I had a similar issue with a Night Train I used to have. The P.O. replaced the rear tire with some cheap brand I had nice ever heard of. I was complaining about it to a friend who told me to replace the rear tire. I went to the dealer and they said basically the same things. Some tire compounds get harder as they age and would rather skid than grip. New tire solved the problem

 

You're saying fishtail, but do you mean the back end actually slides from side to side, or is it more like the handlebars wiggle, like a shimmy? You'd have to be losing traction, like locking the rear wheel, to actually fishtail.

Does it do it if you only use the front brake? Try an easy stop with just the front; if it wiggles bad (might feel like fishtail), then I'd want to check front wheel bearings, make sure the spacers are in the right position, and double check the rotor and caliper installation; it can be installed incorrectly, and you'll feel it. If it just started doing it after that fork polish job, I'd suspect that. If he took the forks off, then I'd want to check the fork clamps for tightness - I've seen those loose enough you could clamp the wheel between your legs and turn the bars a few inches, twisting the forks; that could sure cause a nasty wiggle on the road. You don't have to take the triple tree off to remove the forks, but if he did for some reason, the steering bearing adjustment could be off, too.

Check the tire dates, quite possible the front is original, though that would be a stretch for the rear, and those Harley Dunlops get downright slick at 10 years old - I've ridden on one that old, and it would break the rear end loose so easy it was scary. New tire fixed it. If it's over 5 years old, it's losing traction, even if the tread looks ok. The rubber hardens with age. If it has tubes and/or rubber stems, tube or tubeless, I'd change the tubes with tires, and I always use metal valve stems - I had an old rubber one break off just trying to put air in it.

 

Your brake issue might be something as simple as coming from a single piston caliper bike to a multi piston caliper setup. IDK. But fishtailing is not something I'd want to do in an emergency stop.

When applying the brakes we are to use the front and rear brake equally. If done properly the bike will stay in control and we can stop in the shortest possible distance. We should also remember that these are pretty heavy bikes.

What I do when on a "new to me" bike is find a lonesome place and practice a few test stops. I ease into all of this so I don't get surprised so my first couple of attempts are not all that hard of a stop but more of a feel this thing out type deal. Once I'm tuned up I move on and try some harder stuff. But my idea is to know how to make a controlled emergency stop in the shortest distance possible on "that bike" before I get into an actual emergency stop situation.

I've been in a few real emergency stops and I can say my little practice sessions plays off. Im still here....

Good luck.

 

Unfortunately no you cannot. That's why I wouldn't purchase a bike without ABS brakes

 

Hey, just to be safe, you might want to check your wheel bearings. I have had my back ones fail twice, first hint was trouble with my rear brake...which i ignored until the back wheel almost came off at 65...did 1200 bucks damage plus a new pair of undies...lol.
Hope you find it.
Ride safe.

 

Respectfully disagree. Properly maintained bikes with reasonably skilled operators worked just fine before ABS.

 

That's fine. It's a my personal decision that I based actual data, facts, and my own personal experience on since I've owned more than a half a dozen bikes without ABS. What others do I couldn't careless. He asked if he could get ABS installed and I answered that question. The debate about ABS effectiveness is silly to me. If you don't like it don't buy a bike with it. There are more bikes without ABS then there are with ABS.

 

I never said as you suggest that there is anything wrong with ABS and certainly didnt say I didnt like it.
One of mine has it and it is fine.
However, your response went well beyond answereing if ABS could be added when you had to stick " That's why I wouldn't purchase a bike without ABS brakes" in there. I think he is looking for advice on how to solve a problem and not asking your opinion on what bikes you wouldnt own.

 

But it's a forum and I can offer my opinion anytime I like because that's what forums are for. If you don't like it or disagree with it fine I don't care. I had bikes without ABS and I also researched if I could somehow add ABS. I came to the conclusion I could not and that I would just have to make sure my next bike had ABS. I never understood how people get all bend out of shape on what is said on a faceless Internet forum.

 

Your opinions are fine and dandy.
Still dont understand why you needed to suggest that I dont like ABS and that If if I don't like it I shouldnt buy a bike with it.
BTW the OP is looking for help with a problem. Got any potentially helpful suggs?