View Full Version : DR650 turned into SM, now has a problem
Rider
05-20-2009, 01:49 PM
One of my coworkers has a Suzuki DR650 that he turned into a SM. He took off the 21" front wheel and put a 17" front wheel on it. Now he is experiencing what he is calling a "tank slapper" like condition when he gets to about 70mph. He cant figure out why. I'm guessing that by going to the smaller wheel, he essentially lowered the front of the bike 2 inches and has fucked up the steering geometry. Anyone have any thoughts on what is wrong? Forks are bad? Wheel is bent? It doesn't have any problems below 70mph.
dReWpY
05-20-2009, 01:52 PM
sounds like wheel balance issues
Rider
05-20-2009, 01:57 PM
sounds like wheel balance issues
A wheel out of balance would cause the tire to rotate out of round(up and down) but he is getting the handle bar to shake side to side. Would off balance tires cause a side to side shake?
dReWpY
05-20-2009, 01:58 PM
how tight are the spokes? they might need adjusted or maintained
Rider
05-20-2009, 02:00 PM
how tight are the spokes? they might need adjusted or maintained
It was a brand new rim installed by a Suzuki dealer. Spokes should be tight.
dReWpY
05-20-2009, 02:03 PM
i would check the balance out first, if its off the affects would be magnified by the increased speed, or possibly the bearings in the steering stem could be bad
Rsv1000R
05-20-2009, 02:17 PM
It's the change in steering geometry, dropping the front takes a lot of rake out of the front, and the closer the front gets to up and down, the more likely it is to shake.
Rider
05-20-2009, 02:24 PM
It's the change in steering geometry, dropping the front takes a lot of rake out of the front, and the closer the front gets to up and down, the more likely it is to shake.
How do you fix that, longer fork tubes? He certainly doesn't have 2" of fork to slide back though the triple tree.
dReWpY
05-20-2009, 02:24 PM
or what he said, lol
cuttle
05-20-2009, 02:31 PM
he could try dropping the rear shock in the lower position - it's easy to do, free and doesn't take all that long.
No guarantees that it will help thou...
Rider
05-20-2009, 02:34 PM
he could try dropping the rear shock in the lower position - it's easy to do, free and doesn't take all that long.
No guarantees that it will help thou...
The guy is short(5'7") so he says the rear shock is at the lowest setting.
BobTheBiker
05-20-2009, 02:47 PM
he either needs longer fork tubes to compensate for the 2" change in height, lowering links to put the rear lower and compensate for it, or he's just not going to experience a good ride at that speed.
checking the steering head bearings is a good idea regardless though. at least inspect for good condition and grease appropriately as needed. a steering damper would probably not hurt either.
6doublefive321
05-20-2009, 03:20 PM
I'm saying its the geometry. My SM has been lowered a couple inches, and it gets a little wiggly at high speeds. By putting on smaller wheels, the fork angle has been steepened, which makes it much "quicker" on turn in, but also more unstable. A lowering link in the back should fix it up. There should be a ton of lowering links for that bike. Also, a steering stabilizer would help. All these comments are assuming that nothing else is messed up, i.e. wheel, head bearings, etc.
you didn't say what he did for the rear wheel, what was the tire size change. ideally you want to raise or lower both ends roughly the same amount.
Just pull it up into a mad wheelie. Front end not on the ground = no front end stability problems. :D
Sorry, I have nothing to contribute but sympathy for a fellow 'tard.
Rider
05-21-2009, 08:35 AM
He was looking at his bike last night and noticed that he had about 2 inches of thread on the shock so he is going to adjust the ride height. Cranking that shock spring tighter is going to make for a real stiff ride though.
I suggested he try to find a rear shock from a DRZ400 SM. I'm sure that is a shorter shock.
Rsv1000R
05-21-2009, 09:09 AM
He was looking at his bike last night and noticed that he had about 2 inches of thread on the shock so he is going to adjust the ride height. Cranking that shock spring tighter is going to make for a real stiff ride though.
I suggested he try to find a rear shock from a DRZ400 SM. I'm sure that is a shorter shock.
He'd want a shorter spring. He can however crank it down to see that it does cure the problem before going out and buying a shorter spring.
Gas Man
05-21-2009, 03:47 PM
Most likely he screwed the trail up, making the bike unstable.
Tell him to check it using a rake and trail calculator
This one has more info
http://www.rbracing-rsr.com/rakeandtrail.html
But this one is a bit easier to use.
http://www.goldammercycle.com/hispeed/rakeandtrail.php
Don't tell me its cruiser/chopper shit. Its all about geometry.
Further for balance issues... go dyna beads and STU
http://lowdownchopshop.com/shopping-cart/14.html
Rider
05-21-2009, 03:55 PM
He is going to get some lowing links and drop the ass end 2" to bring it back to the OEM rake.
put some nos energy drink in it
Rider
05-21-2009, 03:58 PM
put some nos energy drink in it
He's not that dumb.
askmrjesus
05-22-2009, 09:26 AM
The stock DR650 shock has an extra bolt hole at the bottom, so you can drop an inch just by relocating the bolt.
Frame geometry modification = Baby steps.
JC
Rider
05-22-2009, 09:38 AM
The stock DR650 shock has an extra bolt hole at the bottom, so you can drop an inch just by relocating the bolt.
Frame geometry modification = Baby steps.
JC
He called the dealer and one of the service guys told him that you can turn the bottom collar upside down and it should lower it about an 1 1/2".
cuttle
05-22-2009, 10:18 AM
Here are the instructions (page 166 and up):
http://www.deakin.edu.au/~mic_adm/DR650.pdf
He may also want to stiffen his front forks a bit...
fnfalman
05-23-2009, 03:11 PM
Also put on a steering damper.
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