i know this is prolly a dumb question but i weigh about 250 im 6'4" and my gf is 6'0" and 173. so that is over 420 pounds, what are the risks to the bike? i mean i can feel it sinking down a decent amount and i only 2-up with her for maybe a half miles maybe once a month. -_- i need to diet lol

I'd bump your tires up to max pressure and up the rear shock preload to max. Risks? Handling won't be as good, tires and shock will wear faster. Chain and sprockets likely wear faster too. Oil will sheer faster due to higher engine temps maybe.

I to am about your weight with wife on my bike to that's 371 lbs.
all I did was to adjust the springs and left tire pressure as is according to the manual.
we ride two up all the time and believe me we have no problem in the handling department.
but what I will tell you though is that on bumpy road and riding spirited it does bottom out the rear shock but that's all.
I have no plan of replacing the rear shock as it keep's me in place and not to do any thing silly
your taking your good lady once a month on a short journey.. DON'T WORRY you be fine.

IMO, the two major concerns are suspension and braking. Adding a 400 pounds to a 400 pound bike obviously taxes the suspension which impacts everything about the way the bike rides and handles. And the other issue is braking. It takes longer to stop an 800 pound moving object than a 600 pound moving object.

I rarely ride 2 up but when I do I feel like it drastically impacts everything about the way the bike rides and handles. It's something that takes practice to be comfy with.

If you are overloading the design limits on the bike, there is a possibility that things could break. Subframe that supports the seat could crack if you hit a bad bump and bottom out. If you don't respring the suspension to support your weight you are changing the bikes geometry which can affect handling, and of course what others have said, parts will wear out faster.

what a load of tosh. I've had mine coming 4 years and I've never had a problem in the handling department nor wear and tear to the extreme that you guys are talking about I've done 6,000 miles(low miles due to serious illness and lousy weather)and always two up.
and I've seen bigger and fatter riders on sport bike and some you couldn't get a passenger on unless he or she is or is a stick.
check your manual for max weight inc rider and you will see you'll be fine.
most of the weight is in the centre of the bike and that is where the frame is at its strongest point.
as for the rear sub frame yes that will be a weak point but you are not sticking a 400lbs on that are you.

Most concerns I would have would be braking as tonybhall pointed out and the second depends on the exprerience your GF has as a rider. She's not obese but at 6' and a little hefty, her high mass could upset your handing if she squirts around on a slow turn. Just make sure you know your preload and rebound settings for the extra weight. Having them set properly will greatly improve the handling.

Originally Posted by johnakay

what a load of tosh. I've had mine coming 4 years and I've never had a problem in the handling department nor wear and tear to the extreme that you guys are talking about I've done 6,000 miles(low miles due to serious illness and lousy weather)and always two up.
and I've seen bigger and fatter riders on sport bike and some you couldn't get a passenger on unless he or she is or is a stick.
check your manual for max weight inc rider and you will see you'll be fine.
most of the weight is in the centre of the bike and that is where the frame is at its strongest point.
as for the rear sub frame yes that will be a weak point but you are not sticking a 400lbs on that are you.

Hardly. It's simple physics. The more weight you put on a bike the more it "wears and tears". Braking, acceleration and handling will all be affected. Ultimately (everything else being the same) tire life, bearing life, chain life and engine life will be decreased. I don't think anyone was saying the bike is gonna simply fall apart as soon as you put the extra weight on it, but it's a machine and subject to the laws of physics.

I'm not sure what to say to someone who thinks that putting 450+ pounds on a motorcycle that weighs just 400 pounds doesn't impact performance considerably. It's not even an arguable point. Like cyclesarge said, it's physics. You may not "have a problem" with the performance change, but to imply that it doesn't exist and isn't dramatic is.... less than accurate.

I'm not one to toss stones on weight at all. (Pushing 250)

When I first commented on this thread, I thought it was a N1K thread. Now that I see its a 650, I would have more concern with shifting mass on the pillon. I've seen some monsterous dudes on a 650 but only one up. I still stick to my comment about suspension setup and throw extra caution on passenger skills

I don't know but Im over 250lbs sometimes I take my wife for a ride on my bike.I did'nt notice any problems on my bike.I did adjust the back shock but I don't worry about cracking the subframe or breaking anything eles on the bike.I guess if I ride my bike like a dirt bike I could see having problems.Im pretty sure there tested to handle the weight,I don't think they made the bike just for little boys & girls.

Originally Posted by jmc6401

I don't know but Im over 250lbs sometimes I take my wife for a ride on my bike.I did'nt notice any problems on my bike.I did adjust the back shock but I don't worry about cracking the subframe or breaking anything eles on the bike.I guess if I ride my bike like a dirt bike I could see having problems.Im pretty sure there tested to handle the weight,I don't think they made the bike just for little boys & girls.

Have you looked at the GVWR of your motorcycle? Or are you just making assumptions and hoping for the best.

Just because you can 'get away' with something doesn't mean it is the 'smart' thing to do.

Accoring to a this review by rider magazine:
2012 Kawasaki Ninja 650 Review | Rider Magazine

The 2012 Ninja 650 has an increased load capacity which is now a GVWR of 902 lbs. The basic bike is supposed to be 456 lbs, so when you include the weight of rider and passenger, gear, etc you should not exceed the 902 lbs.

That said, a bike running around at 902 lbs is going to wear out mechanical parts faster than a bike running around at 600 lbs.

Now you have some knowledge. What you do with it is your decision.

Big deal about wear & tear on my bike.I did'nt buy my bike to look at,I use my bike & Im not worryed about breaking anything on it.If I do I'll mention it. Everytime I put a thread up I get some smart *** remark.Are you a Preacher?

Originally Posted by jmc6401

I don't know but Im over 250lbs sometimes I take my wife for a ride on my bike.I did'nt notice any problems on my bike.I did adjust the back shock but I don't worry about cracking the subframe or breaking anything eles on the bike.I guess if I ride my bike like a dirt bike I could see having problems.Im pretty sure there tested to handle the weight,I don't think they made the bike just for little boys & girls.

No, they dont make it for little girls and boys but Kawasaki's nominal suspension settings are for the weight of an average rider and you and I are 100lbs over that exactly. I havnt been 150 since I was a boy. Just sayin

Originally Posted by jmc6401

Big deal about wear & tear on my bike.I did'nt buy my bike to look at,I use my bike & Im not worryed about breaking anything on it.If I do I'll mention it. Everytime I put a thread up I get some smart *** remark.Are you a Preacher?

If you don't want a response, don't post comments that elicit a response. Are you a polititian?