Uraling in Alaska - Day 25: Valencia has a New Head

All day long I'd been checking the UPS site, tracking the parts from URAL HQ in Redmond, WA coming to Fairbanks.  The tracking tool showed their truck had left Anchorage late last night but then there was an intervening notice saying "adverse weather".  Finally, it showed arrival in Fairbanks at 09:22 AM but there things stayed the rest of the day.  : (

Fortunately, to take my mind off things, RichardM has asked me for assistance in the replacement of his Beemer's fork seals.  It took us most of the morning but we got it done with minimal mess, no cursing, no injuries and we both discovered how easy it is to do this task.  Note, we didn't disassemble the front forks completely, just removed the lower portion to replace the seals.

As we were resting up from our labors and having returned from a successful test ride by RichardM of his rig with the new seals in the front forks; we were chatting and my phone rang at 4:35 PM.  It was Jon from Frozen Motor Works telling me he had the parts and could I come on down.  I was on the road less than ten minutes later, motoring on down to Jon's shop!

So, as reminder, rough-running issues during my first attempt to get to Wasilla, AK on Wednesday of last week, had led through troubleshooting by Jon to discovering that the intake valve seat on my Valencia's left side head had not been "cut" during the manufacturing process.  This is apparently pretty rare but it does happen.

I'll use the below pictures to try and explain why having a cut valve seat is important to providing a good seal for the engine's operation.  Valves, control the ingress of fuel/air mixture into a cylinder's combustion chamber and also the exit of the combusted gases out to the exhaust pipes.

 The new head, and valve, inserted into the valve guide. The bottom

portion of the flat disc "mates" with a "cut" edge on the valve seat, 

proving a seal, to keep compression in the combustion chamber

 Here's a picture of the old "head".  

It's part of the engine's left cylinder in 

this case, aka the left jug.

 Above is the old intake valve, note the ridge formed by the 

the valve's surface hitting the uncut valve seat, as it was uncut and thereby

presenting a 90 degree angle to the valve, it had steadily been

cutting the above groove onto the valve.  Sooner or later it would have 

cut enough to break pieces off and then things would have gotten bad.

Basically, the valve would have gotten pulled into the engine, there to cause 

lots of damage and a ruined engine in seconds!

 Above is the old exhaust valve, note the smooth curved edge

on the valve, curving down.  This curved edge mates with the 

cut in the exhaust valve seat, providing a good seal.

Note: for the cognoscenti, the color gray above was actually the light

caramel color that is sought after on spark plugs.....

 Side by side comparison:

left, the exhaust valve that had a cut valve seat

right, the intake valve that didn't have the cut valve set

 A view of the left piston, those two slots on the side

is where the valves go into during the combustion process.

 Note the red and green arrows above

The red arrows indicated the narrow width of  "sealing surface" that Jon

the mechanic "lapped" onto the valve seat to achieve compression with the old valve.

The green arrows show the expected width of the cut of the valve seat that should

have been on the left valve seat, ready to provide a seal for the valve.

 Hopefully you can see, a wide difference!

 Above is Jon installing the new head

(nice and clean, isn't it?)

 New head installed with existing rocker arms and push rods.

Jon carefully torques down the head bolts to specific values.

Once the head was assembled, Jon set the valve clearances, buttoned everything up and quickly but thoroughly ensured the carburetors were sync'ed up and throttle cables were pulling evenly during acceleration.

It was around 8:00 PM now but still light, though of course it had started to snow.  I thanked Jon and we agreed I'd pay what I owed via Paypal (most of the bill is being footed by URAL as the head was warranty work) and left to meet RichardM, his wife Bridget and son Kyle at the Bulgogi Korean BBQ Grill nearby.

The dinner was a celebratory and thank you dinner combination.  Just a very small token of the gratitude and appreciation I wanted to show for all the hospitality and help they all had provided!  

Valencia ran great all the way back to RichardM's place after dinner!  It was snowing lightly, so will check the forecast and road conditions tomorrow morning before once again trying to get down to Wasilla and resuming my exploration of Alaska!  Snow predicted tomorrow morning for Fairbanks and rain for Wasilla though high temperatures will be in the mid 30s to low 40s as I head southwards on Alaska Highway #3.