Tank slapper - again... getting pretty ****** off now..

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I just don't understand it - my front tire keeps dropping PSI's but I do a good job of regularly managing it and filling it back up to pressure. However, today I experienced a tank slapper AGAIN - this time I'm not far back in my seat, the tyres are NOT cold and they were recently just pressured to spec.

I'm ******.. I don't know why this keeps happening. To those that will tell me learn throttle control, a bike still shouldn't do that at WOT. I gradually roll-on and then pin in so I understand the throttle control rules and abide by them.


Getting new Pirelli's put on this weekend hopefully which I hope to god cures this pain in the *** problem.
 
e90 said:
I just don't understand it - my front tire keeps dropping PSI's but I do a good job of regularly managing it and filling it back up to pressure. However, today I experienced a tank slapper AGAIN - this time I'm not far back in my seat, the tyres are NOT cold and they were recently just pressured to spec.

I'm ******.. I don't know why this keeps happening. To those that will tell me learn throttle control, a bike still shouldn't do that at WOT. I gradually roll-on and then pin in so I understand the throttle control rules and abide by them.


Getting new Pirelli's put on this weekend hopefully which I hope to god cures this pain in the *** problem.
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Many things could be contributing beyond the tires. Are the rims warped? Is there play in the head bearings? Fork stiction? Preload adjustment correct?
 
You could have a small leak from your valve core, Use some soapy water and see if its leaking if so you may need the core changed out as well.
 
Definitely needs to be troubleshooted, but since the only way to test whether you guessed right is to give it WOT again, I'd seriously consider installing a steering damper. Even if you're just borrowing one off a friend's bike, you're just asking for a crash to keep repeatedly pushing the bike until you're sure you have the source nailed down and fixed. A tank slapper's no joke.
 
Will be getting new valve stems with the new rubber installed soon. Will risk another tank slapper after I break the rubber in a bit and see if the problem has been fixed.. if not, I'll have to take it in for a proper setup.
 
Have you had the bike from new? Maybe short previous owner slid forks up (reducing trail and rake) to lower bike and it looks normal to you. I know that's a longshot. We have nothing but time around here.
 
inreb said:
Have you had the bike from new? Maybe short previous owner slid forks up (reducing trail and rake) to lower bike and it looks normal to you. I know that's a longshot. We have nothing but time around here.
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It is definitely not lowered at all.. so I highly doubt it.. I'm the second owner and the previous owner wouldn't have messed with the suspension.
 
e90 said:
It is definitely not lowered at all.. so I highly doubt it.. I'm the second owner and the previous owner wouldn't have messed with the suspension.
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I'm not wasting any more time on this.
 
I'd say your rear wheel isn't aligned properly with the front.
Get someone very precise to check it, not a TAFB.
 
e90 said:
I just don't understand it - my front tire keeps dropping PSI's but I do a good job of regularly managing it and filling it back up to pressure. However, today I experienced a tank slapper AGAIN - this time I'm not far back in my seat, the tyres are NOT cold and they were recently just pressured to spec.

I'm ******.. I don't know why this keeps happening. To those that will tell me learn throttle control, a bike still shouldn't do that at WOT. I gradually roll-on and then pin in so I understand the throttle control rules and abide by them.


Getting new Pirelli's put on this weekend hopefully which I hope to god cures this pain in the *** problem.
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It's simple physics really...

You take weight off the front wheel, it comes of the ground slightly and before landing it you don't straighten out.

Keep doing it, and before you know it the bike will throw your *** off at whatever speed you're doing and that will be the end of that lol
 
^^ Not really. It's a Ninja 250, which is faaaaar from taking the wheel off the ground without clutch action.

OP - go at your regular cruising speed, i.e 60km/h at 6th, and let go off the bars for say 3-5sec, and see what happens. Tell us the outcome. Not sure what it would prove, but I'm just curious to see if your getting any front end shake.
 
Must have something wrong with your tire, I would think. I haven't had a significant pressure drop in my tires in 3 years and I only check them like once a year. Might be like 3 PSI low in that interval.
 
e90 said:
It is definitely not lowered at all.. so I highly doubt it.. I'm the second owner and the previous owner wouldn't have messed with the suspension.
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with the ninja 250, the stock handlebars cover the top of the forks. There is about a 1" hollow in the bar assembly to allow the forks to slide up. This is definitely work checking. Undo the 2 hex bolts that attach the bar assembly to the upper triple. You will know if they messed with it, if there is more than 3/8" of the fork sticking up through the top triple.
 
Head bearings
Wheel bearings
Twisted forks/triples
weird tire wear
Faulty tire


...just to name a few
 
I'm wondering if the frame may be bent a bit.

or even the forktubes are not properly installed in the trees.
 
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