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Author Topic: Melting ground straps. Still!  (Read 622 times)

Offline atvmxr

Melting ground straps. Still!
« on: January 29, 2023, 08:56:28 PM »
Been fighting this issue awhile now.  The ground strap is melting off spark plugs. 
Thought it was lean, put in richer jets/ needles and plug is dark chocolate. No grey specs
205 psi compression.  Running Sunoco 110 with 927 at 40:1
Put in all new 2001 cr ignition
Switched to a colder B9 plug

I thought the ignition swap fixed it.  But this past weekend, after 5-6 tanks of gas, quad wouldn’t start.  Pulled plug and found this.  >:(
Bunch of race quads that run on premix

Offline Langbolt

Re: Melting ground straps. Still!
« Reply #1 on: January 30, 2023, 03:19:02 PM »
I wonder if you got some of those Chinese knock off NGK spark plugs ???

Where did you buy your plugs from ?

Very weird that the weld on the ground strap would let go like that!

:(

Offline The norm

Re: Melting ground straps. Still!
« Reply #2 on: January 30, 2023, 05:25:00 PM »
I have only seen the ground strap dissappear when the cylinder was very lean. Your plug shows that you have the cylinder rich. I am very interested in seeing what you find.
Loren
1986 Trx250r-- Hybrid Engineering 391(Good bye super 310)
1986 Trx250r-- Hybrid Engineering  ported stock 86 cylinder
1986 Trx250r-- craigslist engine with unknown ported 89 cylinder.
1985 Atc250r-- Needs a lot of work (Super 310's new home)

Online Jerry Hall

Re: Melting ground straps. Still!
« Reply #3 on: January 31, 2023, 12:50:11 AM »
Does the top of your piston or head show damage from the missing ground strap?

Does your spark plug ever get loose?
 
Do you have the CR 125 or the CR 250 Box?

Where do you have the timing set? 



All of the heat ranges of a series, have the same ground strap. 

Example:
 B7es through B10es have the same ground strap.  B7EV through B10EV have the same ground strap,  B7EGV through B10EGV have the same ground strap and so on...... 

The heat range only changes the operating temperature of the center electrode and the porcelain that surrounds the center electrode.  Changing the heat range has no effect on the operating temperature of the ground strap unless detonation is occurring.

Common causes of detonation:

1.  Low octane fuel
2.  Lean air fuel ratio
3.  Ignition timing that is too advanced or has an ignition that has the wrong timing curve for the engine combination.
4.  Stinger on the exhaust system that is too small for the amount of power the engine is making or spark arrestor that is too restricted.
5.  Loose spark plug
6.  An air bubble in the top of the head that is not allowing the coolant to keep the spark plug threads and spark plug sealing washer area cool. 



Online havinnoj

Re: Melting ground straps. Still!
« Reply #4 on: January 31, 2023, 11:54:57 AM »
What is the cylinder, carb, and full jet specs?  Are there any lean "spots" in the throttle position?  Maybe your quad is rich at idle, maybe it's rich on the main but lean in the middle somewhere? 

Online croat1

Re: Melting ground straps. Still!
« Reply #5 on: February 10, 2023, 10:33:17 AM »
This was happening before the CR ignition swap?  What ignition was in it before?

Joe

 

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