Saturday, May 04, 2013

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.


8 comments:

BeemerGirl said...

Dom, thanks for the concise explanation and visuals. Great for my brain that likes to see things. I'm aghast at the oversight in an uncut valve!! I'm so very happy Jon's shop found it! Was there any speculation on how long it would have last if it hadn't been discovered? (I just don't want to imagine the situation if it hadn't been seen/repaired.)

Anonymous said...

Dom, pretty amazing that the valve actually held up so well with no seat for 20,000 miles. Hope that's the last of your problems.

Cheers,

Dan K.

Charlie6 said...

BeemerGirl, you're welcome, helps me grasp the concepts in order to explain them later. No speculation as its such a rare occurrence, but once the edge started breaking....

Dan K. Well, almost 16000 miles anyways.... ;) I hope its the last of the unforeseen issues too!

GlennandSun said...

'Morning Dom, it is bright sunny and 55 degrees around Seattle...hoping your day out on the road is warming in that direction! Very pleased with your photos and explanation of the valve, seat and head relationship...was able to use them to explain valve workings clearly to Sun.
As a journeyman marine machinery mechanic, I am stunned that you got 30K km out of a head in that condition....you have won the mechanical lottery of life for it to show up where and how it did instead of somewhere between Lizard Lick, Nowhere and Lost World, Territories.
Keep up the great blog, we follow your every adventure....and misadventures...wishing you good riding here on out. Sun jokingly wonders if you should pick up a bear claw or jade charm to improve your luck. I suppose that is like a rabbit's foot or horse shoe to the headhunter and Chinese in her. Thanks for the daily Blog feeds..., GlennandSun

Erik said...

I would be interested to know if the seat is cut after the installation, or if the seats are pre-cut and then installed in the head. I wonder if it got put in upside down, or if it was machined on a late Friday afternoon?

John Snelson said...

So glad to see you back up and running. Good luck for the future. Will be following.

VStar Lady said...

So glad you have had the needed repairs done and that you found it before it was too late. How lucky that so far away from home you found a great host (port in the storm) plus a great repair shop - definitely good karma follows you.
Hope that is the last of the technical difficulties.
But really - what a great place to have to spend a few extra days, and with such great company.

Charlie6 said...

GlennandSun, 55 degrees...that would be nice right about now. Glad you liked the photos and my poor attempt to convey the concepts involved. Quite the learning experience for me too!

Yes, everyone who understands valves and valve seats is amazed. Just goes to show how durable these rigs are designed to be I guess, even when something so wrong gets past their QA.

Erik, no idea and not sure I'll get an answer from URAL anyways. Proprietary info and all that. We did verify the new head did have cut valve seats though! :)

Thank you all for commenting.