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Sprint distributor
http://forum.triumphdolomite.co.uk/viewtopic.php?f=4&t=34051
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Author:  sprintchris [ Sat Jun 09, 2018 10:23 pm ]
Post subject:  Sprint distributor

Here we go again.

Decided to try and get my engine running properly today. Started on the button but runs extremely rough.
Some questions....
Leyland manual says static ign timing 10degrees, is there a setting different using a strobe light? And when checking should the vacuum advance be connected or disconnected? I have str91 cam and 45s if that makes any difference.
I have currently set it to about 10degrees, but I’ve found the dizzy is almost at the end of its slots.
When I built the engine I meticulously read the manual showing the jackshaft lines crossing between the centre of the guide bolts - see photo, yet I can’t seem to move it one gear round on the jackshaft - then goes too far the other way. Anyone else had this problem? Is there a mistake in the factory manual? I can also confirm the rotor arm pointed to the exact position as shown in the workshop manual.
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Author:  cleverusername [ Sat Jun 09, 2018 11:58 pm ]
Post subject:  Re: Sprint distributor

Before you do anything else, check you have a good spark on every plug. I had a similar problem and it turn out to be an intermittent misfire on two cylinders, thanks to duff ignition leads. Just hook the strobe to each lead in turn and make sure you have a good consistent spark.

I have mine at about 8 degrees, like yours the max I could get was 10, but that is because my engine is made from many different engines and I guessed the correct position for the dizzy. Once I had it close, I wasn't moving it. The manual will be for 4 star, I don't know how unleaded effects it, but it should run smooth at the setting you have.

Don't think the vacuum advance will make any difference at idle speed, but I don't see any advantage in taking it off.

My bet is an ignition fault, if not that it must be a fuel issue or an air leak. Unless you have bad compression, but if it is a new engine, hopefully we can eliminate that. You did put the breather system back? Mine was not happy when I forgot to refit the breather pipes.

Author:  sprintchris [ Sun Jun 10, 2018 10:55 am ]
Post subject:  Re: Sprint distributor

Quote:
Before you do anything else, check you have a good spark on every plug. I had a similar problem and it turn out to be an intermittent misfire on two cylinders, thanks to duff ignition leads. Just hook the strobe to each lead in turn and make sure you have a good consistent spark.

I have mine at about 8 degrees, like yours the max I could get was 10, but that is because my engine is made from many different engines and I guessed the correct position for the dizzy. Once I had it close, I wasn't moving it. The manual will be for 4 star, I don't know how unleaded effects it, but it should run smooth at the setting you have.

Don't think the vacuum advance will make any difference at idle speed, but I don't see any advantage in taking it off.

My bet is an ignition fault, if not that it must be a fuel issue or an air leak. Unless you have bad compression, but if it is a new engine, hopefully we can eliminate that. You did put the breather system back? Mine was not happy when I forgot to refit the breather pipes.
Hi,

Thanks for your thoughts. I don’t have the breather connected currently as there’s nowhere to fit it on the dellorto manifold, something I need to look in to.
I was curious about the spark, ran out of time yesterday to investigate, I have new plugs, leads, cap, rotor and electronic ignition. I’ll try the strobe on various cylinders and I’ll grab my insulated pliers designed to remove leads whilst running and pinpoint weak cylinders. Worryingly there was fuel dripping from cyl 3/4 carb, so may be a problem there, need to establish correct pressure too, not adjusted it yet but was .2 bar, bit high maybe. Also I have my original cap and leads somewhere, so may donor them over. Most annoying the dizzy doesn’t sit in the centre of slots! The book must be wrong!

Author:  Mad Mart [ Sun Jun 10, 2018 11:01 am ]
Post subject:  Re: Sprint distributor

0.2 bar should be ok. On Webers I tend to use about 3-3.5 psi.

Author:  soe8m [ Sun Jun 10, 2018 12:21 pm ]
Post subject:  Re: Sprint distributor

You don't have to concentrate on static or idle timing. After 5 years of use the Lucas dizzy's timing control by springs and weights and a wobbly base plate is way off. Yours is probably 40 years old and the curve has nothing to do with factory figures anymore. Setting the timing perfect at idle will mean way off at 1500 rpm and above. You must set the timing when it runs the best when cruising or high speed. You will end up with a certian figure at idle then and that is your idle timing. If you want it perfect at any revs at any situation and load you need an electronic device. Not a points replacement like lumenition or a cheaper inferior alternative because these will use the same springs and weights and wobbly base plate for timing.

With your type of carbs and camshaft the mixture will be less good good at idle and low revs like any one throttle per cilinder carbs setup. The timing at idle would be around 15 degrees. At higher revs when the carbs and cam become more effective it's possible the advance has to be less than std.

Every engine is different and has different setup and needs it's own specific timing curve. When you are trying to get the most out of it or just trying to keep it running ok with a std old dizzy you have to compromise and accept it will never run optimal. Maybe you can have it running decent but then you are not using all of its potentional.

Jeroen

Author:  sprintchris [ Sun Jun 10, 2018 1:09 pm ]
Post subject:  Re: Sprint distributor

Quote:
You don't have to concentrate on static or idle timing. After 5 years of use the Lucas dizzy's timing control by springs and weights and a wobbly base plate is way off. Yours is probably 40 years old and the curve has nothing to do with factory figures anymore. Setting the timing perfect at idle will mean way off at 1500 rpm and above. You must set the timing when it runs the best when cruising or high speed. You will end up with a certian figure at idle then and that is your idle timing. If you want it perfect at any revs at any situation and load you need an electronic device. Not a points replacement like lumenition or a cheaper inferior alternative because these will use the same springs and weights and wobbly base plate for timing.

With your type of carbs and camshaft the mixture will be less good good at idle and low revs like any one throttle per cilinder carbs setup. The timing at idle would be around 15 degrees. At higher revs when the carbs and cam become more effective it's possible the advance has to be less than std.

Every engine is different and has different setup and needs it's own specific timing curve. When you are trying to get the most out of it or just trying to keep it running ok with a std old dizzy you have to compromise and accept it will never run optimal. Maybe you can have it running decent but then you are not using all of its potentional.

Jeroen
Hi Jeroen,

I see your point, what alternatives are there? I did strip the dizzy completely, freeing off all components and ensuring all moved as it should, the shaft seemed ok, no play that I can remember. Yes, I have the lumenition setup. Any ideas on the dizzy being at the end of the slots? I can only imagine the jackshaft needs to go back a tooth, can’t see there will be any effect on the running but is rather annoying :wary:

Chris.

Author:  soe8m [ Sun Jun 10, 2018 10:01 pm ]
Post subject:  Re: Sprint distributor

A simple alternative is replacing with an 123 ignition what is easy to program the curve that suits the engine.

When all is moving free isn't a guarantee that the timing is correct. The weights do wear so their resting point and max point will change by this wear. Holes become oval and pins wear out. Springs do soften etc. Baseplates do alway's wiggle and change timing easily.

Jeroen.

Author:  tony g [ Mon Jun 11, 2018 6:23 am ]
Post subject:  Re: Sprint distributor

For me the jackshaft needs to go back anticlockwise one tooth to be nearer to the bolt .

Tony

Author:  Mad Mart [ Mon Jun 11, 2018 7:10 am ]
Post subject:  Re: Sprint distributor

Quote:
For me the jackshaft needs to go back anticlockwise one tooth to be nearer to the bolt .

Tony
+1. Been there, done that.

Author:  sprintchris [ Mon Jun 11, 2018 8:33 pm ]
Post subject:  Re: Sprint distributor

Quote:
For me the jackshaft needs to go back anticlockwise one tooth to be nearer to the bolt .

Tony
Tony,

That’s exactly what I thought, trouble is engines in etc, if you look in the Leyland manual that’s exactly how it shows to set it up, so frustrating as I took great care in setting that up, one tooth around and the pulley lines pass through the upper bolt, the rotor arm even sat in exactly the correct position as shown in the diagram.

The timing sets, but is very close to the end of the slots.

Chris.

Author:  sprintchris [ Mon Jun 11, 2018 8:37 pm ]
Post subject:  Re: Sprint distributor

Quote:
Quote:
For me the jackshaft needs to go back anticlockwise one tooth to be nearer to the bolt .

Tony
+1. Been there, done that.
Did you just leave it as is? Too much work to strip again and adjust. Not happy! :snivel:

Author:  Mad Mart [ Mon Jun 11, 2018 10:33 pm ]
Post subject:  Re: Sprint distributor

As long as you've got the timing set correctly, it's ok that it's at the end of the slot.

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