Triumph twin Strombergs...

[philcoyle]

Re: Triumph twin Strombergs...

As a casual observer, it looks to me as if carbs and manifold are mismatched. I cant see how the dashpot can lift when there is no drillings in the manifold to facilitate this.
All the carb faces suggest there should be a way of the depression in the manifold lifting the dashpot also the carb mounting plate shows holes to match the carbs but the manifold does not. The fact that you have run the engine on easy start administered through the air intake confirms that no fuel is getting past the carbs, as would be the case if the dashpots were unable to lift.
Is there a way you could lift the dashpots manually when you start the engine, in a way of mimicking the manifold depression lifting the Dashpots, its worth a try.

Is it possible the manifold was for S U carbs and not Strombergs

[David]

Re: Triumph twin Strombergs...

Back from Halfords, Easy Start in hand and it runs, https://youtu.be/VAtwVuDAKw8.

I checked the old carbs and they do have two holes on the inlet side of the casting but these were covered by gasket, see attached photo.

The 'new' carbs appear to have just one hole (I only checked one carb) and these are also covered with the new gasket and there's no matching hole on the manifold. It would make sense that if these holes were expecting to line up with holes in the manifold for some sort of vacuum or pressure to enable operation then that maybe the problem. But I'm out of knowledge now so will have to call the firm that built them tomorrow.

Final photo of the holes in the front of the carbs and that they are NOT covered up by the front plate, which has corresponding holes.

That's it for the day, I have to attend to the household list now to keep the brownie points topped up

[David]

Re: Triumph twin Strombergs...

Double checked timing, it's not 180 out (was running prior to carb replacement), I will check the spark again today but as I say this is all new kit (disci, leads, plugs, coil etc) that was running fine.

Checked the gaskets and in fact left the air filters off to be sure. I don't think there's a port on the carb to manifold side is there? I vaguely recall seeing a type of gasket for that location with a circular cut out on the ID edge, was that on very late cars, no port to match on the inlet anyway (worth me looking at today!)

Can't fit the old carbs now as I had to cannibalise one for good a part to replace a faulty part on the 'new' carbs.

Andy: No, no great smell of fuel but plugs are wet and smell of fuel. No attempt to fire at all.

So, this afternoon a few things to look at.

[h_m_cumming]

Re: Triumph twin Strombergs...

Hugh, that's not how you spell oblivious!

I'd had 3/4!!

[andyf]

Re: Triumph twin Strombergs...

When you turn it over with the plugs out you should be able to smell petrol escaping from the plug hole.

Is it making any attempt to fire? If you had a problem with the leads being muddled up or the dizzy being a long way out I would expect to hear pops and bangs as the fuel gets ignited at the wrong time.

[greyV8pete]

Re: Triumph twin Strombergs...

Thanks Peter,

All the electrics are working fine, sparks visible on all plugs when taken out and grounded on the head. I will check the voltage though, is it possible I see spark in daylight but there's none when the plug is in the cylinder? Or is it possible that there's 'not enough spark, not in my experiance?

No ballast resister on the setup as working previously.

Beer number two about to kick in.

A spark with the plugs in free air doesn't always guarantee a good spark under cylinder compression. I seem to remember reading that the spark should be really blue. If it's yellowish then not good. Maybe try substituting the coil for a known good one etc. Another thought. Did you remove the distributor? Has it been replaced 180deg out of register so every cylinder is trying to fire on the exhaust stroke say?

On a different tack I am not familiar with Strombergs as I had twin SUs on my old TR3A but looking at your original photos it seems that air can go through the top rectangular port, possibly feeding the diaphragm that controls the fuel jet metering needle? Is there any chance that the gaskets are on the wrong way up thereby blocking those ports? However if all is correct why not try fitting the old carbs temporarily. It seems strange that you don't even get the engine making an attempt to fire. Even with plug leads totally mixed up you would expect to get at least one of the pots trying to fire, or even backfire through the carb.

Time to finish the 6 pack! Peter.

[greyV8pete]

Re: Triumph twin Strombergs...

After beer 3/4 it should be obvious!!!

Hugh, that's not how you spell oblivious!

[h_m_cumming]

Re: Triumph twin Strombergs...

After beer 3/4 it should be obvious!!!

[David]

Re: Triumph twin Strombergs...

It's strange that you don't get any attempt to fire up. So back to the electrics. If you put a meter on the coil do you get 12v when you turn the ignition on? If yes do you get a voltage reading when cranking? I know it will be less than 12v but if no volts then check that it isn't wired for a ballast resistor / cold start system but with the ballast resistor, or wiring to it, open circuit. Just a thought. If all ok then report back and have another beer! Peter.

Thanks Peter,

All the electrics are working fine, sparks visible on all plugs when taken out and grounded on the head. I will check the voltage though, is it possible I see spark in daylight but there's none when the plug is in the cylinder? Or is it possible that there's 'not enough spark, not in my experiance?

No ballast resister on the setup as working previously.

Beer number two about to kick in.

[greyV8pete]

Re: Triumph twin Strombergs...

It's strange that you don't get any attempt to fire up. So back to the electrics. If you put a meter on the coil do you get 12v when you turn the ignition on? If yes do you get a voltage reading when cranking? I know it will be less than 12v but if no volts then check that it isn't wired for a ballast resistor / cold start system but with the ballast resistor, or wiring to it, open circuit. Just a thought. If all ok then report back and have another beer! Peter.

[David]

Re: Triumph twin Strombergs...

Forgive me if it's a stupid question, but I have been caught out many times by ignoring the obvious. With all the fiddling around with carb swaps etc, is the choke still working?

This is where I'm at now, the choke is connected and appears to be working but it's really the last thing to look at as everything else is just fine. As the rear carb had a sticking float chamber valve and plastic IN the float chamber it hasn't given me a lot of confidence that the other carb is 100% OK.

Easy start is a good idea Tony/Adrian, I will have to try that on Tuesday evening. Will also be calling the carb refurb guy to ask if it's possible somethings amiss with the choke mechanism. I suppose the Easy Start will give me some clue on that issue.

Summary video https://youtu.be/GJ6z9DxGYxI.

Day two, failed again, more beer needed.

David.

[dbazdavies]

Re: Triumph twin Strombergs...

Carb clean works as well to start engines too !!

[listerjp2]

Re: Triumph twin Strombergs...

Good call.

David if you want some, I have a can.

I know heritic.

Adrian

Oops just checked can empty.

Apologies for raising hope.

Halfords are open at ten, may see you there to get a new can.

Adrian

[listerjp2]

Re: Triumph twin Strombergs...

I know some people regard this as heresy or abuse but why don't you try some Easystart. If it goes with that then the problem is fuel if it doesn't then it's probably the ignition.

Good call.

David if you want some, I have a can.

I know heritic.

Adrian

[tony.branson76]

Re: Triumph twin Strombergs...

I know some people regard this as heresy or abuse but why don't you try some Easystart. If it goes with that then the problem is fuel if it doesn't then it's probably the ignition.