Low Compression

[Oz Vision]

Motor not started for 15 years. Have done carbs, electrics, new carb boots, new battery, starter motor and upgraded cables to Tiger models.
Turns over great but won't fire. Has fuel and spark, so finally check compression - cold of course. Jumps to 60psi then crawls to 90psi. Drop some oil down plug holes, test again, both jump momemtarily to 120psi. So, I'm thinking as per Haynes either stuck rings or worn out rings/cylinders. Speedo says 60,000 klm (35,000 miles).

I would like to think it's just stuck rings so next step, some diesel down plug holes to see if rings might free up. Any other views?

[Lucky]

had the same problem on an older motor.  once you get it started, it should free up with a good heat up cycle.  the hard part is it'll flood easy until the compression comes back up.

try starting it with as little load as possable (pull the headlight fuse, hold the clutch in, etc) hook up a jump box or jump it off another battery (not running) you want the starter spinning nice & fast. try to start it with no choke but feeding it carb cleaner thru the top of the carb.  if you can get it to kick & run for a few seconds with carb cleaner, rinstall the airbox & tank (or use a pony tank) and try again.  make sure you let the carbs fill on primwe a good 3-5 minuets before hitting the button, and resist the urge to crank the throttle several times.

[Walt_M.]

And when it starts it will blow white smoke out the exhaust for an extremely long time.

[Lucky]

White is water (steam) and while generaly not a good thing, on an engine that has sat a long time, it's not unusual.  even though i changed the oil, one that i resurected smoked for days, but now is one of my daily runners (cafe) no smoke, black white or blue.

[Walt_M.]

The one I brought up to you blew white smoke, not really steam all the while I had it running. But of course you know what happened to that.

[Lucky]

That was my fault though, the window was stained & I thought there was oil in it, I should have changed it first.

[George R. Young]

At around 60,000 km, I had to replace the rings. The compression rings were ok, but the 2nd vacuum rings were worn enough that they didn't create much vacuum at idle.

[Rikugun]

That was my fault though, the window was stained & I thought there was oil in it, I should have changed it first.

Yikes! So that's what happened to that motor.....   Well, let others learn from your mistake.  :)

Never assume there's oil in a used motor - most people drain fluids prior to removal and why one would try and run it on unknown oil condition is beyond me but I digress - just change it.

On your daily rider a sight glass viewer is so easy to use there's no excuse not to use it before every ride. If you can't see the oil move in the window within a few degrees of vertical there's something wrong - investigate it. I keep mine pretty full so after it sits, the window is full. If tilting the bike doesn't reveal the level I wouldn't start it but rather check the fuel level to ensure the tank hasn't emptied into the crankcase!  :o  On the other hand don't be fooled by clean looking oil in the window when actually there is none. Tilt the bike towards and away from you to verify the oil level.   And remember, friends don't let friends ride when their oil bag isn't tanked up or something like that.  ;D

[fret not]

"Oil bag"  That's Harley talk!    :o:police:

[Rikugun]

Why yes it is! But now that you've caught me I'll swear I was referring to the early Honda 750 Four's.... :D

[Lucky]

Hey thanks for the lecture, just what I needed...

[Rikugun]

What can I say....I'm here to help any way I can   :)

Actually, it wasn't intended as a lecture for you but maybe it yanked off an old scab.   :o Sorry 'bout that.

[Lucky]

I didn't say i was upset...