Need Help

2000 xr650r
I have cleaned the throttle housing and replaced the Motion pro cables but still have this problem .
When the bike is off , You can open the throttle and it snaps closed easy peezzy but when you start the bike and its idling and you open the throttle and let go it hangs up about 2000rpms then drops , When your riding and shift between 1st & 2nd that hang up causes a hard clunk gear shift as if you just speed shifted into 2nd without letting off the gas , Same when your riding along and let go of the throttle it keeps motoring a second before deceleration , Almost like a vacuum is holding it open ?





  Could it be a vac hose leaking , the one thats plugged seems old & not very tight at the carb ... Any help guys to get me back riding the bike , As it is now I hate riding the thing

Just out of curiosity why is that air line plugged?

JRZ7285 wrote:Just out of curiosity why is that air line plugged?

I checked the manual and found its the fuel overflow , The one that sits in the rubber pad under the tank , Dont know why its plugged , PO had it that way , Dont believe its the problem since its not a vent tube , Suggestions say I should check the throttle slide might be hanging up , Never in my 47yrs have I had that problem but I guess its worth a look .

JRZ7285 wrote:Just out of curiosity why is that air line plugged?

My idea also, is it?
He is talking about that little cover on the LHS - take it off, watch the spring & diaphragm behind it, and inspect the cover itself.
There's small/tiny hole in it which you better plug with a droplet of epoxy-glue. This will disable this silly, environmental system... which perhaps has the diaphragm torn or deteriorated? If so just plug the hole, put back the junk and forget about it.

Ive got the same damn problem you do. bike hangs at high idle then eventually drops. Checked cables, valves, jets are not clogged, no air leaks, adjusted fuel screw and tried multiple configurations with plugging the air cutoff valve. still doing it. if you google XR650R high idle you'll see this is a common problem with no exact cause. some (like myself) have tried everything short of buying a new carb, others have had success with a valve adjustment or plugging the ACV, some have even had the issue go away on its own which is what I'm hoping for.

Guess you could unhook the cables from the carb and just be 100% sure it's not them ?

Here's another take on this phenomenon.
First, make 200% (yes, do it twice) sure that the valves are set correct (remember the auto-decomp system!).
Then, idle the warm/hot bike sitting vertical on a stand (and run a hosepipe over a radiator to keep it cool enough). Then wave a gasburner withOUT flame (if you want to keep your bike that is, otherwise burn it to ashes) but with gas only over the intake manifold, the rubber bung between head & carb.
If the revs pick up you've found the problem, renew the intake rubber.

this can have a few causes, but for most part they are lean mixture related, you are correct burp to mention the manifold air leak diagnosis, its a common cause of this problem, another cause is a clogged idle jet circuit- and or idle fuel jet, a float level set too low or another less diagnoised cause- blocked float chamber vents, including the rubber hoses connected to such vent. this means that a vacume can build up in the float chamber that starves idle circuit of fuel

Had similar problem and it was resolved by making sure to perfectly align the cables with carb to prevent a slight binding that was occurring. Also make sure the push/pull cable adjustment on the carburetor is just right. This cleared it up for me. To test this when the idle is hanging manually fully close the carb and see if the idle drops.

Hi,
Am having the same problem..
Just bought a used XR, on 2020 January (never touch on carb) and upgraded to supermono.

At cold start, idle rpm stays between 1400-1600, sometimes 1700rpms…….after riding for a while, about 5 to 10min the idle goes up to 2000-2200Rpm, between gears… ok…..but when you need to stop and go to neutral....grrrrr, very annoying, than engage 1gear….. Seems that i'm hitting the gearbox with a hammer.

Found out when idle stuck at high rpm push and let go the throttle once or twice, very fast, sometimes, slowly the idle drops down to 1400-1600, start pushing and riding again, same problem, so I avoid neutral and force with clutch and with 1gear engaged use the brakes, to force rpm drop down.
Ridding, no problem at all, engine explodes with power, no carb/engine hesitations, always consuming revs… amazing.
This already happened when I bought she, i only ride it only two/three times, for 10-15 min each, because of the motocross tires, than the idle went only to 1800/1900 rpm – thought it was normal…. Now, as she warms/hot…..goes up till increase 2000-2200Rpm

After reading your suggestions, here's what i already did:
- Check cables – seems ok.
- Engine running cold (don’t have the gasburner, like BuRP says), but used WD40 – idle rpm stays ok, no alteration.
- Decomp. system lever – free play - ok

Going to do:
Take the little cover on the LHS, watch the spring & diaphragm.
But if you have any idea more, please let me know.
Kind regards

Are you sure the throttle cables (2) are free ?, throttle should snap shut when released ?

I think so, already check and recheck....
Next time i will take with me a regular screw driver, when this happen and i´ll stop the bike and i used the screw to force the throttle link set (on carb to) get it back - if return cable are not free, should force it to get all back...no?
I keep thinking on several ways to check your suggestion, to eliminate steps.
i was wondering also, i have riser bars.......maybe the cables are short....????
going to double check.
Meanwhile already ordered the air cut valve (spring & diaphragm).
thankssss

Mine just did this and it was 100 percent self inflicted for me. As mentioned above by Kiwi, I set the float level to low creating a lean condition at idle. It was the perfect "it ran fine till I fixed it" deal. I run a stock carb jetted for my area, 68s pilot and a 175 main. I used a small round piece of cork gasket with no hole in place of the tiny gasket with a hole under your acv cover. This disables the valve quick and easy. And it's super easy to return to stock if you ever wanted too. My bike ran perfect and I saw no need for an aftermarket carb. Now I just need to readjust that float level.

today i did the 999999…..test drive, weather temp. was around 38 Degrees.... very very hot...
i started the engine:
The push/pull cable adjustment its ok.
Idle rpm good,  1400-1500 rpm.
Waited a few minutes to the engine get hot.

As soon as i left my garage, rode slowly, than start to pull the throttle...same problem.....between gears, hanging revs around 3000-3500 rpm. (Colder days was around 2000-2200)
Pull throttle again, decrease do 1800-1900...grrrrrr
Back to my garage, removed the fuel tank and used a small external fuel tank, so cables run free  - Same problem revs hang.
Have eliminated the cable problem – I think

Use the idle screw to reduce a little the idle rpm... nothing happened, so used and abuse the screw...
Result: no idle rpm at all… tomorrow will see….

I'm starting to get tired of this shi…….
I hate to unscrew and screw the screws more than two or three times .... it always ends up getting all screwed
In fact am so piss of, that, a few minutes ago, bought an extra stock carb from a friend of mine.. another XR650R used Keihin.
After get back my idle rpm going to start switch parts between carbs..

PS: still waiting for the air cut valve (spring & diaphragm),but mine seems ok, not torn or deteriorated.
BuRP, you say to eliminate this… “There's small/tiny hole in it which you better plug with a droplet of epoxy-glue. This will disable this silly”.
May you please explain me………why its there? If we do not need it?
cheers

You didn't set the valveplay did you?
Do that first, my hunch is your revs will come down....

That small cover/diaphragm/spring/thingy is there ONLY for environmental reasons, to lean off the idling mix during overrunning >>> BLOCK it, by a tuny droplet of glue in the cover after you've taken it off fr this purpose.
This will disable this whole system, irrespective of the diaphragm/spring is actually working or in good condition or not.

Thanks for your tips, am going to follow it all.
I did not touch the engine, as it was running good………. But we never know what PO did, he said it was rebuilt (going to measure compression ratio also).
I´ll Start with the valve play, (problem it’s the fan…. Its making more difficult access to the cover valves, probably I’ll have to remove it.
Then remove carb and clean it, understand what jets do I have, jet needle - how many grooves.
Finally recheck cables, and fit carb.
If no good, will fit the extra carb with the original settings (jet pilot 65 and main 175)
Still do not have the diaphragm (no stock from Honda), but am going to replace it anyway.
The place I live it’s between 60 and 100 meters above sea level.

Cannot see it being the valves myself, reading through this does seem like a carb only issue, she almost like syphoning fuel from the bowl causing the rev's to hang high when you roll of the throttle?. It's a mechanical carb as you know, mechanically the cables open the slide and the spring mechancially closes it. Therefor it's either mechanically sticking when she is running there must be some external force or action causing this. If non of these exist as you suggest then what's left ? the internals of the carb, as the choke doesn't increase the fuel being added I cannot see it being this. It's not a big job to swap the carbs and that way you could find the answer straight away.

Mauser wrote:Cannot see it being the valves myself....  

Tsk tsk tsk Mauser, I almost hammered the (new to me!) "Dislike" button!
You being a Briton definitely know the acronym RTFM .... and in it you'll find "Start with setting the correct valveplay before you remove the taillightbulb" followed by an exclamation mark.
Yeah, I lie, but you will agree with me saying 'check all else first before you come to down-the-line conclusions'.
Plus, this bike's auto-decomp system does make setting the correct timing a bit fiddly/complicated - or at least it does for someone who's not overly handy/experienced with such, hence my advice.
Crucially though, for a correct idling the rest has to be spot on, otherwise one's settings tend to compensate for shortcomings.

Ian, good idea to check all the jet/needle sizes, I was going to go there AFTER you had set the valves!

Thanks for all support
I’ll check valveplay, have to remove fuel tank anyway, and should have done this, while engine was off frame, it was much easier.
I have idle again…. And now, i do not need to leave my garage, as soon as i start the engine, a few moments later, as i pull the throttle, the get hang...2500rpm and more….need to pull it 2 or 3 times more to get down….pull throttle again, same problem on and on……..ridding when it gets hot hangs on 3000-3500rpm between gears.
The Carburetor Pilot Screw its now 2turns out – playing with it form 0 till 2turns no difference, after 3 turns out notice idle increasing a bit - have to clean both carbs.
Besides this…..ridding…awesome…..
And while am waiting for the carb spare parts, probably will swap the carbs, just need time!!!!

The time you spend posting on here you could have swapped the carb, you can check tyre pressures and plug gap as well along with headstock play, that's for my friend Burp lol.
If this problem is a valve issue I'm a Dutch Man

Mauser, I understand you perfectly, but I was waiting for spare parts, I ordered from 3 different places, two from eBay and local store and Honda dealer, came all at same time (two weeks ago, insulator came this week, with air cut valve), cause the carb that I got came to me dissembled, and with some issues also.  Already has epoxy glue on the inside (next to pilot screw.)




Swap done, Valve clearance checked ok: 0,15 - 0,20mm intake-exhaust

1-Settings of my Carb - fitted  in the Xr:
Low jet 68S, 178 and needle 2rings from top.
(Showed wearing marks on the throttle link shaft and throttle valve piston)

2– Settings Carb I get now:
Low jet 68S, 175 and 3rings from top.
Note: for me also important was a tiny 5MM screw, fitted on the left side of the engine head, beside the insulator, I changed the washer and tightened the screw better.
After a few drive tests, She’s running fine no more problems with stuck rpms…… while changing gears (think problem its solved)
I seems to me that she´s not so powerful at high rpm.
So I have to thank you, Mauser and Burp……. all for the support and patience you had with me.
If I may help someone, let me know.

forgot this picture...
Note: for me also important was a tiny 5MM screw, fitted on the left side of the engine head, beside the insulator, I changed the washer and tightened the screw better.

Ian,

us guys and screws..... let's not go there
I'd put Locktite on that screw though, not so much to prevent it from loosening but to prevent it from sucking air... which, IF it does that your idle mix hence revs will go for a ball of inpredictables!
It's a blockoff screw where once a de-smogger connection was so now it's just a hole which needs permanent closure - hence my suggestion.

Less power on top?
If you're at sealevel then try the 178 main jet?
Also, search around for the correct float-level setting, if my memory serves me well-enough it is 17mm which is best set to 19mm to prevent pissing, sorry, leaking when leaned over on the sidestand.... something like that, a 2mm bigger value!
No, won't really affect the rest or idle, just warm the bugger up and set the mixture screw again.
Oh, the latter should be or around 1.5 turns (for just about any carb I've seen, cars included!).

Good luck and let us know here if all's dandy now?
I will read it here but that may take some time, don't visit too often anymore

Hi Burp,

Yes I can use epoxy on the 5mm screw, thanks.
As the carb is not mine, it is borrowed, and the owner said he was working well, just needed the rubbers, o-rings etc… ..  so I kept the configurations, and i did not use epoxy on the air cut valve hole, also.

My goal its with the spares I have try to fix my carb and swap it again, to see how it works…
Meanwhile, Probably I’ll buy this carb, (because this it working fine) than I’ll upgrade main jet to the 178.

Yes I did search around for the correct float-level setting,  service manual says  16.0mm I set it on 18.0mm, its ok, no leaks at all.After replace the mixture screw again, did set it 2.0 turns (old mixture screw had 2.0 turns), but i´ll do as you say, around 1.5 turns.

I am assuming that the problem was really the carb, otherwise no idea at all, where was the problem.

Promise, i´ll give you feedback, just need time also, at same time i am rebuilding my old nx650 dominator 1990..
Once again, thank you all