honda one will fit inside the Clarke tank.
Look under fuel tank, part # 2...
http://www.serviceho...frames page.htm

  • xr650r_Maine

Posted July 23, 2006 - 03:50 AM

#18

Do you have a fuel filter inside the tank? The stock Honda one will fit inside the Clarke tank.
Look under fuel tank, part # 2...
http://www.serviceho...frames page.htm


Yup I do now....





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