Almost new RobinSubaru EH035 suddenly stopped and will not restart.

[Oban]

I've just fitted a new RobinSubaru EHO35 to a Staton crankshift kit.
It has worked fantastically but now I've hit a problem.
Motor has only done about 6 hours - always started first time and ran beautifully.
Had gone about 3 miles and was heading up a hill on about 3/4 throttle.
Suddenly the motor cut totally, no coughing, didn't bog, just as if I had hit the kill switch.
Haven't been able to restart it since.
Took the kill switch out of the circuit.
Spark at plug looks good.
Plug does not seem to get wet with fuel even after numerous starting attempts.
I've stripped the carb and checked all the filters and jets - all seem brand new and clear (as they should)
Why might there be no fuel (obviously I've filled the tank and the priming button brings fuel to the carb)?
When the bike stopped it just didn't feel like fuel starvation.
Unfortunately returning the motor to America is not an option (I live in Scotland)
Could anybody help please?

 

[Silvaire]

Particularly because the plug is not wet at all, I would suspect a fuel problem.

Start with the basics - which is what any small engine shop anywhere would do.

Is there spark? If so, try priming the engine and see if it will run on a prime. Take off the air cleaner cover, and pour about half a teaspoon of gas down the intake. Have the throttle open when you do this. If the engine runs for a few seconds and stops, you have some sort of a fuel issue.

Assuming it is a fuel issue, the problem could be anything from a pinched fuel line, a clogged filter or jet, a plugged fuel cap, and any number of other things. If you don't feel capable of figuring it our, any local shop that is competent to repair weed eaters and the like should be able to sort it out fairly quickly.

 

[Oban]

Thanks for that Silvaire,
I'm reasonably competent with small engines although I must admit I didn't know about feeding fuel directly into the air intake.
I started with basics
Good spark at plug
good compression
tried with fuel cap off and on
suspected fuel because plug was almost dry
blew through intake pipe from tank to carb
stripped carb and made sure all jets were clear

I tried your trick of squirting fuel into intake (with throttle wide open)
still no response whatsoever (plug wet with fuel)

What would a small engine shop try now? Am I missing something obvious?

 

[BigBlue]

Check the spark plug really good and make sure it is not cracked. Did you check for spark with the plug in the head or out of the head with the wire connected? I had a brand new spark plug cracked once and was causing me all kinds of headaches.

Chris
AKA: BigBlue

 

[Silvaire]

First, I take it as a given that the engine has reasonably good compression. If not, that needs to be looked into before anything else.

Doing the test I suggested is about as basic as it gets, but it certainly doesn't bypass every possible problem.

If it doesn't fire with this prime start test - and when you pull the plug it is still wet - blow off any fuel on the plug and try starting it again. I'd probably repeat the whole process again just to make sure you had sufficient fuel, and that you haven't flooded it with excessive fuel. Also, use full throttle when you try to get it to fire off a prime.

If still nothing, I would suspect the condition of the spark plug or the quality of the spark. You should see a nice strong blue spark. I do assume the plug is clean? Try another plug if you have one. If a change of plug does not fire a prime, I would next suspect the ignition module. I don't know of an easy way to check one. I've found that they work or they don't work - or that they will work intermittently...

Another rather remote possibility is that the flywheel key has sheared and the spark timing is now incorrect. I would look long and hard elsewhere first, but it is still a possibility.

 

[Happy Valley]

Between yourself and Silvaire's suggestions it seems most bases are covered, spark and fuel usually equals go, though it can be hard to confirm the fuel issue.

Perhaps worth a mention, there is a hidden filter in the carb, a small round metallic screen, found when you separate the carb body. With so few hours on the engine I doubt it's an issue but you never know, it might have picked up some lint or debris.

 

[Oban]

Happy Valley - yes I checked the metallic screen when I stripped the carb - totally clean.
Silvaire - compression seems okay
Tried the prime start test a few times - cleaned and dried the plug between times.
Spark looks strong and blue, plug is clean, looks brand new (which it is!)
I did start to wonder about the spark timing.
Big blue - checked for spark with high tension lead connected and touching plug to the cylinder head.

Even though I cannot get it to start now, what is really confusing me is the manner in which it failed - an instant stop exactly as if hitting the kill switch. Whenever I've had fuel problems in the past it has always been a gradual (over a few seconds) decline.

Thanks again guys for your help, I'm tearing my hair out here (and it's pouring it down with rain!)

 

[Happy Valley]

My bet is something very simple. Try a new plug.

 

[Silvaire]

My bet is something very simple. Try a new plug.

Yes, I would too. Even a "new" or "new looking" plug can fail.

When trying to diagnose an engine performance issue, installing a new plug is the most sensible and most economical first thing to do before digging into an engine looking for other causes.

 

[BigBlue]

Not a plug, I would also guess the ignition.

Others had problems with the switches and grounds:

http://www.motoredbikes.com/showthread.php?t=12326

Hope that helps,

Chris

AKA: BigBlue