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xr600r Carb Gremilin

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Hey guys 1st time poster long time follower. Been diagnosing some carb issues I've been having for awhile now that just wont go away. Here's what's going on and some back story on the bike. 90% of my riding is done within 2-3,000ft 

-'91 xr600r relatively stock with the baffle out uni filter and white brothers slip on muffler

-I'm 2 turns out on the a/f screw clip at 2nd spot from the bottom and 160 main.

-3-5 kicks to fire up idles great pulls hard smooth mid range top end seems to be a little fat but i'm ok with that better than too lean.

-Bike runs good for the most part every once an awhile the bike will bubble and die and I'll have to bump start it to get it going again.

        -I've got a shop manual and have ran through all the electronics and everything checks out. I've done all the resistance and voltage tests that I can make. I've done all the normal things like full tune up oil change, new plug....stuff like that.

        -Definitely feels and sounds like a float issue. I've been through the carb making adjustments 3-4 times now. By now everything in the carb is new (everything from jets, floats and needle, rubber air cut off diaphragm). 1st time apart set floats to factory 14.5mm (.57") ran like crap (dies when going up a steep road), now floats are set dead level with carb base. Runs great right now but when that front tire comes off the ground in a wheelie the bike wants to die. Most of the time trying to do a wheelie up my steep driveway for instance.

-Now an old timer once told me floats should be level with carb base, but what if the carb from the factory does not sit totally level. Where should that put the floats?

Any input would be great!

 

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Next time it falters, do a spark check.  To avoid removing the spark plug, carry a spare and just pull off the spark plug wire and plug it onto the spare to ground against the fins for a spark check.

Look over all the wiring for any loose or corroded connectors, or bare spots that are shorting. 

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I am a firm believer in 99% of the time it's something stupid. All the stupid things have been looked over but no luck. Bike was running great before then it seems like all of a sudden hit a wall and have had nothing but problems. So that being said I found out that there WAS NOT an O-ring on the air fuel screw thus explaining all my issues with running lean. I was stoked to find that thinking that was my issue.......So I set the floats and clip on the needle back to factory just to start with a clean slate. The problems I'm still having with it cutting out leads me to believe its an electrical issue even though with the bike COLD, everything that I could check was within spec. Now I have not compared that to HOT numbers I may find something is breaking down when hot. One thing that did happen if this rings anyone's bell I was passing a buddys place doing 50mph, I pulled in the clutch to throw out a couple revs......and it sputtered and died. It acts like its flooded it spits and sputters like the cylinder needs to clear out.......There's got to be something here I'm missing. If anyone has ideas throw them out.

Uni foam filter, slip on white brothers exhaust stock motor, carb is rebuilt from the ground up

#52 pilot clip in 3rd spot and 160 main a/f screw 1.5 turns out

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I had intermittent issues with my ford diesel, and everyone I spoke to said very rare to have a computer module fail. after 2 years of getting stranded, and trying everything else,  I found a used one moduleand now going on 2.5 years with no issues. I hope you find your problem.

On 4/24/2017 at 2:06 PM, heart_of_darkness said:

Next time it falters, do a spark check.  To avoid removing the spark plug, carry a spare and just pull off the spark plug wire and plug it onto the spare to ground against the fins for a spark check.

Look over all the wiring for any loose or corroded connectors, or bare spots that are shorting. 

Also did you check spark as H O D suggest? (when issue occurs?)

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11 hours ago, motoman_xr600 said:

#52 pilot clip in 3rd spot and 160 main a/f screw 1.5 turns out

I ran a #65 pilot, or maybe a #62 at the leanest.

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I have had cdi failure act like that before on mine. It always started great cold but would die hot when the clutch was pulled and not restart for 20 minutes. New cdi fixed it but no guarantees on yours.

@backwoods bomber I do have a spare cdi box so I will give that a shot good point.

Quote

Next time it falters, do a spark check.  To avoid removing the spark plug, carry a spare and just pull off the spark plug wire and plug it onto the spare to ground against the fins for a spark check.

Look over all the wiring for any loose or corroded connectors, or bare spots that are shorting. 

Quote

I ran a #65 pilot, or maybe a #62 at the leanest.

@Heart of darkness

I have not done this yet but I will have to. Most of the time when It dies while riding before coming to a stop I can usually bump it to get it going again since dang near ever road I ride on isn't flat. A weak coil will break down when to bike gets hot. The xr's bubbles more the longer I ride so that makes sense and the harder I ride for longer periods of time causes issues too. Think i've got a combination of things. Do you do most of your riding up here? It got great power now that I put the o-ring on the a/f screw mostly have issues 3/4 throttle. Got something up my sleeve that would aid in tuning.......

 

I APPRECIATE IT GUYS! Sorry I couldn't reply till now its so much easier with a laptop.

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Can't stop thinking about the headache I would save running one of these bad boys. Pretty straight forward weld the bung in, + - and o2

s-l1000.jpg

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Pretty sure it's stock pretty positive about that just wrote the wrong #. Turn the screw all the way in, it dies like it should. Starts bubbling at .5 turns and then 3 turns out so I'm right there close to the middle at 1.25-1.5 turns out on my air screw.

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Pretty confident the carb is dialed. I'll throw on the other cdi box today and do a spark test when she dies. My guts telling me somethings breaking down electronically when it's hot...

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Brian B might be interested in the old throw away. He likes to do autopsies.

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Wanted to give you guys an update on the xr. Well it turned out to be something stupid after all. Unfortunately it took me 3 weekends to find some way in hell the oring on the air fuel screw was missing.....also in the process went from a 160 main to 155. She runs like a champ now. Thanks again guys for all the help!

  • Like 4

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Is the fuel delivery constant?  Turn on petcock and drain bowl for 5 minutes to see if there is any hiccup in fuel delivery.

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