Tall shocks, chain clearance and tension, oh my

[kawabunga]

A couple questions for those who have pumped up their back ends.

I installed a set of 14.25" shocks on my XS and am running into some chain clearance and tension issues.
Prior to installing them, I did a bunch of searching to find out if there would be any problems to address with it, but didn't really find definitive answers. Just a post here and there, so here I am.

First, I adjusted the chain according to the book stating 3/4" slack above the swingarm.

When the suspension is fully extended (on center stand) the chain rubs the swingarm by the pivot.

Put the bike on the kickstand, the chain just barely touches the swingarm now.

With me sitting on the bike, the chain now clears the swingarm. But, it's craaaazy tight. Like, no play in the chain.

I can think of two options to address the clearance issue. Either come up with some sort of chain slider or install larger front and rear sprockets. Or both. I currently have 16/34 gearing. 17/34 is stock from what I've found. Is that correct for a 1979 XS-F? Would bumping things up to 17/37 give me enough clearance? Or is there not much to be gained with larger sprockets? What about going crazy with a 18/39...?

As for the tension, what's up there? I'm guessing the chain tension is being set when the swingarm is below the point that the chain is at its tightest. I can see this potentially leading to binding issues. Will the chain loosen as the swingarm goes through the rest of its travel? I need to get some extra weight on the bike and see what the chain does. What should I be doing for chain tension here? Leave it at 3/4" or increase the slack?

I know I'm not the only one that has run 14.25" shocks, I saw the posts. But nobody really seemed to report problems. Any advice for this?

Thanks

 

[fredintoon]

A couple questions for those who have pumped up their back ends.

I installed a set of 14.25" shocks on my XS and am running into some chain clearance and tension issues.
Prior to installing them, I did a bunch of searching to find out if there would be any problems to address with it, but didn't really find definitive answers. Just a post here and there, so here I am.

First, I adjusted the chain according to the book stating 3/4" slack above the swingarm.

When the suspension is fully extended (on center stand) the chain rubs the swingarm by the pivot.

Put the bike on the kickstand, the chain just barely touches the swingarm now.

With me sitting on the bike, the chain now clears the swingarm. But, it's craaaazy tight. Like, no play in the chain.

I can think of two options to address the clearance issue. Either come up with some sort of chain slider or install larger front and rear sprockets. Or both. I currently have 16/34 gearing. 17/34 is stock from what I've found. Is that correct for a 1979 XS-F? Would bumping things up to 17/37 give me enough clearance? Or is there not much to be gained with larger sprockets? What about going crazy with a 18/39...?
As for the tension, what's up there? I'm guessing the chain tension is being set when the swingarm is below the point that the chain is at its tightest. I can see this potentially leading to binding issues. Will the chain loosen as the swingarm goes through the rest of its travel? I need to get some extra weight on the bike and see what the chain does. What should I be doing for chain tension here? Leave it at 3/4" or increase the slack?
I know I'm not the only one that has run 14.25" shocks, I saw the posts. But nobody really seemed to report problems. Any advice for this?
Thanks

Hi kawabunga,
like you say, fit a teflon block like on a dirt bike because those over-length rear shocks force the chain to rub on stuff at full extension
and effin' around with different sized sprockets ain't gonna fix it except if you go to a ridiculously large rear sprocket.
(Which could work OK if you spent a fortune on importing a lower ratio primary gear-set from Australia)
17/34 is stock gearing for North American XS650s except my '84 Heritage Special came with 17/36. Which is about the same ratio
as your 16/34 and is just about perfect for sidecar use. FWIW, I briefly ran my sidecar on 17/38; rode like it had 4 speeds + underdrive.

 

[Signal]

Adjust the chain so that with you sitting on the bike you have around 20mm of slack in the bottom run of the chain.
The method you describe to adjust the chain on the centre stand your chain will be tight.

With the chain adjusted correctly do you still have a problem?
If you do you can fit a larger rear sprocket a 16 tooth front is available (from Worlds end Motorcycles) so you can run a larger rear and a UHMD plastic slider on the swing arm if needed.

Why did you go so long on the rear shocks?

http://www.xs650.com/threads/max-rear-shock-length.51823/#post-545501

For suspension set up Grizld1 has posted a good start point for these bikes, I have copied it and it was happy enough to leave it as he suggested.

 

[gggGary]

It's a pain to set slack properly sitting on the bike AND adjusting the axle LOL. I've got to do that today on the bandit, just put on a new tires. I've never run a 16 front. That's gotta be at least part of the issue. I'll do some measuring of madness and resto, they both have longer aftermarket shocks but I'm not sure of length. Madness has a rub block, resto doesn't.

 

[kawabunga]

like you say, fit a teflon block like on a dirt bike because those over-length rear shocks force the chain to rub on stuff at full extension and effin' around with different sized sprockets ain't gonna fix it except if you go to a ridiculously large rear sprocket.
(Which could work OK if you spent a fortune on importing a lower ratio primary gear-set from Australia) 17/34 is stock gearing for North American XS650s except my '84 Heritage Special came with 17/36. Which is about the same ratio as your 16/34

I have found up to an 18F and a 38R readily available. If I went to 17/37, it would be basically what I already have for gearing at 16/34. 18/38 would be close as well, a touch more top end though. I just wonder if going from a 16 to 18 front and a 34 to 38 rear will actually yield meaningful clearance between the chain and swingarm. I'll probably need a slider either way so is it worth spending money on it...?

Adjust the chain so that with you sitting on the bike you have around 20mm of slack in the bottom run of the chain. The method you describe to adjust the chain on the centre stand your chain will be tight. With the chain adjusted correctly do you still have a problem?

Why did you go so long on the rear shocks?

Thanks for the adjustment tip.

Reason I went to such tall shocks was to level out the bike. I went with Progressive Suspension components. I was planning on just going to 14" but they only had a eye-to-clevis available as a 12-series at 14", had to go to 14.25" to get an eye-to-eye 12-series.

I'm quite happy with how the bike sits. I have yet to ride it. Doing bounce test in the garage I'm already thinking I'll need to do something to stiffen the front end but we'll see.

Stock rear shocks.

Progressive Suspension 12-series 14.25" shock with 75/120 rate springs.

I've never run a 16 front. That's gotta be at least part of the issue. I'll do some measuring of madness and resto, they both have longer aftermarket shocks but I'm not sure of length. Madness has a rub block, resto doesn't.

That would be great, Gary! Would you mind sharing what you did for chain slider? Perhaps some photos so I can get some ideas stirring up. Would appreciate it very much.

 

[gggGary]

Ok went and looked both bike's shocks are 12 3/4" eye to eye and that seems like a good number to me. With low profile 18's FRONT and rear the steering is plenty steep for street use. Just stable enough. IE induce a wobble and it won't self cancel. I moved the 110/70/18 off resto and put a 100/90/19 back on, it was noticeably more stable ( read not quite as flickable.) you can see the guide in there on the custom arm on madness. Not long ago someone here detailed fitting a guide to a standard swingarm.

 

[kawabunga]

Excellent, thanks Gary! My stock shocks measure 12 1/2" eye to eye so you're not far from stock. I've got a 19/16 for wheel sizes. We'll see what this setup does to my steering.

In other news, in doing more digging, googles lead me to these chain guide/slide solutions.
http://www.xs650.com/threads/final-drive-chain-guide.50536/
http://www.xs650.com/threads/made-my-own-swingarm-chainguide.11083/

Some good ideas out there. Looks like sourcing some delrin is in order.
I found one guy that said he super glued a slider to the swingarm...that doesn't sound like it would hold. Are most people drilling and tapping the swingarm to affix the slider with a countersunk bolt?

 

[5twins]

I'm pretty sure around 12 3/4" is about the stock shock length. I run about 13 1/3" shocks on mine (340mm actually) and they're fine. An 18" rear wheel would raise the rear end a little too. Yes, definitely change back to a 17T front sprocket. What are you gearing for, stump pulling?

Even with stock length shocks and stock gearing, chain clearance is close at the swingarm pivot. The grease seal on that side is chewed up on every one I've ever taken apart. Yes, you must sit on the bike and check the chain tension after an adjustment, it gets tighter. You should also roll the bike around and check it in several different spots. Chains stretch unevenly and will have tight and loose spots. You want to make sure you haven't set it too tight at one of the tight spots. If you run your chain adjusted too tight, it will stretch out prematurely.

 

[fredintoon]

It's a pain to set slack properly sitting on the bike AND adjusting the axle LOL. I've got to do that today on the bandit, just put on a new tires. - - -

Hi Gary,
save yourself from suffering by compressing the rear suspension to ride height with a ratchet-strap running from one side of the swingarm.
across the bike seat and down to the swingarm's other side.

 

[fredintoon]

I have found up to an 18F and a 38R readily available. If I went to 17/37, it would be basically what I already have for gearing at 16/34. 18/38 would be close as well, a touch more top end though. I just wonder if going from a 16 to 18 front and a 34 to 38 rear will actually yield meaningful clearance between the chain and swingarm. I'll probably need a slider either way so is it worth spending money on it...? - - -

Hi kawabunga,
nah, don't waste your brass on sprockets that don't give you good ratios.
18/38 is just about the same as 17/36 and as posted, that's sidecar gearing.
Also running an 18T up front don't leave enough clearance to run an O-ring or a heavy duty chain
(& I got the shifter shaft gnaw-marks to prove it) so you are stuck with running normal chain instead.

 

[txrenegade]

I've been down this road by putting 16.5" shocks on my XS. With some slight modifications to a YZ450 chain slider, I cured the problem on the top of the swing arm. Because my swing arm is also stretched and under-braced, I then had to address the clearance below also. I made up a mount and with a wheel bolted to it that mounts to an engine mount. This not only solved the rubbing problem on the brace for the swing arm, but because it is rigid mounted, it effectively moved back the pivot point make the slack issue pretty much non-existant.

 

[kawabunga]

Beautiful bike, txrenegade! I'm heading down a similar road with my build so that really helps.
The sprockets on these things are little.

Thank you for sharing your solution. I was thinking a modified dirt bike chain guide might be a viable solution. I'm between either that or a chunk of delrin/UHMW, drill and tap the swingarm, and counter sink a bolt to hold it on.

 

[Signal]

I was offered a choice of white or black material to make the slider out of next time I will go for black.
White looks good at first but with use soon looks shabby if you can get the black stuff.

 

[kawabunga]

Fer funsies, I gave the chain adjustment another shot. I'm probably going to go with different sprockets regardless, the ones on there should probably be replaced anyway. I got the bike with the 16/34 setup and have no experience riding a stock XS650 so I have nothing to compare it to. I'm thinking 17/36, see how that goes. Should give me some extra chain clearance, close to stock with a little extra bottom end, I like wheelies.

As for the adjustment, I loosened everything up and stacked roughly 150lbs of sand bags on the bike. That's not quite my weight but I'm just experimenting at this point.

I set it to 20mm of slack and tightened everything down.

With no weight on the bike the chain is super sloppy. Just like a dirt bike. It rests on the swingarm. However, when I sit on the bike it tightens back up to roughly 20mm slack (guesstimating since I'm sitting on the bike, nothing exact yet).

With weight on the bike after the slack adjustment, the chain is sitting like this.

I was originally thinking a little chunk of delrin up by the pivot point of the swingarm, but I'm leaning towards a dirt bike chain guide/slider now. Like the kind that txrenegade suggested. Mainly because the chain can easily come in contact with the swingarm much further back than just the pivot point. About 8" back is where it touches again.

I could probably source some delrin close to what I need and shape it accordingly relatively easily, but this is already shaped how I need it (close enough anyway), long enough to cover both points of contact and it's made specifically for this type of use. Modifications are needed either way, and this one has a nice channel and taper built into it.

 

[kawabunga]

After doing more digging on gearing and finding a lot of people saying that stock is pretty low to begin with, I'm just going to go back to stock gearing for now.

The front sprocket needs to be replaced, the rear really isn't that bad after looking at it again. Since I need to add a chain slider anyway, putting bigger sprockets on to gain clearance doesn't really add value.

 

[5twins]

Yes, most of us change the gearing slightly. By slightly, that means 1 or 2 teeth on the rear. Most of us leave the front alone. Personally, with my 18" rear wheel, I like the 17-33 combo. It's only a one tooth change from stock but it makes a nice difference. But keep in mind, your 16" rear wheel is slightly smaller in diameter and that equates to about a tooth in sprocket size. A 32T on your 16" wheel will be nearly the same as a 33T on an 18" wheel. Here's a chart showing the common sprocket sizes used .....

 

[kawabunga]

I wanted to follow up with my solution to my chain/swingarm interference issue after I installed 14.25" rear shocks.

I ordered a UFO chain slider for an '08+ Yamaha YZ450F, also listed to fit many other Yamaha dirt bikes like the YZ125 and 250.

I then cut it in half, separating the top from the bottom, since there's no need for the bottom portion.

I then held it in place by hand, rotating the wheel a few times to see where the chain naturally wanted to fall on it to find the best mounting location. The slider also has a curve on the front that naturally sits on the front of the swingarm so I used that for my fore/aft placement.

On top of the chain.

Under the chain.

I then marked, drilled and tapped a hole in the swingarm for the front mounting hole. I believe I went with an M5.

With that done, I was able to lightly tighten the front mount down to find a natural home for the rear mount since it was going to be on a rounded area of the swingarm. I then tapped a hole for that.

With mockup hardware in place, here how it sits. It works very well and looks pretty sharp.

I plan to get button head screws so they sit a little more flush and tidy. With no weight on the bike, the chain rides on the slider nicely and with me on the bike it barely touches the very front of it. I'm very happy with how it turned out.

I hope this helps anyone else with similar issues. Thank you all for the suggestions.