JR50 Bogs off Idle/Run away idle

mx724
Posts
114
Joined
6/15/2016
Location
Cleveland, OH US
4/23/2021 1:14pm Edited Date/Time 4/24/2021 9:10am
Pretty common problem. I have disassembled the carb and cleaned every passage twice with compressed air, let the jets soak over night and still just seems like there is an air leak somewhere or maybe its time for some new jets?

I noticed in the OEM carb it appears to have 2 pilots (See parts 2 & 3 in the diagram) I poked around on some JR 50 forums, some people remove one of these 2. Im not looking to do that, but the owner bought a ebay carb and it appears that the ebay carb only has one jet in this location. He was trying to make it run with the ebay carb.

I went back to OEM which initially it wouldn't even run with, after a cleaning its running, albeit erratic.

Ebay carb jets have no markings at all. Took a quick look on the left side crank, dont see any oil, not to say that the crank seal couldn't be leaking? Maybe someone with JR experience can point me to known problem areas before I go chasing all over.

I will also mention that the air screw is 1 1/4 out and the idle set maybe 3 turns in. Ive fiddled with both while running at at times just seems to cause the idle to run off, regardless of turning in or out.




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JB500
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285
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7/14/2018
Location
Granger, IN US
4/23/2021 4:16pm
Any chance the throttle cable or cap has to be modded for the eBay carb? I’ve seen those cheap carbs before where the OEM cable wouldn’t work properly, so the owner jacked with it, and when going back to the ORM carb, nothing worked correctly. Just an outside the box thought. You are probably on the right track with new OEM jets/o-rings etc. for starters.
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mx724
Posts
114
Joined
6/15/2016
Location
Cleveland, OH US
4/23/2021 4:36pm Edited Date/Time 4/23/2021 4:40pm
I was going to try swapping those 2 as it's the only component I stole from the Ebay carb, tho I don't expect different results.

I kept the oem needle and slide(Needle on 3rd position from the top). I figured no harm in keeping the physical top cap and the choke plunger. Simple enough to rule out.

I don't see any oring in the diagram? Ebay carb had one that was destroyed already inside the bowl(pinched between the needle jet and main jet), none in the stock carb at all.

Maybe that's the issue, I've seen missing orings on FCR cabs cause similar idle run away. The manual for these things is pretty sparse.
mattyhamz2
Posts
10850
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7/6/2015
Location
So Cal, CA US
Fantasy
760th
4/24/2021 7:51am
Order fresh keys for the oem carb. No amount of cleaning will truly clean them out completely, especially with how small they are. I don’t even bother trying to clean main or pilot jets on big bikes anymore.

If you suspect an air leak, put everything together and spray contact cleaner around the intake boot and see if the idle changes.
mx724
Posts
114
Joined
6/15/2016
Location
Cleveland, OH US
4/24/2021 9:10am
ended up being the rubber grommet from ebay messing with the cable. Seems to be running much better now.
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