No Go Beta Techno

[Will]

Hey there guru's

A little puzzle for you to think about .....
.... On Sunday, after completing the last section of the day and on the short commute back to camp, the bike gave a splutter and fart, ran fine for another 10 seconds and promptly died. I coasted to the ute thinking nothing more than I had run out of go juice..... that's exactly what it felt like ..... no fuel.
Got home that night and gave the bike a quick hose down to get the bulk of the muck off and parked it. Next day, wheeled it out and gave it a scrub with truck wash and a quick gernie off ensuring not to direct and high pressure spray into the delicate areas.
Once dry and greased I flicked the fuel tap onto reserve and gave the bike a kick, nothing, another kick, almost, another, nothing. I thought perhaps the reserve circuit in the fuel tap was blocked so I proceeded to put a litre or so of fuel in the tank, to my surprise it nearly overflowed...... strange, I thought it was a 3 lt tank? You were right Peter, I shouldn't have run out of fuel considering I filled up at lunch. Anyway, with the tap in the 'on' position I kicked a few (20) times, nothing.

Sorry for the lengthy tale so far, but it helps to know the full story

So I started eliminating possible causes.
Air filter clean but a little moisture in the bottom of airbox, probably from cleaning. So I was getting air.
Drained carbie bowl, a couple of drops of water in drain plug, no real drama. Turned on fuel to make sure fuel was getting to bowl, all OK.
Spark, checked plug (black and not really wet) spark appeared a little weak and wasn't consistently arcing from electrode to earth tip, jumped about a bit. I put that down to my girly arms trying to crank the bike over and watch the plug at the same time.
Compression, present.

So after all of that, the old girl still won't start. My final thoughts are that I possibly have a blocked jet somewhere in the carbie. Any way to test that theory without pulling the carb out and physically looking? Any other ideas on what may be going on?

Your thoughts are most appreciated....

Will

[paulm]

Sounds like fuel starvation… Try checking that Tank vent or vent hose isn’t blocked – if it is, it causes a partial vacuum. Problem is the partial vacuum also stirs up any crap in the system and then leads to blocked jets so you’ll probably need to clean out the carbie now anyway.

Use compressed air through the jets – don’t be tempted to try and poke out the jets – that usually causes more problems.

While you’ve got the carbie in bits check the floats still ‘float’ and reset the float height – somewhere on the here, or the Beta thread on Trials Central ,you’ll find the 'good oil' on setting up a techno carbie. It’s not difficult just a bit time consuming – if you can’t find the info send me a pm and I’ll try and dig out the info.
Hope this helps.

Paul Mac

[don.howison]

Check out the connection to your top coil. These can become corroded as the Techno's have a bad habit of expelling coolant from the reservoir bottle. It ends up all over your wiring and causes corrosion. I had this happen at Oz tiltes many years ago. It causes the junction to go high resistance which in turn gives you a weak spark. Also check your spark plug lead where it screws into your coil and also into the plug cap.

With the choke on, if you had any bloked jets this would not prevent the bike from firing as you draw fuel from the choke circuit not via the jets. If the jets were blocked, as soon as you turn the choke off the motor would stop/starve for fuel.

Good luck
Hollywood

[Will]

Thanks for the ideas guys..... I'll keep plugging away at it.
Interesting re: choke circuit.... I never knew it was independent of the jets

Cheers
Will

[Will]

Hooray, she fired up this arvo.
Still not 100% sure what was wrong which annoys me a little.
But I know all the electrical connectors and earths are now clean and appropriately protected.
Carbie is all flushed out and fuel lines/breathers all clear.

Thanks again for the ideas :)

[FM350]

You did fit a new spark plug, before looking at anything else? Modern fuels do tend to leave deposits on 2T plugs, which mean that while spark will appear ok while the plug is outside the motor, it will fail under compression. Other problem affecting Beta which even today does not seem to have been resolved is stator failure, but this usually means no spark at all, and new stator before bike will run again.

[Will]

No, I didn't fit a new spark plug. I did clean up the near new plug that was in it...... I should get a new plug and throw it in the tool box anyway!

[FM350]

Always fit a new plug in non run situations, and keep a couple of new ones spare. In lots of cases running problems are caused by bad plugs, and most people dont understand that plug which sparks fine outside the motor, may break down under compression.

[Will]

Picked up a couple of new plugs on the way home from work today.
Set the plug gap as per user manual (0.5 - 0.6mm seems small, but that's the specs) and threw one in the bike....... Started as usual (second kick) but definately idles better and seems a little crisper.

New plug will be step one in any future engine diagnostics

[Pgately]

Hi Will
Yes always keep a spare spark plug on hand as the bike has occasionally done that to me and the new plug always fixed the problem.
Did you sort out the rear brake problem?