Page 1 of 1
Black Jack problems
Posted: Thu Apr 19, 2018 10:33 pm
by Mike1nw
My wife's boss has a Black Jack.
I replaced the Keihin Carb with the stock one a week ago.
It ran great! For about a day.
Now it won't idle- Feels like it's trying to shake apart. Like it's missing, until you get it above 25 or 30 mph.
So I'll check:
vacuum leak
is it getting gas?
Spark plug (easy to put a new one in)
What electrical fault would cause this?
It's so noisy, I wonder if variator has a bad roller(s) or is stuck somehow.
Posted: Fri Apr 20, 2018 1:30 pm
by Stanza
Wasn't Keihin the original carb that was used on these? Where did you source the replacement carb? Was it jetted correctly, or did they just send you a 125 carb and call it done? Stock jetting on a blackjack should be 92 and 38, possibly 94 depending on elevation.
Posted: Fri Apr 20, 2018 4:43 pm
by k1dude
Why did you replace the carb in the first place?
Posted: Fri Apr 20, 2018 7:12 pm
by Mike1nw
Replaced carb about a week ago because he wanted the other one installed.
Like I said, It ran good for about a day or two. Now it "misses" at low speeds.
He already had the replacement carb. So I dunno where he got it.
So I don't know the history of the carb nor the needle sizes.
It ran good. Suddenly it doesn't.
That's the weird part. Like it's a failure of some component.
Posted: Fri Apr 20, 2018 8:49 pm
by k1dude
Did it run fine with the old carb?
Posted: Sat Apr 21, 2018 4:13 am
by sc00ter
I had the exact same problem with my old Buddy 125. I had a shop fix it (thread is on this site), they messed up the stock carb (broke accelerator pump tang), didnt bring it back to get it done right, ended up buying a new carb, problem came back, sold scooter "as is". The guy who bought it replaced a vacuum hose and the low speed stuttering and such went away! Still not sure exactly what he changed out but if I stop by his place this weekend I will ask. I also need to take rear rack repair pics for another member here. Im lazy and the guy with my old Buddy(s) works strange hours.
Posted: Sat Apr 21, 2018 4:04 pm
by Mike1nw
yeah I will replace vac hoses, there aren't that many of them anyway, thanks
Posted: Sat Apr 21, 2018 11:32 pm
by Mike1nw
FOUND IT!
After replacing vac hoses, new spark plug, recheck carburetor, adjust valves....
Took belt case apart- one roller was half gone and jammed in the variator, another was flat spotted.....
Runs like a turbine now! Needs rollers and a ramp plate.
What an adventure
Posted: Sun Apr 22, 2018 2:14 pm
by Mike1nw
"Wasn't Keihin the original carb that was used on these?"
Might have been. The one I put on, has "Keihin" on it. I didn't notice that before. It looks much different than the Keihin I took off. Again, I don't know how it ran before.
Because he has a loud exhaust pipe on the bike, I think I will add a shim to the main needle. Once I get the variator re-installed
