19 replies to this topic

[redboy]

For quite a while now my Sprite1275 carb 1994 won't start from cold. Only way to start it is put a little fuel down the carb to which it will fire straight away then die.

Do this 1 or 2 more times and it will keep running.

Plenty of fuel getting to carb, just fitted new fuel pump.

Just don't know what to do now.

[imaparana]

Are you trying the choke ?

[redboy]

Yes mate    To be fair the more the choke is out it seems harder to start sometimes.

[Ubertech_s]

Just a few questions:

 

could you check the timing marks while it is running - I assume you get it running eventually

 

is the difficulty starting something that started all of a sudden, or is it something that has got worse over time

 

is it on electronic ignition?

 

is it running rich/lean/about right?

Edited by Ubertech_s, 05 April 2016 - 09:58 PM.

[Stu.]

All the symptoms of a vacuum leak.

 

When you're turning it over, it sounds like air is being drawn into the inlets preventing it catching.

 

When you pour fuel down the carb it seals the gap / hole and allows correct vacuum and fuel flow to the head ports.

 

Spray WD40 around ALL areas of the carb manifold gaskets and also the inlet and exhaust manifold gaskets while a helper is turning the engine over with 1/2 choke on. If it catches take a note of where you were spraying and you'll have found your leak.

 

Could be somthing else but I'd give it a try. It's only a bit of WD40 you'll have lost if it's not a vac leak.

 

Let us know how you get on

Edited by Stu., 05 April 2016 - 10:30 PM.

[redboy]

All the symptoms of a vacuum leak.
 
When you're turning it over, it sounds like air is being drawn into the inlets preventing it catching.
 
When you pour fuel down the carb it seals the gap / hole and allows correct vacuum and fuel flow to the head ports.
 
Spray WD40 around ALL areas of the carb manifold gaskets and also the inlet and exhaust manifold gaskets while a helper is turning the engine over with 1/2 choke on. If it catches take a note of where you were spraying and you'll have found your leak.
 
Could be somthing else but I'd give it a try. It's only a bit of WD40 you'll have lost if it's not a vac leak.
 
Let us know how you get on

Thanks I'll give this a try. I'm ordering a new oil filter housing and braided pipe so will put some gaskets on the order just in case.

[redboy]

Just a few questions:
 
could you check the timing marks while it is running - I assume you get it running eventually
 
is the difficulty starting something that started all of a sudden, or is it something that has got worse over time
 
is it on electronic ignition?
 
is it running rich/lean/about right?

Can't check timing as I havnt got a timing light.

I'd say it probably got gradually worse. It doesn't get used a lot.

Can't really say if it's running lean or not! What's the best way to tell?

[bikenutmart]

If its running lean it will tend to die on idle, mine was doing this, and slightly richening the mixture cured it, a couple of flats on the nut, (downwards) to richen. Mart.

[fwdracer]

Alternatively, when you get the engine running, spray WD40 around the outside of the entire intake system, including the vaccum and charcoal canister lines. If the engine note changes and rpm temporarily increases, it is because the WD40 has (temporarily) stopped/sealed an air leak. Repeat a couple of times to pinpoint.

 

All the hallmarks of a vacuum leak.

[redboy]

Ok so I've put a new air line from the advance to the carb, sprayed WD40 all round the carb to manifold gaskets but still nothing.

Then I put my hand over the air intake of the carb, turned it over and BRRUUMm started straight away!!!!!!

What does this mean? Does it still mean a vac leak as I just don't know where else air could be getting in.

[fwdracer]

Does your choke actually work? (By sealing off the intake you are effectively choking the air inlet and artificially enriching the intake charge). Get someone to pull the choke out from inside the car. Is the mechanism working (Cable hasn't pulled through?) in order to drop the jet and cause cold start enrichment?

 

Sorry if this a bit billy basic.

[fwdracer]

Did you spray WD40 around everything intake related when you got it running? Did the idle speed change and then revert?

[Stu.]

Incorrect choke adjustment or vac leak. Keep hunting till you find it.

[redboy]

This is choke off.

This is choke out

[fwdracer]

That is OK