4a. Won’t start after full rebuild. Any ideas what to check next pse?

[gloide69]

Check there is no air leak at the carbs, I think the spacer orientation could be important.

[Steven Whitaker]

13 hours ago, BlueTR3A-5EKT said:

Is the black tube on the adaptor in the rear part of the inlet manifold balance tube blanked or breathing to atmosphere?   Needs to be blanked and air tight.

Yes I blanked it off.  Thanks.

[Steven Whitaker]

56 minutes ago, gloide69 said:

Check there is no air leak at the carbs, I think the spacer orientation could be important.

Will do,  ur all nipped up tight with spacers and gaskets in place.  Thanks.

[Steven Whitaker]

5 hours ago, Lebro said:

If it cranks over then the earth connection is ok. My first thought was ignition timing.

Bob

It cranks.  Out of interest, can you watch the video I uploaded showing it cranking?  Thanks Bob.

[Steven Whitaker]

4 hours ago, Michel Higuet said:

To see if the motor can talk inject a little of START PILOT if it don't talk think "ignition" if it start running and direct stop think "carburation". (On the third pics the fuel is empty but it was taken before filling the little tank or the it was not yet open I suppose ).  

Thanks.  I’ll order some easy start.  Cheers.

[Steven Whitaker]

4 hours ago, Rob Salisbury said:

This usually works for me with a reluctant engine, take all the plugs out, spin the motor with one of the plugs earthed to see if you have sparks, then spin the motor for a few more seconds with the throttles wide open to get some fresh air into the cylinders,  with a funnel put a few mls of petrol into each cylinder, put the plugs back in and see if the engine will run, if it doesn't run then ignition or valve timing is the problem,  if it runs and stops then fuel is the problem.                                                                                           Cheers Rob

Thanks for your suggestions.  I’ll try them.  Strange thing is neither altering the choke or throttle seems to make any difference to proceedings?  I rebuilt the carbs and never done it this job before.  Wonder if I got them wrong.,,!  Plugs are dry.

Edited November 20, 2023 by Steven Whitaker

[Steven Whitaker]

4 hours ago, iain said:

Is part 34  Driving Gear Inserted 180 out? Dizzy will line up with the offset drive slot but still be wrong. Easy to check move you leads round in the cap by 180 degrees. 

That’s a good question!  Is there a right and wrong way?  I’ll have a look.  But first I’ll swap the leads as you say.  Will report back when battery has recharged!  Cheers,

[Steven Whitaker]

2 hours ago, BlueTR3A-5EKT said:

If you lot won’t say it…..

Ha ha.  Like it.  Ordered!

[Steven Whitaker]

2 hours ago, Bfg said:

Excuse me if I'm mistaken but from the video it appears, from the angle of the lift quadrants on the carb's linkage rods, that the choke is not on and you are not even blipping the throttle.  From cold my car's engine will not start without these.

Pete

p.s.  If I might also suggest ; the in-line fuel filter is the wrong way around.  It is more usual is for the fuel pipe feed to go into the clear bowl side of the filter, so that you can see if there is a blockage around the outside of the paper element.  The way around yours is would takes any blockage or sediment inside the paper element, which is then not visible.  Most likely this will not be the cause of the engine not starting from a motorcycle petrol tank, but it is worth reversing for everyday use especially if the fuel tank has been disturbed during restoration and paint.   Fuel feed from a small capacity motorcycle fuel tank petcock (possibly with filter inside ?) may be a bit limited for much more than starting the engine.  

Hi Pete.  You are right.  I’m not trying either on the video.  Neither adjusting the throttle or the choke makes any difference.  Tried all combinations.  Plugs dry even after trying to start several times.  I’ll swap the filter around.  There’s fuel in the float chambers.  I’m baffled, but have new things to try now, cheers.  

[Steven Whitaker]

Just want to say a huge thanks to everyone so far for your advice on what to try next.  This is a first for me so I’m on a steep learning curve.  Cheers all.  Wish me luck for tomorrow afternoon when I have a few more hours in the garage.  

[stuart]

If you have spark then just try tipping some fuel into the carb mouths,

Stuart.

[BlueTR3A-5EKT]

Simple question.

how will you stop the engine when it starts?     In case there is an issue like no oil pressure, rattling noise, oil or water leak.

[rcreweread]

1 hour ago, stuart said:

If you have spark then just try tipping some fuel into the carb mouths,

Stuart.

+1 but don't put too much in - I typically fill up the cap from an oil can and pour into each carb mouth - some of it usually spills so have a wet towel handy in case it spits back and sets fire to the excess petrol so you can quickly douse it - if it fires and runs for a few seconds before stopping, you will then know you have a fuel supply issue.

Have you tried priming the carbs with the fuel pump lever - if all is quiet, you can usually just hear the fuel flowing from the pump through the pipes -  what sort of pump is it? An original AC Delco unit or a repro or have you gone electric?

Also do everything one at a time so you will know exactly what the problem issue was when it eventually runs.

Good luck and keep us posted!

Cheers Rich

[Steven Whitaker]

4 hours ago, BlueTR3A-5EKT said:

Simple question.

how will you stop the engine when it starts?     In case there is an issue like no oil pressure, rattling noise, oil or water leak.

I have a switch on the live from the battery to the coil.  Failing that I have isolator on the battery to earth.

[Steven Whitaker]

2 hours ago, rcreweread said:

+1 but don't put too much in - I typically fill up the cap from an oil can and pour into each carb mouth - some of it usually spills so have a wet towel handy in case it spits back and sets fire to the excess petrol so you can quickly douse it - if it fires and runs for a few seconds before stopping, you will then know you have a fuel supply issue.

Have you tried priming the carbs with the fuel pump lever - if all is quiet, you can usually just hear the fuel flowing from the pump through the pipes -  what sort of pump is it? An original AC Delco unit or a repro or have you gone electric?

Also do everything one at a time so you will know exactly what the problem issue was when it eventually runs.

Good luck and keep us posted!

Cheers Rich

Thanks Rich.  Gravity is my pump!

[roy53]

Have you tried fuel directly into the carbs as suggested? You should at least get a firing 

as mentioned dizzy drive part 34 can be put in 180 out

i think fuel is your problem 

manually hold the choke open when trying and pump throttle 

Roy 

[Michel Higuet]

18 hours ago, BlueTR3A-5EKT said:

Simple question.

how will you stop the engine when it starts?     In case there is an issue like no oil pressure, rattling noise, oil or water leak.

First prime the oil  see at 17.02

 

[Michel Higuet]

19 hours ago, Steven Whitaker said:

Hi Pete.  You are right.  I’m not trying either on the video.  Neither adjusting the throttle or the choke makes any difference.  Tried all combinations.  Plugs dry even after trying to start several times.  I’ll swap the filter around.  There’s fuel in the float chambers.  I’m baffled, but have new things to try now, cheers.  

Plugs dry,  seems it is a carburation problem,  have you check when starting if there is vacuum in the venturi ( the inlet of the carbs ) otherwise fuel will never climb, a vacuum gauge could be interesting to place on the inlet screw in the manifold.

[Bfg]

On 11/20/2023 at 12:11 PM, Steven Whitaker said:

Hi Pete.  You are right.  I’m not trying either on the video.  Neither adjusting the throttle or the choke makes any difference.  Tried all combinations.  Plugs dry even after trying to start several times.  I’ll swap the filter around.  There’s fuel in the float chambers.  I’m baffled, but have new things to try now, cheers.  

Just a long shot but I'd suggest you temporarily pull the fuel pipe off the carb and lead it into a clean jar or pot, to then check the free flow of fuel from the motorcycle tank, down the pipe and through the filter.  A trickle of fuel may be getting through under gravity, which fills the float bowls, but perhaps not enough for starting.  I wonder if the (wrong way around ?) filter includes a one-way anti back-draining valve. ? or whether the petrol tanks vent is blocked. There may be a piece of the pipe that's collapsed or blocked with a foreign body.  Laborious perhaps but, re-running through each element in a back to basics systematic manner, to check / eliminate from suspect ; (richer to start) Fuel feed, Spark, Compression, Valve and Ignition Timing.., will reveal the issue. 

It's unlikely with professionally rebuilt carburettors but another item to check is the float level. These carburettors rely on a correct fuel level within the bowl, so that the venturi (low pressure) doesn't have to lift the petrol very high to the jet.  This would happen if the float bowl is sitting too low.  Shown below is how to check ; Remove the float bowl cap and invert so gravity shows the float level relative to the rim when the fuel feed valve is closed. Repeat for both carburettors . . . 

Hope this helps and you get to the bottom of the problem soon.

Best regards, Pete

 

below the fault finding chart from 'SU Carburettor Tuning Tips & Techniques' Brookland books, which I'm led believe is a reprint of G.R.Wade's book.  

NB. Although there are many useful items of information in this book - it is exceptionally poorly written and equally as badly edited and published. As a consequence, it is very much more confusing than it ought to be and with great superfluity.  It needs to be rewritten, this time with a proof reader..  In all good conscious I cannot recommend it. 

 

[Steven Whitaker]

So another session on the car tonight.  First I checked the float levels and both at 4mm so that’s in tolerance.

Next I put a new fuel filter on, this time the other way around.  Fuel is flowing without question.

Next I took the carbs off to check everything was ok and I cannot see an issue.  I rebuilt these with new chokes and needles.  All seems as per the SU manual.

Next I tried to start it and no difference, but it did try a little.

Next I swapped the plug leads by 180 degrees but it doesn’t even try that way.

Each time I tried to start, I had the choke fully on.  I varied the throttle but to no avail.

After about 3 hours of messing and trying, I checked the plugs and they are all dry.  I tried some easy start in the carb mouths but made absolutely no difference even with the chokes on.

Im at a loss now.  I think the only thing I can check now is valve timing.

Losing the will now.  Pesky thing.  I wonder if it’s a diesel ha ha.

 

 

[Steven Whitaker]

8 hours ago, Bfg said:

Just a long shot but I'd suggest you temporarily pull the fuel pipe off the carb and lead it into a clean jar or pot, to then check the free flow of fuel from the motorcycle tank, down the pipe and through the filter.  A trickle of fuel may be getting through under gravity, which fills the float bowls, but perhaps not enough for starting.  I wonder if the (wrong way around ?) filter includes a one-way anti back-draining valve. ? or whether the petrol tanks vent is blocked. There may be a piece of the pipe that's collapsed or blocked with a foreign body.  Laborious perhaps but, re-running through each element in a back to basics systematic manner, to check / eliminate from suspect ; (richer to start) Fuel feed, Spark, Compression, Valve and Ignition Timing.., will reveal the issue. 

It's unlikely with professionally rebuilt carburettors but another item to check is the float level. These carburettors rely on a correct fuel level within the bowl, so that the venturi (low pressure) doesn't have to lift the petrol very high to the jet.  This would happen if the float bowl is sitting too low.  Shown below is how to check ; Remove the float bowl cap and invert so gravity shows the float level relative to the rim when the fuel feed valve is closed. Repeat for both carburettors . . . 

Hope this helps and you get to the bottom of the problem soon.

Best regards, Pete

 

below the fault finding chart from 'SU Carburettor Tuning Tips & Techniques' Brookland books, which I'm led believe is a reprint of G.R.Wade's book.  

NB. Although there are many useful items of information in this book - it is exceptionally poorly written and equally as badly edited and published. As a consequence, it is very much more confusing than it ought to be and with great superfluity.  It needs to be rewritten, this time with a proof reader..  In all good conscious I cannot recommend it. 

 

Thanks for your suggestions.  I think I need to revisit valve timing next.  I rebuilt the carbs but they seem ok, I think.  I was very careful and meticulous along the way.

Im going to sleep on it now, after a full night in the garage playing, and getting nowhere.  But thanks again.

[Steven Whitaker]

14 hours ago, Michel Higuet said:

Plugs dry,  seems it is a carburation problem,  have you check when starting if there is vacuum in the venturi ( the inlet of the carbs ) otherwise fuel will never climb, a vacuum gauge could be interesting to place on the inlet screw in the manifold.

I haven’t checked this.  I don’t have a vac gauge.  Is it possible without?

[keith1948]

Hi Steven

Long shot but have you got the points electrics wired correctly. Once I spent some hours trying to work out why a Triumph Vitesse would not start. Had got the wiring from the condenser connected the wrong side of the insulators on the points. A simple mistake but took a while to find. See here on the link

http://www.mgb-stuff.org.uk/points.htm

I can't see the cloth covered earth wire between the contact breaker fixing plate and the left hand fixing screw in your photo compared to the info in the link.

Try a different condenser and coil just in case it is one of these that is faulty.

Keith

 

Edited November 21, 2023 by keith1948

[Andy Moltu]

Have you mis-timed the cam?

These engines are non-interference so the valves & pistons won't meet if you get the timing wrong.

So you can really do one of two simple errors - time using no1 exhaust valve or set it so that no1 inlet is fully open say 105 degrees btdc rather than after. (105 is an example as many non-standard cams will have different numbers to 105)

 

[John Morrison]

Hi Steven, 

I feel your frustration, but getting the bloody thing to run will be so satisfying!

Reading all of the above I too would l be thinking a fuel issue, I would have thought all that trying to start her etc., would have let a strong smell of petrol around.

You mention dry plugs etc., it doesn't add up to fuel in the cylinders.

All that said, have you tried rotating the distributor as you spin her over? Just slacken the clamp enough for the distributor body to move and then rotate slowly, you've nothing to lose.

John.