Norman T300

blue cat wrote:As you can see, the governor rod moves inwards by about half its length, which catches a few people out.

Yes, I'd found that. I think it wasn't doing anything because it wan't even close to the lever in either position.

The normal position of the variable parts of the throttle are shown here.

I think that these parts on your engine are in the correct position. You can alter the position of these two parts to give different engine speeds.

Alter by undoing the brass nut and moving the plate around to another hole?
I came to the opinion that mine couldn't be right, so I moved it round a hole, then couldn't get it to start at all, so I put it back.
With hindsight, there must've been something else going on, because at the idle position that shouldn't make any difference: at idle, it should be up against the stop screw.
Which hole do you have your peg in? I can't see on that picture.

As the engine speed increases, the governor rod will move inwards, causing the throttle levers to move outwards which should then close the throttle to a position set by the variable parts of the throttle noted previously.

Yes, I'd seen the rod move, but I'm wondering if it moves soon enough: shouldn't it be all the way in at the normal operating speed?
I think mine moves when it's faster than that.
I can't claim to have observed it closely enough to know on that, I shall aim to have a look tomorrow.

There is also a small amount of speed adjustment with the very small knurled knob within the throttle lever assembly itself.

I'm not sure I'd call that "Very small": the threaded section is quite long, so that knob can go long way, and does seem to make a considerable difference...

I have also assumed that you have a return spring attached to the bottom part of the throttle spindle underneath the carburettor.

Yes, though I am wondering if it is a bit tired: it doesn't always pull the throttle back properly.

The current state of play is that I've got it running fairly nicely at idle, but it dies when I try to turn up the revs.

Hairyloon wrote:

Which hole do you have your peg in? I can't see on that picture.

The peg is in the first hole of the top variable plate.

Sounds like you are getting there.

blue cat wrote:

Hairyloon wrote:

Which hole do you have your peg in? I can't see on that picture.

The peg is in the first hole of the top variable plate.

Hmm. Mine it the same. So much for that theory.

Sounds like you are getting there.

I'm not convinced that I have made much progress...

I'm not familiar with that engine or carburettor; but think you should disconnect the operating link from the throttle arm on the carb. and check that all jets are both the correct ones, and have no obstructions, and the float level is set correctly. You should be able to run the engine through it's speed range by just operating the throttle by hand.
If it idles ok but then dies on opening the throttle; there can only be a incorrect air/fuel ratio, or, the ignition system is breaking down.
Apologies if you have already tried this; but I have an extremely limited short term memory.

oldgit wrote:I'm not familiar with that engine or carburettor; but think you should disconnect the operating link from the throttle arm on the carb. and check that all jets are both the correct ones, and have no obstructions, and the float level is set correctly. You should be able to run the engine through it's speed range by just operating the throttle by hand.
If it idles ok but then dies on opening the throttle; there can only be a incorrect air/fuel ratio, or, the ignition system is breaking down.
 Apologies if you have already tried this; but I have an extremely limited short term memory.  

Good suggestions, thank you.

I don't think the link prevents the manual operation of the throttle, at least not when the control knob is set to idle.
The jets are the ones that came with the engine, but beyond that I don't know what they should be. It can run at higher revs though: I have had it doing so. At one point it went so fast that it blew the meter I had connected to the dynamo, so that's over 60V. I don't know how that translates to revs, but I think it's a linear relationship.
I didn't spot any adjustment in the float level.
Check the fuel filter (again), I think, but not today: is a bit noisy and various people are out in their gardens.

Just a thought: blue cat's carb body has a 26-75 venturi fitted; from your earlier pictures it looks to me as though your original carb. had a smaller venturi.
This may be an optical illusion or just the imagining of an old silly me; but is another straw to clutch at. Maybe worth a look.

oldgit wrote:
Just a thought:    blue cat's carb body has a 26-75 venturi fitted; from your earlier pictures it looks to me as though your original carb. had a smaller venturi.
  This may be an optical illusion or just the imagining of an old silly me; but is another straw to clutch at. Maybe worth a look.

Supposing the venturi is wrong, is it hard to find replacements?
Or are they as simple as they look: might it be possible to cast a replacement and finish off on a lathe?

I don't know if you could still get a replacement from a carburettor specialist; maybe someone else does.
I would think it is a die cast item. It may be possible to machine one; maybe from alluminium bar; but getting the curve of the restriction correct, might be tricky.
 First you need to measure the original, or read the numbers (if present) in it. If the original is smaller; it may be possible to replace the 'blue cat' venturi with your original. I believe the venturi tubes will be removable (with care). They may be held in by a screw; blue cats picture in page 2 shows a cheese head screw that may retain or locate the venturi tube.
 
Just check that the venturis are different sizes, first, and if so, clean them up so that you can see the joins and which direction they need to travel before trying to extract either of them; as there is always a danger of unrepairable damage.

oldgit wrote:I would think it is a die cast item. It may be possible to machine one; maybe from alluminium bar; but getting the curve of the restriction correct, might be tricky.

I have access to a 3d printer, so I can probably make an accurate thing to make a mould from. I doubt the curve it needs to be exactly right: close enough is good enough.

First you need to measure the original, or read the numbers (if present) in it. If the original is smaller; it may be possible to replace the 'blue cat' venturi with your original.

The part that I got had no venturi, so I had to use my original... that doesn't mean it is the right one: who knows what has been changed in its lifetime?

I believe the venturi tubes will be removable (with care).

Appropriately applied brute force did it: it had been glued in with epoxy putty or some such thing. Getting it back in was much harder: carefully applied brute force wouldn't do it, but a big hammer got it in.
The real devil was getting it in straight... I expect someone will be along shortly to tell me a clever trick to do it...
 

Just check that the venturis are different sizes, first, and if so, clean them up so that you can see the joins and which direction they need to travel before trying to extract either of them; as there is always a danger of unrepairable damage.

There was a bit of damage: it cracked up a bit, but I don't believe it is critical, and I don't see how it would cause the symptoms that I'm getting.

o.k. I had assumed that blue cat's carb. body came with it's venturi fitted.

As a matter of interest; what is the minimum throat diameter of the original one, fitted to your engine?

oldgit wrote:o.k. I had assumed that blue cat's carb. body came with it's venturi fitted.

I foolishly didn't take up Blue Cat on their offer and got one off ebay on the basis that it didn't need a tickler hole drilling...

As a matter of interest; what is the minimum throat diameter of the original one, fitted to your engine?

I've no idea. I'll try to have a look in a bit.

oldgit wrote:As a matter of interest; what is the minimum throat diameter of the original one, fitted to your engine?

I make it 1/2".

Had a play today. By treating the control knob as a throttle, I had it running and producing a fairly steady 35V with no load.

Compare and contrast the governor rod running at that speed with it running at idle...





I make that a difference of very approximately bugger all...
That's not right, I think. If it's running at the right speed, then the rod should be fully retracted, so that if the engine slows down, it can push the throttle open to maintain the speed.
Have I got that wrong?
I there some means to adjust it that I haven't found yet, or do I have to get in there and service it?

Also, the exhaust is very sooty, suggesting that it's running too rich.
Have I misread the manual or is the way to adjust that by changing the jets?

don't governors normally close the throttle?

When an engine is running and a load is applied that slows it down a governor is set to open the throttle to increase the speed until it reaches the set speed again.

maryalice wrote:When an engine is running and a load is applied that slows it down a governor is set to open the throttle to increase the speed until it reaches the set speed again.

Well, you can look at it either way, but given that at rest, the governor would not be operating and the throttle would be open, then it's arguably more proper to say that the action of the governor is to close the throttle.
This is a semantic discussion though and it doesn't help... (which is not to suggest that we shouldn't have it).

when the engine is at rest the throttle will be open otherwise it wont start, as the engine increases its speed the governor will come into play by setting the throttle at its set speed and if the engine slows under load the governor will open the throttle to get it back to its working setting.

I make it 1/2".

Thanks for that.

Can anyone tell me the bore and stroke of the T300.

oldgit wrote: Can anyone tell me the bore and stroke of the T300.

According to the manual, it's 56mm bore x 60mm stroke.

Woodsman wrote:Have a look at my thread - page 2

https://ukengineforum.forumotion.com/t9440-another-norman-t300?highlight=another+t300



Note typos

By "Typo's, do you mean "TDG" in the first image? Or is it a TLA that I haven't come across?
I'd expect "TDC" for top dead centre, but I can't think what the G could be...

TDG - should read TDC
ICN  - should read IGN

should have gone to specsavers!

I think your carburettor should have the following :-

Venturi, 12mm (that's good; you said about half inch)

Main jet size, 65 G x 51

Slow running jet, either, 050 or 055
These should all be marked.

The float should weigh 26grms.

To check the fuel level:- dismount the float chamber, unscrew the main jet cap and take out the main jet.
Now refit the float chamber, turned through 180 degrees so that the main jet holder is outside the carb. now turn on the petrol; when it has filled the float chamber, the fuel level should be 3mm from the top of the main jet holder.

oldgit wrote:Main jet size,         65  G x 51

Slow running jet,         either,  050 or 055
   These should all be marked...

Are the marks likely to be fairly obvious? How hard to come by are replacement jets if they're wrong?

Well, I've taken the housing off to get a look at the governor, and it seems that the only way to adjust the governor is to change the springs, and the springs don't look like they want to come off easily. They're a good bit stronger than I expected.
I think I just need to have the confidence to apply more BFI, but as I don't yet have a plan for what to do next, I've put it back together to think about it some more.
As the current diagnosis is that the springs are too strong, a possible option is to fetch them off, stretch them a bit and put them back...
Seems a bit hit & miss, I think.

Decided to have a look at the fuel warmer thingy. It was not what I expected.
For a start, the throat of it is distinctly conical, going from about 26 to 14mm, then behind it there's another conical section.
Looks like a good recipe for turbulent airflow, but maybe that gives good mixing?

On the exhaust side, I've chipped out the epoxy and was rather surprised to find a metal plate right across it to force the exhaust into a hollow bit. They're really not into smooth airflow on this engine are they?

Doesn't really show in the picture.

I don't know how easy it would be to obtain any of these parts. These jet sizes are what would be expected for an engine of that type; that is an engine with that bore and stroke and similar bhp. So they are sizes that may have been varied slightly during the development of the T300.

The slow running jet should be visible if you dismount the float chamber; I would expect this jet to stand proud of the float chamber top, and the size to be stamped on the visible face of the jet.

On the top of the bit that sticks up into the venturi there should be a brass part marked 13 300, that is the jet cap. Unscrew this and you should be able to lift out the main jet with your fingers. This item is like a brass tube with holes drilled along it's length and should be stamped 65 and Gx51, Gx52, Gx54 or Gx56.
65 is the jet size; and the other numbers relate to the hole sizes and position along the tube.
If you decide to check these it would be a good time to check the fuel level, and also check that all jets and holes and drillings are clear using compress air if possible (no wires).
Good luck.

oldgit wrote:I don't know how easy it would be to obtain any of these parts. These jet sizes are what would be expected for an engine of that type; that is an engine with that bore and stroke and similar bhp. So they are sizes that may have been varied slightly during the development of the T300.

I've been giving some thought to changing the carb for something that I can run propane through. I suspect that some here might consider that as heresy, but in my book originality must take a back seat to practicality and I'm told they can make bio-propane now, so it may yet be the fuel of the future...

ETA: most of the LPG carbs I've looked at can also run on natural gas and I can make that myself... not that I'm a doomsday prepper or anything. :?