XR650R Carb on a XR650L

[HondaXRider]

Even if the bike pulls really HARD and have great throttle responce compared to the vac-carb....

there is still one, (two acually) big troubles with these carbs.

One: The most significiant: the off-idle bog and the abrupt bog when closing the throttle. (too-rich stumble)

This behavior is really easy to to test when you want to do a wheelie.

When you want to hold the front wheel at the same height, you have to moderate the throttle opening: open, close, open, close an so on... you get me.

When you do like that, you will notice that the thottle works like pushing the kill button over and over again. This carbs need to run a TOO big pilot jet to get rid of the off-idle bog. But when closing the throttle a little, it appears that the engine suddenly dies for a second, due to a too rich a/f ratio, making the engine to stumble.

This makes controlled wheelies both hard and sometimes dangerous!

Two: the throttle sticking to the bottom of the carb, a worn throttle linkage can make this worse too. Not a good thing either.

I ended up with the mikuni hs 40 and i have now a bike that i can wheelie alot easier, "as smooth as fuel injection" is a good comparsion.

All is up to how you use your bike, but for me it was dangerous and boring to have a carb acting like a on -off button. cause i like to do wheelies.(without being thrown off the bike)

If there are more TT:ers that have discovered the same thing as i have,

I can recommend the tm 40 pumper carb (hs40) as a problem solver!

I am 100% satisfied!

Sorry my bad spelling:bonk:

// Richard

Edited February 23, 2010 by HondaXRider

[Kenzo]

w/ the carb jetted correctly the of idle bog can be controlled w/ ur right hand...

...and if the slide is sticking anywhere u have a worn out piece-o-chit carb...?

...pardon my bluntness

it ain't no "pumper" but i've never had the slide stick and it is sensitive to throttle/slide position but so are most carbs.

[zeusthegoose]

sounds like a lot more fun than getting no feedback at all from throttle inputs on the stock cv carb!

[HondaXRider]

yeah.. your right. if you dont mind these defects even after a long period of use, you are for sure happy with the r carb...

Throttle sticking is only common on a well used carb thats right

It dont do this the first years of use.

Over the stock -L vacuum carb, it is for sure a big improvement.

And the good price these go for, its worth testing one..

(Sadly the improvement from R carb to mikuni pumper is the same big step up, once again... not walletfriendly facts:smirk:)

//

[RoHo]

I just got a 650L. I also bought a 650R carb off ebay. When the carb gets here I will clean it and replace all gaskets and o-rings. I will get the b53e needle and some jets (hopefully by then). I have the stock header with the welds ground down. An fmf Q4. Uni filter. And snorkel removed.

I will start with a 65/165 and the hrc needle. Any recomendations on clip position?

How many holes in the side of the air box? How big?

What is an AJCV? Where is it, what is it, and how and WHY would I disable it.

I am not trying to make it a hotrod. I have a 540 KTM for going that. This bike will be used for Dual Sport riding. I just want it to run good and smooth and be able to pop the front wheel over obstacles.

[zeusthegoose]

so i got the bike back from the mechanics yesterday. carbs on, had to get a 650r throttle assembly too. ended up with much leaner jetting than expected. i see what richard was saying about the touchiness of the throttle but it really doesn't seem like anything that can't be overcome with your right hand (though i admit i'm not trying to ride balance point wheelies on my pig). vast improvement in low/midrange throttle response and far less popping on decel. i'll have more updates (and perhaps some photos) after i terrorize the mountains this weekend. thanks for all the help so far thumpertalkers!

[pdxthumper]

so i got the bike back from the mechanics yesterday. carbs on, had to get a 650r throttle assembly too. ended up with much leaner jetting than expected.

What jetting did you end up with, did you use the B53e needle or stock, did you disable the AJCV?

[zeusthegoose]

What jetting did you end up with, did you use the B53e needle or stock, did you disable the AJCV?

these are all things i do not know. i just handed my mechanic the carb and told him the baseline jetting from this thread. he went through several sets of jets to get it lean enough. it's got the choke flapper out i know that but as far as the the race needle and final jetting i am unsure. i think it was around 150 and 58? i dunno i am just the rider, all i know is it feels great!

[RoHo]

What jetting did you end up with, did you use the B53e needle or stock, did you disable the AJCV?

What is the AJCV? What does it do? Why and how would I disable it?

[RoHo]

it's got the choke flapper out

why??

[Kawidad]

why??

Because there are internet reports that it can vibrate out and get sucked into the engine with bad results.

[RoHo]

Because there are internet reports that it can vibrate out and get sucked into the engine with bad results.

Thanks.

[pwrpapa]

Because there are internet reports that it can vibrate out and get sucked into the engine with bad results.

I know alot of R riders and I have never talked to one that has had this happen. Have you talked to any that has had that happen?

I keep an eye on mine and haven't found any cracks or loose screws or bad springs. I'll probably take mine off just for safety's sake.

I put 12000 miles on an R and the choke looked like new so I dunno..

I just sold my old R and bought a new 07 with only a few hundred miles on it, I would hate to have it eat the flapper plate.

I do know that the older 600's had the problem but the 650's have a better flapper.

Just askin.......

[HeadTrauma]

I believe the '88-00 XR600 carb's choke plate and backfire flap are the ones better known for coming apart, not so much the 650R's. BTW, the screws are all staked; they cannot fall out unless someone has removed or replaced them before. The choke plate cracks and actually breaks off. It's still not a common problem, just a possible problem.

[Kenzo]

of primary concern are the older cast style 600R plates w/ reports of them break'n ...at sum point they changed to a non-cast ss plate like on all of the 650R's...

ur chances of the newer style break'n(spring & pin coming loose) are minimal and if ur climate dictates (cold) a "full" choke for start'n...i'd keep it

if not...wut ain't there can't break

?

[pdxthumper]

What is the AJCV? What does it do? Why and how would I disable it?

It is an air cut off valve, that richens the fuel mixture when the vacumm drops on decel. It can lead to some poping on decel, and from boyack's page is supose to soften engine braking. If you search this thread, or 650R carb stuff on the web you will find his page which gives more info on it and why and how to disable it if you chose to.

[Kawidad]

I know alot of R riders and I have never talked to one that has had this happen. Have you talked to any that has had that happen?

I keep an eye on mine and haven't found any cracks or loose screws or bad springs. I'll probably take mine off just for safety's sake.

I put 12000 miles on an R and the choke looked like new so I dunno..

I just sold my old R and bought a new 07 with only a few hundred miles on it, I would hate to have it eat the flapper plate.

I do know that the older 600's had the problem but the 650's have a better flapper.

Just askin.......

Not me. I'm not saying they are accurate reports, that's why I qualified it. They are out there, like Kenzo said.

[HeadTrauma]

According to 4strokes.com, the purpose of the ACV is to reduce the amount of air available to the pilot jet's emulsion holes at high manifold vacuum. That obviously will richen the mixture under deceleration, but is supposedly done to reduce popping, not cause it. I also interpret that to mean that disabling the ACV will richen the pilot circuit all the time.

Think of it as the deceleration enrichment that all auto manufacturers I know of have used in their EFI algorithms in some form or another for the last 30+ years. In their case, decel enrichment is done to improve throttle response and it's probably even more important in a carb without acceleration enrichment. It helps cover for that lean spike when the throttle is opened quickly and prevents stalling when the throttle is closed quickly. IMO, it was not put there due to a lack of purpose.

[RoHo]

Thanks for the replys! I am getting some good info.

[BLSBRKR65]

Finally got the XRR carb on the XRL. It has a 65 pilot, 165 main with fuel screw 2 turns out. I am at seal level (Houston). Carb is clean as a whistle. I couldn't get it to run except with the choke on (lever up). It will die as soon as i turn the choke off (lever down). When running it will stumble at 1/4 throttle. What could be the issue? I checked for air leaks by spraying carb cleaner on the manifolds but didnt notice any change in idle. It's a pain to remove and re-install the carb as it is.