Poor starting when hot

[muskrat]

Cheers Musky - so 12 and 16 - what'll that do performance wise?

Can't hurt to try. It ain't performing now 
Had similar when I first converted the A7SS to a A10 CR. Once hot she was down on power and wouldn't start till cooled off.
Cheers

[Worty]

Cheers Musky - cheeky question, do you know what size the front spindle clamp bolts are and the mudguard studs on the lower fork leg?

Nice to hear from you again.

Worty

[muskrat]

G'day worty.
Wasn't that ? asked a few days ago? 42-5084 = 5/16 cei x 1, 7/16"
Cheers

[Worty]

It was mate, but I didn't get any replies - very much appreciated though.  I've got a problem with a sheared mudguard stud and a stripped thread for the clamp bolt - got an adequate spare on at present but wanted to refurb the other.  I guess the stud is welded on so I may need some expert help.

Cheers

[Worty]

Ok.  Slip ring cleaned, new pickups, cleaned earth brush, new sparkies set at 16thou rather than 18thou, inlet at 12thou - exhaust at 16thou, points correct at 12thou.  Kicked up first time cold.  Am I right in guessing that, if I get spitting and backfiring now, I'm in for a maggy rebuild?  Does seem weird to think that the maggy is failing only when it's very warm, but I note that this is fairly common.

What do you reckon??

[RDfella]

Most magneto failures occur when they're hot. No idea why (no doubt groily can enlighten us). Maybe it's the condenser / capacitor more likely to fail when temp rises?

[Swarfcut]

 A correctly gapped contact breaker can still result in an error to the timing, if the drive gear was fitted with the gap incorrectly set  initially. Opening the gap advances the timing, closing the gap retards it. So you need the correct points gap, armature correctly set, piston height set/backlash eliminated......then  on with the drive gear  with  auto or manual set at full advance.  Only then  will you get the correct  timing by the book. Which may then require a tweak depending on the fuel being used.

 Erratic running/ misfiring. Number one suspect is  steel points backplate type contact breaker spring touching the cam ring. Brass points carrier is a different electrical path. All detailed in previous posts.

 Easy starting cold, with poor ignition, no starting  and sudden ignition failure when hot are symptoms of  a condenser on its last legs. The remedy is relatively inexpensive, and consists of  substituting the well respected modern EasyCap for the failed electrolytic condenser originally fitted. If the magneto works well otherwise,  and from the description it produces sparks in the right place, this will transform the magneto and add reliability for a reasonable cost.

 Swarfy.

[Worty]

Points toward a failing condenser (no pun intended).

Timing was pretty good up until now.  Ran smoothly, excellent acceleration, no issues.  Timing was done by me and the geezer who helped rebuild the engine.  Same thing applies to points backplate.  Can't see how either of these issues have changed from when it was running really well until now.

Bike starts very easily from cold.  Depending on how hot the ambient temp is, it starts misfiring after around 20-30m, especially on acceleration, this is becoming more common.  Bike refused to start from very hot for around forty minutes last weekend, then fired up unexpectedly and ran on for another 100m with a fair few pops and bangs along the way.

I'm not competent enough to do a maggy rebuild myself.  I also know there's a chip in the top of the slip ring.  Priory Magnetos seem to offer a rebuild for around £300ish, don't know if that includes the EasyCap but it seems sensible to get this done.  Ignition timing seems a right PITA, but may give it a shot.  I've just created a thin rod which has the 11/32 markings on it for the btdc timing method, but I may get my mate to help out as he knows more about what he's doing than me.

To create my timing rod, I put a shrink insulator on the rod, put it up against a straight fixing bracket secured by one of the head steady bolts, made a cut on the insulator then measured the 11/32 with a digital Vernier gauge.  I then cut the insulator again at that point and removed the section of insulator.  That way, I get a nice edge on the insulator to measure the distance by instead of relying on a permanent marker.

Cheers in advance.