question about shocks

[JPG1911]

After thoroughly reading Spud's excellent write up about rebuilding the shocks on his Zong, I have determined that this is not a job I am in a position to do right now. I am on the hunt for a house with a shop/garage so that may change soon, but for now, I feel I will be much better off just replacing them with new China parts. I have found a set that look identical to mine here for $50

I have two reasons for wanting to do this. 1) the right shock boot is badly torn, and once I begin riding the bike, I don't want debris to get into the shock and damage it. It looks like the only way to replace the boot is to remove the shock from the triple tree. I figure if I'm going to have to go to all that trouble anyway, I might as well put new parts on. 2) I'm a dense fellow at 5'10" and weighing in around 245, and when I sit on the bike and engage the brake, I can rock the bike front and back and observe the forks compress several(3-5) inches. If I am rolling the bike at a walking pace and engage the brake, the front will dive 2-3 inches. I assumed this was normal since this is a dual sport motorcycle, but my friend who is a backyard/shadetree motorcycle mechanic says that I should absolutely NOT be able to do that, and unless I'm landing from a jump, the suspension should only compress an inch or two, and that the shocks are blown. I don't necessarily believe him, but I figured it was worth checking with the expert shadetree mechanics on here Going by the old car shock test method of jumping off the bumper and observing whether the car bounces once or several times, I believe the shocks are still relatively good. The suspension does have a lot of travel, but it does not bounce when it rebounds, it returns to normal ride height and stops. Thoughts? Opinions?

[pchitti]

I would suggest at least trying to change the oil before any parts are replaced.

[Weldangrind]

X2. I bet the forks don't have enough oil in them.

[Krasi_BG]

You can't actually check motorcycle "shocks" as you do on cars. Btw, on the front they're called "forks". Only the back is referred as shock

The only reason for a fork failure would be to have a worn/torn seal. And you can easily detect that by the oil you'll see on the inner tube after a compression-extension cycle. In your case you might need to pull up the protective boot to see the "cross section" between inner and outer tubes. Unless, the seal is so bad that all the oil is already gone, but in this case it should have been dripping from the boot!

Fork compression depends on a number of variables, and there is no specific rule of thumb on how much it should compress. It's more of a rider feel and preference. (Pure motocross bikes are an exception, and even there sag setting is "controversial" to say the least!)

[SpudRider]

Originally Posted by JPG1911

After thoroughly reading Spud's excellent write up about rebuilding the shocks on his Zong, I have determined that this is not a job I am in a position to do right now. I am on the hunt for a house with a shop/garage so that may change soon, but for now, I feel I will be much better off just replacing them with new China parts. I have found a set that look identical to mine here for $50…

That is a good price for new forks, but the price only includes ‘domestic shipping.’ After you add the international shipping charges, the price will increase significantly.

Originally Posted by JPG1911

…I have two reasons for wanting to do this. 1) the right shock boot is badly torn, and once I begin riding the bike, I don't want debris to get into the shock and damage it. It looks like the only way to replace the boot is to remove the shock from the triple tree. I figure if I'm going to have to go to all that trouble anyway, I might as well put new parts on…

Removing the forks and replacing a fork boot is much easier than you might think. Also, changing the fork oil is a relatively simple process.

Originally Posted by JPG1911

…2) I'm a dense fellow at 5'10" and weighing in around 245, and when I sit on the bike and engage the brake, I can rock the bike front and back and observe the forks compress several(3-5) inches. If I am rolling the bike at a walking pace and engage the brake, the front will dive 2-3 inches. I assumed this was normal since this is a dual sport motorcycle, but my friend who is a backyard/shadetree motorcycle mechanic says that I should absolutely NOT be able to do that, and unless I'm landing from a jump, the suspension should only compress an inch or two, and that the shocks are blown. I don't necessarily believe him, but I figured it was worth checking with the expert shadetree mechanics on here Going by the old car shock test method of jumping off the bumper and observing whether the car bounces once or several times, I believe the shocks are still relatively good. The suspension does have a lot of travel, but it does not bounce when it rebounds, it returns to normal ride height and stops. Thoughts? Opinions?

Chinese forks typically perform in this manner. I agree with the others, and think you probably need to change the fork oil, and increase the level of the fork oil. I highly recommend the Valvoline MaxLife Dex/Merc ATF, which is currently on sale.

http://chinariders.net/showthread.ph...487#post168487

However, fork oil only affects the compression and rebound damping. The excessive fork travel is caused by the fork springs, which are too weak for your weight. Both the Chinese and the Japanese design their fork springs for a typical, oriental, 150-pound rider. We occidentals are much larger, and we need stiffer fork springs to support our greater mass. If you bought new forks, you would most probably discover they perform the same as your current forks.

I don’t know where you can find stronger replacement springs for your Chinese forks. Perhaps Cogent Dynamics, or some other suspension specialist can sell you stronger fork springs. If you want stronger fork springs, you will need to disassemble the forks, and give the spring vendor the spring measurements, et cetera. He would also ask about your weight, riding style, et cetera, to determine the correct strength for the new, stronger fork springs.

I think your best course of action is to remove the forks, change the fork oil, and fix the fork boot. The job is a little messy, but it is not hard physical work, and we can help you if you encounter problems.

[JPG1911]

Thanks for the thoughtful and informative replies! I'm going to purchase some new boots and oil and give it a go when I have time. I plan to fab some mounts and re-install the headlight, adjust the valves, install new petcock, battery, and UNI pod air filter next weekend when I am no longer on call. After that I'll apply for a Vermont title and see how the bike does on the road with my weight.