2004 r850r low compression bike only has 25000 miles

[Bikesmikey]

Bike cut out but idiot lights still on, it restarted, ten miles later did it again, but it wouldn't start.
Got it home by trailer, next day it started as normal I shut it down in surprise lol.
However, it would not start again. I v replaced the fuel filter and fuel pump as i had the tank off while checking for a loose connection.
I then did a compression test with a proper gauge. left cylinder 60psi. right was 110psi. Iv removed the cylinder head presuming
a head gasket problem but it looks fine. considering the bike has only 25,000 miles and service history its unlikely to be rings?
Any suggestions?

 

[Popell]

Bike cut out but idiot lights still on, it restarted, ten miles later did it again, but it wouldn't start.
Got it home by trailer, next day it started as normal I shut it down in surprise lol.
However, it would not start again. I v replaced the fuel filter and fuel pump as i had the tank off while checking for a loose connection.
I then did a compression test with a proper gauge. left cylinder 60psi. right was 110psi. Iv removed the cylinder head presuming
a head gasket problem but it looks fine. considering the bike has only 25,000 miles and service history its unlikely to be rings?
Any suggestions?

Have you checked valve clearances/valve seats?

 

[frodi]

Try checking the side stand ignition cut off switch. A build up of crud can leave it permanently on.

DAMHIK

 

[Bikesmikey]

I have reground the valves in so now both cylinders are 110psi.
But the problem remains so far iv renewed fuel pump/filter valve seals. I have a fat healthy spark sometimes it will fire up for a few seconds then dies but not every time
Im thinking perhaps Hall sensor, I hope not lol I have to work on the floor and my knees are well gone so are my 70-year-old hands so im hoping
it not. So next i will check the side stand switch.

 

[Bikesmikey]

I have tested the stand switch works fine.
Then! I did the test on the hall sensor as described here via the rear wheel ignition on, plugs out resting on the cylinder,
fuel injector out. I manged to turn the rear wheel in 4 gear fuel inject was good but no spark. even though earlier when I used the starter
there was. Seems the hall sensor is the next job.
I must say though when was setting up the valve testing, I got great help from Ross at Motorworks so Thanks Ross.

 

[Bikesmikey]

AAArgh It's not the Hall sensor I borrowed one but the same symptom.
The bike fires using the starter soon as i release the button it's all stop no firing; I have confirmed the spark nice big fat one.
and their wet so fuel is there. Fuel pump is b new as it the filter.
Im thinking perhaps im a tooth out when fitted the valve timing sprocket but which way?
Im going to check it all lines up next.
So any input is welcome

 

[Bikesmikey]

Update.
I checked id got the valve timing right and the ignition which i had, but i forgot the throttle position sensor needed looking at I tried just turning it anti clockwise
and hey she's running and ticking over fine.
so acid test tomorrow.