Choke operation / cold start

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Mjolinor
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Choke operation / cold start

Postby Mjolinor » Thu Oct 11, 2018 8:02 pm

Should there be springs pulling the choke off on each carb or is it normal for the cable to push it off?

I cannot start this thing too well first thing, it is easier to bump it down my drive. I know (or think I know) that my starter is slow but even so it seems to whirr over fine but no start. It mostly starts if I turn it over, apply about half choke then turn choke off and keep whirring. Plugs are a good colour during normal running and it runs fine once started.

Putting the choke to off involves all three of my hands, one for each carb + throttle because the cable outers take up the space rather than the carb lever going off.

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Rob Frankhamr
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Re: Choke operation / cold start

Postby Rob Frankhamr » Thu Oct 11, 2018 9:12 pm

First assumption...

You have the choke lever arrangement which is 'native' to the bike, that is to say a lever on the left side of the air filter controlling the chokes via 2 seperate cables.

The cables fitted for this arrangement are a little unusual as the inners are single wires, almost rods. The purpose of this is so that they can apply a push to close the chokes... with multi strand cables, this just won't happen. There is no spring fitted, closure is solely by the positive pressure of the cable.

Later bikes with the lever on the left handlebar, use conventional cables and there are springs to return the choke arms.

It should be possible to adjust the choke cables so that the chokes are fully applied when the lever is in the full on position and fully off when it is in the off position. If this doesn't prove to be possible, then either the chokes themselves are sticky enough to prevent the closure or the cables are defective. Your comment 'the cable outers take up the space rather than the carb lever going off' seems to imply the latter.

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windmill john
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Re: Choke operation / cold start

Postby windmill john » Thu Oct 11, 2018 9:30 pm

Your choke cables are solid, if there is the slightest kink in them, they are hard to use.
Also the outer cable needs to be fully screwed in at the air filter lever. That’s great fun when you see the worm drive inside the choke lever.

Give them a strip, remove any kinks or new cables, grease them, job done; I’ll swap you that job for my timing chain...
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Re: Choke operation / cold start

Postby Mjolinor » Thu Oct 11, 2018 9:32 pm

Yes I have the standard arrangement. I set it up such that when the hand lever is horizontal (pointing towards the rear of the bike) both carb choke levers are fully down. When I put the choke on by pushing the hand lever down both carb choke levers go all the way up.

The problem then is that the outers are not fixed to the carbs or the hand lever so when I put the choke off the carb choke lever stays where it is and the outers come away from the carbs and hand lever. Possibly cables too tight but they seemed free enough before I fitted them. The only two solutions I can see are fit springs to the carb levers or fasten the outers to there respective location places on the carbs and hand lever.

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Re: Choke operation / cold start

Postby Roy Gavin » Thu Oct 11, 2018 11:13 pm

On my R75/7 the choke cables do not screw into the carb like the throttle, there is a clear hole with a nut top and bottom.
On the end of the cable there is what looks like an adjuster, but it is actually a ferrule which screws on to the end of the cable, so it is never intended to be turned.
If yours looks the same, slacken both nuts and see if you can screw the ferrule on to the end of the cable----.

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windmill john
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Re: Choke operation / cold start

Postby windmill john » Fri Oct 12, 2018 6:56 am

As Roy says. The ferrule drops in and out of the carb top and you rely on the two nuts for adjustment and positioning.
Last edited by windmill john on Fri Oct 12, 2018 10:39 am, edited 1 time in total.
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Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch - 1978-80 R65 - Has gone. No, not talking about it.
Max - 2009 F800GS- where’s the desert at!?
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Re: Choke operation / cold start

Postby Mjolinor » Fri Oct 12, 2018 7:32 am

My cable outer just sits in the carb. I will video the problem later.

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Re: Choke operation / cold start

Postby barryh » Fri Oct 12, 2018 9:39 am

Mine is the same as Roy describes The spiral wound outer cable screws into the ferule/adjuster on the carb. To make an adjustment you have to use the lock nuts. Turning the ferrule will just mess things up.

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Re: Choke operation / cold start

Postby Mjolinor » Fri Oct 12, 2018 10:32 am

What holds the outer into the hand choke lever?

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Re: Choke operation / cold start

Postby windmill john » Fri Oct 12, 2018 10:40 am

If I recall, it screws into the actual body of the lever. When you fit new inners, it's a faff putting the worm drive for both cables in the right place.
http://www.kittos.co.uk
Best roads: 623 Burgos to Santander. A back road to Metz; can't remember which!
Schorsch - 1978-80 R65 - Has gone. No, not talking about it.
Max - 2009 F800GS- where’s the desert at!?
Too many bikes have come and gone, trying to be sensible now!

Mjolinor
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Re: Choke operation / cold start

Postby Mjolinor » Fri Oct 12, 2018 10:43 am

Ah. Mine pushes in only, doesn't screw. Looks like a need for PTFE tape or a new lever. I have one of the adjusters missing on the carb too. No idea what to do about that, either find one or fix it with some other method. 3D printer to the rescue methinks or maybe araldite.

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Re: Choke operation / cold start

Postby vmx1200 » Fri Oct 12, 2018 11:29 am

Hi

Watch this video, the bit you want regarding the choke cables starts at 13 minutes, the bit about screwing on the barrels is covered very clearly

https://www.youtube.com/watch?v=5W90V8sZAgM

The whole set of videos are, in my opinion, excellent
1978 R100RS owned since 1981
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Re: Choke operation / cold start

Postby Mjolinor » Fri Oct 12, 2018 11:35 am

Ah, there's me problem. The video cleared it up.

I do not have any ferrules on the hand lever end of the cables.

I feel a dismantlement coming on. :)

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CaptAirhead
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Re: Choke operation / cold start

Postby CaptAirhead » Fri Oct 12, 2018 11:48 am

What a coincidence. After getting the old girl started up and running, the choke lever started to stick. Problem was that the cable outer would not screw into the lever body and kept coming loose. I went out this morning to sort the problem so took a couple of pics:-

Bing carb showing cables and adjusters:-

ImageBMW Airhead Bing Carburettor by Ian Beat, on Flickr

The naughty cable:-

Image1979 BMW R80/7 TIC. Choke lever and cables. by Ian Beat, on Flickr

I found a spare cable adjuster:-

ImageBMW Airhead Cable adjuster. by Ian Beat, on Flickr

Not sure if the problem is the cable outer or the lever so I will figure it out after I've had my cup or coffee but if you ( Mjolinor) want that spare adjuster, PM me your details and I'll post it down to you. No point in doing a bodge job.
Ian.
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Re: Choke operation / cold start

Postby Mjolinor » Fri Oct 12, 2018 11:51 am

Exactly my problem that. I may take you up on the offer but first I will go through all the bits I have left and have a closer look at it. Seeing you picture I tend to think I may have those two small lever end ferrules but the weather is certainly not good enough for me to go look at the moment.

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Re: Choke operation / cold start

Postby CaptAirhead » Fri Oct 12, 2018 1:11 pm

Problem solved. A bit of adjustment and some PTFE tape over the metal spiral sorted it. You may have a problem if the threaded ferrule thingies are missing from the lever. If you can't find them, Motorworks are good at supplying odd bits and pieces from their stock of used bits.
Ian.
If you don't make mistakes, then you aren't trying hard enough!

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Re: Choke operation / cold start

Postby Mjolinor » Fri Oct 12, 2018 4:45 pm

Ferrules are there so PTFE tape looks like the solution for that end or squeeze the outer slightly to make it oval so it stays in the ferrule.

All a tomorrow job I think or maybe later if the rain stays away.

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Re: Choke operation / cold start

Postby Mjolinor » Mon Oct 15, 2018 1:09 pm

PTFE tape solved the problem of the outers coming out but serious searching and I do not have the adjuster for one of the carbs.

If the offer still stands I will take the spare one. I will PM you if I can get PMs to work, I have had some problems of late doing that. :)

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CaptAirhead
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Re: Choke operation / cold start

Postby CaptAirhead » Mon Oct 15, 2018 3:55 pm

OK. No prob. If you can't get it to work, I'll PM my mobile number and you can text me your details.
If you don't make mistakes, then you aren't trying hard enough!

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Mjolinor
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Re: Choke operation / cold start

Postby Mjolinor » Mon Oct 15, 2018 4:11 pm

PM sent when I posted, if you aint got it then it didn't work. :)

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CaptAirhead
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Re: Choke operation / cold start

Postby CaptAirhead » Mon Oct 15, 2018 4:53 pm

It didn't work but I got your text.
If you don't make mistakes, then you aren't trying hard enough!

1979 BMW R80/7 (ex-Police)
2002 Yamaha Fazer 600

Mjolinor
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Re: Choke operation / cold start

Postby Mjolinor » Mon Oct 15, 2018 4:56 pm

Hmm. I think I can reply to one I have received but I do not seem to be able to send one to anyone for the first time.

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CaptAirhead
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Re: Choke operation / cold start

Postby CaptAirhead » Tue Oct 16, 2018 2:45 pm

If they persist in coming loose, as a last resort, perhaps a piece of shrink tube in addition to the PTFE might also do the trick.
If you don't make mistakes, then you aren't trying hard enough!

1979 BMW R80/7 (ex-Police)
2002 Yamaha Fazer 600

Mjolinor
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Re: Choke operation / cold start

Postby Mjolinor » Thu Oct 18, 2018 2:40 pm

Part arrived today. Much appreciated. :)


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