[rich_exf]

Dear all,

I'm having some problems starting the engine on my newly aquired Norlett rotovator. It's a B&S 5hp circa 1978. Problem is that the engine will not start from cold unless you manually inject some petrol into the carb. Once this is done it's starts no problem and runs fine too. Also if you start it up straight away after running it it starts ok too.

Fuel is fresh, spark plug is new and sparking well. As far as i can tell it seems that the problem is whats termed 'dry plug' as the recoil starter isn't generating enough of vacuum to draw fuel through the carb and into the engine. I've also taken the carb off, taken it to bits, soaked it in degreaser, inspected all the gaskets and diaphragms and everthing seems fine. I've now refitted it and it's no different. I've also checked and adjusted the fuel mixture using the needle valve and again no difference. It does need a new air filter as it's had it but i can't see this being the problem.

Anyone have any ideas or suggestions? I should mention it's a Pulsa-jet carb.

Thanks,

[jack russell]

sounds like you have had it on the operating table    I have no idea as to what it could be you have done the thing i would try which is remove, clean, replace.

gwiz should be able to give sound advise soon

[Gwiz]

hello Rich-exf,
These can be a bit of a pig to start when they get old. The first rather silly question to ask is, (seeing as you didn't mention it) are you pulling the choke out? some people don't see it at the back of the carb..... I've had quite a few "non starters" that start very well when the owners are shown where it is.....
The air filter is quite critical to the starting (helps to create a bit of a vacumn) as is the condition of the square little diaphragm along the carb body (if fitted), also the tiny gauze mesh on each of the pick up pipes must be 100% clean ( they are white when clean, brown/gold-ish when dirty)
Obviously, all the gaskets need to be in very good condition, or you will loose the vacumn generated from turning the engine over on the recoil.

my money is on the gauzes on the pick ups and the diaphragm.you can clean them out with an air line and some carb cleaner.
let us know how you get on, and do shout out if you need any more advice.
 

[rich_exf]

Dear all,

Thanks for the advice.

Gwiz, yes i do pull out the choke but it seems to make no difference. Interesting when i pull the starter the vacuum is powerful enough to pull the choke in so there must be a fair amount of vacuum.

I must admit that i was suspect about the air filter although my dad was telling me it wouldn't make much difference. As i said it's quite clearly ready for the bin so i think the first thing is probably to replace that and see if it makes any difference.

When you refer to the square little diaphragm do you mean the one that sits between the carb and tank or the one on the fuel pump? I have inspected all the gaskets and diaphragms and they looked fine to me. The carb/fuel tank diaphragm did seem to be seperating slightly though so i wonder if it needs replacing or might some gasket goo do the trick?

I think the pick up pipe screens were the brown/gold dirty colour you describe but i have soaked the whole thing in degreaser so should that not have cleaned things out or do i need to use a special carb cleaner?

[Gwiz]

I reckon that unless you have used an airline on the pick-ups, they will still be dirty.
can you post a picture of the engine? There have been so many models, all more or less called the same, and so many of the more, shall we say, "vintage" or indeed, "veteran" models of rotavator are still proudly pulled out of dusty sheds and are still being used, that it's almost impossible to keep up with whats out there!!!
A picture tells me more than a hundred words as regards the excact engine model.....

[Larkshall]

Don't use degreaser on engine internals, it is only meant for external cleaning (it could de-nature the petrol. The only safe thing to use for cleaning air filters and fuel filters is petrol.
Air filters should have a very small amount of oil applied after cleaning and drying (leave out for the petrol to evaporate). Squeeze the foam filter several times to distribute the oil evenly through the foam.

[rich_exf]

Gwiz,

I didn't use an airline to blast out the pipes but we do have one so will try that. I would post a pic of the engine but i don't know how to on here. If it helps at the engine code is 130232, unless someone can tell me how to post a pic or two.

Larkshall,

I should have pointed out that i haven't cleaned the air filter as it's the paper cartridge sort which i understand is basically a throw away job once it's dirty. It basically gone the colour of rust and is all shrivelled and horrid looking - bit like a giant prune.

[Gwiz]

Hey ho,
If you go to the list of topics, you will find one at the top called notice board.
There is a post on there called "how to post a picture in a thread"
it explains things far better than I can.

[Larkshall]

Gwiz,

Larkshall,

I should have pointed out that i haven't cleaned the air filter as it's the paper cartridge sort which i understand is basically a throw away job once it's dirty. It basically gone the colour of rust and is all shrivelled and horrid looking - bit like a giant prune.

Definitely time for a new one. The old Briggs and Stratton filters were foam and lasted for years (properly cleaned).

[rich_exf]

Having looked around the net a bit and also refering to my B&S manual it seems as though the air filter is actually missing a wrap around foam pre-filter which is fitted in addition to the paper cartridge filter. That can't be helping matters!

As far a photos go if you have a look at this thread from Welshboyo

http://www.chat.allotment-garden.org/viewtopic.php?t=15544&highlight=norlett

the photos of his Norlett depict the same machine as mine and the engine looks the same except my exhaust is different (not a home made job) and the air filter on mine is the conical kind with the paper cartridge filter installed. As seems to be depicted on the illustration here

http://www.chat.allotment-garden.org/viewtopic.php?t=5011&highlight=norlett

[Gwiz]

they normally do have a foam element wrap around, as you say, but that just acts as a pre-cleaner to keep the paper element cleaner, for longer.
my money is still on your intake pipes/ mesh screen being blocked, and the diaphragm being dodgy.
the diaphragm on this model, is usually along the carb body, halfway from the choke pull out, and where it bolts onto the engine block.