Potential pickup coil problem

[Back Roads Rider]

I have a problem starting my 1983 39E Tenere when hot or rather after sustained highway riding. It is particularly frustrating when stopping to fill up with petrol only to be unable to start it for the next 10 to 30 minutes. All my research points to a potential pickup coil problem.
I say potential because all that I have read have had the motor stall first and then not being able to start it. I have never had any stalling nor any misfiring. It just wont start or give any indication of a spark after the engine has been turned off. I have yet to do any testing of the various components of the ignition system. Not sure how I can test when hot as it only happens away from home. It has always started at home after I turn it off and then kick it over again.
Any thoughts or ideas on what the problem could be?

[jibber]

Plug, coil, lead. . ..........connection.........cdi......pick up.........

[charliext1vj]

Interesting...I have starting problems only when it is cold - I too am struggling to diagnose...and it has been suggested that it is the pick up coil.
Whats interesting on yours it is with a hot engine.....in my experience with Xt's that this has been a result of either a weak coil or weak fuel mixture. I would change the coil in the first instance and then do a compression test and check valves. Either way I share your pain. I rebuilt mine and did not touch the engine other than check the valves. I have looked into replacement pickups and there seem to be aftermarket ones in the states but looking to do a compression check first. Annoying but once started and engine is warm it works really well!

[Mezo]

Plug, coil, lead. . ..........connection.........cdi......pick up.........

I agree, start with the cheap stuff & make your way to the expensive stuff.

The clue is "sustained highway use & half hour to work again" so that could be the stator or pick up coils bathed in hot oil.

Mezo.

[motorang]

You can measure those pickups from the connector.
This is cheap (although replacement parts are hard to find)
Basically the pickups are two coils with a common ground which lives in the middle of the 3-bay-connector.

Ohms to be expected:

Outside to center bay = 115 Ohm (both)
Outside to Outside = 230 Ohm (you measure both coils serially there)
No connection from any of the wires to ground (frame/cylinder) or only in the 6 digit kOhm range
All numbers are stated by Yamaha as plus/minus 20% at 20 °C

One coil is for low revs, one for high revs, the CDI overlays them to get sparks all over the range right. Of the low range pickup fails you still can ride home but starting is a pain.

https://transmic.net/2016/07/14/yamaha/

Andy

[charliext1vj]

Thanks for the help so far...when I rebuilt the bike I did a nut and bolt restoration but left the engine alone and as is apart from new external seals drive shaft sprocket etc and to adjust the valves to within manufacturers tolerances.

So in short bike poorly starts but when running works ok.

So revisited the carb - even tried easy start but doesnt help.

I have now done a compression test which is low at 110 PSI (open throttle and electrically cranked).

So I am in the mind to drop the engine out head off, check piston and re-lap valves - what do you think?

The bike was rebuilt by Dave Lambeth before it did a tour of Morocco but that was some years.....hence my hesitation

thanks for all your help

[Mezo]

I would ask him first, i did message him on FB last week asking him to cast on eye over that 55W/1VJ bike but no reply back as yet so he could be on one of his overland jobbies in northern Africa.

Mezo.