Sticking exhaust valve???

[RagingMain]

Hey Guys
I posted here about a problem I was having at idle
http://www.vmaxforum.net/showthread.php?t=9801
Well found the throttle plate too far open and there was not enough manifold vacuum to pull fuel. Vacuum was 1/2-1/3 of all the cylinders.
Well that is all better now. Got the carbs all synced up, but there is still a stumble at idle, just not as bad.
I was wondering if maybe one of the exhuast valves might be hanging up a bit and still open when it is time for the intake. Yes I am aware there is an overlap. Just thinking maybe I am losing manifold vacuum if the exhaust valve is hanging open. It is only happening on cylinder #2.
Thanks in advance.

 

[satariel666]

I've rebuilded my engine with 1300cc core from Sean.
Valves - check
Gaskets - check
Compression - check
Exhaust/intake leaks - check
electrical/ignition - check
fuel - check
carbs - check even completly clean it up and shotgun

But its still stumbling at idle, its like out of sync but it is synced.

Bike runs like a angry bull, no problem above 2-3k but still stumbling at idle.

I've gave up :ummm:

Do you run with afermarket exhaust?

 

[RagingMain]

I've rebuilded my engine with 1300cc core from Sean.
Valves - check
Gaskets - check
Compression - check
Exhaust/intake leaks - check
electrical/ignition - check
fuel - check
carbs - check even completly clean it up and shotgun

But its still stumbling at idle, its like out of sync but it is synced.

Bike runs like a angry bull, no problem above 2-3k but still stumbling at idle.

I've gave up :ummm:

Do you run with afermarket exhaust?

Yeah I used to run a Kerker 4-2-1 and now I have a Marks 4-2
Not that I am happy that yours stumbles as well, just glad to hear I am not the only one. :bang head:
You are right, it is like it is not synced but mine couldnt be any closer, the vacuum is spot on.
It is like it is dropping a cylinder then picking it back up.
Cheers

 

[satariel666]

Yeah I used to run a Kerker 4-2-1 and now I have a Marks 4-2
Not that I am happy that yours stumbles as well, just glad to hear I am not the only one. :bang head:
You are right, it is like it is not synced but mine couldnt be any closer, the vacuum is spot on.
It is like it is dropping a cylinder then picking it back up.
Cheers

I've asked you witch exhaust do you running couse i have an theory.
Just my toughts but personaly i've never seen a v-max running that smothly at idle like inline four sport bike, never heard any v engine to run that clear also besides vtwins ofkoz.

Maybe i want it to run to good? :ummm:

What im trying to say is that aftermarket exhaust system may be the cause.
When i've rebuilded my engine last time with 1300 core i've get rid of down pipes connection from front cylinders.
I use to run with stock headers and two brothers slipons.

And what i can say that my stumbling mostly comes from right side and if my ears are not mistaken its comming exactly form cyl 3.

Just an theory, need to vefiry that by instaling stock exhaust.

I've synced my carbs with typical sync tool and also with webber sync tool. It cant be more acuralty :bang head:
So what the heck?

Another theory:
Check spark with many criterias, strong constant spark, no problems at all.

But...when i was diassembling my bike after my accidient i've found cracks at front coils :ummm:

At the end im waiting for COP's and Mark exhaust 4-2-1 so when i will get those i can write some conclusions

 

[RagingMain]

It is not just the lumpy idle that the Vmax has. I can live with that, infact it sounds cool.
When I am syncing the carbs you can see when #2 just looses manifold vacuum. I mean gone, as in the bar just drops to the bottom and then the bike stumbles. Right after that my A/f meter will show way lean 18-20:1

No vacuum leaks that I can find using starting fluid and the carbs are clean enough to do surgery off of.

I will try to take a video tomorrow and post it.
Cheers

 

[gamorg02]

hey guys, u know a shit ton more than me, and i'm not sure what it would prove. But what happens if u leave vboost wide open all the time, does it still stumble on this off idle issue ur talking about? not sure what it would prove, or just go rich but i can only imagine how frustrating it is.

 

[satariel666]

hey guys, u know a shit ton more than me, and i'm not sure what it would prove. But what happens if u leave vboost wide open all the time, does it still stumble on this off idle issue ur talking about? not sure what it would prove, or just go rich but i can only imagine how frustrating it is.

I've use to run with v-boost full time open.
No problem with sync but you need webber sync tool.

When i use to run with 1200cc i've had no problems with sync, af or whatever.

It just started after rebuilding it with 1300 core.

 

[satariel666]

It is not just the lumpy idle that the Vmax has. I can live with that, infact it sounds cool.
When I am syncing the carbs you can see when #2 just looses manifold vacuum. I mean gone, as in the bar just drops to the bottom and then the bike stumbles. Right after that my A/f meter will show way lean 18-20:1

No vacuum leaks that I can find using starting fluid and the carbs are clean enough to do surgery off of.

I will try to take a video tomorrow and post it.
Cheers

And thats why i've told to myself:
"Nahhh...screw this"

I have no problems with vaccum and af ratio. Its all in perfect conditoin but stumbling :bang head:

 

[gamorg02]

I've use to run with v-boost full time open.
No problem with sync but you need webber sync tool.

When i use to run with 1200cc i've had no problems with sync, af or whatever.

It just started after rebuilding it with 1300 core.

and the stumble was still there on the 1300 with vboost wide open?

 

[satariel666]

Yeah, no any stumble with 1200 and v-boost open and, idling stumble with 1300 and v-boost open.

 

[RagingMain]

I am going to do a compression check today. Keep your fingers crossed

 

[RagingMain]

Results of compression check, cold
Will do NOT one later

#1 185
#2 185
#3 185
#4 200

Dont know what to make of this since they are all good numbers, better than when Sean and I first did after the intial build. Just weird that one cylinder is much higher than the other three.

 

[satariel666]

Numbers seems ok.

I was wondering, we both run with 1300. Maybe theres something here? :confused2:

 

[Birdoprey]

What kinda of vaccum are you guys reading at idle?

 

[Birdoprey]

Fargo,

Here is an article that explains what i was "trying" to recall when talking with you the other day. I "think" this may be the source of your problem. I know its a car carb, but the priciple is the same. Explains the rich idle, but dead lean once you tip into the throttle. Not sure what the fix would be on the Mikunis though. Not familiar enough with them to know what might be needed to fix it.
Knowing your vaccum at idle may help. Did you have to adjust your throttle blades to open the throttle up a little after the cam swap?
http://www.carcraft.com/techarticles/ccrp_0409_fix_off_idle_stumble/index.html

 

[Birdoprey]

Found this VERY interesting:
"Poor ignition performance can be confusing when using the LM-1 air/fuel ratio meter. When a cylinder misfires, the air and fuel do not combust, meaning the oxygen in the air moves into the exhaust where the O2 sensor will immediately pick up the additional air and indicate a lean condition. Simply put, this means a dead cylinder or occasional misfire will show up on the innovate meter as a lean condition not a rich mixture as you might thing. Fix the misfiring cylinder(s) and the air/ fuel ration will read as a richer mixture"

Got this from Innovates site...

 

[Birdoprey]

Yet another, on a bike this time. Shows simmilar operations as to the carbs idle circuit.
http://www.sportster.org/tech/carb/rejetting-bussy.shtml

Also shows an interesting way to set your idle circuit.

 

[satariel666]

What kinda of vaccum are you guys reading at idle?

Cant remember and cant check it know. I dont have the radiator :bang head:

 

[satariel666]

Found this VERY interesting:
"Poor ignition performance can be confusing when using the LM-1 air/fuel ratio meter. When a cylinder misfires, the air and fuel do not combust, meaning the oxygen in the air moves into the exhaust where the O2 sensor will immediately pick up the additional air and indicate a lean condition. Simply put, this means a dead cylinder or occasional misfire will show up on the innovate meter as a lean condition not a rich mixture as you might thing. Fix the misfiring cylinder(s) and the air/ fuel ration will read as a richer mixture"

Got this from Innovates site...

That is not out of the question, i've considered this.
COPs and radiator are one the way to me so soon hopefuly i can post some more details.

 

[RagingMain]

Found this VERY interesting:
"Poor ignition performance can be confusing when using the LM-1 air/fuel ratio meter. When a cylinder misfires, the air and fuel do not combust, meaning the oxygen in the air moves into the exhaust where the O2 sensor will immediately pick up the additional air and indicate a lean condition. Simply put, this means a dead cylinder or occasional misfire will show up on the innovate meter as a lean condition not a rich mixture as you might thing. Fix the misfiring cylinder(s) and the air/ fuel ration will read as a richer mixture"

Got this from Innovates site...

This is exactly what I see. I am not ruling out the ignition right now but when a spark plug is placed in the COP and grounded then turned over it does not seem to miss a spark and it is a nice bright blue. I guess the amount of liquid fuel isnt seen by the meter and just the air going by the sensor. I will swap COPs around and see if it happens on any other cylinder to rule out spark.

I will try to get a video up of what is happening with the vacuum. If I remember correctly it was at 18-20 cm of vacuum. Initially my sync was way off and needed to be reset.

Just basically what is happening is when I have the sync tool on you can watch vacuum just disappear momentarily then come back. As soon as it does it reads lean and then stumbles. If it doesnt have any manifold vacuum it cant pull fuel from the pilot circuit causing the cylinder to miss fire.

I am also going to do a leak down check and make sure the valves are tight.