CaptCardboard's Quandaries and Questionable Repairs

[CaptCardboard]

The only real advantage to the BS carbs is the ability to go from sea level to 10,000 ft... which a VM will never manage.

Something I hadn't considered!
I almost exclusively exist at sea level, but I do enjoy rides up around Mt. Hood once in a while. What type of altitude range could I expect from VM carbs?

 

[Jim]

What type of altitude range could I expect from VM carbs?

Quick story....
Back in the '70's I was stationed in N. Mexico. Had a Yamaha R5C. Had the VM28's... 26's maybe... long time ago, not sure. Anyway...
Me and a buddy used to go camping up around Las Vegas... the one in N Mexico.... up in the mountains. Sometimes had others along. My bike was the "camping spot marker." We'd ride up trails into the mountains until my bike died.... wouldn't run enough to continue. That's where we'd pitch tents for the night.
Where we started in Clovis was about 3000ft iirc and my bike was tuned for that. I don't remember ever going above about 9,000ft before it refused to go any further. My buddy had a Honda 450 scrambler with CV carbs. It'd run just fine up where my VM's absolutely refused to work.

Break camp in the morning and I'd coast down until it'd run again. Was a couple of plug changes mixed in there iirc.... but the trusty ol' VM's didn't like running outside the zone they were jetted for.

 

[CaptCardboard]

I got gas in Clovis once...

Timberline lodge is at 6k feet, and I rarely go all the way up there. I'm gonna guess that I probably don't need to worry about the little adventure riding I do. I've yet to make it out that far with this bike anyway!

 

[Jim]

I got gas in Clovis once...

I got 20 bucks says the wind was blowing to beat the band while you were pumping?
Actually, that's a suckers bet, the wind ALWAYS blows there.

Sea level to 6,000ft is prolly doable... but just. I wouldn't let that hold you back from switching. Just make sure to carry extra plugs.... just in case.

I guess I should add too that the R5C was a 2 stroke. It's a lot more sensitive to altitude than our XS's are.

 

[member43148]

I’m in the “fix the BS 38’s” mind set for a few of reasons.
1 - you have them
2 - they are linked, and fit well with the stuff you have. (UNI’s ), single throttle cable.
3 - you can find parts here and jetting recommendations too
4 - I just like them
It’s your XS , I’d call it a “resto mod” and park it at SeeSee coffee proudly which ever way you choose

 

[member43148]

Timberline lodge is at 6k feet, and I rarely go all the way up there.

Best XS riding memories.. just pass the Timberline exit and run down the White River to Hood River early morning.
Beautiful curvy roads and scenery there

 

[CaptCardboard]

Best XS riding memories.. just pass the Timberline exit and run down the White River to Hood River early morning.
Beautiful curvy roads and scenery there

My favorite playground. I try to get as many day hikes, backpacking, and camping trips as possible up there.
When I'm too old to play drums and ride motorcycles, take me up to Mt. Hood, cover me in moss and leaves me there.

 

[CaptCardboard]

park it at SeeSee coffee proudly which ever way you choose

Also closed...

 

[JJames]

Best XS riding memories.. just pass the Timberline exit and run down the White River to Hood River early morning.
Beautiful curvy roads and scenery there
View attachment 329379

I'm jealous.

 

[member43148]

Moved 200+ miles east.
No riding like that over here. Just nice open skies

 

[Mailman]

Moved 200+ miles east.
No riding like that over here. Just nice open skies

And wineries?

 

[member43148]

Not much of a vintage motorcycle scene here at all. Harleys of course. Wineries yes.
Leash law ? lol na , pass (voice commands well)

 

[5twins]

I replace the Phillips screw in the clamps with an Allen. It tightens up much easier and better. The original screw is rather long, 25mm I think. You don't need it that long. I use an M5 x 16 or 20.

 

[CaptCardboard]

Well today was fun! I took my carbs apart again to see if I can't smooth things out a bit.
I found I didn't secure my slide to the diaphragms quite right and the right side (the bitchy side) slide had rotated nearly 180 degrees backwards. I reglued my slides and diaphragms, hopefully better than last.
I also took gggGary's advice and drizzled some wintergreen oil on my shaft seals before slathering em with silicone grease.
Put it all back together with new plugs and synced the carbs again. The damned thing hasn't run better in my care!
Fired up on the second kick. No more hesitation on the throttle! I'm still getting a couple little baby backfires once in a while as I decelerate in gear, but not loud pops every single time I slow down to a light. I suppose it could be that my absolutely cheapest possible vacuum gauges aren't reading quite right, but it's a quad set and I swapped the leads around between all four gauges to make sure they were balanced right. I'm thinking some tinkering with the mix screw might be in order at this point.
Either way it's not perfect, but at this point it's perfectly acceptable.

I also finally bought a 36mm socket to properly tighten my sprocket nut. Everything there went fine until I was finishing up and putting my foot pegs back on. Snapped one of the studs off.. dammit!

This, I feel, is a perfect hamhanded example on why the delicate work of disassembling and replacing my shaft seals may not be the job for me.

 

[5twins]

Rear axle nut is 27mm. The front sprocket nut is 36mm though.

 

[CaptCardboard]

Rear axle nut is 27mm. The front sprocket nut is 36mm though.

Yup. Words are hard. I edited my post to correct.

 

[5twins]

A couple other sockets you'll want/need are the 27mm, as mentioned, and a 22mm. The 22mm fits the front axle and the acorn cover nut for the cam chain adjuster. The 27mm, besides fitting the rear axle nut, also fits the oil drain plugs and the lock nut on the cam chain adjuster, which you probably don't have, lol. Unless it's been changed and "updated", your '78 will have the type "D" cam chain adjuster assembly. You should "upgrade" it to a type "E". For the "how" and "why", see post 22 in this thread ......

https://www.xs650.com/threads/cam-chain-tensioners.1056/page-2

 

[gggGary]

Footpeg stud can be repaired.
Not super fun but cut flush with the shoulder drill and tap run in a bolt with red locktite then cut it off to the length of the old stud.
Keep the hole fairly shallow 1/2" deep or so. a good fab shop could do that or a similar solution.

 

[CaptCardboard]

Unless it's been changed and "updated", your '78 will have the type "D" cam chain adjuster assembly. You should "upgrade" it to a type "E".

I already had a 22 and 27mm. The 36mm was the one I didn't already have.
My bike is a '75, and appears to have a type C tensioner with lock nut. I've been thinking I should pull the engine over winter to replace the cam guides and chain. It sounds like a common bit of maintenance the gets neglected. I've never done anything that in depth before, so I just keep thinking about it and we'll see how winter goes.

Footpeg stud can be repaired.
Not super fun but cut flush with the shoulder drill and tap run in a bolt with red locktite then cut it off to the length of the old stud.
Keep the hole fairly shallow 1/2" deep or so. a good fab shop could do that or a similar solution.

I figured I'd just lop the stud off and drill through it. Ill probably run a bolt through and crank it down tight. I don't understand why there's rubber bushings on the mounts and the acorn nuts don't hold the pegs right to the frame.

 

[member43148]

I don't understand why there's rubber bushings on the mounts and the acorn nuts don't hold the pegs right to the frame.

Vibration dampening to the feet.