XR650L Need help getting a basket case to run without choke

[nwright98]

I picked up a 2008 XR650L a while back that had been completely disassembled.  It was mostly there, but I could not evaluate the engine before getting it.  I put it back together and replaced what was necessary to try starting it.  One thing that was missing was the choke plunger, and I bought one of the $25 aftermarket ones from ebay https://www.ebay.com/itm/CARB-FUEL-CHOKE-PLUNGER-ASSEMBLY-REPAIR-KIT-HONDA-XR650L-XR-650L-XR650-1993-2020/274358850613 (it may be important for my issue.)  Other than that, it seems to be in stock condition with around 14K miles.

It would start, but I could not get it to run with the choke off.  I cleaned the carb multiple times, including running copper wire through the passages.  The intake manifold looked good.  It also smoked on startup and there was some air leakage through the right exhaust valve so I tore down the top end.  The valve seat had moved around in the head, and there was a low spot on the cylinder wall (looks like water sat in it and rusted the cylinder at the low spot.) 

I had the cylinder bored .5 mm over and got a new OEM piston, rings, and wrist pin.  I bought a used XR600R head instead of repairing the original, and cleaned it up & lapped the valves.  I put it back together with all new gaskets, valve seals, intake o-ring, etc.  The cam chain and adjuster seemed to be in good shape without too much stretch.

I still can't get it to idle well with the choke off.  The carb has all stock jets, idle screw is set 2 1/4 turns out, stock exhaust with the baffle in, valve clearance set properly, new battery with a full charge, new NGK plug, smog pump removed / blocked off.  It will idle well with the choke on and revs fine, but if I turn the choke off it will only run poorly if I hold the throttle open a bit.  If I try to rev it with choke off it pops & dies.  I have tried spraying brake cleaner around the intake manifold and there is no change in rpm.  The carb is clean and in good shape.  The slide diaphragm looks good, and is installed correctly.  The vacuum port on the intake side is connected directly to the air cut valve, I took out the tee for the smog pump.  The carb vent hoses are in place and are not kinked.

Could the aftermarket choke plunger be the issue?  I don't want to throw parts at it, so I'm trying to figure out the most likely problems and tackle them first.  Searching turns up possible things like coil, pulse generator, stator, but I feel like it is fuel rather than spark.

I don't know if this is related, but the stock muffler is noisy.  There is a sharp metallic sound coming from it, but if I remove one of the cleanout plates that sound goes away.  I'm not sure if that's how these are supposed to sound since I have never heard it run, but I had an NX650 and GB500 years ago and I don't remember them sounding like this.  The muffler is in good shape with no rust.  I'm also running it indoors, which could affect the sound.

Can anyone recommend the most likely things to try first?

Thanks,

Nick

[brianhare]

It sounds like your pilot jet is plugged,,,or the passage from it...

i know you have had the carb apart numerous times...but a new pilot jet would be my first area to start,,the holes are super small and almost impossible to clean..

On these carbs,,if it runs with choke but dies when the choke is turned off,,it`s almost always that jet..get a 52 or 55 pilot..

 

B

[nwright98]

The pilot jet was my first thought, but I have had it under a microscope and it is clean. All holes are open with no blockage.  I have blown through the passages with compressed air and everything seems to be open. 

[brianhare]

the pilot circuit and fuel mix circuit let it idle though...it sounds like you know quite a bit,,everything you`ve done is spot on what i`d go at..

try this....turn the idle up some,..turn the fuel screw out and see if it idles better,,if after adjusting the throttle plates open more,,and the fuel screw out more and it still won`t idle but runs good otherwise...you gotta start somewhere,,replace that pilot..

if i had a dollar everytime someone said the pilot was good and replacing it solved the issue,,,i`d have a free bottle of Whiskey for my trouble..

 

lol

 

B

[nwright98]

Thanks for your help. 

I went out this morning and cleaned the grounds and coil connections and checked the spark again - looked good.  Then I spent a long time fiddling with the idle and fuel screws without much luck.  I feel pretty sure it's the pilot circuit or an air leak.  I can back the idle screw out entirely so I know the butterfly is closed then just open it a bit so I have a fast idle on full choke, then slowly push the choke lever in and it dies right at the half choke point.  If I try to keep it running with the throttle at that point it just doesn't respond well.  I have tried the fuel screw all the way out to 4 turns and it doesn't help.

I have cleaned the carb with brake cleaner, again with degreaser in an ultrasonic cleaner (I couldn't submerge it fully because my cleaner is small, so did the best I could), pushed copper wire through the passages, and sprayed all the passages with compressed air.  I can feel air flow through the pilot hole in the carb throat when I blow air into the pilot jet passage in the float bowl, so I know it is at least partially open.  I will order a couple of pilot sizes (52, 55) to try out, but do you have any tips on another way to clean it?  Anything else that might keep the pilot circuit from working?  The o-ring and washer are on the fuel screw and look good.

[baldy110]

Are you sure the choke is operating correctly? Like when you think it's closed it's really open and visa versa?  Like Brian said if it will only run on choke it's usually a clogged pilot curcuit.

[nwright98]

I thought about that, so I double-checked the owner's manual and I have been using it correctly.  Pull the lever towards the rear to the second click for full on, push to the first click for half choke, push all the way in for choke off.  I also adjusted the choke cable so the plunger has the right clearance at full on.

[ossagp1]

1 hour ago, nwright98 said:

Thanks for your help. 

I went out this morning and cleaned the grounds and coil connections and checked the spark again - looked good.  Then I spent a long time fiddling with the idle and fuel screws without much luck.  I feel pretty sure it's the pilot circuit or an air leak.  I can back the idle screw out entirely so I know the butterfly is closed then just open it a bit so I have a fast idle on full choke, then slowly push the choke lever in and it dies right at the half choke point.  If I try to keep it running with the throttle at that point it just doesn't respond well.  I have tried the fuel screw all the way out to 4 turns and it doesn't help.

I have cleaned the carb with brake cleaner, again with degreaser in an ultrasonic cleaner (I couldn't submerge it fully because my cleaner is small, so did the best I could), pushed copper wire through the passages, and sprayed all the passages with compressed air.  I can feel air flow through the pilot hole in the carb throat when I blow air into the pilot jet passage in the float bowl, so I know it is at least partially open.  I will order a couple of pilot sizes (52, 55) to try out, but do you have any tips on another way to clean it?  Anything else that might keep the pilot circuit from working?  The o-ring and washer are on the fuel screw and look good.

FYI solvents and brake cleaner have never worked to clean up a carburetor for me.  Seafoam and avgas are about the mildest things that I have used to clean a carburetor, where it actually worked.

[cfaber]

Will it run at half throttle with the choke off?

[nwright98]

14 minutes ago, cfaber said:

Will it run at half throttle with the choke off?

Yes, I just tried that.  If I drop down into the pilot range of 1/4 throttle or less it starts popping and sputtering.

I tore the carb down again earlier today and boiled it and the pilot / main jets for 30 minutes with a little degreaser added to the water, then blew it out with compressed air again.  No improvement.  I'll try a new pilot jet; if that doesn't help, I have seen new OEM carbs on ebay for around $220 so I guess I will go that direction.

[nwright98]

I made some progress - it will idle with the choke off now, with the occasional hiccup.

I had noticed that the aftermarket choke plunger was blunt on the end, but pics of the OEM part show more of a pointed end.  I chucked it up in the drill and made a taper with a fine file and sandpaper.  After I put it back in then I could raise the idle speed and get it to idle without the choke.

Before:

After:

It makes me think this plunger is interfering with the pilot circuit.  Maybe the tip needs to seal fully for the pilot circuit to work correctly.

Here is a clip of it idling with choke off now.  

 

You can hear the sharp exhaust note I mentioned at the beginning, and there is an occasional stumble (sometimes it dies.)  I will sharpen that tip a bit more, but should probably get an OEM plunger.  It's around $50, though, so may still get the entire carb so I have a known good starting point.

[cfaber]

Checked for air leaks. Also ultrasonic clean the body of the carb.

[cfaber]

Um.. Sounds like a pinging. What's your spark plug say?

[nwright98]

I agree, it seems like an air leak.  I can't get it to run consistent enough to do a good leak test; I will pick up some starting fluid and try it.  The carb insulator seems to be in good shape with no cracking, and it has a new o-ring.

The carb seems worn.  The PO ran it somewhere pretty dusty (it was filthy when I got it) and used a K&N filter.  It might be leaking around the throttle butterfly shaft.  The slide looks like this:

The plug looks okay, just black from idling with the choke on so much.  

The metallic sound in the exhaust goes away if I open one of the cleanout plates or even just put my finger over the opening a little.  Not sure what's up with that.

[cfaber]

Which plate are you referring to?

Also is that a CV carb?? Sure looks like it with that diaphragm. If so just replace it with a slide carb, those CV carbs suck and are difficult to tune and impossible to tune for after market mods.

Edited May 24, 2020 by cfaber

[baldy110]

What's a clean out plate?

[nwright98]

1 hour ago, baldy110 said:

What's a clean out plate?

The removable plates on the bottom of the stock muffler for blowing out the spark arrestor. 
 

It has the stock CV carb. I’m considering spending the money on an FCR MX or TM40 instead of getting a new CV.  I just hate to put more variables in since I have never had it running. 

[baldy110]

Got it thought we were talking about the carb and never heard of a cleanout plate on the carb.  I have an extra OEM carb I can sell you. It's been thoroughly cleaned and comes with a Dynajet installed.

[nwright98]

I found an old Mikuni roundslide in my shop that fits the XR650L intake manifold, so I threw it in for a quick test.  The bike idles perfectly with it, so I have a new carb on order.

Thanks for helping narrow this down.

[cfaber]

Good to hear you got that sorted. CV's suck.