oldgreyandslow wrote:The fuel hose I have is the right ID but quite a bit larger OD, needless to say they didn't have the right size clip.

I suspect this won't cure the shite idle problem though

Nope somethings still not quite right. Have you balanced the carbs after having them cleaned out? This will give you a smooth idle.

See if any of the following havn't been checked properly.

As you are aware the engine cycle consists of

Induction - Compression - Ignition - Exhaust.

Lets have a look at what is involved in each component.

Induction

The fuel is drawn out through the various jets and passageways in the carbs and mixed with air to form an appropriate fuel/air mix for the air-speed.

Requirements:

This needs a complete set of clean jets and passageways. No air-leaks as this will affect the mixture.
The inlet valves need to open and close properly at the appropriate times.
The airbox and filter need to be clean and in-place.
The piston needs to have good rings in it in order to be able to create appropriate vaccum to suck in fuel/air mix.

Areas of Issue:

Vaccum leaks

The main point is the carb-rubbers. As you know applying a flammable liquid around the rubbers will reveal an air-leak.. make sure it isn't being sucked in by the 'snout' when working on the front carbs.

There are two other possible places that can leak vaccum. The carb balance take-off points, these are small screws with an aluminium washer on them, if there missing / loose they can leak vaccumn.

There is also the fuel-tank vaccum hose. This can leak / split causing poor fuel flow if the tap hasn't been modified and also a bad idle.

Compression:

The fuel air-mix is compressed by the cylinder before being ignited, this next stroke (ignition) sends the piston back-down generating power... the better the compression the more power you produce.

In order to have good compression you need a set of piston-rings that are in good working order and sealing against the bores well, you also need valves that are both opening and closing at the right position and sealing properly, otherwise compression will go down and power will go down too, as well as poorer induction due to loss of vaccum.

Ignition:

Poor / intermittent ignition on one or more cylinders will cause a lumpy idle. The igition system consists of the coils and plugs, pickup coils and ecu (TCI unit)

All of the specs are freely available to be able to test the coils, plugs are known to be fragile, a duff plug will give intermittent results and a choppy idle.. if a plug is suspect always try replacing it with a new one. (i've had problems with duff-plugs from new and spent hours overhauling carbs only to find it is the plug.

Can be made certain by replacing the plug then swapping it back, if problem appears / disappears then plug is at fault.

Another area often over-looked that can produce 'carb' like systems is the electrical system, the Ignition system needs a good working electrical system in order to have sufficient power to produce a spark. Dodgy electrics can also play up with the TCI box causing bad running.

Make sure the battery is in good working order and that the charging system is giving out correct voltages. Check all earth points and make sure they are clean and making good contact.

Exhaust

This cycle expels the waste gasses as a result of the other 3 cycles, the piston rings again need to be in good order to avoid blowback and oil contimation, as well as the valves opening and closing at the right time.

Final notes

It's 4:22am so i'm a little sleepy and may have omitted some things, but i've tried to cover everything I can think of, if somebody knows any-more bits then please add.

Carb balancing is best done after shim adjustment or messing with the carbs, vaccum gauges are the best way to get perfect accuracy, due to vaccum differences in the engine and air-paths cylinders will have slightly different vaccum rates at idle, which is why the drill-bit method is close but rarely spot-on. For peace of mind adjust all carbs until the vaccum gauges are within spec.

When setting the float heights have the carbs at a 35 degree angle.. make sure the float tang is resting on the little pin and not pushing it in else you will have a false reading.

Also after adjusting a float, invert and revert the carbs to reset the float and measure again to double check.

Great pointers thanks
valve clearances done
Carbs balanced by drill bit method
New reg rec and battery but I did notice the engine revs drop when I put the headlights on so I'll check the electrics again
Plugs are new, I'll check the leads coils etc
I'm hoping I can find something before I have to take the carbs off yet again

If, or when, its carbs off time I'll check the float heights for the third time! The jets are all new, emulsion tubes cleaned, 2.5mm holes drilled, not sure about needles they are the right ones in the right places though

Plenty to check - thanks

Are all 4 pipes getting hot? check at the same distance from the head on each one. If one is cold or takes noticably longer to heat up then you know which carb isnt right.
I think ive sorted my issue which sounds similar to yours, it turned out to be a faulty carb inlet seat/filter, the bit the needle valve sits in. What ever carb i swapped this into produced to problem. Not saying this is your problem but its worth a try

Drunkn Munky wrote:Are all 4 pipes getting hot? check at the same distance from the head on each one. If one is cold or takes noticably longer to heat up then you know which carb isnt right.
I think ive sorted my issue which sounds similar to yours, it turned out to be a faulty carb inlet seat/filter, the bit the needle valve sits in. What ever carb i swapped this into produced to problem. Not saying this is your problem but its worth a try

Thanks I'll add this to all the other shit to check,

This is pissing me off big style

Update: new fuel hose, no smell of petrol. Started it up from cold ran ok had to keep it on part choke for a bit then it ran ok ish, front piopes got warm very quickly the rears were still cool and took ages to warm up even when the water temp was nearly half way they were still only warm or cool eniugh to touch while the fronts were very hot. Tried spraying carb cleanerr around no change apart from front left, not sure if it was air or maybe cleaner on something else but the revs raced to 2500 and stayed there, drpped idle back to 1500 and it didn't do it again.
Also when throttle blipped it is slow to return and hangs about 2000 revs so I need to turn pilot screws in 1/4 turn, correct?

While at I checked batt volts all ok not above 14.6 v

So what do you reckon? I have run out of carb cleaner to check the air leak and also out of ideas!

Drunkn Munky wrote:.
I think ive sorted my issue which sounds similar to yours, it turned out to be a faulty carb inlet seat/filter, the bit the needle valve sits in. What ever carb i swapped this into produced to problem.

Tony,
Was your needle valve seating leaking [rich] or sticking [weak].

Dave.

Got more carb cleaner sprayed at front left carb rubbers and the revs rose to 2k fell back after a while so I sprayed some more but this time there was some cracking from the ht leads and the revs fell so is it an air leak or an ignition problem, or both?

Dave, I'm not sure mate. Revs were hanging so I assume weak. If I'm honest its still not what I would call perfect but its good enough for a test ride tomorrow

I found that the carbs can suck the carb cleaner through the snorkle when sprayed at the front left carb rubber so I wouldn't rely on it. If your confident its on well and clamped up then look elsewhere

oldgreyandslow wrote:Got more carb cleaner sprayed at front left carb rubbers and the revs rose to 2k fell back after a while so I sprayed some more but this time there was some cracking from the ht leads and the revs fell so is it an air leak or an ignition problem, or both?

sounds like the rear coil isnt working.

Swap the coils over and see if the pipes get hot in the reverse order