XR650R Carb Borrow / Help

[dakkman]

hey everyone, still trying to dial in my carb but running into a lot of issues.


Things you should know:
-stage 1 cam
-uncorked air box
-full FMF pipe exhaust
-side panel cut out
-68s Pilot Jet
-180 main @ sea level @ about 25 deg C (77F)
-needle clip 4th down


Ok, so my bike usually cuts out at IDLE when it gets hot. I'm almost certain it is because my bike is running too rich because when it is dead cold and trying to start with choke ON it runs for 1-2secs then dies (yes choke in correct position). What is also weird is my air/fuel mixture screw is ALL THE WAY IN and this is the only way to prevent from cutting out. But then it gets even more weird, the bike pops a lot on decel which usually means running lean. I find idle can be all over, sometimes at a nice health 1500-1600 (stage one cam seems to like that idle) and then sometimes it goes up to 2000rpm to idle


What I have tested:
Spark plug
ignition system, healthy bright spark
air intake leaks (used a propane tank and sprayed around the sealing boots)
Ultrasonic cleaned the carb, blow air through orifices
float level looks pretty good 16-17mm -ish
valves lash checked 0.006" IN / 0.008" EX
What I plan on testing next:
65s pilot
cam shaft position at TDC, maybe it was installed a tooth off?

Does anyone have a stock XR650R carb I could borrow or purchase? Seriously getting desperate, can pay in beer/food/money

 

[vortexman]

hey everyone, still trying to dial in my carb but running into a lot of issues.


Things you should know:
-stage 1 cam
-uncorked air box
-full FMF pipe exhaust
-side panel cut out
-68s Pilot Jet
-180 main @ sea level @ about 25 deg C (77F)
-needle clip 4th down


Ok, so my bike usually cuts out at IDLE when it gets hot. I'm almost certain it is because my bike is running too rich because when it is dead cold and trying to start with choke ON it runs for 1-2secs then dies (yes choke in correct position). What is also weird is my air/fuel mixture screw is ALL THE WAY IN and this is the only way to prevent from cutting out. But then it gets even more weird, the bike pops a lot on decel which usually means running lean. I find idle can be all over, sometimes at a nice health 1500-1600 (stage one cam seems to like that idle) and then sometimes it goes up to 2000rpm to idle


What I have tested:
Spark plug
ignition system, healthy bright spark
air intake leaks (used a propane tank and sprayed around the sealing boots)
Ultrasonic cleaned the carb, blow air through orifices
float level looks pretty good 16-17mm -ish
valves lash checked 0.006" IN / 0.008" EX
What I plan on testing next:
65s pilot
cam shaft position at TDC, maybe it was installed a tooth off?

Does anyone have a stock XR650R carb I could borrow or purchase? Seriously getting desperate, can pay in beer/food/money

Ignition faults cannot be confirmed by the bright spark method. If it cuts out when hot richen the mixture with your propane bottle at idle to confirm fault but be warned richening the mixture during diag can mask ignition problems. Float level cannot be confirmed by looking good.

In my shop we put everything back to stock after customers complete carb mods and start all over again with the basics. Cyl leak down test to confirm engine compression and valve integrity, ignition test (measure KV with tool) stock sea level jetting and then if need be primary ignition scope analysys with a Fluke 120 scope meter.

I think I did offer to come by a few months back ???

 

[dakkman]

Ignition faults cannot be confirmed by the bright spark method. If it cuts out when hot richen the mixture with your propane bottle at idle to confirm fault but be warned richening the mixture during diag can mask ignition problems. Float level cannot be confirmed by looking good.

In my shop we put everything back to stock after customers complete carb mods and start all over again with the basics. Cyl leak down test to confirm engine compression and valve integrity, ignition test (measure KV with tool) stock sea level jetting and then if need be primary ignition scope analysys with a Fluke 120 scope meter.

I think I did offer to come by a few months back ???

Interesting, a lot more in depth than I would have imagined. Ill send you a PM man.

 

[vortexman]

Interesting, a lot more in depth than I would have imagined. Ill send you a PM man.

I have two bikes ahead of you right now but we can get you sorted out. Do you have a shop to work in? The emulsion tube that the main jet screws into is very difficult to clean as the tiny holes that mix fuel and air get plugged. When people let bikes sit for extended periods with no fuel stabilizer and gasoline cracks back to base components the varnish that this process produces is almost impossible to clean from these small passages.

But I have also seen customers get fixated on a component and something simple like a spark plug cap not secured to the high tension coil lead was all that was wrong after hundreds of dollars of components were changed. Confirm the fault by process of elimination and yes sometimes I must change out a pulse coil or ignition coil assembly as these do fail at times when cycling from cold to hot.

Review the attached link put the airbox back to stock for now, install original OE jets make sure the float is installed correctly as I have also seen customers put the float needle securing clip to the float tab incorrectly and cause all sorts of problems.

Use the external float level method (clear tube) Use this cheap tool to confirm good spark when hot

http://www.thetoolwarehouse.net/thexton-458-P54519.aspx?gclid=CLLnwIuUu8wCFbgy0wodInAL1w

review basic carb theory and operation

https://www.fix.com/blog/motorcycle-carburetor-float-height-adjustment/

Carb float level setting

 

[Ti welder]

hey everyone, still trying to dial in my carb but running into a lot of issues.


Things you should know:
-stage 1 cam
-uncorked air box
-full FMF pipe exhaust
-side panel cut out
-68s Pilot Jet
-180 main @ sea level @ about 25 deg C (77F)
-needle clip 4th down


Ok, so my bike usually cuts out at IDLE when it gets hot. I'm almost certain it is because my bike is running too rich because when it is dead cold and trying to start with choke ON it runs for 1-2secs then dies (yes choke in correct position). What is also weird is my air/fuel mixture screw is ALL THE WAY IN and this is the only way to prevent from cutting out. But then it gets even more weird, the bike pops a lot on decel which usually means running lean. I find idle can be all over, sometimes at a nice health 1500-1600 (stage one cam seems to like that idle) and then sometimes it goes up to 2000rpm to idle


What I have tested:
Spark plug
ignition system, healthy bright spark
air intake leaks (used a propane tank and sprayed around the sealing boots)
Ultrasonic cleaned the carb, blow air through orifices
float level looks pretty good 16-17mm -ish
valves lash checked 0.006" IN / 0.008" EX
What I plan on testing next:
65s pilot
cam shaft position at TDC, maybe it was installed a tooth off?

Does anyone have a stock XR650R carb I could borrow or purchase? Seriously getting desperate, can pay in beer/food/money

Google xr650 pig pen
a worth of knowledge

these bikes run stupid lean stock
i have most of the mods you did and there jetting works good although a tad rich, some engines need that
Has the restriction plate been removed from intake boot on head side?
I also have completely unkorked and stage one cam... Runs fine!
Until I did the mods and jetting it was a total pig to start
i changed all jetting to there spec. Needle, tube, main, pilot... Do them all or don't bother!

 

[dakkman]

Google xr650 pig pen
a worth of knowledge

these bikes run stupid lean stock
i have most of the mods you did and there jetting works good although a tad rich, some engines need that
Has the restriction plate been removed from intake boot on head side?
I also have completely unkorked and stage one cam... Runs fine!
Until I did the mods and jetting it was a total pig to start
i changed all jetting to there spec. Needle, tube, main, pilot... Do them all or don't bother!

Scott,

I have followed the pig pen jetting guide and been digging through the info on that site. The restriction plate has been removed.

 

[Ti welder]

So you changed the tube, needle, both jets?
The only issue I have is hanging idle... Revs a bit then settles
The factory carb is a bit of a gem, lean fat lean is the hardest to cure
some of the USA bikes had air pump mounted to the back of the right rad, the bracket is there on my 2006...
Pumper carb is the only true fix but my bike runs well enough to start second kick every time.
when you installed cam, did you get rid of the auto decomp?
What head pipe?
my complete exhaust is stock other than drilling out the but plug to get the air out, the spark arrester is there and stock
you may still be lean with a open exhaust