Newbie with an Oldie Quest. Bout Suspension - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 13 (permalink) Old 12-21-2009, 11:42 PM Thread Starter
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Newbie with an Oldie Quest. Bout Suspension

Well this is my 1st bike and i got a question. Riding my 86 vn when going into a corner it seems like it kinda bobs around in the corners and im afraid to lean too much incase the front tire kicks and sends me flying wondering what could make it soft in the corners?
Possible fork oil needs changing?
Shocks gone?
It rocks pretty easy when i push on the handlebars and when i had a tune up they didnt meantion anything bout fork oil etc...
Im stumped
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post #2 of 13 (permalink) Old 12-22-2009, 01:01 PM
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Go ahead and change the fork oil, especially if you don't know how old it is. Could be low, in which case you might have a leak and need to replace the seals. Seems like I heard here that the '86 had air adjustable forks. Might need to add some air.

Also, make sure everything on the front suspension is tightened to specs. Get the front wheel off the ground and see if you can wiggle the tire side to side. Front axle bearings might be going out and have too much play. Assume you have the tires aired up to the proper pressure.

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Currently 23,298 miles

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post #3 of 13 (permalink) Old 12-22-2009, 02:21 PM
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Folks here have mentioned the same concerns. Some have the hard to find fork brace to stiffen up the front end.

2x on check and tighten the nuts and bolts. Check air pressures (F&R) in tires and rear shocks, dampen rear shocks to #4 or 5.


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post #4 of 13 (permalink) Old 12-22-2009, 06:06 PM Thread Starter
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Thanks for the help flite! I took it to the dealer to get a tune up. The bike had sit for awhile and only has 14,000 miles on it probably sat for about 4 yrs so they checked and adjusted the tire pressure but im gonna see if theres some movement in the tire lifting it off the ground.
Also i do have adjustable springs in the rear but im pretty sure front might need fork oil i didnt see any leaking around the forks but ill have to get that checked before riding season starts next yr
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post #5 of 13 (permalink) Old 12-22-2009, 07:09 PM
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Definitely put the rear shocks in the number five (stiffest) position, and inflate the tires to the max pressure on the sidewalls. There is really nothing else you can do with the rear shocks. My bike has almost 44,000 miles on it, still has the original rear shocks, and as long as you don't overload it, they are fine. My first Vulcan 750 (bought new) had over 80,000 miles on it when I sold it, and still had the original rear shocks. You don't replace shocks on most motorcycles like you do on cars, they should last the life of the bike. You are looking at several hundred dollars for new shocks.

While the '86 model did have provisions for adding air to both the front forks and rear shocks, and later models still had Shrader valves on the rear shocks, both the forks and shoks were designed to be used under normal conditions with 0 psi in the forks and shocks.

As for the forks, you should be able to tell if the fork seals are leaking, because there will be oil all around them. First drain and refill the fork oil, according to the manual, if this does not help, drain it again, and refill with heavier oil. Don't overfill, that will blow the seals. If the seals are leaking, more than just a bit of seepage, they will need to be replaced. Again, follow the procedure in the manual. The springs should be fine, like the rear shocks, they are meant to last the life of the bike, or at least 100,000 miles or so.

On many motorcycles, people shim the front springs with pieces of pvc pipe to preload them, I don't know if this is possible with the Vulcan or not.

One more thing. Check the tire wear. Many riders, like me, tend to rack up a lot of miles on interstate highways, which results in wearing out the center of the tire, changing the tire profile, and causing the center of the tire to be flat, kind of like a car tire. When you lean over very far with a tire in this condition, it can cause some strange handling characteristics.

Also remember that while the Vulcan 750 actually handles very well for a cruiser, it is not a sportbike, and won't handle like one. Thankfully, it is a whole lot more comfortable. Jerry.

I am a motorcyclist, NOT a biker.

1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
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post #6 of 13 (permalink) Old 12-22-2009, 08:46 PM Thread Starter
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I totally agree. I drove my bike then got on my friends Sv650. I felt like a God Damn Ornament sitting on the hood of a truck. Im 6'1 and id rather enjoy the scenery instead of flying down the rd. The tires still have the rubber nubs on them when i bought the bike in sept. and i got the pressure tested when i got a tune up. Im gonna get the fork oil changed as im not a mechanic and tend to break stuff taking it apart.
Oh and my spring coils in the back are set on 2 Ill have to bump that up to a 5 and try er.
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post #7 of 13 (permalink) Old 02-26-2010, 05:12 AM
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Actually, my rear suspension is fine. The front absolutly is horrible!!!
I have been riding for over 54 years and have never had a set of forks work like these on my 2002 VN.
As long as the pavement is smooth as a pool is the ride.
Get on some concrete surface and it hammers me to death.
I changed the fork oil and added a 3/4" preload and it is a "little" better.
I know that Progressive Springs are the way to go and I will be ordering some soon but has anyone done a Race Tech Emulator set up one a VN?
It seems to me that the "dampening" part of the fork action is what the problem is, not so much the spring rate.
I added the spacers cause I had over 1" of sag. Now I have about 5/8" which is pretty acceptable for a "street" bike but as I watch the forks moving when I'm riding it I see the forks working like there is 5 weight fork oil in them!!! I'm running 20/40 motor oil with 12 oz in each leg.
Don't go crazy about my 20/40!!!! I've used it for years on a lot of bikes and it works very well. Yeah 10 or so oz's is what they need but I've found that if you add a little more it can make up a bit in compression action.
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post #8 of 13 (permalink) Old 02-26-2010, 05:42 AM
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Interesting. I also have an '02, with stock size ME880s on it, 44,000 miles, still has the original fluid in the forks, and it handles just fine. I have no problems dragging the pegs, and it feels firmly planted at that lean angle. Not the least bit squirrelly. Has your bike ever been crashed or dropped? Like I said earlier, the Vulcan 750 is not a sportbike, but I have never found any quirks with it's handling. It's always been very consistent, stable and confidence inspiring. Jerry.

I am a motorcyclist, NOT a biker.

1997 Vulcan 750, purchased about a week ago
2006 Sportster 1200 Low
2013 Royal Enfield Bullet 500, converted to carb
2001 Yamaha XT225, heavily modified
2004 Honda Rebel 250
1979 Vespa P200E
2002 Vulcan 750 parts bike
1994 Yamaha XT225 parts bike
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post #9 of 13 (permalink) Old 02-26-2010, 10:12 AM
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The handling on my VN was pretty rough, giving similar problems to those experienced by Al. The other problem I had was under hard braking the handling was really unpredictable. I put progressive fork springs in last month and although I've only done about sixty miles since I can say the handling is definitely improved. I'm taking corners faster in the wet now than I was in the dry with the old springs.
When I took the old springs out I held them out level with the ground. They bent under their own weight to nearly 90 degrees and were so soft I could compress them by hand. The new springs when held out did not bend at all. I know its not a very scientific comparison but I would definitely say my old springs had gone soft.
I would say that if you can bottom out your front forks easily by pushing down on the bars and the bikes handling like a supermarket trolley your front springs are shot.

'89 VN750
14000 miles on 20th April 09
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post #10 of 13 (permalink) Old 02-26-2010, 12:55 PM
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I've dealt with front end/handling issues on 2 '86s.

1) First, change out the front fork oil. That by itself is simple - just undo the drain bolt at the bottom back of the fork, put a pan down (or a bag tied to the fork), and pump air through the valve at the top of the fork. When empty remove the valve core from the valve at the top of the fork. Then use a large syringe of some kind and some clear vinyl tubing to "inject" the the new oil through the valve-core-less valve. It's drippy and maybe messy but fast enough to do.

2) With the proper amount of fork oil in your forks, you should be able to tell whether your seals are leaking. Whether you're replacing fork seals or not, silicone spray is the way to go to preserve them.

3) If you are leaking from a fork seal, Lance has a good write up on how to replace them. It's a fairly quick process once you get used to it. Bulldog also has a photo write up of him and Chad replacing fork seals.

4) Progressive springs are worth their weight in gold. My front end feels so much more improved now that I have them. It's very very stable, even at 75mph on grooved highway slab in greater Miami. Putting them in is also fairly fast.

My one big recommendation if working solo is to leave the forks on the bike when trying to depress the top of the fork to get at the retainer clip. Otherwise you have to wrestle with the fork and/or clamp it somehow. When it's on the bike it's already "clamped".

5) One way or the other, use that same syringe and tubing to change the oil in the rear shocks. I put ATF in mine and the difference was immediate and noticeable for the better. The old oil didn't look that bad really, but I was completely surprised by the improved smoothness of the ride. (I weigh 140 and keep my dampers on "3" for highway travel. With the GF on the bike I set them to "4").

This is more of a pain because you have to hang the shock upside down and inject air into it via the syringe to force the old oil out. Then you have to hang it right side up and inject the oil in to force the air out. But it's still an hour job tops once you start working.

It is totally worth it though, and costs only a few dollars and an hour to try.

6) The CC for front and rear shock oil can be found in the on line manual and here in various posts. Measure it into a holding container (kitchen measuring pitcher will do) and then fill the syringes from that. It's easier. That way you can simply pull the plunger of the syringe out, fill it, put the plunger in, inject it, and repeat. Unless you've got a Really big syringe.

7) You could also check for steering bearing play / wheel bearing play per the on line manual.

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