Missed that post earlier, a hearty lol to you, sir!
Welding in new motorcycle swing arm/engine mounts?
- Thread starter peejay75
- Start date
RoninB4
Well-known member
-First of all I don't want to see/hear of you getting busted up if/when the welds break off and you have serious injuries from the ensuing wreck. I want to give you credit for enthusiasm and willingness to try but this project seems to be beyond your ability to do it all yourself. The third posting of yours about the cross threaded bracket hole convinced me that something bad could/would happen if you did the swingarm bracket welding yourself. Even just fitting the new swingarm itself requires some attention to details and careful measuring with instruments you likely don't have. The swingarm should just barely slide in between the brackets. Bending the brackets, even a bit, will stress the welds and may cause failure. This would call for measurements in the .*** range IMO with maybe .002-.003 (inch) clearance on either side.
The excess width you now, supposedly, have would likely be better served by taking it off the "pucks" that are on the swingarm. This could be easily done on a lathe without molesting the existing brackets. Next up would be where does the swingarm sit in relation to the frame and front tire? It's not always in the center of the frame nor is the rear tire always in the center of the swingarm. I know of one bike where it does not because I have, and others, have taken measurements to determine this. Why does this matter? If the rear tire isn't tracking the same as the front it will fall into a turn too easily one way and be more difficult the other direction. This will matter less on a dirt bike than a street bike but it still has crash potential. There's also a matter of aligning the front motor sprocket to the rear sprocket but that's a subject for a different discussion. I don't like to discourage anybody unless I see potential danger from a DIY project. When I modified the swingarm (bracing for stiffness) of my street bike I didn't attempt to do the welding and I've decades of machine shop experience and welding, I had another shop we used do it to ensure nothing would go wrong. Things go wrong in proportion to the consequences and usually at the worst time.
If you lived closer I'd have you drop by and I'd take measurements and machine this all for you, probably at no charge.
-Yes it will get better because you're willing to investigate what could be done. Just don't let your ambition override your ability when the stakes for personal injury go up. Crashing at speed, even fairly slow, will sideline you from doing any further projects. I've got the scars and broken bones that will testify to that. Planning what needs to be done is half the battle. I noticed you posted a CAD drawing of a modified bracket. If you did this then that's something well within your abilities to do and I would encourage you to do this. A great many things I do for the house, cars, or motorcycles begin with modeling everything in CAD. Good dimensions lead to good shop drawings and less problems when assembly time comes. If this bike project began with reading about swapping swingarms on an internet board then perhaps somebody that's done this would be willing to share the dimensions with you. Those dimensions would go right into CAD modeling or even just paper sketches. Working from the dimensions will be less expensive and less machining/welding. Just a suggestion if you decide to hand over part of this project to the pros or anybody else for that matter.
-The stairs and the cross threaded hole are, or could be, within your ability. I don't mean to come across as a jerk, I just don't want you to be injured or do a lot of work for poor results.The stair problem, I didn't measure twice, cut once! But the old me would've just left it...oh, and not sought counsel on GJ first!
ArcIndWeld
Active member
If this came to me to be done I would cut out the existing bracket completely and replace it with a newly designed one from Send cut send or similar Tig weld in, Then machine/ shave the swing arm itself down to fit the frame.
Dealing with the warpage possibilities from plugging the original hole and welding an extension on seems like a waste of time and could be avoided. Plus I don't like the look of fish plates generally. Imo. That being said I'm all for diy and getting good penetration on that thin of tubing isn't all that difficult. I don't think its an unreasonable thing to do yourself. That being said if you're nearby ill show you how to tig weld it or do it for you if you'd like.
I'm in about 99% agreement with you, @RoninB4...
The feeling of accomplishment from DIY-ing the whole thing would be nice, and I think I have a decent grasp on what needs to be done, and also the understanding that most, if not all of it, is probably beyond my [current] abilities. I'm just trying to do as much as I can, and get as best of an understanding of the process, so I don't go into it with "here's my money!" or worse, pay somebody and be unsatisfied with the job and their response be "you told us this us what you wanted/we did what you asked"...had that happen before, I can do a crappy job myself, for "free"!
I appreciate that you'd be willing to take on the job for me, wish I was closer! Could you estimate what I'd be spend to have this done? Oh, also like that you farmed your work out, too, I don't mind that, just don't like being taken!
I will update you on the stairs and the cross threads once complete! (The wife and kid were on vacation this week, so it was my free time to tackle a bunch of things on my to-do list!)
The feeling of accomplishment from DIY-ing the whole thing would be nice, and I think I have a decent grasp on what needs to be done, and also the understanding that most, if not all of it, is probably beyond my [current] abilities. I'm just trying to do as much as I can, and get as best of an understanding of the process, so I don't go into it with "here's my money!" or worse, pay somebody and be unsatisfied with the job and their response be "you told us this us what you wanted/we did what you asked"...had that happen before, I can do a crappy job myself, for "free"!
I appreciate that you'd be willing to take on the job for me, wish I was closer! Could you estimate what I'd be spend to have this done? Oh, also like that you farmed your work out, too, I don't mind that, just don't like being taken!
I will update you on the stairs and the cross threads once complete! (The wife and kid were on vacation this week, so it was my free time to tackle a bunch of things on my to-do list!)
Sniff, sniff, you all are the best! I'm in Georgia if anyone is really feeling charitable! I don't mind paying for quality work, either!
("Quick" backstory, when I bought this bike (about 10 years ago), the seller actually test drove it, but I brought it home and couldn't get it to run...I'm thinking he goosed it before I got there! I had a new piston in it (no DIY!) and got it to run a little, but still not right...figured the crank seals (and case) were leaking...parts for this were/are getting impossible to find, thought I'd put in a later engine with better parts availability...7 model years later seemed ok...bought engine cases, a swingarm, and realized they weren't gonna be an easy fit...bought a used frame to modify so as not to mess up the original frame, and here we are...recently got into 3D printing and CAD stuff, so I figured I could at least design the brackets and let someone else put them in, but if I could practice with some plate and tubing, and if I gained some competence, then I would know if I could/couldn't do it myself).
iagsxr
Well-known member
I got sick of reading.
Has anyone told him it would be easier to narrow the swingarm yet?
Has anyone told him it would be easier to narrow the swingarm yet?
"He" looked into that, but then he'd hafta get custom bearings and sleeves and stuff, and something else was a problem that he can't remember right now.
iagsxr
Well-known member
No really, stock everything should still work. Shorten the sleeves. Deepen the bearing counterbores by the amount you take off each side of the swingarm.
Your chances of success are way better doing that than trying to reman the mounting plates.
Jim greengo
Well-known member
Ever watch a bike go down the road with a bent frame/swing arm, or just a rear wheel out of alignment?
Being passed by the *** end of a bike when you hit the front brakes ain't no fun! Hahahs
RoninB4
Well-known member
-There's a lot of that available at (so called) "professional" shops, it's my prime motivation for still doing as much of my own work as possible.
-If the solution is merely facing off the "pucks" then at a shop rate of $150/hour (high rate) I can't see it taking any longer than 1 hour, should be about 15-20 minutes of actual machining. Some machine shops could very well charge a lower rate. Part of the problem in giving you a solid figure is:
1) I can't say for certain that your swingarm is made like the others I've had. I'd have to either see the swingarm itself or an exploded diagram to determine this. You still haven't, unless I missed it, stated what the swingarm and frame are from.
2) The second problem is not knowing exactly how much metal needs to be removed to make a proper fitment. All the swingarms I've removed/installed only allow about a sheet of paper (.003) to fit between the swingarm and the mounting brackets. You really don't want the brackets squeezed (weld stress) or a gap (lateral movement of swingarm) that allows the swingarm to move around in the frame. Dimensions are needed, both the distance between the frame brackets AND across the swingarm "pucks" as assembled.
3) Working on a spare frame was a reasonable approach but it might be different than the frame you intend to actually use for riding. There are not only production tolerances, which can vary the distance between brackets, there's also the possibility that the spare frame has had the brackets "tweaked" from abuse during use or careless handling when it was no longer a working motorcycle. I believe you even stated that the swingarm is from a later model year. So how come it doesn't fit if it's from the same model? That's because things change at the factory and the model from last year can be different than this year. Extremely common with motorized contraptions. When doing a custom project it's almost always best to work with the intended components, measuring them lets you know if there's a difference. Imagine getting everything fitted for the spare frame and now it doesn't fit the intended frame as it should. Working with reliable measurements ensures there are no surprises. This is especially true with previously owned components regardless of who owned it. Sometimes who previously owned it makes it particularly suspect.
-Nobody likes being played for a fool once they discover they've been played. This is where/why you need to inform yourself before proceeding, which you're trying to do. Start by attempting to pull the "pucks" out on both sides of the swingarm. Look inside to verify there's grease in the bearings, lots of people fail to grease the swingarm and the bearings are toast. Be careful not to allow any dirt/crud to get in there, now put the pucks back in. This will verify that these might be the only components that need altering. Next would be taking accurate dimensions. We'll get to that later. I would strongly suggest keeping dimensions on either a sketched drawing or a CAD model for reference. Data is easy to forget/lose over the course of a few days/weeks. What CAD program do you have?
-Finish the stairs and cross threaded bracket first, the frame project will take longer to finish than those will. A to-do list is like eating an elephant, one bite at a time.
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M.Brane
ALLIANCE MEMBER
Yeah a serious misalignment is gonna be a problem. A slight one you won't even notice. We're not talking about MotoGP here.
I'll take a closer look at the swingarm components again!
iagsxr
Well-known member
I think people would be surprised how imprecise a lot of bikes are straight from the factory. An old school chopper builder told me one time that as long as the wheels are parallel to each other having them in exactly the same plane isn't that critical.
Looking at the pics this is some manner of old dirtbike. My concern would be keeping the swingarm pivot in exactly the same relationship to the countershaft if the OP goes ahead and cuts off the mounts.
ericm
Well-known member
When was into RZ350s one mod was to fit an FZ600 swing arm. It was slightly wider than the space between the frame brackets, like your problem. The answer was to mill the swing arm.
If the bearings in the arm are larger ID than the old pivot bolt OD you can make spacers or have them made.
The swing arm pivot bolt is also an engine mount. If you move the pivot you have to move the other engine mounts, and then you need to modify everything else that touches the engine- exhaust, intake, shifter. The engine is the heaviest part of the bike and moving it will change the weight distribution. If you can move the pivot back without moving the engine then you make the critical countershaft sprocket to swing arm relationship worse, which causes suspension issues.
It's probably easier and cleaner to mod the swing arm.
What bike is this?
Edit: I see other posters suggested the same thing- I didn't read all the posts before posting. Often the needle bearings in the swing arm are one on each side with a space between them. There may be bearing pockets or the swing arm may be bored all the way across, in which case you just drive the outer bearing in 2mm farther.
If the bearing was full width, find a narrower one. Exact width doesn't matter.
Do the suspension mounting points on the new swing arm match the ones on the old arm?
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danielbuck
Well-known member
- Joined
- Apr 15, 2014
- Messages
- 919
for stuff like control arm mounts on vehicles that need (or ideally should...) be parallel, I use a piece of tube, thread the ends and use a bolt and washers to mount the brackets to the tube.
This works out pretty well, but it's fairly custom width to that one project. I did this one on a frame that wasn't parallel (it was tapered, from the 1930s), so I couldn't use the frame as a reference for what was "straight". Alot of things are more complicated when the frame rails aren't parallel to each other
you could do the same thing for tabs or anything else that need to have holes that are in line and keep the brackets parallel. for smaller distances, you could probably use threaded rod if it looks straight and a few nuts. that would have an adjustable width..
This works out pretty well, but it's fairly custom width to that one project. I did this one on a frame that wasn't parallel (it was tapered, from the 1930s), so I couldn't use the frame as a reference for what was "straight". Alot of things are more complicated when the frame rails aren't parallel to each other
you could do the same thing for tabs or anything else that need to have holes that are in line and keep the brackets parallel. for smaller distances, you could probably use threaded rod if it looks straight and a few nuts. that would have an adjustable width..
@danielbuck Posting pictures of lathes is expressly forbidden to those of us who do not have them!
Thank you all for the tips, advice, and warnings! In the spirit of full disclosure (and as I told @RoninB4) I will give you all a complete breakdown of the bike, the project, and a link to all the pics I have showing the old and new swingarms, the measurements I made of the sprocket relationship (and how U did) it, engine cases, the whole shebang! Gimme a bit to get it all uploaded to Flickr and I'll post the link to 'em!
Oh, of course all of this info is hopefully useful to someone else who may be in a similar situation.
And also, ok, nah, I can't even tell y'all what brand and model if stick welder I own, and since it was pretty unanimous that stick is out and TIG would be king for something like this, that's kinda moot!
So hopefully some of the advice would be get a TIG (I have ALOT of projects that need welding) and practice, or get a TIG and take classes, etc...(that is, let a pro do this job, but practice for your other stuff).
Oh, of course all of this info is hopefully useful to someone else who may be in a similar situation.
And also, ok, nah, I can't even tell y'all what brand and model if stick welder I own, and since it was pretty unanimous that stick is out and TIG would be king for something like this, that's kinda moot!
So hopefully some of the advice would be get a TIG (I have ALOT of projects that need welding) and practice, or get a TIG and take classes, etc...(that is, let a pro do this job, but practice for your other stuff).
(Also, thanks for making me Google "RZ350", a 2-stroke street bike??? Sounded very cool, I saw they even made a 500!)
ericm
Well-known member
Yep, the last two stroke street bike officially sold in the US, in the mid 1980s. They sold a reasonable number so there were a lot available in the '90s to modify or turn into road race bikes. I had a couple and my wife even had one for a while. Prices are insane now.
I had one of those too. They didn't import them into the US but there were ways around that, some more legal than others. In stock form it wasn't much faster than a four stroke 600 of the same era but Yamaha tuned it conservatively and built it strong so there was a lot of room for improvement.
M.Brane
ALLIANCE MEMBER
The coolest thing about the RZ500 is it was a 2 stroke V4. I've seen one in person:
I've also seen the infamous "Widowmaker" 750 2 stroke I4:
Wouldn't throw a leg over that if you paid me.
I've also seen the infamous "Widowmaker" 750 2 stroke I4:
Wouldn't throw a leg over that if you paid me.
(just read up on that one, too, thanks!...and googled "tank slap", as I thought that was an exaggeration, but nope!)
Link to the album: https://flic.kr/s/aHBqjC9bcx
(Sorry, I thought I had pics showing me doing my best to check the alignment of the front/rear sprockets, but can't find 'em, but I did make sure they were true/aligned with each other).
(Sorry, I thought I had pics showing me doing my best to check the alignment of the front/rear sprockets, but can't find 'em, but I did make sure they were true/aligned with each other).
RoninB4
Well-known member
-Viewed the album and "pucks" are on the inside, not the outside. I still contend that it's easier to mill the swingarm than to fool with the mounting brackets. Any of the spacers in the swingarm can be reduced to length in a lathe. Are the spare frame and the intended rider frame the same? Regardless, you still need dimensions from between the brackets and across the swingarm before work can begin. JMO.
The original frame and the "practice" frame are the same bike, both '87 RM250's...I will get those dimensions for you, and try to take pictures of the measurement, if I can! I will also try to find comparison pics of an '87 vs '94 frame, in the swingarm mounting area.
danielbuck
Well-known member
- Joined
- Apr 15, 2014
- Messages
- 919
oh well. figure out life and get a lathe