Bang for Buck mods & upgrades

[peanut]

So....once again Skull650 has taken one of my threads off topic so that he can have a go and be his usual obnoxious insulting self.
I'm going to abandon this thread before it turns into his private slanging match

well now that my classic car is sold I have some spare cash burning a hole in my pocket. ...
so I have started making a list of things that I'd like to do with my 79 special .

One of the most urgent issues that I need to address is the tendency for the bike to wander and wobble in head and side winds. On a calm wind less day there is no stability issue at all but it is really noticeable on windy days and I have to keep my speed down to around 35-45 mph
I was planning on
Replacing both tyres,
Adding a fork brace
Upgrading the swing arm buses
Replacing the fork bearings .

Apart from losing 30kgs is there anything else I should be considering to resolve stability issues ?
I should mention that I have retained the high rise special bars with a lean back position so most of my weight is probably on the rear tyre


I would appreciate any advice and tips on improving stability

 

[shotgunjoe]

You could, lower the forks. This will reduce the rake angle and increase high speed stability.

 

[member28833]

Peanut, how well does your XS fit you for height ? Perhaps slightly longer shocks and a taller , flatter seat like one of those nice cafe seats would allow more legroom ? Slightly more weight on the foot pegs, dirt bike seating style might help stabilize you ?

 

[gggGary]

Those stock front springs are quite flaccid. several guys have recently gone to the 35mm harley springs, I've done two sets, really helps that front end. As you hint above an unequal weight, and wind profile probably excaborate the situation.Keeping your body further forward should help a bit. In aviation there's a term PIO, it applies to motorcycling as well.

 

[peanut]

You could, lower the forks. This will reduce the rake angle and increase high speed stability.

thats an interesting idea that I hadn't considered.

 

[gggGary]

You could, lower the forks. This will reduce the rake angle and increase high speed stability.

hmmm...........

 

[peanut]

Those stock front springs are quite flaccid. several guys have recently gone to the 35mm harley springs, I've done two sets, really helps that front end. As you hint above an unequal weight, and wind profile probably excaborate the situation.Keeping your body further forward should help a bit. In aviation there's a term PIO, it applies to motorcycling as well.

The problem is that I have an easy rider type position on the bike with my weight leaning back which is attenuated by the 16" rear and 19" front wheels. Unless I switch to straight bars I'm not sure how I am going to move more weight forward . I see if I can find something on the Hadley spring conversion

 

[peanut]

Peanut, how well does your XS fit you for height ? Perhaps slightly longer shocks and a taller , flatter seat like one of those nice cafe seats would allow more legroom ? Slightly more weight on the foot pegs, dirt bike seating style might help stabilize you ?

With the 16" rear and 19" front wheels and high swept back special bars my body position is leaning back rather than upright. I don't think I would like switching to a straight back or leaning forward position because of my back issues. I'm even collecting parts to fabricate forward controls as I enjoy the laid back riding position
I'll try and get a picture of me on the bike which should help. i'm 5'11" 240 lbs

 

[5twins]

All you've mentioned should help but until you change out those buckhorn bars, I don't think you'll be getting at the underlying issue. You're like a sail sitting on top of the bike with those bars. There's a good chance your steering bearings are totally shot but you won't feel that at all through those bars. They give no steering feel or feedback what so ever.

I was quite surprised how nicely my Special rode when I first took it out. All I had changed then was the handlebars and steering head bearings. Rear shocks are originals and the swingarm bushings are noticeably worn (you can wiggle the rear wheel side to side). But it still rode and handled pretty good. Now I've done the forks (Minton Mods, 7 ounces of oil, 1" preload spacers added to stock springs, tubes raised 1/4" in the trees) and added 19"/18" Standard flanged alloy wheels. It rides even better but these additional tweaks are emphasizing the rear end's shortcomings more. Plans for that are slightly longer aftermarket rear shocks and a TX750 swingarm.

Slowly but surely, the old girl is starting to get her "bling" back, lol .....

 

[shotgunjoe]

A secondary effect of reducing rake, is more forward weight bias, which also increases the front tire contact patch. I too have felt the lightness in the front-end of a bike setup the way yours is. Lowering the forks gave it a much more solid feel, more connected to the ground...ialso switched to superbike bars though.

When Yamaha changed the styling of the xs650 to be more like the Harleys, making it into a cruiser, they failed to change the weight bias of the bike. Harleys are heavier in the front.

Another option would be to make the bike longer. Maybe a stretched swingarm. This will change the weight bias as well. You will either want slightly longer shocks or to move the lower shock mount forward to maintain the current shock length and/or angle. I hope that makes sense...

 

[peanut]

All you've mentioned should help but until you change out those buckhorn bars, I don't think you'll be getting at the underlying issue. You're like a sail sitting on top of the bike with those bars. There's a good chance your steering bearings are totally shot but you won't feel that at all through those bars. They give no steering feel or feedback what so ever.

I was quite surprised how nicely my Special rode when I first took it out. All I had changed then was the handlebars and steering head bearings. Rear shocks are originals and the swingarm bushings are noticeably worn (you can wiggle the rear wheel side to side). But it still rode and handled pretty good. Now I've done the forks (Minton Mods, 7 ounces of oil, 1" preload spacers added to stock springs, tubes raised 1/4" in the trees) and added 19"/18" Standard flanged alloy wheels. It rides even better but these additional tweaks are emphasizing the rear end's shortcomings more. Plans for that are slightly longer aftermarket rear shocks and a TX750 swingarm.

what kind of bars did you switch to / were they Triumph T120 style ? and did you keep the 19" front wheel ?

i think I am going to be a sail on any bike unless I go for clip-ons lol I am a bit of a lump.
I don't know what was done to this bike before I bought it so I'm sure it would benefit from swing arm bushings and steering bearings and new tyres are sure to help . i'll take another read through Mintons Mods thanks for your suggestions 5T

I'm back.....my dinner had just been put on the table mid sentence and I couldn't think of anything except eating lol.......

So the issue I have is this weird sort of bendy feeling like I have a hinge in the middle of the frame somewhere. I think I need to replace the 12 year old tyres which are as hard as rock first and then reassess . It could be that they are the main contributory factor .

 

[5twins]

I run the Euro bend handlebars on all my bikes. The way they droop down slightly on the ends makes them extremely comfortable. They turn your wrists to a more natural angle than straight, flat bars. That droop also allows the angled Special MC to sit nicely, almost level .....

But I probably won't be running that stock MC much longer. I have a 1/2" bore MC from a Yamaha Vision in the wings to try out.

 

[peanut]

I run the Euro bend handlebars on all my bikes. The way they droop down slightly on the ends makes them extremely comfortable. They turn your wrists to a more natural angle than straight, flat bars. That droop also allows the angled Special MC to sit nicely, almost level .....

But I probably won't be running that stock MC much longer. I have a 1/2" bore MC from a Yamaha Vision in the wings to try out.

yes I could imagine that those bars are extremely comfortable due to the angle of the grips.
I remember reading an article some years back about finding suitable bars. The writer suggested holding your arms loosely by your sides then slowly raising your arms up to horizontal in front of you and observe the angle your palms are at . They end up being at exactly the angle of your grips and the same as the high special bars.
Looking at the bar rise I should imagine that you would be putting some weight on the bars and leaning slightly forward yes ?

 

[peanut]

A secondary effect of reducing rake, is more forward weight bias, which also increases the front tire contact patch. I too have felt the lightness in the front-end of a bike setup the way yours is. Lowering the forks gave it a much more solid feel, more connected to the ground...ialso switched to superbike bars though.

When Yamaha changed the styling of the xs650 to be more like the Harleys, making it into a cruiser, they failed to change the weight bias of the bike. Harleys are heavier in the front.

Another option would be to make the bike longer. Maybe a stretched swingarm. This will change the weight bias as well. You will either want slightly longer shocks or to move the lower shock mount forward to maintain the current shock length and/or angle. I hope that makes sense...

yes it makes sense sort of . I may be wrong but if more weight is shifted onto the front wheel doesn't that increase the likelihood of getting a tank slapper ?

If I decrease the rake , increase the length of the rear shocks and reduce the size of the front wheel etc it would change the bike into a roadster wouldn't it ? i'm keen to retain the special styling as I really like the riding position.

 

[shotgunjoe]

What you want is more of a neutral weight bias. Sport bikes for instance are very stable at high speeds but unstable at low speeds, a stretched chopper is as well. Which one is more likely to be get speed wobble? The chopper. I've only seen that happen on a sportbike when the front tire comes off the ground then touches down again.

My last xs650 had 2 inch shorter forks, stock length shocks and swingarm. I had it over 100 and it felt planted. Superbike bars (similar to eurobend). It still had the original stem bearings, which were in good shape when I inspected, cleaned and regreased them, stock swingarm bushings, cleaned and regreased. The tires were upgraded though.

You wouldn't want to do all those mods at once. Pick one that suits you. Since you sound like you like the laid back feeling, stretching the swingarm probably more up your alley.

I don't know what a roadster is.

 

[member28833]

All right. A Stock like Special.
You do need tires . I believe better shocks would also be noticeable.
While the shocks are off grease up the swing arm well while moving it up and down. Feel for play !
Confirm your steering stem bearings are also greased and tight. Change out the fork oil to 15wt and fill with 7oz.
Add a spacer if you need.
Try it for noticeable improvements ?
Bars ? Internal weights in the ends.
Quality bar end mirrors to catch the wind !
Go Sail it and report
-RT

 

[peanut]

Quality bar end mirrors to catch the wind !
Go Sail it and report
-RT

..I daren't lift my hand to my face at the moment or i'd take off lol.

yes I should have said right in the beginning that I did not want to change my riding position or the bars but to be frank I never considered that the conversation would take that sort of direction .....

The bike needs a complete renovation ,having come to me in as bits in a box with no history.
I suspect that the instability is largely as a result of the tyres and worn bushings and bearings. Until I have replaced all of those I couldn't really start to consider altering my position and weight distribution on the bike.

I think tyres first followed by swingarm bush kit then steering bearings then forks and then test and take stock
I'd also like a fork brace like Hughs but I'd need to remove the mudguard for that and with our weather ...............

 

[peanut]

I run the Euro bend handlebars on all my bikes. The way they droop down slightly on the ends makes them extremely comfortable. They turn your wrists to a more natural angle than straight, flat bars. That droop also allows the angled Special MC to sit nicely, almost level .....

But I probably won't be running that stock MC much longer. I have a 1/2" bore MC from a Yamaha Vision in the wings to try out.

where did the 18" rim come from ? it looks much more balanced. i need to strip my wheels and relace them with some new spokes and clean up the rims. if i'm going to all that trouble maybe I should consider changing the rear rim from 16 to 18"

 

[wannabridin]

How'd you pass road/safety inspection with 12 year old tires? I thought y'all have more stringent requirements than us

 

[Jim]

I suspect that the instability is largely as a result of the tyres and worn bushings and bearings. Until I have replaced all of those I couldn't really start to consider altering my position and weight distribution on the bike.

That's sounds like a plan. I suspect your bike will behave just fine after you do that.