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Post by oxfordshirejohn on Oct 30, 2021 16:39:15 GMT
A bit more work today. Reattach the carburetor to the engine, replace same back into the frame and reconnect the decompression cable. Need to sort out the throttle next. Altogether too much slack in the cable and insufficient adjustment at the carburetor, turned out that the adjuster had snapped of sometime in the past. Half was still in the carburetor cap, the other half lose inside the carburetor body. Will need to find or make another before any more progress.
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Post by oxfordshirejohn on Oct 31, 2021 17:53:48 GMT
Finding another throttle adjuster would probably take quite some time, if even at all. As the weather was not so good I decided I could spend sometime indoors making another being the simplest and quickest solution. One problem the thread of the original adjuster did not seem to correspond to any tap or die, metric or imperial that I possessed. It was however very close to 1BA, so re-taped the top of the carburetor and turned a new one to suit. Used a piece of 10mm stainless steel bar that was to hand, at least it won't go rusty.
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Post by JamesCentral on Oct 31, 2021 18:58:01 GMT
the thread of the original adjuster did not seem to correspond to any tap or die, metric or imperial that I possessed. Here's a handy thread table as a reminder that standards are such a good thing, we should have lots of them:
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johnt
New Member
Posts: 24
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Post by johnt on Nov 1, 2021 8:37:29 GMT
Now that really is useful. I wish I'd had that 20/30 years ago.
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Post by JamesCentral on Nov 1, 2021 9:34:57 GMT
I wish I'd had that 20/30 years ago. Strangely, it was 20 years ago that I found it in 'The Shed'.
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Post by oxfordshirejohn on Nov 1, 2021 16:01:07 GMT
Here's a handy thread table as a reminder that standards are such a good thing, we should have lots of them:
Very true, and that's not even all of them. Once upon a time before the EU or ISO every country in Europe had their own set of standards, something you soon find when trying to work on elderly continental machinery. But if you really want to confuse yourself try working on Morris (pre BMC days) engines that used French metric standard nuts and bolts with whitworth standard hexagon head sizes.
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Post by davwat on Nov 1, 2021 22:01:40 GMT
Here's a handy thread table as a reminder that standards are such a good thing, we should have lots of them:
Very true, and that's not even all of them. Once upon a time before the EU or ISO every country in Europe had their own set of standards, something you soon find when trying to work on elderly continental machinery. But if you really want to confuse yourself try working on Morris (pre BMC days) engines that used French metric standard nuts and bolts with whitworth standard hexagon head sizes.
and not that I know what I.m taking about here but model engineers have 32,40 and 60 tpi sizes.
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Post by oxfordshirejohn on Nov 2, 2021 9:10:08 GMT
and not that I know what I.m taking about here but model engineers have 32,40 and 60 tpi sizes.
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Post by oxfordshirejohn on Nov 11, 2021 15:48:38 GMT
A bit more progress, finish sorting the throttle cable, not of course straightforward (is it ever?). In the processes of removing it from the machine the little brass nipple at the handlebar end pulled off, them promptly rolled away into "never never land". Rather than order another and wait goodness how long for it to arrive I made a new one from a brass cheese-head screw, a bit fiddly, but didn't take too long. Throttle cable with home made nipple.
Also needed find another fixing screw for the the throttle itself as one was missing. Sent off for a NOVA and will follow up with date cert. request - having found the frame number under the paint on the nearside chain-stay.
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Post by oxfordshirejohn on Nov 13, 2021 17:23:04 GMT
With the throttle cable back in place and the carburetor refitted would it start? Well not before I found a way to keep the rear wheel of ground it wouldn't, you may remember I had bought a rear stand for it some while back and wondered at the time whether it would be up to the task of supporting the bike and rider. The short answer- despite the claims made for it- no it did not! OK for standing the bike up display or parking, but that's the limit of it's usefulness. Spent some time modifying a paddock stand - which are of course meant for full size motorcycles and are rather too wide for peddle cycles - into doing the job. Made up some two stroke petrol/oil mix and fill the fuel tank and with the bike with it's rear wheel clear of the ground it was time to try. Did it start? After quite some vigorous peddling and trying various throttle opening it made some encouraging pops and bangs, then suddenly bursting into life. Sadly not for long, after a short while accompanied with much blue smoke it stopped and then refused to restart. Clearly will need a bit more thought, but just enough encouragement to keep trying.
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Post by solexineScott on Nov 13, 2021 18:07:59 GMT
Keep at it. You’ll get there. I always find it’s not the destination, it’s the journey that’s the most satisfying.
Have you tried heating the spark plug with a blow torch, (the electrode end obviously!) then quickly popping it back in and trying it? I find that often works to get it running long enough to make adjustments and get the ‘juices’ flowing through.
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Post by oxfordshirejohn on Nov 15, 2021 15:50:28 GMT
Had another look at things today and once more the engine started and ran for a short while before stopping, then refusing to restart. I did however notice that fuel continued to drip out of the carburetor body, removing the top of the float chamber, cleaning out the needle seating plus insuring that the float did in fact "float" made no difference at all. Too much fuel in the chamber will of course effect the mixture which is probably not helpful . Also for want of a better word there is a brass rod atop of a spring alongside the float chamber which I'm guessing is some sort of fuel enrichment devise for cold starting although I don't see how it works. It does not depress the float as in some types of carburetors. I have not been able to find any information, or even a model number anywhere on the carb. body. Any ideas anyone?
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Post by JamesCentral on Nov 15, 2021 16:06:32 GMT
Also for want of a better word there is a brass rod atop of a spring alongside the float chamber which I'm guessing is some sort of fuel enrichment devise for cold starting although I don't see how it works. I think it's like a pump, press it and it squirts more fuel into the float chamber.
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Post by solexineScott on Nov 15, 2021 18:28:12 GMT
I don’t know the specific type of carb you have but I have noticed on some that it’s actually possible to install the float upside down. The float jet then stays open because the float chamber top pushes the float down when you screw it back on.
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Post by oxfordshirejohn on Nov 16, 2021 17:02:30 GMT
"I have noticed on some that it’s actually possible to install the float upside down."
True enough, but with this carburetor it's pretty obvious which way up it goes. the fuel valve is in the top of the float chamber plus the float needle has a sharp point at one end. However looking at it more closely I notice that the needle is slightly bent, so clearly that will need to be attended to first before I go any further.
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