Hyosung GV250 shuddering (flat spot?)

[Swartie]

Hi , first post for me, I have recently purchased an old GV250 and notice the bike "shudders" maybe a has a flatspot at around 7000rpm.

I really notice this is 5th gear, and it seems worse when riding into a headwind, the issue is gone once i hit 8000RPM,

I find it hard to notice in other gears but do have "niggles in 4th at roughly the same area, not sure in 1st, 2nd and 3rd maybe has the same isue in lower RPM.

I am not sure when the bike was last serviced and am waiting on the parts to arrive to do an oil, filter and spark plug change, just wondering if that may help or is there anything else i could try?

Is there some sort of additive i can get to perhaps clean the carbs out?

Sorry not much more information, I can say the CDI does seem to have had the "wire" removed so is not that.

The flatspot does seem to be getting worse, I noticed this morning on the way to work.

[Rhys]

What is the chain like? a stiff link can have similar symptoms

[Swartie]

What is the chain like? a stiff link can have similar symptoms

the chain seems ok, but it is on the list to replace, it does also pop and stuff when deaccelerating, and i noticed this morning that where it was "popping" I f i tried to accelerate then i would have the same issues, does tend to be in the high gears only.

I am a bit weary to pull the carb off really, not much experience in this area, i might take it in to be looked at once i have serviced it

[Taxythingy]

Any more detail on your shudder? As in, just generally less power at that point, or power has a sharpish on-off cycle, or the bike has a pogo effect through the bars, or bars just have heaps of vibration at those revs? Aftermarket exhaust making the bike run a bit lean, or stock?

I've currently got a pogo thing going on at about 50km/hr - I'm guessing the front wheel was balanced by a one-legged drunkard (or it threw a balance weight or two).

Sorry, no experience with carby cleaning stuff. I'd tending more to the pull-it-apart stage. I'm guessing the advertising material is awesome though, and suggests it will polish your grandmother's silver at the same time.