The Sportster and Buell Motorcycle Forum - The XLFORUM®

The Sportster and Buell Motorcycle Forum - The XLFORUM® (http://xlforum.net/forums/index.php)
-   Ironhead Sportster Motorcycle Talk (1957-1985) (http://xlforum.net/forums/forumdisplay.php?f=7)
-   -   Ironhead Extended fork tubes and low speed handling (http://xlforum.net/forums/showthread.php?t=2079753)

jsandidge 11th July 2021 00:10

Extended fork tubes and low speed handling
 
I'd really like to do something to help with low speed handling on my 81. It came to me with longer than stock fork tubes, and it has a bit of a low speed flop to the steering (especially when pushing it around in the garage, etc.) What can I do to help improve the flop? Will raked cups help or hurt?

Medyo Bastos 11th July 2021 02:05

Has the neck been raked? Have you measured trail? The raked trees might help bring trail in line if the neck has already been raked. But, might give negative trail if the neck hasn’t been raked. Negative trail will give you uncontrollable high speed wobble…


Sent from my iPhone using Tapatalk

bustert 11th July 2021 22:21

stock tubes
been there done that.

SHAKY DAVE 12th July 2021 03:33

listen to bustert.absolutely the way to fix it

ericfreeman 12th July 2021 07:40

Yeah, stock tube length is the way to go, unless you're re-making an old biker flick with Peter Fonda and his pals!

Ferrous Head 12th July 2021 08:41

You could keep the front end and throw the rest of the bike away.

Now, just build a frame with the neck area moved up far enough to bring the geometry of the rake/trail back into line.

Easy !

11B40 13th July 2021 19:10

In the 70s the chopper was in style. Front forks would get extended past 6" usually with screw in spacers covered with chromed sleeves. The handlebars of choice were Z Bars sometimes less than 2' across. If you take that situation and add a 21" front spool with an Avon speed master and no brake, you were styling. The Sportster tank was sometimes raised a bit to look even more cool and that cut a 2.2 gal tank down to about 2 gal. 6" was OK and they didn't handle all that bad. The problems were that some dopes would extend them way out and the front wheel would just flop over at a certain point at low speeds. I had a person who was a fringe rider in our group (Fringe rider= A person who is not wanted or needed, generally just hangs on without permission and crashes a lot. Usually removed by stealing his bike while parked in front of the bar) this dope took a really nice 62 Sportster and put it in a custom frame that was so bad that it was unridable. A single mechanical disk in the back which didn't work at all and a front end that was so long that it flopped at high speed. One day he didn't show up and we all
just crossed our fingers.

Later in the 70s all of that stuff came off. Everyone went to K model triple clamps, stock tubes with rubber covers stock front brakes and 19" tires. A few people hung on but most didn't. They can still be seen, on a Pan or Knuckle, with no primary cover and a cork in the timing hole. We called him stubby because he was missing a few fingers on his left hand.

Ferrous Head 13th July 2021 23:16

There is a point where a bike crosses over from being a bike into a sculpture. A piece of art.
Once you start modifying a bike in some way that effects performance, (not engine performance but frame/brakes/suspension) it's all to easy to start moving into the arts area.
And that's fine if that's what you want to do. I have admired some totally un-rideable bikes over the years.
But I'm old enough to appreciate what can happen when you start altering performance just for looks.

11B40 13th July 2021 23:51

That is gospel Gene, but an Arlen Ness creation is still a pretty good ride in a straight line. He didn't build anything that was just plain dangerous unless it was a pure showpiece.

In the 70s some of those frames were just flexy flyers and all wrong. Mechanical disk........I actually had one on the spool up front for a while and it just flat didn't work at all. Looked cool but wouldn't stop a bike for shit. The stock single leading shoe HD felt like an MV Agusta in comparison. The bike I talk about the 62 I actually took it for a spin and made it about a half block before I returned it the the pinhead laughing. He was stunned, he thought he had the world by the tail with a downhill pull. If I recall, he was arrested or hurt and we never saw it or him again.

jsandidge 24th July 2021 22:03

Quote:

Originally Posted by bustert (Post 5904361)
stock tubes
been there done that.

Ordered up a set of stock tubes today. I'm looking forward to the improved handling.

ryder rick 26th July 2021 17:21

I hope you got the high ground clearance fork tubes. Or it may wind up pointing down hill.

Raked cups are not for highway use, show use only. Structurally compromised.....

jsandidge 26th July 2021 17:58

Everything will be stock. Currently it has only extended tubes - nothing else had been changed. My stock length tubes will be in Thursday.

ryder rick 26th July 2021 18:42

Perhaps you are not aware there are two different STOCK lengths for 35mm forks.

There are 2 part# for tubes for that vintage 45407-75 & 45644-77
Pretty sure the number differences are std and high ground clearance. (2" difference).

Be sure to shim your springs for 3/4" sag for best handling.

Gold Member 26th July 2021 20:03

Stock tubes. I had a Suzuki SAvage 650. I thought I had never ridden a motorcycle I didn't like until that one. Too much rake sucks. In order to go around something, you have to countersteer into the oncoming lane. I'm all for style, but they sure ain't for me.

jsandidge 26th July 2021 20:31

Quote:

Originally Posted by ryder rick (Post 5907353)
Perhaps you are not aware there are two different STOCK lengths for 35mm forks.

There are 2 part# for tubes for that vintage 45407-75 & 45644-77
Pretty sure the number differences are std and high ground clearance. (2" difference).

Be sure to shim your springs for 3/4" sag for best handling.

I did not know there were 2 stock tubes. I hope I ordered the right ones. They are 23-1/4" length.

wedge 26th July 2021 21:01

You should check that out right now, before the new tubes get to you. I totally agree with Rick, you should be using the longer tubes for both travel and handling. A little higher in the front is a good thing in my opinion, especially on the freeway, but lower is moving towards headshake territory.

Another note is that you should check to see what damper tubes you have and make sure you use the longest dampers too.

jsandidge 26th July 2021 23:25

Quote:

Originally Posted by wedge (Post 5907368)
You should check that out right now, before the new tubes get to you. I totally agree with Rick, you should be using the longer tubes for both travel and handling. A little higher in the front is a good thing in my opinion, especially on the freeway, but lower is moving towards headshake territory.

Another note is that you should check to see what damper tubes you have and make sure you use the longest dampers too.

According to the parts book, the longer tubes are stock for an XLS. My bike is an XLH, and the shorter ones are correct. I hope that's right.

ryder rick 27th July 2021 06:44

It used to be an XLH.

If you have long rear shocks you will likely want the longer tubes irrelevant of the model.

jsandidge 27th July 2021 11:58

Quote:

Originally Posted by ryder rick (Post 5907433)
It used to be an XLH.

If you have long rear shocks you will likely want the longer tubes irrelevant of the model.

Very good point.

ChinCactus 28th July 2021 14:20

Stock isn't ALWAYS the answer. My buddy has a 2003 Night Train. Near As I can tell, it is all stock. Thing has BAD low speed flop.

SHAKY DAVE 30th July 2021 00:53

Quote:

Originally Posted by ChinCactus (Post 5907664)
Stock isn't ALWAYS the answer. My buddy has a 2003 Night Train. Near As I can tell, it is all stock. Thing has BAD low speed flop.

what do you expect from a stinkin evo????????

Ferrous Head 30th July 2021 01:16

A 2003 Night Train was never built to go around corners. Fine in a straight line (just not at speed).

It was built to satisfy people who buy on the "Chopper" look. Big and heavy in the back end, long and light up front.

It's exactly the direct opposite for what is required to go around a corner fast.

Have a look at something like a 2003 Ducati to see what is done for fast, good handling bikes. Built for speed, not for looks.

At a walking pace a kids pump up scooter handles OK (or we wouldn't let our kids have them) But at 60 MPH ? I don't want to be on that thing.

jsandidge 2nd August 2021 20:24

I sure am glad I took the advice of you wise folks. I put the longer stock (+2) tubes on and just got back from a ride. I love the ride now. I was able to return the shorter ones, so I'm only out the return shipping on them. Thanks guys!

Ferrous Head 2nd August 2021 23:03

Despite it's less than ideal geometry, poor suspension and excessive weight the Sportster does handle better than any Jap bike made before 1972.
It's low center of gravity and the weight help a lot with this.
If you were to lengthen and strengthen the rear swing arm, add longer adjustable dual rate shocks and replace he front forks with modern cartridge type with adjustable rebound and compression the bike will handle better than any 80's Jap bike.

But then, it wouldn't look like a Harley.

It would no longer be a chick magnet and the guys on those little 600 pocket rockets will still eat your lunch.

So, enjoy !

kitabel 3rd August 2021 00:17

low center of gravity?
Iron cylinders and heads above the cases, large diameter iron flywheels - no jap bike has that.

Ferrous Head 3rd August 2021 00:40

You'd be surprised.
Centerline of the crank on a Sportster is just below the centerline of the bike. All of the 70's Jap 4 cylinders carry the weight much higher than you would think.
The seat height adds to this with most of the 4 cylinder bikes using "plank" type seats.
The width of these 4 cylinder bikes limits how low you can put the engine in a frame.
OK with frag bikes but try and get around a crooner on a CBX 6 cylinder Honda !

It's

here's another interesting fact.

When I went to build my first Sporton it finally dawned on me that the centerline of the engine was not on the centerline of the frame !
ie the engine is heavier on one side of the bike than the other.
Annd the engine is "offset" in the frame from where you would assume the centerline to be.

The good news was that it all made installing the engine in a Norton frame a piece of cake.


All times are GMT +1. The time now is 09:20.

Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2021, vBulletin Solutions Inc.
XL Forum® - Linson Media LLC