Wednesday, March 29, 2023

Yagi Loses a Nut and Stewie is getting New Tires

 So today, I decided to check the valve clearances on Yagi, my TW200 motorcycle.  This was part of the continuing diagnosis as to why she was suffering severe power loss when above 2d gear.

The Z's dropped off a new spark plug and a torque wrench for me at the junction of I-8 and Ogilby Road where I met up with them as they were headed to El Centro, CA to pick up tires for Stewie, their overlander.

The new spark plug didn't fix anything so it was time to check the valves.

It took me a while to get the valve covers off, the allen head bolts holding them in place were on very tight!   I'm pretty sure I'd only use the specified 10 nm the last time I had the covers off for a check but who knows.  It has been quite a while I admit, I've not been following the scheduled check every 4000 miles; and Yagi is approaching 19K miles on her odometer.

I had to grind down a 5mm Allen Wrench so that it was short enough but finally got all the bolts to break loose and removed the valve covers.

And that's when I finally found the cause of the power loss:

Yep, the locking nut is gone!
This is the intake valve spring and tappet

Exhaust valve spring and tappet
note the locking nut on top

So, where did the nut go after it obviously backed off?  It's got to be somewhere in the cylinder head; I can't see how it could get past the piston to get into the cylinder and the crankcase!

I spent some time fishing about the intake valve spring and tappet housing area, hoping to find the missing nut.  No luck.  Dammit.

Obviously, it was someplace inside, but apparently in some location where it's not interfering with the operation of that portion of the cylinder head mechanisms!  After all, I'd ridden it home at least five miles, slowly of course but still.

I've also taken her out at least three times for real short rides as I did one diagnosis step or other.  She seemed to move fine in first and second gear but would not accelerate when shifting to third gear.

I plan to try some more fishing with the magnetic pickup tool tomorrow while I debate next steps.

The options as I see them are:

a.  Locate the missing nut, put into place with some blue Loctite and carry on.  Obviously, this is best case scenario.

b.  Not locate the missing nut, get replacement nut, adjust valves and carry on.  I would of course have to rename the motorcycle from Yagi to Time Bomb.

c.  Remove the cylinder head (dicey given my skills and experience), locate the nut and put it all back together.  

d.  Find a dealer who can work on Yagi and fix things.  Pricey I am sure.

Much research and thinking ahead.  On the positive side, Scarlett, my Ural Patrol sidecar rig started fine this morning and seems to be holding a charge.  

So, as the "heir and a spare" saying goes, it's good that I had both Yagi and Scarlett together again!  Can you imagine the travail it would have cause for Yagi to malfunction while in Baja California, Mexico!  Yikes.

There was quite a dust storm this evening so no sunset pics from here.  Lori Z. sent me this one of their overnight lotdocking location.  The tires they got for Stewie, shown below, will be installed tomorrow I think.

Sunset, El Centro, CA

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