Smooth running

[Barry20383]

Am having problems getting the Javelin to tick over smoothly. It seems to be running too fast 1000 revs with the carb stops fully out. Should the timing be firing at TDC on tick over. Have set the carbs with a flow meter to balance them . Am thinking now to go back to the start set up as per manual and try again. The oil pressure is 50 at tick over and rising to 65 when reved is this correct or to high the oil is classic 20 60 should i reduce this to a classic 20 50
Thanks

[Keith Clements]

The most likely cause is that the butterfly valves are not properly set as I think you are using reconditioned carbs.
If you can see any light through the butterfly when holding the carb up to a strong light then undo the two set screws and reposition. Sometimes this is impossible to achieve due to worn barrel.
If you are using a flow meter then you should be able to shut each carb off with its stop fully retracted.
The engine will probably continue to run on one carburettor although it may not be smooth.
Set Ignition timing to TDC when static that is zero revs.
Oil pressure should be about 70 psi with oil at running temp and above 1000 rpm. But many run a lot lower than that but should be above 50 . It can safely drop to 10 psi on idle on a worn engine but I prefer it to be above 30. This upper pressure is set by the blow off valve. Your oil grade should be fine.

[bodgeman]

If we give the reconditioned carbs the benefit of the doubt , then it might be an idea to check the pintle valve and it's pipe work and unions. Check
both ends.Two and a connection under the oil filter, and the other end to the pintle valve, not forgetting the felt washer between the valve and the tube.
Start the engine and remove the oil filler cap. Be careful of the running fan belt and rotating waterpump , and stick you middle finger over the hole
in the valve. If the engine slows down then that might be the problem, or at least a contributing factor. Remove the valve and soak it in petrol or
thinners.

[Barry20383]

Still no joy tried everything today have taken off the oil filler cap and put my finger in the valve suction hole seems very strong vacuum and engine didn't flicker.
Have checked both carb air inlets with a syncrometer both are showing 10. Will this reading be there if the butterflies are closed. Checked the plugs after warming up the engine they are dark grey. Static timing set at TDS.
Fully opened stops on carbs engine still running at 1200 revs. I was wondering if JS made better balance rods as people have mentioned these if i could fit one with a new pull off spring and start the set up from scratch again.
Thanks

[Keith Clements]

This is what I previously said so flow should be ZERO when stops retracted.

If you are using a flow meter then you should be able to shut each carb off with its stop fully retracted.

But you do not need a flow meter. Just listen at each inlet stack. There should be no hissing on the one shut off but hissing on the side which is set properly.

[Nick Webster]

I am afraid I beg to differ with Keith and his suggestion you do not need a flow meter. Listening for the hiss will be a fairly coarse method of setting balance. Remember that each side of the Javelin is a mere 750 cc and the Zenith carb is not the most refined device known to man. In practical terms, air flow of zero will only be when the engine is stopped. The idle circuit bypasses the butterfly. Don't forget that the air flow measurement is merely a comparison, the value means nothing but must be the same for each side. I don't know which device you are using but there will surely be some kind of restrictor on it to enable you to put the indicator into some kind of range. Infact - with regard to the tiny flows involved - my very basic Gunson meter had to be retricted so much that at 750 rpm I struggled to get the pointer to come up beyond 1.5 on the scale without the engine threatening to stall. Worn balls on the throttle linkage will make balancing difficult and may even result in the butterfly being held slightly open. Likewise a badly adjusted choke link.

With regard to plug colour. All the old colour comparisons went out the window when leaded petrol was withdrawn. It is my personal opinion that you are better off with a slightly blacker colour, providing the engine is not running obviously rich. I prefer this because it shows combustion to be on the cooler side and currently available petrol in general burns hotter than suits most classics. Assessment should only be made with a plug that has been run around for a few miles under average driving conditions.

Crankcase valves are notoriously difficult to test because they are basically a two stage valve. Have you tried putting your air flow meter over the oil filler hole to see if the flow varies at different engine speeds? Your 1200 rpm tick over may be a bad starting point though. The trouble is that although the pressures the valve operates at are known, I have no idea what that relates to in engine rpm! My personal opinion (again) is that most problems attributed to the valve can be traced to dirty felts on the pushrod covers anyway.

Nick

[Forumadmin]

Nick,
The hiss will tell you if the carb is shutting off, particularly if you stick a piece of tube in your ear.
Quite frankly a flow meter is not as reliable as my ear for this, which you , I think, admitted in your response.
I have used a flow meter and a balancing manometer, but my ear and experience is pretty good at balancing the carbs. You can easily be misled by gadgets but by all means use them as a second opinion.
Having rebuilt a dozen pairs of Jav carbs, I can tell you the butterflies are very hard to get closing fully.

[Keith Clements]

Barry,
You can make sure the throttles are shutting off by disconnecting or releasing the clamp gland nut on the throttle linkage, then winding back the throttle stop screw on each carb in turn.
If this does shut off each carb but the idle is still too high then add springs on each carb. These springs need to be low to medium tension and be long so as to give closure when short but not too much pull when extended.
If the engine stalls when trying this, just wind the stop screw in on the carb you are not checking.
I always have springs on each throttle as a safety measure in case one comes off or the linkage comes off.

20210618_094239.jpg

Note this spring acts on the cable clamp not the butterfly spindle as there is no room on a Jav to fit the preffered way like on a Jup where I fit a plate to the rocker cover bolt to anchor the spring.
Often the need for a spring is evident if the fast idle reduces when pushing each throttle back with your finger, but mind that rotating fan!

20210618_094315.jpg

20210618_094154.jpg

You can also add springs on the choke to make sure they return.

These carbs fitted are 30vig with accelerator pumps as fitted to Jup.

[Barry20383]

Did check the butterflies on the recon carbs before fitting they seemed a good fit in the bores.The meter i am using
Is make ( Syncrometer ) for carb flow. The recon carbs came with new butterfly control lever balls.

[p.p.]

i hade in the beginning a big problem.... in the end i find out: the recon carbs hade a crack.... hardly to see... now i fit the old one and it works perfekt!! check it.....

[Keith Clements]

Peter, Worth saying where the crack was.
Barry, I realize this is a long saga and you are getting closer to a working machine. You might find after a few miles the butterflies will bed in and the fast idle will resolve itself. That said it may not be them that is causing the problem. So do the investigation and see if you can shut each carb off.

[Mike Allfrey]

Hello Barry,

In my experience, when using an air flow meter, the male and female portions of the throttle rod assembly must be completely free to slide individually.

In addition, make sure that the choke control is not holding the butterflies just slightly open.

The position of the throttle butterfly edge, on the side where the advance/retard port is located, is super-critical. I had one RHS carburettor modified because someone previously had botched the throttle spindle location in the carburettor body. $A800 later, all is well.

As an aside, when I was playing around with a pair of Solex carburettors from a Peugeot 404 on my Jupiter, I managed to reduce the idle speed to just on 450 RPM, but it had to be increased a little to cope with the clutch being operated. I am now running standard Javelin carburettors and all is well - when I can use the car, that is.

Keep well,

Mike A.