Balazs Farkas
Just got it firing!
Hi everyone,
A little feedback on a problem I had with my ZGULK Nevada. I share it since I have not found any solution anywhere until I bumped into it my accident. Hope it will help someone in the future.
So, my ride was running very rough after I installed a new set of piston rings, so I picked the carbs apart, cleaned them up with carb cleaner, replaced all that needed to be replaced, then mounted everything back on. I hooked up my trusty Carbtune to balance, set the cable lengths well, then set a stable idle with an estimated mix. Had to go back and redo it a few times, but in the end I ended up with a perfect and stable idle, plus two brownish colored spark plugs. I was pretty pleased with the result.
The bike also ran like a charm...or so it seemed. All went well until I went for a long ride. That's when I noticed some rough riding, popping, backfires, albeit only in fifth gear and at some very specific, low throttle positions, mostly going downhill and at cold weather conditions.
I could not figure out for weeks, what the problem was, since I found no vacuum leak, no compression problems, no carburetor balancing issues.
In the end, I came to the solution by chance: I had to make the mix a bit richer and increase the idle. As it turns out, there are some temporary lean cycles in the engine, for instance, when you shift down from fifth that can mess up the balance between the cylinders a bit. These lean cycles are usually not a problem, but if you adjust the mix screw a bit too lean initially, it can result in some popping, bckfiring and rough ride when cruising.
My findings are that the idle could be stable with a somewhat leaner mixature and a properly adjusted idle screw, the tuning instrument would not show any issue whatsoever. Nevertheless, these aforementioned temporary lean cycles can make the bike run rough in certain scenarios, so always add atleast a quarter extra on that mix screw to be safe, even if Carbtune says otherwise.
Cheers
B
A little feedback on a problem I had with my ZGULK Nevada. I share it since I have not found any solution anywhere until I bumped into it my accident. Hope it will help someone in the future.
So, my ride was running very rough after I installed a new set of piston rings, so I picked the carbs apart, cleaned them up with carb cleaner, replaced all that needed to be replaced, then mounted everything back on. I hooked up my trusty Carbtune to balance, set the cable lengths well, then set a stable idle with an estimated mix. Had to go back and redo it a few times, but in the end I ended up with a perfect and stable idle, plus two brownish colored spark plugs. I was pretty pleased with the result.
The bike also ran like a charm...or so it seemed. All went well until I went for a long ride. That's when I noticed some rough riding, popping, backfires, albeit only in fifth gear and at some very specific, low throttle positions, mostly going downhill and at cold weather conditions.
I could not figure out for weeks, what the problem was, since I found no vacuum leak, no compression problems, no carburetor balancing issues.
In the end, I came to the solution by chance: I had to make the mix a bit richer and increase the idle. As it turns out, there are some temporary lean cycles in the engine, for instance, when you shift down from fifth that can mess up the balance between the cylinders a bit. These lean cycles are usually not a problem, but if you adjust the mix screw a bit too lean initially, it can result in some popping, bckfiring and rough ride when cruising.
My findings are that the idle could be stable with a somewhat leaner mixature and a properly adjusted idle screw, the tuning instrument would not show any issue whatsoever. Nevertheless, these aforementioned temporary lean cycles can make the bike run rough in certain scenarios, so always add atleast a quarter extra on that mix screw to be safe, even if Carbtune says otherwise.
Cheers
B