I really lost myself this weekend
Thread Starter
|
Grand HDF Member
Joined: Nov 2009
Posts: 4,315
Likes: 1,663
From: Tampa
A thermocouple is something that allows a temperature sensing device to read a temperature based on a voltage passing thru the thermocouple. See the pic above, the ring goes under the spark plug and the plug goes into a K-type thermocouple reader (which I've already got). You have to make sure you buy the correct size for your spark plug. The Evo takes a 14mm. The reader sends a very small voltage out, then what voltage comes back is interpreted by the reader what the temperature being sensed is. It literally works no differently than a digital meat thermometer, just this one has a larger temp range.
The reason I'm putting it under the spark plug is that's the most accurate representation of cylinder heat temp anywhere on the head. The combustion chamber heat is hottest at that point.
Jegs and Autometer sell them, for over $30 a piece. I found them on eBay, from China, for $6 ea.
https://www.ebay.com/itm/CHT-K-type-Thermocouple-Temperature-Sensors-for-Cylinder-Head-Temperature-14mm/221410249204?epid=1062332703&hash=item338d1449f4:g :q2cAAOSwaMhZv2Um:rk:3
f:1&frcectupt=true
Last edited by Mattbastard; Feb 11, 2019 at 07:17 AM.
Thread Starter
|
Grand HDF Member
Joined: Nov 2009
Posts: 4,315
Likes: 1,663
From: Tampa
The ones I have currently came with the reader but don't have the ring on the end for going under a spark plug. They're just two wires with a really small solder blob on the end. I suppose I could JB Weld it to the head, then chisel it off when my testing is done, but I'd rather do this elegantly with the official spark plug leads rather than ghetto-fab style.
Here's the one I bought:
https://www.ebay.com/itm/4-Channel-K...x3NB:rk:9:pf:0
Here's the one I bought:
https://www.ebay.com/itm/4-Channel-K...x3NB:rk:9:pf:0
Elite HDF Member
Joined: Mar 2006
Posts: 3,673
Likes: 606
From:
i hate to tell you this but the rings on the end that go under the spark plugs can be had at an ordinary hardware store for 89 cents. i had one break on my 85's head temp. gauge , went to a hardware store and found one there in the electrical dept.
Thread Starter
|
Grand HDF Member
Joined: Nov 2009
Posts: 4,315
Likes: 1,663
From: Tampa
Nope. Not only is that electrical connector not rated for the temperature range max of a cylinder head, it's too large for the spark plug. The thermocouple based ones are stamped steel to fit perfectly under a 14mm spark plug.
Thanks for the pointer, but I'm way too OCD to be half-assing it considering this is the 3rd time I've put the damn motor together.
Thanks for the pointer, but I'm way too OCD to be half-assing it considering this is the 3rd time I've put the damn motor together.
Elite HDF Member
Joined: Mar 2006
Posts: 3,673
Likes: 606
From:
the factory copper one lasted 30 years when it finally broke. the one i replaced it with was exactly the same.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
7 Surprising Harley-Davidson Products that Are Not Motorcycles
Verdad Gallardo
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
