Author Topic: K1 start-up after carb rebuild, teething problems.....  (Read 1420 times)

Offline Andrew-S

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K1 start-up after carb rebuild, teething problems.....
« on: September 15, 2021, 09:20:50 PM »
Well, the K1 started up first prod after the carb rebuild, however when the choke leaver is down (fully open) then raised slightly it revs to about 3,000 rpm and when it's up (fully closed) it cuts out.  I've checked the opening throttle cable and it doesn't appear too tight and the return cable is doing it's job. It will idle at 1,000 rpm at a little before the lever is fully up. I haven't adjusted the idle thumb screw yet so will look at all the linkages and idle setting tomorrow

In the meantime, any thoughts or suggestions gratefully received.

Video: https://youtu.be/KjWbOuseLOs

Thanks,
Andrew
1972 UK XL250 K0 Motosport
1976 UK Z900 A4
2018 BMW R1200 GS

Offline McCabe-Thiele (Ted)

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #1 on: September 15, 2021, 09:57:26 PM »
Well, the K1 started up first prod after the carb rebuild, however when the choke leaver is down (fully open) then raised slightly it revs to about 3,000 rpm and when it's up (fully closed) it cuts out.  I've checked the opening throttle cable and it doesn't appear too tight and the return cable is doing it's job. It will idle at 1,000 rpm at a little before the lever is fully up. I haven't adjusted the idle thumb screw yet so will look at all the linkages and idle setting tomorrow

In the meantime, any thoughts or suggestions gratefully received.

Video: https://youtu.be/KjWbOuseLOs

Thanks,
Andrew

What you describe sounds like when I first had my 400/4 running - in my case I had inverted the situation in my head. When I pushed the choke one way I thought it was "more on" when in fact it was the other way around if you get my drift. The increase in revs was the fast idle cam,  normal running when warm  was off. I convinced myself it would only run when the choke was partially on in reality when I looked at the carb flaps it was off. My choke markings on the lever were confusing to say the least.

I could be talking rubbish - just shared my findings.
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Offline Andrew-S

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #2 on: September 17, 2021, 10:02:05 AM »
Thanks Ted, I shared your frustration in thinking 'on' was 'off' and 'off' was 'on'...... :o

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1976 UK Z900 A4
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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #3 on: September 17, 2021, 10:53:47 AM »
The 750 has no lift of throttles when choke is used as it just drops guillotine type plates down into venturi on airbox side.

Throttle modulation is entirely on twist grip and rider control, usually you've got to juggle just rich enough to run with choke lever against how much you hold slides open until warm enough to run off choke. Choke lever down and flat against the carb body for fully open, no enrichment.

If you need someone else to come round and scratch heads in unison  :) let me know as I'm not far and often going past near you.

Nigel.

Offline Andrew-S

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #4 on: September 17, 2021, 11:24:38 AM »
The 750 has no lift of throttles when choke is used as it just drops guillotine type plates down into venturi on airbox side.

Throttle modulation is entirely on twist grip and rider control, usually you've got to juggle just rich enough to run with choke lever against how much you hold slides open until warm enough to run off choke. Choke lever down and flat against the carb body for fully open, no enrichment.

If you need someone else to come round and scratch heads in unison  :) let me know as I'm not far and often going past near you.

Nigel.

Hi Nigel,

I'm going to have another look over the weekend, but failing that a head scratching session in unison would be most welcomed, thank you. :)

Andrew 
1972 UK XL250 K0 Motosport
1976 UK Z900 A4
2018 BMW R1200 GS

Offline Andrew-S

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #5 on: September 19, 2021, 02:07:26 PM »
The 750 has no lift of throttles when choke is used as it just drops guillotine type plates down into venturi on airbox side.

Throttle modulation is entirely on twist grip and rider control, usually you've got to juggle just rich enough to run with choke lever against how much you hold slides open until warm enough to run off choke. Choke lever down and flat against the carb body for fully open, no enrichment.

If you need someone else to come round and scratch heads in unison  :) let me know as I'm not far and often going past near you.

Nigel.

Hi Nigel,

I'm going to have another look over the weekend, but failing that a head scratching session in unison would be most welcomed, thank you. :)

Andrew

Yesterday I fired the old girl up after readjusting the throttle linkages and idle stop both static and whilst running and it was only running on 2 cylinders, sometimes just one. ??? I've Just came back in from the garage having checked there is a spark at the points, at all four leads, that fuel getting to 2, 3 & 4 and the valves are opening and closing, and it's a 'yes' to all those.

That's all the time I have for it for today, so tomorrow I will pull the plugs and see if their fouled and go for there. Thing is, it was running fine and sounding great first and last time I fired it up back in Jan 19, but it wouldn't idle hence the carb strip and rebuild:
https://youtu.be/8aL1cXomjuk

Cheers,
'Frustrated from Farnham'



1972 UK XL250 K0 Motosport
1976 UK Z900 A4
2018 BMW R1200 GS

Offline Andrew-S

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #6 on: September 20, 2021, 10:23:33 PM »
The 750 has no lift of throttles when choke is used as it just drops guillotine type plates down into venturi on airbox side.

Throttle modulation is entirely on twist grip and rider control, usually you've got to juggle just rich enough to run with choke lever against how much you hold slides open until warm enough to run off choke. Choke lever down and flat against the carb body for fully open, no enrichment.

If you need someone else to come round and scratch heads in unison  :) let me know as I'm not far and often going past near you.

Nigel.

Ok, so the plugs on 2,3 & 4 were fouled and no spark, but also the plug gap on No4 had increased to about 35 thou, strange?

All plugs cleaned and checked/regapped at 25 thou and it fired on all four pots, back-fired a few times then suddenly shot from 1000 to 4,000 rpm and stayed there so switched it off. Then on few restarts it fired up and stayed at 4,000.

I'm now thinking the carb bank will have to come off again...... :-\

Nigel, 
I may end up taking you up on your offer of a head scratching session in unison whenever is convenient for you and when you're nearby.

Cheers,
Andrew
1972 UK XL250 K0 Motosport
1976 UK Z900 A4
2018 BMW R1200 GS

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #7 on: September 21, 2021, 02:06:39 PM »
PM sent to arrange.

Most bits you can get to without removal that change settings, hopefully we can figure it out as is with a bit of creative analysis.

Nigel.

Offline Andrew-S

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #8 on: September 21, 2021, 02:29:30 PM »
Look forward to seeing you tomorrow Nigel - the kettle will be on and the Hobnobs opened!

Cheers.
Andrew
1972 UK XL250 K0 Motosport
1976 UK Z900 A4
2018 BMW R1200 GS

Offline Nurse Julie

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #9 on: September 21, 2021, 03:07:55 PM »
I hope you two chaps get it sorted, Hobnobs always help in the diagnostic process ☺️☺️☺️☺️
LINK TO MY EBAY PAGE. As many of you know already, I give 10% discount and do post at cost to forum members if you PM me direct.
https://www.ebay.co.uk/sch/julies9731/m.html?item=165142672569&rt=nc&_trksid=p2047675.m3561.l2562

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Offline Bryanj

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #10 on: September 21, 2021, 03:23:02 PM »
Oooh cant handle hobnods, too bitty! now dark chocolate digestives, that of course i never have cos my doctor tells me off

Offline Laverdaroo

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #11 on: September 21, 2021, 06:33:44 PM »
I'm with Bryan on the dark chocolate ones! or dark chocolate rich tea's. :o
Mornings are the invention of the devil!

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Offline Andrew-S

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #12 on: September 21, 2021, 10:07:50 PM »
I'm not grown up enough for dark chocolate, but I do also have milk chocolate digestives, Kit-Kats and chocolate mini rolls but of course these are only here in case my sons pop in........ ;)
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2018 BMW R1200 GS

Offline Bryanj

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #13 on: September 22, 2021, 08:11:07 AM »
Andrew, how can you not be old enough? ive preferred bournville since me teens( in the dark ages before anybody else sez it!)

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Re: K1 start-up after carb rebuild, teething problems.....
« Reply #14 on: September 22, 2021, 08:36:19 AM »
It's all ok, I'm accredited to war office standard in the removal and safe disposal  ;D of a whole range of biscuits.  It's a crunchy job but someone has to do it.

Draw the line at a Bourbon,  pre french revolution bourgeois manifestation of a biscuit. Also a Garibaldi, which surely can't be counted as a real biscuit   ;D

 

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