Little issue during Valve Clearance adjustment...

1981 XS400 - Picked it up a few months ago and was a non runner that was supposedly "running ok last year". It had a handful of new parts like carb rebuild components and whatnot. ...anyhow

Been lurking here for a few months and wanted to say thanks to everyone that has helped me without even knowing it.
I've set the carbs and she seems to start right up. After a few minutes it begins to idle funny and wants to die. I've done some digging and someone had described an over tight valve clearance shutting the bike down once it heated up. I thought I'd dive in and see how these ones are set.
- First off I cracked the small stator cover and it began to drizzle oil.... I quickly grabbed a stray soda can and placed it under the drip. That actually filled and I had to scramble for another.... and another... and another. I ended up filling 5 cans with what I now see is a gas and oil mixture (can't believe I had been running this engine)
[Could this have been my issue all along and not the valve clearance?]
- I rotated to what appeared to be LT and checked the intake clearance and it seemed good. The exhaust seemed a bit off so I reset it.
- As I went to cycle the engine again I noticed another mark on the stator (i think that's what it is) that said "LT"... I cycled through again and the one that I had checked at was "LF". I rotated to "LT" and both valves had no clearance. [What's the LF?]
- I thought "ah ha!" and went to reset these to the right specs. As I went to adjust the intake I found the nut was locked on the bolt. I removed it completely to try to free it and ended up stripping the nut out and beating up the bolt. Reset the exhaust and went to do the other side and the first valve adjuster I touched was also locked up.
- At this point I realized I was chasing my tail and decided to just order 4 new adjuster bolts. (gotta go find those)

so that's where I stand.
Do those bolts lock up often?
What's that LF?
Could all that extra gas/oil have been my problem?

LF- "Left Fire". Has nothing to do with setting the valves.
I've got a 40 year old XS400 with the original tappet adjusters and nuts. The jam nuts should las the life of the bike. the tappet adjusters sometimes wear out.

Most of your questions will be answered with the simple download of this:
http://www.xs400.com/threads/re-run-free-full-yamaha-service-manual.14495/

As for the gas in the oil, make sure the petcock is shutting off the gas when the engine is off, check the floats and the float needle and seat.

I had a feeling that's what the "LF" meant.
I have the manual and even printed it out....couldn't find reference to the "LF" in there.
..ya... these adjuster nuts were NOT moving. Makes me think the PO cross threaded them or something. Eitherway they were NOT adjustable.

Petcock is shutting off. When I got bike home I put gas in the tank and tried to fire it up. The carbs had been "rebuilt" but the floats were not set at all and therefor were way too high. So the bike flooded out quickly but apparently dumped more gas than I thought into the cylinders.

Pages 1270-1271.

Thanks! I think that's a different manual than the one I have. ... it may be a bit much to print out haha

As for the problem with the adjusters. I'm thinking someone over the years over tightened them thinking they had to be extremely tight to hold the adjustment. They either pulled the threads in the nuts or stretched the adjuster screws causing the thread pitch to be off causing the nuts to bind.

If new nuts turn on free and then get to a point where they become hard to turn the screws are stretched and to be safe need to be replaced.

Some oil dripping from the stator cover is normal upon removal. Id probably drain and renew the oil and filter just for piece of mind.

LF and RF are timing marks, Left and Right Fire. LT and RT are Left and Right Top ( top dead center)

I bought the Haynes manual for my XS360 and followed it entirely for my engine rebuild. Its always nice to have a hardcopy rather than having to check the computer with greasy hands or having loose pages blowing around.

When I set my valves, I found it to be somewhat difficult. Maybe it was due to my set of tools, I had to bend and get crazy with the feeler gages.

When doing valve adjustments put the bike on it's center stand. Then only a very little oil will drain from that spot.

xschris said:

When doing valve adjustments put the bike on it's center stand. Then only a very little oil will drain from that spot.

Click to expand...

I had read that here on the forum so I was a little shocked as 60oz. or so came trickling out! I actually ran up to the fridge and grabbed a beer... ya know, just incase i needd another can!

Reminds me of the time I used a 6 quart drain pan to do an oil change on a 5.9L Cummins turbo diesel.