Dazed & a bit confused

I shall do so and thanks for suggesting this - Even having lived and worked all over the world and being back here for 8 years now, I forget how wonderful NZ & the South Island is for riding.
 
Thanks all. I’ll get an inline spark tester and see what that tells me. The charge system is a new Mikes XS stator, rotor and regulator - I’ll get a voltmeter into the system and check this also. The coil is a new one that came with the ignition system and I believe both to be OK - I swapped them across to my other xs and they worked fine.
Fuel is good - clean sealed tank with two new taps both giving good flow rates. Carbies are I believe fine also - float levels at 22-24,, as per the VM manual. I’ll have one long play around the electrics see what I can find.

I have chased my tail on more than 1 occasion with a brand new coil that was a dud.
 
I have a similar problem with my 74. After finishing the rebuild, it ran great with numerous mods: extended manifolds, VMs, pancakes, PMA, single points, reed valve, +++ and the two guys next door both test rode it as I am unable and it ran great. Then, it just refused to start. I checked absolutely everything, must have cleaned the carbs a dozen ties, checked the timing, plugs, coil, points, condenser, compression, valve clearance, +++ everything was fine, but I was left pulling my hair out. Out of desperation I made an adapter for the spark plug hole and connected it to acomressor and discovered the inlet valves were leaking.
When I rebuilt the engine, I had it rebored and also trusted the same guy with the valve seats as they were badly pitted, the only jobs I've farmed out. I took him at his word, he said the valves were ready to go and so I never checked, so much for that.
I haven't got aroumd to restarting it yet, as I broke the point bucket and lost the sump filter plate, then went on a cruise to NZ, only returning today.
When I get aroumd to it, I'll look around for a sump filter plate, already have a point bucket. Hopefuly, the leaking valves are the problem, although, I can't work out why the compression was up around 150 with leaking valves???
 

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Hello all and Happy New Year to all; It shall be a good one.
Now back to the saga of the bike:….
I’ve now eliminated I believe many if not most vaiables that could cause the erratic running of the bike. I am satisfied that the fuel, plugs, ignition and charging system are not causing the issues I am experiencing.
The bike now starts and runs well, idles beautifully and revs smoothly through the rev range.
Until it gets hot - after say 5 or so minutes of running, it starts to miss stutter and ultimately stops running. It then will not start. Leave it to cool down, come back and it starts and runs. Until it gets hot and then starts to stutter etc..
So I’m now thinking mechanical things; head gasket or cracked head or barrel or piston perhaps?
I’d love your opinion here - I will run it up and check compressions when it is hot - but I’m kinda thinking that it’s pointing to a mechanical issue as opposed to a fuel/ ignition matter.
Hi @Crashedkiwi
My bike suffers the exact same symptoms as your machine. I have yet to get to the bottom of it after trying all sorts of known remedies. Even with a Gonzo igniter box (GN250) it fires up first press, idles and revs up fine. Five minutes when warm it splutters and mis-fires. I have done a full rewire using Moto-Gadget m.Unit but still no joy. It ran fine before the rebuild.
 
Thanks all. I’ll get an inline spark tester and see what that tells me. The charge system is a new Mikes XS stator, rotor and regulator - I’ll get a voltmeter into the system and check this also. The coil is a new one that came with the ignition system and I believe both to be OK - I swapped them across to my other xs and they worked fine.
Fuel is good - clean sealed tank with two new taps both giving good flow rates. Carbies are I believe fine also - float levels at 22-24,, as per the VM manual. I’ll have one long play around the electrics see what I can find.
So there is a lot of new parts
New Charging and New Ignition
Please give info on what those are
If I recall right maybe Jpdevol said that certain PMA Systems combined with certain ignitions was to ask for problems

But if these are new and Working setup it gives info for other thoughts.
 
Longtimeago when they put MTBE in the fuel I had terrible problems with my XS, it dissolved some plastic bits and left me in a bad spot. I would verify that the tank coating is nice...as in not dissolving Good luck.
 
So there is a lot of new parts
New Charging and New Ignition
Please give info on what those are
If I recall right maybe Jpdevol said that certain PMA Systems combined with certain ignitions was to ask for problems

But if these are new and Working setup it gives info for other thoughts.

Post #1
 
Thank you more info helps -- progress

Tri spark ignition and a MIkes XS stator/rotor kit.

As I understand it it is that ignition
https://www.trispark.com.au/technical/

They have a support
https://docs.google.com/forms/d/e/1FAIpQLSejhAF8BEml06PRY2lc9NyShhb0UP9vlBhdH74y9XzIOYq1bw/viewform

perhaps ask
If PMA and Trispark can be a problem and more coil problems

And Mikes has several charging options but the "Kits " are PMA

I am still at electrical problems I feel it would run on one cylinder or have a difference left right if other
I have no experience of tri spark and very little of PMA systems .

But I do know that Boyer Bransden don't like Voltages out of range To high or to low weird things can happen
I have also heard off fake regulators for PMA sometimes of poor quality

The Voltmeter installation is one way forward
 
OK guys thanks all. So I’m landing on a blocked vent in the tank - when I take the bike tank off & use my workshop fuel tank, the bike runs fine. I’ve checked the voltage and I’m seeing 13.v at idle & 14.6 off idle. I’m now quite comfortable that the ignition and the charge systems are working well and are not causing the issue - (I have two xs650’s both running Trispark ignition systems and they are good & I‘ve swapped them between bikes to prove both).
I’ll take a look at the cap vent and see if it’s blocked and report back. Greatly appreciate all the insight and suggestions received here!
 
OK guys thanks all. So I’m landing on a blocked vent in the tank - when I take the bike tank off & use my workshop fuel tank, the bike runs fine. I’ve checked the voltage and I’m seeing 13.v at idle & 14.6 off idle. I’m now quite comfortable that the ignition and the charge systems are working well and are not causing the issue - (I have two xs650’s both running Trispark ignition systems and they are good & I‘ve swapped them between bikes to prove both).
I’ll take a look at the cap vent and see if it’s blocked and report back. Greatly appreciate all the insight and suggestions received here!
Just a hint. If the bike acts up again, get a 3000 rpm voltage measurement please. That would absolutely put the question to rest.
 
Well thanks to all that offered suggestions to find what was going on. These things are always a matter of elimination & having differeing perspectives means you're sure to cover every potentiality. I finally tracked the issue to be electrical; (Jan_P called it!) There was a broken internal wire on the ignition circut. The break only occurred when the tank was fitted, as this moved the wire slightly and failed the circuit. So a rewired, re-routed ignition system and I have a sweet running bike. Thanks all and once I finalise the side cover fitment, I will get some pictures of the bike against on of our wonderful rides we have down here.
Thanks to all again.
 
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