350x swing extension questions

[three50x]

so im going to extend my 350x swingarm, but don't know how far. what Is the safest/ best looking extension? what are the pros and cons of extending it?

[DohcBikes]

Some pros are less tendency to wheelie when drag racing or climbing hills. The cons would be a wider turning radius and ride height\suspension tuning choices and issues.

Anytime you extend a swinger its a good idea to sleeve it on the inside or outside and use long enough pieces to plug weld it as well. Many builders add a horizontal brace between each side of the swingarm in a location that will strengthen it.

The 350x swingarm is not an easy swinger to extend. The metal is not a uniform shape, and without building a jig first you will kick your own ass all the way through it and possibly still end up with something that performs worse than stock. Also the welds must be really good, cuz when a swinger breaks there's a damn good chance the riders gonna get hurt.

I'm not trying to dissuade you in any way, I see that you have 2 swing arms so if you ruin one its probably not a big deal. Just want you to know that extending swing arms, especially 350x swing arms, is not to be taken lightly.

Good luck on your research, maybe try the search function to see how some the excellent builders on here have extended their swinger.

Looking forward to progress

[three50x]

what do you mean its not uniform shape? and also what do u mean building a jig?

[DohcBikes]

Since the box tubing is not parallel, it becomes much harder to center the carrier once you cut it and pull it away from the front half of the swinger. If you don't make a jig to exactly center the carrier, side to side, up and down, diagonally, and front to back on each side, then the chain and sprocket won't line up or won't run true.

Building a swinger with no jig is a guessing game, and since metal swells and shrinks the chances of you guessing correctly is not good, especially on your first attempt.

A jig can be as difficult to build as a swinger, but basically it becomes an adjustable clamping tool that mocks the base dimensions and allows you you move the location of the cut carrier while keeping it true and centered, so you can clamp it again and do your fab work without the pieces moving at all. This way the swinger ends up being useable.

[HairyJR]

Every one will have different ideas to modify or extend an original swingarm. Of course what’s done depends on several factors, money first, then skills and ability and tools or equipment.
I extended two ’85 350x arms 8 inch’s back in 1990, first of all as what has been mentioned in another thread extending a 200x swingarm, a fixture or jig is needed to keep everything in alignment, parallel and spaced correctly no matter what the length of extension. Sorry no pictures during original build but will post some of the final construction welded assembly. This was my first attempt at welding and haven’t welded since. Cut swingarm on band saw @ 1-1/2” from carrier, positioned it to the length desired then split 2”x3” (.085”) mild steel box tubing and laminated over the outside of original box sections. Pie cut and shaped the original box tubing too match the outside laminated plates and plug welded.
Granted 8” is way too long for your build, but works well on my ’83 XR500 hybrid trike, but I used a 350x swingarm for the build.
Had a 3” over Westcoast arm (loved it) on my ’85 350x until ’91 when I had the 3-4 Astro quad conversion kit installed and put a stock length arm back on. No I don’t have it, sold years ago.
Plenty strong enough, maybe not the prettiest construction but very functional.



"HJ"

[DohcBikes]

Seems that HJs story doesn't match the pics but the photos show several of the fab tips we've discussed, thanks hj!

EDIT: story matches now lol

[HairyJR]

Thanks DohcBikes, made me read my own post, had cut and pasted wrong write up, had to edit, if you read it now maybe makes better since. Wrote another lengthly response to your statement before reading my wrong post but think I'll post it anyways, might help someone else'

I knew when I posted the pictures people wouldn’t fully understand the process I performed. Picture with box tubing examples were first of the 2x3 tubing before cutting and the second was of the cut laminate sections welded together as I practiced tig welding before final fabrication. That’s OK it’s hard to explain step by step the complete process, lower inside “L” plate sections welded first to the original swingarm box tubing that was split, bent to match laminated plate angles and welded on the inside. Then the outside upper “L” plates welded and then welded full length seams of the two plates.
Pics of fab’d swingarm were of swingarm #1, which needed additional weld repair where the tubing cracked around the left side shock mount bolt attachment boss, caused by broken bolt, my weld fabrication didn’t fail. The trike has swingarm #2 which has been in place for the past fifteen years and freshly powercoated this summer.

"HJ" must stop before posting

[barnett468]

so im going to extend my 350x swingarm, but don't know how far. what Is the safest/ best looking extension? what are the pros and cons of extending it?

Hello;

In addition to what's been mentioned above, the following things will also occur and be more noticeable the longer it is extended.


It will have less rear wheel traction which will be noticeable after around 1 1/2" of extension. You can move rearward on the seat to compensate some for this.

The steering will feel slightly heavier.

If you are not "sliding", it will have more tendency to "push" the front wheel in a turn instead of turning the vehicle.

It will be easier to slide sideways however I would install a wider axle if I planned on doing this especially for high speed sliding.

If I mainly did tighter turn riding, I would not extend it more than 1 1/2" if I extended it at all.

It will flex more which will actually smooth the ride out a hair but I would install an additional cross brace right behind the shock mount to reduce flex.

Imo, anything over 3" is best suited to more straight line riding and huge high speed slides.

must stop before posting

Maybe we should simply start drinking before reading your posts instead.

[barnett468]

so im going to extend my 350x swingarm,

Hello again;

Sorry, I forgot to ask the obvious question, which is why?

If you read the posts then tell us what you like about your bikes turning and wheeling now, and what you are wanting to change/gain by extending it, we can suggest how long of an extension might best suit your needs.

[HairyJR]

“Three50x” the 4 stroke 350x is heavier and has a higher c/g than 2 strokes, therefore will always run in it’s own class. Long extended swingarms are basically for straight line racing or hill shooting. Mine was built when we could race on Competition hill any day or night before the Holiday closure came into effect, the other benefit I got it handled well through the whop-de-do’s and rough terrain. 3 wheelers dune differently than the chairs (quads) and I can hang with the best of them.

“Glamy” saw a thread someplace recently where an aluminum swingarm was extended, looked great and that pic looks like test hill.

Here’s the only picture I have of my 350x with the 8” swingarm, me, my son and a friend from Phoenix racing at Oldsmobile hill.


"HJ"

[scuba]

I have extended and built several swingers for my 350X over the past 7 years or so. I have cut them up and even bent a few, till I found the right length.

I settled on +2 because even though the bike looks awesome at +4, the front end became to heavy in the soft sands as you top a big dune. And the stocker just wanted to stand up on me when it began to slow down at the top. +3 was nice, but when I did the +2 it planed out real nice with little effect on the steering and such. As for another question I saw from you, the lowering of the 350X is a good thing to do. It is allot more top heavy then most trikes, and when it is down with the swinger almost level it is strong in the corners and sticks to the ground nice. So either build a new arm with a jig all together or cut the stocker up to stretch it like the pics harry posted and lower it like Geralds 350X showed with the plates relocating the shock to the bottom hole. Either way you will be glad that you did it.......

[fallguy666]

Here's mine that I'm doing rite now.[ATTACH]undefined[/ATTACH]

[fallguy666]

I didn't use a jig or anything.I cut it,slid two 1"×1" solid stock into each side,used a porta power to spread the stock tubing open far enough and slid the carrier section on.squared it all up with a level and a tape and boom.welded it all up.waiting on the bearing kit and chain to come in and I will install it.....after I finish painting it of course.

[DohcBikes]

Here's mine that I'm doing rite now.[ATTACH]undefined[/ATTACH]

I didn't use a jig or anything.

That's good for you if it it works out but often times even a slight misalignment will ruin chains and sprockets like crazy. It can be done, but it is best to use a jig. There are several failed extensions even on this site that I have seen, because they thought they could just whip one together.

To be clear, I am not judging your work in any way, just giving my opinion on fabrication techniques. Let us know how yours works out

[fabiodriven]

A jig is nice, but absolutely not a necessity. I've extended two 85 Tecate swing arms, one on a driveway, and both came out great. It's just like anything else, measure carefully and really look at what you're doing.

As far as a misaligned swing arm wearing chains and sprockets, you'd have to be so far off with your measurements that it would be ridiculous and blatantly obvious how far off you are. I can tell you this for certain because the first swing arm I extended was off a hair. Nobody would have ever noticed if I didn't actually show them, but I knew it was. It was just a touch, but by really particular builder's standards it may as well have been a mile. You couldn't tell from riding the bike or even after looking it over really closely. You'd really have to be particular to notice by eye without someone telling you. My sprockets and chains wore just fine.

My point being, you would be so far off with the measurements in order to cause premature sprocket wear that the rear end being kicked would be a much bigger issue.