Engine Won't Start

[muskrat]

G'day again Alan,
                       you probably have a timing light tucked away with the colour tune, so use it as you would on a car but use another battery (not the bikes). I love my colour tune, helped me dial in the pair of flat slide Kehins on the cafe. Use a cig lighter to burn off the plugs. Ron's tester looks handy.
A blocked main jet will affect the slide but not the pilot. Pilot = 0 to 1/8, slide = 1/8 to 1/4, needle clip = 1/4 to 1/2, needle jet = 1/2 to 3/4, main jet = 3/4 to full, they overlap a bit and float height affects all
Cheers

[Alan @Ncl]

That is a fine device indeed Ron.  Think I will 'lash out' and get one.  Thanks.

Thanks also M.  The only light I have is a small 3w one with croc clips I used to use for static timing the car (I actually used it to time the mag this time after removing the centre CB bolt).  If I use that as shown in my little diagram (but with an external battery) will that do (until I get a Ron light)?

Alan

[chaterlea25]

Hi Alan and All,

Quote: "Mag is a replacement (but not rebuilt) "

"Normally" the bike will make some signs of starting if the mag is good!!!!

a couple of drops of petrol down the plug holes should give a few fires of the engine!!!

Have you tried to push start the bike with some help from some "friends" or buy a house at the top of a big hill LOL

Cheers
John O R

[Alan @Ncl]

Thanks for your input John.
Had my daily workout on the kickstart with new plugs, leads and unsuppressed plug caps fitted.  Nice fat blue sparks in the open but only the very occasional, half hearted splutter from the engine when trying to start with them fitted.

Waiting to get an in-situ spark tester as identified by Ron and meanwhile have removed my diagram from previous post as I don't think it represented what Muskrat was trying to tell me.  However, on the face of it, the maggy seems fine.  I will try spraying a bit of petrol down the hole though, as you suggest.  Have not had a push yet (can't face the indignity) but it may come to that yet.

Meanwhile, carb is off yet again for yet another inspection.  

Also tested compression again.  It now got up to an unbelievable 180ish on both using my crappy little push on tester which if we believe the result, seems very healthy?

So. in summary, I seem to have fat blue spark, 3/8 BTDC timing and great compression.  Air screw is out 1.5 turns (and tried up to a turn either way) and throttle stop is 1/16th open (also tried a turn either way where 1 turn = about 1/332 inch).  So why won't the bloody thing start?

[kiwipom]

hi alan, if i was in your situation after checking all posibilities and adjusting to suit, i would spray some eather (model aeroplane fuel) into the air intake and kick it, i have some here for purposes you decribe it is an Aussie product called "Start Ya Bastard" (had to be Aussie) no offence guys i think it is great and works for me. If the bike shows no sign of firing after that even a back-fire then you have no spark so the obvious problem would be mag related, good luck,Bob

[wilko]

Could be the old(once wetted NGK's never work again) symptom? I have lots of them in the shed!

[Alan @Ncl]

Thanks Bob
I have got some equivalent stuff but can't quite get into the air intake with the can due to the long belmouth on my carb which I can't get off now due to having loctited it on 30 odd years ago.  I must have another go perhaps using a bit of wide flexi hose or something.  Might just try that first next time before tickling and choking etc., just in case I am flooding it (though the plugs seem quite dry).

Alan

[BSA_54A10]

Bell mouth ?
Well that says a lot
99.999999999999999999999999999999999999999999999 % chance of crud being drawn into the primary air intake and totally blocking the primary circuit.
Open the slide & spray some WD 40 down the primary air intake while looking for it spraying up into the mixing tube from the tiny primary feed holes

[Hubie]

You beat me to it bob, i have a supply of start ya bastard (actual product name  ) here just in case.  I have only used it when I have finished putting a motor back together.  MY enfield twin is a 1 kick starter and so was the flash before i pulled her down.

Good luck with it, you're almost there mate,

Dave.

[Alan @Ncl]

Thanks for your encouragement Dave.  I need every ounce of it at presence!

Thanks also to Trevor. I did have a go at that air passage when I had the carb off earlier this week as it did all look a bit black round there.  I used carb cleaner spray and saw that it spurted as you say. The downstream spurt was good (pilot outlet as they call it on the diagram) but the upstream (bypass) a bit feeble.  Today's job is to do it all again, now the carb is off.

Why does the bellmouth contribute to this problem?  

Like you, my instinct is that this is carb blockage or wrong setting somewhere but I'm foxed as to where or how?

Am I right in assuming that the primary air flows past the mixture screw, over the pilot jet, picking up fuel into a rich mixture which is then sprayed into, and mixed with' the secondary air flowing over the throttle edge that is above and between the two outlet holes you mention?

[BSA_54A10]

Yep that is exactly how it goes.
Bell mouths are designed to facilitate the fast flow of air into the carb.
This air is of course not filtered so you are also sucking in all of the airbourne crud.
If you are not in the habit of covering the intake ( most use a bath plug ) when not riding then dust settles on the bottom of the tube and gets sucked directly into the primary intake. Particularly when you are trying to start the bike as the slide will be down so all of the crud has only 1 place to go.
I have oft wondered if you could shove some thing like a fag filter in there to stop the crud.
It dose not matter for track use as you are running 2/3 to WFO most of the time and if it dosn't idle, who cares but for a street bike bell mouths spell "trouble" with a capital T , ( stands back in asbestos suit waiting for enflamed retorts )
When you try to clear the bleed holes , try to spray the cleaner down the outlet holes after removing the primary air screw.
This blows the crud into wider holes & hopefully out of the carb all together.
Blowing the other way compacts it into the smaller spacs 

[Alan @Ncl]

Great explanation Trev and makes perfect sense.
Have been scrubbing and squirting away with carb cleaner for the last hour. Have squirted down every conceivable orifice now in every direction possible (to an extent that the prurient might find obscene). Seem to get a nice spray out of both spray holes when blasting down the air hole with air screw at 1.5 turns.  Also blasted the the other way first, up the pilot jet hole, so it seems all clear.  Poked the pilot jet again as I though it seemed a bit reluctant to spray carb cleaner at first.  

Had another good go at cleaning the float chamber as it was still a bit lacquery. Going to try and flatten the cover a bit more later on then refit and have another workout.  

How far in would you set the throttle stop screw as a first try?  I reckon its 32 threads per inch and slide is fully shut if you wind it back 5 turns from the fully-in position (fully in corresponding to slide about 5/32 inch open).  I was guessing about 1/16 open which is 3 turns from fully in.  What do you think?

Much appreciate your expertise.

Alan

[chaterlea25]

HI Alan
I wouldnt worry about the throttle stop screw "setting"
To get good suction through the pilot circuit the throttle slide should be almost closed
If you have the slide too far open the suction is less and no petrol is pulled through the pilot circuit at kicking speed
My method is to just take the slack out of the throttle cable with the twistgrip as I kick the engine over
(ie almost no throttle until the engine fires up)
(I hope this makes some kinda sense???)

BTY Have you drained the sump? too much oil in there causes a lot of drag and very hard starting?????

HTH
John O R

[Alan @Ncl]

Well! I was really expecting to have cracked it this time but still no go.  A few half hearted sputters after a lot of kicking but that was it.  Tried squirting petrol in the plug holes then in the carb but nothing, despite having good fat blue regular sparks with plugs out (better than it ever was with the old mag, back in the days when the bike was in running order).  

Tried burning off plugs and tried Easy-Start spray but still no good which would seem to suggest no spark?  Its a puzzle.  

Waiting for plug tester to arrive in post to see if plugs are sparking when in-cylinder but that will be several days.  If there is a spark, then I will then try to get a push.

One thing that is different from the good old days days when it was a runner is that there was a thin steel plate (an anti bias device I assume as it is tapered) between the carb flange and the head.  This was 1 inch diameter rather than  the 1&1/16 bore of the carb and head so I just left it out (was not sure which way to put it back anyway as did not note which way it as mounted).  Could this be a factor?  As you see, I am really clutching at straws now.

ps. Just saw the post from John.  Thanks for that as it does indeed make sense.  I may have the stop too far in and will try your technique next time.  Sump is clear as I have a drain cock (not that its wetsumping much at all with the thick new oil combined with Newcastle UK temperatures).

[jfligg]

Hi Alan
  I am wondering if it is time to start over.  Three things make an engine start and run.  Compression, spark and fuel then there are variations in between.  I know alot of this has been covered.  But I find; If I take a break and start with the basics. Then BINGO I find the Issue.   What does a new set of plugs look like after a few kicks?   Are they dry or wet.  What is the compression?  Is the timing correct?  Did you switch the plug leads from side to side?  Did you set the timing while turning in the correct direction?  Is there crud in the fuel cap?  Try starting with the cap off.  Anyhow Have a cup of tea for me.  Jeff