Won't start, has spark - driving me nuts
 

I've pretty much run out of things to try so I'm hoping for some ideas please. The bike ('89 3AJ) had been getting very reluctant to start so I sent the carbs away to be cleaned and reset to factory settings. When they came back I fitted them and now it won't start.

I checked for spark and after tracking down a bad connection in the key ignition barrel I now have spark. This was tested by taking the plug out and firing it resting it on the engine fins.

I drained the fuel and put fresh fuel in.

Exhaust pipe smells of fuel after cranking it for a bit.

It was working before so it shouldn't be anything major but I've run out of things to try:-( Ideas anyone?

A few possibles
 

I would maybe replace the sparkplug, and check the valve clearances. Always worth doing a compression check too....

You have vapour reaching the exhaust, but that does not mean you have enough to ignite. Have you check to see how good the fuel flow is from the tap to the float bowl?

Then it might be worth checking to see if the main and pilot jets are unblocked. WHo knows.

It could even just be a case of a flooded engine if you were used to starting it up with a bit more gas, perhaps you don't need to anymore.

Testing
 

Alex,

If it's not the plug i'd suspect something has gone wrong with the carb rebuild.

You're welcome to use anything from my bike to test if it helps.

Air filter? Will it run on choke?

I've been trying to get an engine I bought recently to start, checked everything still no joy, I was getting a spark, fuel was getting through but was backfiring, yesterday decided to remove the generator to check the woodruff key which was found to be broken, this causes the ignition timing to go out, i've replaced this and it started first time

:scooter:

keep 'em coming
 

Thanks for the suggestions folks.

Warthog:
I'm getting a good spark from the plug that's in there, I might swap it out to check though. With the drain screw open it lets plenty of fuel through and doesn't stop. I've been using the car to jump it so I've tried lots of combinations of choke, no choke, throttle and no throttle. I wait too to let it clear in case it is flooding.

I could try the clearances and a compression check but I can't see these changing since it was running a few weeks ago.

Roamer: Might take you up on that, it would be hard to prove the carb was poorly set up otherwise.

KTMmartin
It won't run at all now, choke or not, it used to like me using the choke. Air filter looks ok, but I haven't soaked it or anything.

Coils?

Where was the bike when it had the inlet manifold open?

You've got a spark and you've got fuel, are they meeting at the right time ? Check the timing, if you can. As far as the air cleaner is concerned, take it right out and try to start it, if it starts, it's the air cleaner ! It should run ok without the air cleaner, but don't do it for too long.

Texastrike:
I'll give the air cleaner thing a whirl, easy to try. The timing thing I'm dreading, I don't really want to start pulling the rotor out of the alternator. It should be ok since it was running before...

Warthog:
The bike was in its luxury spot under some trees on my street while the carbs were off. I stuffed the head with rags and then taped a plastic bag around them. Are you thinking moisture in the cylinder? The coil works cos it sparks.

Got a spark tester? Little clear plastic types that go on the plug in the cylinder, or a thing like a drawing compass that goes in the HT lead gives a certain answer.

It has been known for plugs that work rested on the head not to work down the plug hole. Usually it's a corrosion issue at the cylinder head or main earth connection, or a weak coil. You get a fat blue spark in one place, weak and yellow down the plug hole.

Trust a Triumph rider to know about engine electrical faults :blushing:

Andy

Possibly water or corrosion. If the bike was fine, but now is not..it could be. I am think that the carb work may have been pants. Carb works, leaves, comes back and doesn't work...

As for the coil: its working when the plug is out, but under compression conditions it might not. My mechanic once said that spark with plug out and spark with plug in were not always the same... My only thought

Get a can of power start or carb cleaner etc...

Spray it into the airbox while turning the engine over...

The mixture mixture should EASILY ingite and the engine should turn over...

If it does run with the power start then its your carbs/fueling...

If it doesnt run, its either electrical or mechanical..

As well as the above advice, you could try the old trick of heating up the plug in a flame, like a camping gas or something; when it's very hot, quickly screw it in the cyl.head and try to start it quick before it cools down.

It's fiddly because you have to do it all without finger contact.

hi there i agree with the spark plug tester idea ,as you cleaned the ignition switch and got a better spark you may have more bad wiring , this may have been your problem all along. did the carb rebuilder find a problem with your carbs. you need a big fat blue spark not a faint yellow dancing all over the place one. a clean air filter and proper tappet clearance are a must , do one thing at a time then try to start it then you know what has improved matters. zigzag

Hehe, I developed asbestos fingers through having to do that nearly every day on an old Jawa two-stroke I used to own. Throwing them in the air like a juggler is good for reducing skin contact :) Or wear gloves ...

It's amazing how skilful you get as a juggler!:Dhot hot hot!

Grease it up.
 

The plug spanner that is. Takes maybe 30 seconds- 1 minute before the grease goes soft and stops gripping, enough time to line it up and start turning.

Andy

... and ***start the thread off by hand***. Both heads on the Jawa had to be helicoiled before I learned this.

:(

Are you the 9-foot tall, three meter pry bar owning body builder I bought my last BMW twin off ? Ever worked for Ural? :rofl:

The BM is the only piece of machinery I've ever had where I had to use an impact gun on M5 cap heads. The number of adapters to go from 1/2" impact drive to tiny hex would have had the health and safety bloke at work turning in his (shallow) grave. Oddly the corroded fasteners came out in one piece, unusual for the toffee/cream cheese based materials most bike manufacturers use.

Ural of course avoid the standard bodgers torque settings (Tight/V tight/B Tight/BF tight/RBF tight/STRBF tight) and instead used the two stage zero to Vodka fuelled gorilla method.

I was taught a very simple method for gas tight fittings: hand turn until it stops then as far as your wrist will go without letting go.

Andy

News, but not fixed yet...
 

As a variation of one of the suggestions here I dribbled some petrol into the open spark plug hole, put the plug back in and hit the button - it fired instantly but only ran for a second or so. So there is definitely spark at the right time, just no fuel.

Before I go back and complain that my carbs were set up wrongly, can someone confirm I put them on right! I have connected the 'big' inlet pipes, two in and two out of the carb and the clamp things are nice and tight, I can't slide them around or along.

I have connected the fuel pipe up to a barb near the float bowl. Fuel runs out of the float bowl when I open the drain screw. There are a couple of narrow pipes that sort of hang around which I'm hoping are breather pipes. That's it, I didn't connect anything else on the carb to anything else on the bike. Is that right?

Comparing
 

Alex,

I should get mine back from the garage tomorrow with the oil leaks fixed so i can run it over tomorrow night if it's urgent or on Saturday morning.

Euan

altitude compensation ...
 

Probably not - if it's a real 3AJ it has altitude correction - a cilindrical device on the left side of the main frame beam. From there 2 hoses go to the carbs. If these hoses are not connected, and you are at sea level, the mixture will be very weak. The carburettor has the following hose connections:
1. Fuel in. On the left carb, outside, pointing backwards.
2. Altitude correction. On the left carb, outside, pointing forward. Copper pipe without edge. Connect to one of the 2 connections on the compensation device, or close.
3. Altitude correction. On the right carb, between the 2 carbs. Copper pipe, pointing upwards at an angle, without edge. Connectio: see 2.
4, 5. Aeration of float bowl etc. Two hose connections, both pointing backwards. Officially to be equipped with a hose dangling around behind the engine and ending nowhere. For now, not worries.

Good luck!
Auke

Euan,

I'm away this weekend, hoped to go on the bike:-( I'll have a crack at following Auke's instructions, if I get stuck I'll ask you over to compare our pipes:-)

Auke,

Sounds good, I'll check that out as soon as I can. Thanks very much.

Are the carb rubbers, to the head, in good order? If they are de-laminating around the metal, they will suck in air. I had this problen when I first got my 3aj.

Oh yeah - check your vacuum hose as well.

Still not there:-
 

Auke,

Mine does not have the pipes you are talking about on the sides of the carbs but it does have a cylindrical thing on the "beam" at the front of the carb. This is unconnected to anything, is this right?

Cheers.

Still not there:-(
 

Auke,

My carb does not have the pipes on the side of the carbs but it does have a cylindrical thing on the "beam" at the front of the carb. This is not connected to anything, should it be?

Cheers.

??
 

That would mean somebody changed the carburettor for another one. If you do not have the altitude connections on the carb, no need to connect the compensating device. You could leave it out.

Then it is back to carburation; squirt fuel into the air filter and try to start, as an earlier post mentioned, if the bike then starts the problem is in the carburattor.

Auke

Blow out all the airlines, then make sure you drain the petrol through so it runs out of the bottom, there is a small screw on the left hand side of the carb (at the bottom of photo in red, mine has a lever attached to the screw to make it easier to drain the float bowl), unscrew this gently (don't chew up the head) until the fuel runs through. try that and start the bike without the fuel taps on, if it starts ok, then turn on the left tap and see what happens. Good luck

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