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Discussion Starter #1
What is the relationship here? I took my 05 train back to the dealer for Pa. inspection and some warranty work which included new valve seals and a dyno run to check the afr. My front cylinder was fouling up pretty well and I had to keep after the plug. One of the things I notice now that I have it back is its not popping on decel nearly as bad as it used to. Why? Pulling oil under high vacuum will make it pop? It pops worse on syn then on dino? It makes my ass look fat? I don't know it just doesn't make sense to me.

Anyway its an stock 88 with a Stage 1 and an LSR.

Thanks

Steve
 

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You could of had a leak in the exhaust system, possibly at the head. Or, the tech looked at your engine's vitals with his laptop, and saw that you had the wrong or outdated data file, and reflashed your ECM with the correct, or a closer mapping. Why don't you ask the tech?

Thorns
 

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machinist said:
What is the relationship here? I took my 05 train back to the dealer for Pa. inspection and some warranty work which included new valve seals and a dyno run to check the afr. My front cylinder was fouling up pretty well and I had to keep after the plug. One of the things I notice now that I have it back is its not popping on decel nearly as bad as it used to. Why? Pulling oil under high vacuum will make it pop? It pops worse on syn then on dino? It makes my ass look fat? I don't know it just doesn't make sense to me.

Anyway its an stock 88 with a Stage 1 and an LSR.

Thanks

Steve
Red pill, blue pill....You DID get it! Congrats! Soooooooooo, is it "ALL THAT?" Send me a pic! More important, follow Totenkompf's saga for some future trend outcomes! Gotta admit, he did his research well and he might, just might, have convinced me to go his route rather than the Edelbrock setup I have my eyes on.

Now about this popping thing--don't know. Pulled my plugs and the front looked perfect--the rear looked a bit black for my preference. Further, I do a LOT of short rides right now--perhaps that "Start up" rich fuel mixture is causing the infamous "pop." Take that sled out on a hour's cruise and see if it "pops" on decel--my guess is, like the slogan says, Dyna's where meant to devour miles (your bike needs to be thoughly warmed and perhaps since you got the new pipe you put some miles on the bike an--it got warmed up--does that make sense?) Further, I notice after an hours ride, my rear jug is much warmer than my front--that would make sense because it is, after all, an air cooled motor, which leads me to another thought about the EFI management factory settings about 'why come' the rear comes preset "rich."

Well, DUH! The boys like hang but, when the moisture wicks into my crack--that becomes downright nasty when it's laundry time! Maybe I could stuff a couple of depends in my drawers--it could be a better way to collect the lizzard juice secret ingrediant?

Congrats on the pipe!
 

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Afterfire on decel is quite common and not easy to completely eliminate. I imagine that it is possible that a leaky seal could alter the AFR enough to cause afterfire.

It's possible they tweaked the AFR in the map in the ecu. Ask the tech what they did.

I know with my SERT on heavy decel from speed, the injectors are completely off and you can feel them come back on at about 2000 rpm. Pretty hard to get decel popping when there is no fuel at all. I know prior to my engine makeover I used to get afterfire with the Pythons but since the SERT mapping with v4.5.0, that's all gone
 

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Popping/backfire on trailing throttle I'm told is almost always a lean condition or an exhaust leak. Make 'em check it again.
 

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jrehm said:
Popping/backfire on trailing throttle I'm told is almost always a lean condition or an exhaust leak. Make 'em check it again.
He said it's better now, was wondering if the valve seals were the cause. It's possible they were leaking compression, changing the AFR or burn efficiency.

They also re-dynoed the bike, he probably wasn't there and didn't see what they did. It's possible they tweaked the AFR table or Decel Enleanment or VE tables.

Who knows for sure? the tech that worked on it. ;)
 

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Discussion Starter #7
The tech says he did not reload the map or tweak it in any other way. It popped like a sonofabiatch before. Sorta reminded me of a kid with a new cherry bomb on his dads car. I had em put it on the dyno because I wanted to know the AFR. Its way lean below 1800rpm and above 4400 rpm. It hangs around 13.5 in between. I see an ingnition controller in my future. The tech suggested a sert although he did say he would do a PC too. I know they expect me to outgrow the motor but I don't think I am going to get to that this winter. 69 hp 72 tq in 4th gear. They put it right against the rev limiter. I didn't ask him about an exhaust leak. The before and after is significant though. Nothing they did to the bike should have changed the pop but it did.
 

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machinist said:
The tech says he did not reload the map or tweak it in any other way. It popped like a sonofabiatch before. Sorta reminded me of a kid with a new cherry bomb on his dads car. I had em put it on the dyno because I wanted to know the AFR. Its way lean below 1800rpm and above 4400 rpm. It hangs around 13.5 in between. I see an ingnition controller in my future. The tech suggested a sert although he did say he would do a PC too. I know they expect me to outgrow the motor but I don't think I am going to get to that this winter. 69 hp 72 tq in 4th gear. They put it right against the rev limiter. I didn't ask him about an exhaust leak. The before and after is significant though. Nothing they did to the bike should have changed the pop but it did.
Well, they did several things. They changed the valve seals and they took off the exhaust, they removed the heads, which means they removed the intake manifold. Lots of opportunity to fix leaks! Glad it improved for you!

Now the next important thing to look after.
I would do a SERT or a PCIII as soon as you possibly can, if it is as lean as you say. Ideally, AFR should be between 12.8:1 (on the fat side), to no leaner than 14.7:1 in light, to no load conditions. In wide open throttle condition, the air/fuel ratio that makes the best power is usually right around 13.2:1. As you can see, for best operating function, the AFR band is quite narrow.

The SERT and PCIII have been talked about a lot here. You can search for other threads for information on them.
 

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Oil in the combustion chamber will detonate way before gas will, so that being true its very posibable the oil was your popping. Lets face it with the throttle closed the manifold vacuume is at its highest and a leaking valve guide will supply oil much faster and more volume under that condition.
 

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Discussion Starter #10
FYI I am hell on an engine. My daily commute is 3 1/2 miles one way so I am cold starting something at least twice a day. Usually I take the bike as I will in just a few minutes. I had oil consumtion issues from about the 250 point. I am at around 4000 now in 11 months. Lotsa short hauls so I am going to bewearing stuff out faster then most. The sooner I wear it out the sooner a bigger one replaces it though. I didn't want the bike down at the 1000 mile point so I held off then on the seals and switched to syn. Syn blew through faster then carbon oil. I had a regular plug maintenance program by 3500. I probably went through 5 quarts of Mobil 1 deisel between 1000 4000.

Doc, even though I had probably an unusual volume of oil generated I didn't think there would be enough there to warrant a combustion issue. I do not believe I had an exhaust leak. Dunno about intake.

Steve
 

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machinist said:
FYI I am hell on an engine. My daily commute is 3 1/2 miles one way so I am cold starting something at least twice a day. Usually I take the bike as I will in just a few minutes. I had oil consumtion issues from about the 250 point. I am at around 4000 now in 11 months. Lotsa short hauls so I am going to bewearing stuff out faster then most. The sooner I wear it out the sooner a bigger one replaces it though. I didn't want the bike down at the 1000 mile point so I held off then on the seals and switched to syn. Syn blew through faster then carbon oil. I had a regular plug maintenance program by 3500. I probably went through 5 quarts of Mobil 1 deisel between 1000 4000.

Doc, even though I had probably an unusual volume of oil generated I didn't think there would be enough there to warrant a combustion issue. I do not believe I had an exhaust leak. Dunno about intake.

Steve
It only takes a little oil in the combustion chamber to detonate under the compression....it doesn't have to smoke to be a problem.
 
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