Suddenly won't start

[zed9]

Originally Posted by Smoky

Yes. Running fine, didn't ride for maybe a week went to start it, nothing. The compression gage even if it's off was still reading consistently across the cylinders 1 and 4 the same and 2 and 3 the same but at a double difference. 30psi to 60psi

A bike won’t fire with 30 to 60 psi. Not enough compression.
That’s not your problem. A bike doesn’t go from normal running, high compression, to low compression, overnight. (Only a Harbor Fright gauge can say such a thing). You’ve got a bad connection somewhere.

[CeeJayTee]

Here in the UK some of our tool hire places will hire out professional compression testers for the diyers. Do you have those in the US? that my be your best option.

[3alfa3]

Originally Posted by Smoky

Yes. Running fine, didn't ride for maybe a week went to start it, nothing.

Did you ride mostly short distances, and with low RPMs? Is petrol you use good quality? Does bike burns oil and/or antifreeze?

Carbon buildup on valves and their seats (almost always intake) is possible, sometimes stuck piston rings etc.
If bike ran fine on the last ride, its impossible to have compression that low on all cylinders caused by wear, but there is instances when carbon buildup on valves and piston rings was cause of low or no compression after prolonged pause and cleaning was all it needed.
What engine oil do you use? Maybe burnt low quality oil was deposited on valves, valves seats etc, got hard over a week of pause and now compression is low because of that.

Do check compression tester to be sure its reading was accurate.

[Smoky]

Low compression verified. Not enough for combustion

[Led Zed 70]

Dang that sucks! We’ll hopefully simple like head gasket or piston rings?

[Smoky]

Hoping cam chain jumped a tooth. This would explain identical psi on cyl. 1 and 4 ...2 and 3.
Have done this on a Ninla 400, ( top end work) before. Just more stuff..a lot more.

[Led Zed 70]

Well good luck and can’t wait to hear what it turns out to be and you get her running soon.

[Smoky]

I'll keep posting as I go through the process
Thanks everyone

[Smoky]

Valve cover is off. Timing marks are curiously 180° out from my manual. So I find it safe to assume that my manual must be wrong or more likely I am interpreting it wrong. If the bike jumped time it wouldn't be but a tooth or two off. Gonna have to ponder on this.

[Zaniac948]

Not to insult your skill level at all but did you hold the throttle butterflies open during the compression test? My friend did not do this and it gave him a deceptive low reading. Best of luck with a very weird problem