Do these plugs tell anything after 96 gtx died?

[Legacy37]

My other ski is a 96 gtx. I just got it running with a known running 787..original engine ate a piston so i pulled the engine out of my xp. Go to the lake it runs for a minute then dies like it was pulling air. I replaced the fuel lines (it didn’t have the old gray lines), the fuel filter, o ring, and the fuel selector. Both carbs were rebuilt two years ago with genuine mikuni kits and I rechecked popoff before installing the engine. It was within specs but on the lower end. I go to run it and it took off planes out 6k rpm for about 20 seconds then it slowed down, came off plane and then quit. The starter at this point would only spin and not engage the flywheel so crud, done for the day. Do these plugs help identify the why? You guys have such a wealth of knowledge it is amazing. Thank you!

 

[burtshaver2021]

Well, I’m no expert but I would say the one on the right looks like it ran lean

 

[Legacy37]

Guess i will bore

Well, I’m no expert but I would say the one on the right looks like it ran lean

Guess I will scope the cylinders to see if they are damaged and then figure out the lean

 

[mikidymac]

Yes, left looks good right is lean.
What’s the compression?

 

[Legacy37]

Was great before this run, will test it tomorrow. I think found an air leak at the fuel filter

 

[Legacy37]

Yes, left looks good right is lean.
What’s the compression?

Work getting in the way of my fun. Compression is 165 both cylinders. I removed all the zip ties in the fuel system and replaced them with worm clamps. Vacuum tested the fuel system and it held 15” so I am guessing I fixed an air leak unoess the problem is in the carbs but I did check popoff before I put it together. It was on the low end of spec but within spec on both carbs

 

[burtshaver2021]

Somebody correct me if I’m wrong please but with only one plug being lean, would that not mean it’s from something that would only cause a lean issue on one cylinder? Like the carb base gasket or a crank seal? If it was somewhere in the fuel system like selector valve or fuel line fitting would it not lean out both cylinders equally?

 

[mikidymac]

Somebody correct me if I’m wrong please but with only one plug being lean, would that not mean it’s from something that would only cause a lean issue on one cylinder? Like the carb base gasket or a crank seal? If it was somewhere in the fuel system like selector valve or fuel line fitting would it not lean out both cylinders equally?

1996 GTX is dual carb. So could be only one being starved. But typically it’s that carb or intake leak.

 

[Legacy37]

1996 GTX is dual carb. So could be only one being starved. But typically it’s that carb or intake leak.

 

[Legacy37]

Is there a way to test for that or should I pull the carbs and start over at pop off and inspect intake/carb gaskets? The way it quit was like when my single carb gti had a air leak at the fuel filter. Ran hard for a couple of seconds then quit

 

[Legacy37]

okay pulled the carbs, rechecked the popoff 36/37 they both held 10psi with no issues. Carb gaskets looked good. I didn’t remove the intake so I can’t imagine the gasket has failed? Is that a thing?

 

[bradleysomers73]

Was it pto side that was lean? The crank seal on that side flogs well before the front seal and sucks in air.

 

[burtshaver2021]

okay pulled the carbs, rechecked the popoff 36/37 they both held 10psi with no issues. Carb gaskets looked good. I didn’t remove the intake so I can’t imagine the gasket has failed? Is that a thing?

Yes, it happens. When I was doing the leak down test on my challenger 717 it was leaking from the prong beneath the intake