Loss of power and White Smoke

[Jacob Simkins]

Hey guys, I recently purchased a 1981 Yamaha XS400. Took it out for a test ride and noticed it was leaking oil. Turns out there was probably a liter or more excess oil in the crank case. Cleaned it up and took it for another ride to see where the oil was leaking from if there was any coming out. Halfway through my ride when all was going well I decided to make a bit of a pull. Upon hard acceleration the bike had a sudden jump in rpm (sounded almost like a clutch slip or wheel spin) and then it was way down on power. Limped it home and it began to smoke. Guess I should start with a compression check?
Thanks, Jacob.

 

[buztabuzt]

Doesn't sound good . How did you clean up an extra liter of excess oil, you drain it all and replace or drain down to proper level? Could be gas in there which does NOT lubricate...

Hopefully you paid accordingly noting the oil leak ahead of time. Yes, compression test to start

 

[sandmanred]

And check the float valves in the carbs. Most likely the extra volume of oil was not oil but gas. Most likely way to get gas in the engine case is a stuck float valve.

How does the clutch handle feel? Is the travel right? My 78 Xs400E hadn't been ridden in a while when I got it last fall. Through the course of getting it running again about 1/4 of the friction pads delaminated from metal base plates and caused all kinds of problems with clutch slip and adjustment. You could possibly assess by looking into the oil cap for brown/black flakes that are roughly 3/8 x 3/8 inch square and about the thickness of a dime.

 

[Jacob Simkins]

Doesn't sound good . How did you clean up an extra liter of excess oil, you drain it all and replace or drain down to proper level? Could be gas in there which does NOT lubricate...

Hopefully you paid accordingly noting the oil leak ahead of time. Yes, compression test to start[/QUOT

Doesn't sound good . How did you clean up an extra liter of excess oil, you drain it all and replace or drain down to proper level? Could be gas in there which does NOT lubricate...

Hopefully you paid accordingly noting the oil leak ahead of time. Yes, compression test to start

Drained the oil down to appropriate level. Maybe I'll do a complete oil change...

 

[Jacob Simkins]

And check the float valves in the carbs. Most likely the extra volume of oil was not oil but gas. Most likely way to get gas in the engine case is a stuck float valve.

How does the clutch handle feel? Is the travel right? My 78 Xs400E hadn't been ridden in a while when I got it last fall. Through the course of getting it running again about 1/4 of the friction pads delaminated from metal base plates and caused all kinds of problems with clutch slip and adjustment. You could possibly assess by looking into the oil cap for brown/black flakes that are roughly 3/8 x 3/8 inch square and about the thickness of a dime.

Clutch feels good to me. And no slippage. I'll rip the carbs apart tonight. I should mention that so far compression in both cylinders is the same but its only smoking out the one pipe. I'll check the valve, thanks!

 

[buztabuzt]

What is compression PSI? If they're both equal but below 125.... Doesn't much matter they're equal...