Throttle feel

[Zombie Master]

I temporarily unhook the return springs on the carbs

There's always a smart ass with the correct answer.

Mechanic from hell.

[Zombie Master]

So I cleaned up the teeth on the throttle tube and disk, and same thing rough throttle.

With 65,000 klms on the bike should I really need to replace the cables?

If I just order the throttle tube and disk I can change that without pulling the tank again.

Finding these parts has not been easy so far. There is an upgraded (superseded) disc that requires the replacement of the cap, or the entire housing. But there is no instruction on where to measure the disc to see which version I have. Also I've seen a lot of NA's on parts lists.
Here is a shot of my throttle cable split-er. Rubber cover is ripped. Do these split-ers normally need replacing?

PXL_20210308_024843157 copy.jpg (406.16 KiB) Viewed 1682 times

[Rob Frankham]

I fear that the replacement gear and top will be required... I don't think BMW have supplied the old type for a long time. It's not a completely bad thing because there is a tab on the cover that fits into a groove on the twistgrip tube and holds the tube in place on the bar. This is also subject to wear and when it does, it allows the twistgrip to move outwards on the bar increasing wear at the gear.

As far as cables go, if they are smooth, unfrayed and the outers are sound, why change them? The life of a cable depends on a it's use and the care it's received. There is no set life. Examine them... if they're good, use them. Any replacement cables you get will probably have nylon sheaths on the inner cable. These can be a two edged sword. On one hand, you don't need to lubricate them so they are low maintenance, on the other you shouldn't lubricate them so they can suffer more from water ingress with the associated rusting issues and, when the nylon sleeves wear out (as they do), then they can be troublesome.

It's a good idea to change the rubber cover... it protects the adjuster and, to a certain extent, stops it from working loose. They are easy enough to source and you can probably get a perfectly satisfactory one from any bike parts store if you don't want to go BMW.

Getting the cables oput of the splitter can be a knack. On first examination, there doesn't seem to be enough play in the cables to allow them to be removed... however... the trick is this:

1) Loosen off the cable adjuster on the splitter as far as it will go.

2) Unscrew the cap and pull the twin cables out to the farthes extent. It's possible to do this with the cables connected but MUCH easier if they are disconnected at the twistgrip and the carbs.

3) Push the slide back into the splitter so that the single cable is protruding from it. The nipple should now be clear of the body. Move the end of the cable with the nipple sideways in the slot in the slide until the nipple is clear of the slide, then pull the slide out with the cable sliding through the slot.

Like most knacks, once you have done it once, it's easy.

Rob

[barryh]

There is a view that the throttle returns springs are in typical German fashion, too strong. Besides a heavier than necessary throttle action, I wonder if this also contributes to increased wear on the gears. Lighter aftermarket springs are available and might be a good idea if investing in new gears. I have reduced spring rates on mine.

[Zombie Master]

Thanx Rob great info as always!

Never though of lighter springs Barry. I will look into this. Thanx!

GSPD has shamed me into new cables. If they last another 37 years I should be good LOL

Think I will get rid of the throttle damper. I never used it anyway and I can see how it could be hard on the system.

My cap doesn't have the "bump up shown in this pic of the new model below.

I'm thinking black moly grease? I know....I think way too much

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[Zombie Master]

Installed new parts today and the rough throttle feel is gone.

I haven't changed out the cables yet. Will do that next just for a comparison.

Then on to tires.

Ordered from Bob's in Maryland, and received great informed service. Ordered on Friday and correct parts were on Vancouver Island on Tuesday.

[Zombie Master]

Installed the new cables and lubed the new splitter. I won't be needing lighter springs as it has a nice light feel, and smooth as silk. I'm looking forward to my free 10HP! Well.... not free

[Zombie Master]

Well I took her out for ride today, after a bunch of repairs and maintenance, the new throttle gear and cables are smooth as silk now, the bike feels like much newer machine. Definitely worth the effort. I adjusted my valves (4&8) and set the new cables by feel, so that they both open at the same time. I took a short 10 mm wrench along for the test ride, and never needed it to adjust the cables. It idles at 1000 rpm and seems to be smooth, slow speed manuvers requiring small throttle movements are fine. Is this result even possible without fussing about?

[Rob Frankham]

Possible is a big word. I would still want to put a pair of vacuum gauges on it. If it's spot on, then you've been lucky... and you'll know it's as good as it gets. If it isn't then it could get even better.

Rob

[gspd]

Is this result even possible without fussing about?

That's what happens when you listen to the mechanic from hell
You've had that bike for decades, and like your guitars, I'm sure your musician's ear would let you know if it wasn't tuned to perfection.
Chuck Berry's Maybelline sounded perfect, and I bet he only tuned her by ear.

I literally haven't used my vacuum gauges in decades, but they look good hanging on the wall.
Human ears can very easily detect "spot-on" when they know what to listen for.

My bike has 2 separate throttle cables, one to each carb, no splitter.
One of my cables was modified and has an adjuster where it exits the throttle assembly.
As little as 1/16th (a smidgeon?) of a turn either way from "spot-on" just off idle simply sounds HORRIBLY WRONG, even to the uninitiated.
As much as 1/4 turn either way at highway speeds makes no noticeable difference, even to a discriminating expert.
Trying to match vac gauge readings at higher rpm's with or without a load on the engine is an exercise in futility and simply does not work.
BOTTOM LINE: The only 'sync-ing' that matters is just off idle, just as the butterflies start to move. PERIOD