Building a "first bike" for my 17yo son...

AlphaDogChoppers said:
Well, since you asked....

The chain fender strut looks stupid. Not because it's hastily fabricated just to look at it, but because it's, well, icky. :)

Try experimenting with some square stock with a twisted section in the middle.
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I actually came with another idea. It will be fender strut/sissy bar combo. But neither one of use like the 5 foot tall sissy bars so many others do. This will be less MAYBE 20" above the fender. Just enough to strap a bag too. And it's going to incorporate some "Japanese" influence ;)

That fender is going to hit the frame loop. You need more clearance than that. I realize that your shocks may be different, but this is mock up. Now is the time to square that away. It will piss you off if you smash the fender the first time you hit a bump. You were generous with the tire to fender clearance. I suggest you start by making the fender hug the tire much closer.
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Thanks for the tips. The fender actually has about 3" of travel before it hits the loop. The pictures don't do a good job of conveying that. With the 40 year old shocks on there, my 200lbs TRYING to make contact between the two was unsuccessful. My son is about 140lbs soaking wet. I will give it some more attention though, just to be sure.
 
axelcrypt said:
have you considered how to tension your chain? if you run the fender too tight to the tire, you loose chain adjustment.

i'm not sold on the chain fender struts either. tried a mock up on mine once and scrapped it.

your boy doesn't look too heavy. could set shocks quite stiff and avoid fender hitting frame loop, however, it looks pretty close. got any longer shocks around?
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I purposefully left a little extra space around the tire (As Alphadog pointed out) in order to allow for some chain adjustment. It's going to be a somewhat custom setup anyway, since I need a custom (tiny) sprocket with a harley bolt pattern for the rear and a larger sprocket in the front (because you can only go so small in the back) in order to get the gear ratio close to original. That job will be tackled soon. Then I'll look at tensioners (if needed) and make any fender adjustments if necessary.
 
timberwolffxdl said:
This will be less MAYBE 20" above the fender. Just enough to strap a bag to
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Don't forget that the sissy bar will move up and down in a violent manner, and probably break off.

timberwolffxdl said:
The fender actually has about 3" of travel before it hits the loop.
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Not nearly enough. If the shocks have 3" of travel, the swingarm will have about 4 1/4" of travel due to the angle of the shocks. That fender WILL hit the loop, guaranteed.

timberwolffxdl said:
my 200lbs TRYING to make contact between the two was unsuccessful. My son is about 140lbs soaking wet. I will give it some more attention though, just to be sure.
Click to expand...

What's the expression? "You argument is invalid."
Bouncing your fat ass on the seat is not even close to hitting a pot hole. The suspension WILL bottom out at some point, and it WILL fuck up the fender. I can see that just by looking at it.
 
Mock up the fender with the axle all the way forward. Use 3/8" OD fuel hose for your spacer, and wrap it around the tire, not running longitudinally along the tire. Working with a closer spacing, you will want to be sure the fender doesn't interfere with the sides of the tire, too.

Take one shock off, and set it to it's softest setting. Use a bar clamp of ratchet strap to fully compress the remaining shock to make sure the fender doesn't hit anything. Alternatively, you might consider removing the spring altogether for mock-up purposes.

You MUST assume that the shock will bottom out at some point, because it WILL.
 
Imagine the motion of the swingarm, which is an arc. When the swingarm moves up, the sissy bar will be whipped forward. Then when the swingarm goes down, the sissy bar whips back. The longer the sissy bar is, the more the effect is amplified. I don't think you quite appreciate the G forces that must be endured by anything that is attached to the swingarm. A couple years ago, Harley came out with a model that had a tire hugging fender. They had problems with the fender struts breaking.

If you get on a moderately bumpy road with a 20" sissy bar attached to the swingarm, that sucker is gonna be whipping violently fore and aft until it will simply break off, shedding whatever luggage you had strapped to it. Metal fatigue is not to be dismissed lightly.
 
so how do the few thousand guys out there putting sissybars on their "old school" chopper wannabes get away with it?
 
Hardtails, not swingarm. The sissy bar is mounted to a rigid frame, not a moving suspension component.
 
AlphaDogChoppers said:
Hardtails, not swingarm. The sissy bar is mounted to a rigid frame, not a moving suspension component.
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Gotcha.

Ok, while you're here... how come 3" between fender and loop isn't enough, but there is literally a shitload of guys out there with fenders strutted to the frame itself, and an inch of clearance between the tire and fender? How are they getting away with it?

Heck, I think my 2003 FXDL has about that and it hasn't touched, even with a passenger. It just has base line progressive suspension shocks. (you can see it in the background of some of the pictures in this post)
 
Having the tire contact the fender is one thing. It will cause wear to the tire, and eventually to the fender. You might also be thinking of something like a Harley Softtail, which have very limited suspension travel. Not a very good ride.

Having your fender crash into the frame is another thing, and much worse. It will cause immediately obvious and objectionable damage.
 
Small update.

I planned to work on the struts for the fender. Haven't had time to mess with them too much after all. Well, I take that back. I tried my hand at making a strut/sissy bar combo with a piece of 1/2" rebar. Didn't like it though. But I have other ideas :)

In the meantime, I drew up some shock mounts and the minions here at work machine them up for me so I can use these progressive shocks I picked up. The upper mount is a weld-on. Goes through a hole I made in the frame. Then gets welded from both sides. Lower uses the existing mount holes in the swingarm. Uppers and lowers are both cold rolled steel.

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also I cut the standing spot weld seam from the backbone and welded it up. Picked up a set of GS850 pistons and got those cleaned up and ready. Also stripped the tank.

Didn't really get any pics of that stuff yet. More to come after this weekend hopefully :)
 
first thing you need to shove axel all the way forward before setting fender. This will help to avoid trouble when adjusting the chain in the future. I made the bracket on mine, adjustable.

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Im no engineer, but I dont like the idea of cutting on the swing...especially the tubes nearest the axel. It just looks like a weak spot to me. With all the forces and flexing the tubes of swing are subjected to. And now that the thinner tube of the swing has been heated by welding it to thicker tube, and is more brittle, it made more sense to me to add 4 inches to the front. Using the same thickness material as the swing itself.

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Mine has 2.5 - 3 inches of clearance before fender bottoms on frame. I have pretty stiff shocks. (Made for at least a 750) I haven't bottomed out yet and we got some pretty nasty railroad crossings here in Illinois. I have been a little bit airborne more than once.

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I re-used the original fender strut, holder, brace, thing...Hasnt shown any signs of fatigue or cracking yet.

The thing that surprises me most. My cheap little plastic Ebay special LED taillight is STILL WORKING after being beaten to death on the fender. Like 3 years now.

Go ahead Alpha, awaiting your 2 cents. . . .lol

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Just how FAT is that rear rim/ tire?

Just wondering about getting the drive chain from the rear wheel sprocket past the fender and tire and line up square w the front drive sprocket. :eek:
 
trek97 said:
first thing you need to shove axel all the way forward before setting fender. This will help to avoid trouble when adjusting the chain in the future. I made the bracket on mine, adjustable.
Click to expand...

yep, been there done that since the pics. no problems at all. And the chain is LONG gone. :)

Im no engineer, but I dont like the idea of cutting on the swing...especially the tubes nearest the axel. It just looks like a weak spot to me. With all the forces and flexing the tubes of swing are subjected to. And now that the thinner tube of the swing has been heated by welding it to thicker tube, and is more brittle, it made more sense to me to add 4 inches to the front. Using the same thickness material as the swing itself.
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Don't tell all those bridge builders about welds making the metal brittle... we may have an infrastructure crisis in this country!! :p
The DOM tubing is stronger (thicker wall section) than the OEM swingarm by far, and it's inserted an inch past the weld.
Mine has 2.5 - 3 inches of clearance before fender bottoms on frame. I have pretty stiff shocks. (Made for at least a 750) I haven't bottomed out yet and we got some pretty nasty railroad crossings here in Illinois. I have been a little bit airborne more than once.
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Current shocks on the bike are from progressive suspension (seen in the pics above), and were used on a triumph 650 triple for about 3k miles. They are about an inch longer eye-to-eye than those honda stockers in the pics.
I re-used the original fender strut, holder, brace, thing...Hasnt shown any signs of fatigue or cracking yet.

The thing that surprises me most. My cheap little plastic Ebay special LED taillight is STILL WORKING after being beaten to death on the fender. Like 3 years now.

Go ahead Alpha, awaiting your 2 cents. . . .lol
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My latest thought involves a one piece brass strut/sissy bar. I have rubber isolaters that will be hidden after installed (salvaged them from the stock tail light setup). I think this will dampen vibrations enough to alleviate any harmonic stress.

BTW, do you still have your twin? I read your engine rebuild thread with interest and have bookmarked it, since that's the next thing to tackle.
 
trek97 said:
Just how FAT is that rear rim/ tire?

Just wondering about getting the drive chain from the rear wheel sprocket past the fender and tire and line up square w the front drive sprocket. :eek:
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Back tire is an MT90B-16. Wheel hub is pretty wide though so I shouldn't have issues clearing the fender. I may have to offset the drive sprocket, but since it's going to be a custom from SS, it should be ok :)
 
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