Mk3 kick start locking and kicking back - Advice or help?

Option 1: Sounds like classic Boyer kick back due to low voltage (has no impact if ignition is off :-)  - the low voltage causes tha Boyer to advance - leading to Option 2 is your timing set correctly (again, no impact if ignition is off)?

'battery appears fine'  what voltage do you have? 

Also possible, poor connection in points cover (the wires work harden & fracture) could possibly affect battery draw.

Mike

Mk III ES (with a Boyer ;-)

How is your kicking leg.

They need a good kick.

If a Boyer is kicking back and battery voltage is OK (as has been mentioned, this is the most likely cause), I'd check that the leads from pick-up to ignition unit are correct.

Has the wiring been handled since it was last running OK ?

Although the Boyer runs with a 'wasted spark' and it shouldn't seem to matter which way round the pickup is wired, it actually does if the advance-retard system is to work...and the default value for a Boyer if the battery is flat or the signal incorrect is full advance...They can still be started on full advance but it takes confidence and a good swing...

Hi Alex,

Have you had the bike running? is this new behaviour? how old is the battery?- if it's getting on a charge can rapidly drop my Guzzi has this issue) as Richard said, has anything been changed,  etc.?

Usually the layshaft bearing issue manifests as a prod in the calf after engaging first & under load e.g. pulling away (that's not to rule it out, but before you strip the gearbox, check the simpler possibilities first) - if kickstart operation is `fine without ignition, then this would, on balance of probability, suggest that it's an electrical/timing problem rather than a 'mechanical' gearbox type issue (a loose kickstart retaining bolt could slip/lock up -  but won't kick back as that requires energy acting in  the opposite direction!) .

Another thing to check is whether the Boyer rotor has slipped on the shaft? Do you have a booster or jump start capability to really max out the battery when kicking (will it start on ?

If it helps, I had a fractured wire to the Boyer backplate back in 1999 (Nellie returned home to our then house in Kingston in splendid isolation on a 30ft articulated low loader). I modified the connection by replacing the soldered wires with spade connectors secured to the Boyer back plate by brass bolts with two brass locknuts (iirc this was a mod from the old NOC-L list) & added a piece of foam into the points cover to reduce vibration of the wires (not touched it to date, 46k miles covered since then!)

I also have a 1975 Mk III ES, my starting process is usually:

1) Ensure sump is clear (depends how long she's stood), drain sump if required & top up with fresh oil (what's drained has not been through the filter)

2) Side & Centre stands up, i.e. supported on wheels 

2) Tickle both carbs (I've twin Amals without chokes)

3) Pull in clutch & a couple of kicks to clear the plates (should be no resistance. else plates are likely contaminated with oil or clutch centre is notched - latter will be really noticeable trying to get 1st & when waiting in gear with clutch in - damhikt!)

4) Ignition on, & use kickstart to nudge pistons 'just onto compression', let the kickstart reset & then the proper 'long swinging kick' (I sometimes use the ES, tho' more when the engine is warm, or I'm in the garage & testing with a battery charger handy! Kicking is more entertaining for civilians ;-) 

If you're bored there's more than one thread on here/Access Norton on starting procedure ;-)

Good Luck & Let us know how you get on!

The slot in the crank is actually 30 BTDC. 

You should alway keep your knee bent and not fall into the trap of kicking straight legged. If I kick I do it from the side, bike on stand Kick start engaged and knee bent. Sounds like ignition  timing and advance problem. 

If you haven't already done so, I would recommend that you purchase the Official Norton Workshop Manual for the MK III - you'll find it a very useful reference source!

& welcome to the club :-)

Why not just retard the ignition a tad with the backplate and give it try?  Sounds like it's slightly advanced to me and all these timing marks and settings are very confusing and not always correct.

With the Mikuni I wound put the enrichment on, ignition and kick. Not turn the engine over first as Mikuni enrichment is a full on device, you may be getting hydraulic lock with too much fuel mix in the chamber when slowly moved by leg?

Yes.

That's it set statically but it still needs to be strobed, the electric components inside the Boyer box all have a tolerance and this affects the final timing. 5000 rpm and 31 degrees is the target, if it's on the centre stand put a rubber mat under the stand or the bike will go walkies.

Get someone to sit on the bike & hold it in position on the front brake while you use the strobe, they can hold the throttle at 5k & shout out as y ou approach the magic number (& stop the bike moving by holding the front brake).

The bike will walk all over the garage floor even if you have a someone on the bike whilst on the centre stand (my ex did this @ 8 months pregnant  so 2 on the bike!) - much easier on the wheels.

Batteries can be funny things. Is your voltage check just an open circuit measurement ? Have had oldish bike batteries that show a healthy 13 plus voltage when putting a meter across terminals with no load but with even a small load applied voltage drops right down to below 12. Try substituting a newer / known good battery , if you haven’t already done this.

On the face of it the timing cover/camshaft seal is on its way out. Not, iirc, a big job, but be sure to acquire the conical ramp thingy (part no. 06.1359) to guide the new seal over the camshaft end, or your work will be in vain.

That's very high. Is it just after charging in which case it's showing the surface charge which can be misleading. As James says, look to see what it is with the ignition & pilot lights on when it should be 12.6 or above.