94 banshee seizing right piston and rod

[Silentsoul]

Hey guys! Just a quick question on a 1994 banshee that I owned. It would run like a raped ape for about 10 hours, then it would seize the right rod to crank, and the right cylinder,piston, would be trash. I tore complety down, and did a leak down test when I rebuilt it, it passed, The top of the pistons both had the leathery brown look to them, so I know it was not running lean or rich. It was a stock stroke, bored .40, with a mild port job, and timing advance plate tors were not removed. Any ideas?

[Silentsoul]

Hey guys! Just a quick question on a 1994 banshee that I owned. It would run like a raped ape for about 10 hours, then it would seize the right rod to crank, and the right cylinder,piston, would be trash. I tore complety down, and did a leak down test when I rebuilt it, it passed, The top of the pistons both had the leathery brown look to them, so I know it was not running lean or rich. It was a stock stroke, bored .40, with a mild port job, and timing advance plate tors were not removed. Any ideas?

 

 

Anything??????????

[Jereme6655]

Anything??????????

 

you can't really judge the whole rich/lean thing by the carbon that is left on the pistons.......you really need to do a plug chop in order to get it dialed in correctly........so it actually could have been running a little lean for all 10 hours.

 

What fuel/oil ratio were you running?

[Larry's Shee]

Also, what kind of oil? What was timing set at? Has this only happened once?

Edited April 15, 2011 by Larry's Shee

[Silentsoul]

I was running klotz at 32:1. This happened 3 times in a row. I went through both carbs, played with jetting, timing was at +4.

[WINDYCITYJOHN400]

Have you verified that the crank is not out of phase? (Could effect the timing in the right cylinder if the cranks not at 180 degrees from the other cylinder.) That's my first guess.

[sleeper06]

same crank all three times or diffrent cranks,and what mods an jetting were you running

[Silentsoul]

Have you verified that the crank is not out of phase? (Could effect the timing in the right cylinder if the cranks not at 180 degrees from the other cylinder.) That's my first guess.

 

 

Would you mind explaining a little bit more on the crank being out of phase? I have never heard of this, so this could have very well been the problem.

[Silentsoul]

same crank all three times or diffrent cranks,and what mods an jetting were you running

 

It was a new hotrods crank everytime. Mods are in the first post, nothing to radical.

[WINDYCITYJOHN400]

OK, I'm going to speculate that your porting isn't matched side per side. I've had that on a few motors. One side might need the jet to be 1-2-3 sizes larger. You can still get a good looking piston top, and even a good plug. But you just might be detonating at a certain RPM. (You would have a better idea of how often your motor makes long pulls at high RPM's) But if the long hard runs are spread out far enough between your regular riding, you might be getting some damage to the bearings from detonation as the motor goes lean. Other than that....I go back to looking at the crank. You said it was a new crank each time, so that rules out a twisted out of phase crank causing the timing to go off. But I had a motor that would pass a leak test....untill you started it. The problem was the bottom end was assembled into cases that were too loose. So the bearings would have too much play in them. This would cause the crank to wobble and when it did, air would leak in through the crank seals. I'd look real close at clearances in the cases. Your issue might be related to a running motor air leak or from friction heat from misalignment. Also you might check your pipes. (not sure if you run a pipe with a spark arrester) but they can get clogged and hold heat in the cylinder. That can back too much heat into the motor and cause issues too. Have you inspected your filter situation? I had a friend who's K&N filter adapter was not sealed to his airbox well and dust and dirt got into the motor. 20 hours later the pistons were junk.

I'm just throwing ideas out there for you. You'll have a better idea if any of them sound like they might fit your situation.

[Larry's Shee]

Windy, that motor you had, were they factory matched? To O.P. , are your cases factoy matched?

[slag_350300]

This happened to me also. For some reason teh two paul turner national cylinders were ported differently. The left side intake bridge was grinded down to a point. and the right side intake bridge was flattened.

[WINDYCITYJOHN400]

Windy, that motor you had, were they factory matched? To O.P. , are your cases factoy matched?

 

Yes, factory matched. The porting LOOKS the same from cylinder ot cylinder, but they are off just enought to run different. I'm 2 sizes leaner on my right then my left. Crank is true. I've tried different pipes and carbs and reeds. Finaly desided the motor runs fine, it just needs different jets per cylinder.