11 replies to this topic

[Yams]

As the title says, it just wont start. Its a 998 stage 1, however on a HIF44 carb.

 

I have fuel, spark, engine block earth, new coil, battery.

 

It was running yesterday as i was trying to tune it a little by ear. I was doing the standard Hif44 setup, tune down till engine starts to drop then tune back up to high idle then get the balance right. I think i made it too lean and it died. After that it wouldn't start not matter how rich i made it or choked it. The plugs arn't wet, and i don't think its flooded as i left the plugs out for a while.

 

Thanks in advance.

[crazypainter]

did you record what adjustments you made so you could put it back to how it was?

 

if you didn't you could always static tune the carb

[Ethel]

Think I'd crank it with all the plugs out, to confirm all the plugs are sparking. You could also check the timing with a strobe while you're at it. Also check you haven't inadvertently caused an air leak by knocking a breather hose off etc.

[dklawson]

Start with a quick screening test.  Put the plugs back in and tip a thimble of gasoline down into the carb throat.  Try to start the engine.  If it fires, runs briefly, then stops, you have a fuel delivery problem.  If it won't try to run with the gas sent down the carb throat, you may be dealing with an ignition problem.

 

I know you said you had spark and fuel.  How did you determine you had each?

[Yams]

Start with a quick screening test.  Put the plugs back in and tip a thimble of gasoline down into the carb throat.  Try to start the engine.  If it fires, runs briefly, then stops, you have a fuel delivery problem.  If it won't try to run with the gas sent down the carb throat, you may be dealing with an ignition problem.

 

I know you said you had spark and fuel.  How did you determine you had each?

 

I checked the spark by attaching an old plug onto the HT leads on at a time and holding it against the block. The spark looks good enough for ignition. To check the fuel i took of the fuel-in off the carb and fuel came out.

 

I also had the idea of fuel delivery, and i think you're right. The engine isnt flooding even with full choke, and when i took the dashpot off and the needle out, the carb was dry. i oiled up the piston again but still no ignition. I will try putting fuel into the carb tomorrow when its light. if it is a fuel delivery problem what do you suggest?

Edited by Yams, 18 January 2014 - 07:54 PM.

[Yams]

Clogged jet maybe?

[Dusky]

You say your spark plugs aren't wet?

Defenitly a carb problem, set it to 'standard' settings ( as in vizards manual)

[dklawson]

If it will run on a thimble of gas or spray of starting fluid but not keep running, it is almost certainly fuel related.

 

Your test of disconnecting the fuel hose at the carb verifies that fuel is reaching the carb.  However, it may not be getting into the float bowl due to a blocked or stuck float valve.  On HS series carbs, remove the 3 screws securing the lid to the bowl and remove it.  At the bench disassemble, clean, and adjust the height of the valve.  Put the lid back on and hopefully the engine will run for you.  

 

On HIF carbs... I defer to others.  I think the only way to work on them (including their float valve) is to remove them from the intake.  

 

However... as ludicrous as this may sound... you may get lucky by taking a small hammer or the ring end of a combination wrench and tapping on the float bowl.  On more than one occasion I have freed stuck float valves on HS series carbs by tapping on the float bowl lid with a wrench.  

[Yams]

so basically give it a bit of a bash on the bottom side of the carb. I take it i'm trying to free this? Large orange plastic float looking thing?

 

[Ethel]

The float valve is the brass nut you can see under the brass lever attached to the brown plastic float.

 

Blowing in the vent pipe should easily produce fuel out of the jet, as a quick check for a fitted SU.

 

Hif's have separate choke jet which can be a less obvious cause of starting issues. It's the little hole  between the main jet and throttle, there's a rubber O ring around the choke spindle that can perish.

[Yams]

Got it running and tuned up now. It runs pretty lumpy through to about if i accelerate hard 3000rpm but goes smooth if i go gentle.

 

Spark plugs are a moderate-dark brown. 

 

What Dk said seemed to have fixed it, many thanks guys.

[Dusky]

To make it smooth it could probanly use a new tune up, glad it runs again:)