Author Topic: problem setting up stay up float level.  (Read 271 times)

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pockets

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problem setting up stay up float level.
« on: 25 May, 2022, 13:20:36 »
It seem that however much I tweak the float tangs to raise the fuel level it stays at below the recomended tolerances of between 4.3 and 6.3mm . its more like  6.7mm , is this possibly to do with the brass float needle as have read that they  suggest using an ally one as its lighter ? , I noticed that the tangs were originally set unevenly by previous fitter ,wonder if that was to accomodate the use of  the heavier valve.

ducati2242

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Re: problem setting up stay up float level.
« Reply #1 on: 25 May, 2022, 13:38:34 »
Is it possible that the float valves are too long maybe the wrong type for the carb .
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pockets

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Re: problem setting up stay up float level.
« Reply #2 on: 25 May, 2022, 14:53:11 »
its possible as not fitted myself ,  am going to get a friend to give me a hand to kickstart later and  if that fails  try  bump start it down a  gradient  , if that fails then will reasses , have kicked it over a good few times without ignition and plugs seem dry , dont understand as the carb tickles well ,  a bit confusing , will find out better if it doesnt bump start and the plugs stay dry , the comrpession seems good . getting frustrating now , it fires up then dies off ,  , may need just to set the choke correctly on starting. [Refer to my other postS for background].

spaceman

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Re: problem setting up stay up float level.
« Reply #3 on: 25 May, 2022, 15:28:25 »
Would it be possible to clarify what type of carb the bike has. I believe the bike dates to 1964 but this sounds like a Concentric carb rather than the original Monobloc?

Editor

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Re: problem setting up stay up float level.
« Reply #4 on: 25 May, 2022, 17:27:18 »
Amal changed to the Aluminium float needle for weight reduction as they found the brass ones were lifting later than desired due to being too heavy. Sounds plausible as the changed from the much lighter all nylon to the viton tipped brass to counter ethanol issues.

pockets

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Re: problem setting up stay up float level.
« Reply #5 on: 25 May, 2022, 19:52:46 »
Yes its  a concentric mk1 Amal. Also from what I've gleened the brass float needles    tend to seat under there own weight before the float has fully lifted making the fuel level in bowl lower , however i dont think the starting issue is related to the fuel level as when tickled it fills beyond the setting of the needle valve and would only run a little lean after starting if I'm not mistaken . It'll fire up and then cut out if I prime the pots with some fuel , have checked the jets and blown them out with carb cleaner and airline , but maybe theres a problem with it .Its sat for 18mnths without starting wondering if its a valve issue. running out of ideas.

spaceman

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Re: problem setting up stay up float level.
« Reply #6 on: 26 May, 2022, 08:42:00 »
Just to recap: this is a 1964 A65 Thunderbolt fitted with a Concentric carb?

I know you originally said the bike had been laid up for 18 months and I assume it was running ok at that point but it would be worth double checking the carb jetting. I assume this will have been done to suit a later Thunderbolt with a 230 main jet, 106 needle jet and 20 pilot jet and 3 1/2 throttle cutaway. Needle position is less clear with Haynes saying it should be position '1' but this depends which needle is fitted.

I's unlikely the float height will cause the bike to stop after a few seconds. The first question to ask is whether the bike is fitted with a choke. Tickling a carb is designed to get the bike to fire up but, depending on the temperature conditions, you sometimes need a bit of choke to keep it going until warmed up. On the other hand, if you use too much choke or keep it fully on for too long, it can cause problems.

If this is not a choke problem, it would be worth checking you have good fuel flow from the tank to rule out fuel starvation - removing the carb drain plug and carefully checking for good fuel flow out of it will rule out this being a cause of the problem.  The other thing worth checking is that the breather hole in the fuel filler cap is not blocked - the easiest way of checking this is to loosen the cap to see if it makes any difference.

If not a carburation issue, the problem could be electrical but worth ruling out the former first.

pockets

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Re: problem setting up stay up float level.
« Reply #7 on: 26 May, 2022, 11:39:55 »
The bike was running before  but not used much since the previous owner did a  unleaded conversion before my brother inlaw purchased it , think its only done 200 miles in 7years.   Is it true that the bike will not start if idle circuit is blocked , im convinced its fuel related plenty of flow to carb and yes it has a choke setup .[Amal concentric mk1 ]

spaceman

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Re: problem setting up stay up float level.
« Reply #8 on: 26 May, 2022, 16:32:13 »
I don't think a blocked pilot jet will stop the bike from starting unless you attempt to do it with the throttle fully closed. I believe that when you tickle the carb, this normally produces a rich mixture via the needle jet making it easier for the engine to fire into life.

The problems with kickstart bikes is that they will normally only start if everything is set up correctly. If you inadvertently flood the engine, this may stop it from starting. Although you need two people to do it safely, bump starting will give the engine a much better chance of firing up if the kickstart method doesn't seem to work. What's even better is to use a roller starter but this is not something most people have access to.

pockets

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Re: problem setting up stay up float level.
« Reply #9 on: 26 May, 2022, 18:43:04 »
Iv'e had another look at carb and cleaned the idle jet circuit with thin brass wire and it all seemed good, no obvious blockages and carb cleaner seemed to come out of all the correct places, also flattened all the gasket surfaces as they were a bit off wih glass and wetndry to get a better surface for gaskets , managed to set float level to around 5mm the float was rising unlevel so tweaked the arms  and that seemed to sort it , still running and then dying off and also kicking back sometimes , maybe timings off , have contacted bike shop earlier about the roller start as thought of this before reading your post and gunna book it in , if that doesn't get it going obviously some issue with it not just me flooding it on cold start.