number 5 cylinder not firing

[jimnvalk]

i was working on my bike today and noticed that the plug over the vacuum inlet looked cracked.  I pulled it off and sure enough you could blow through it.  I noticed when i plug it with my finger that there was no change in engine.  I pulled the spark plug wire off while running and no change again.  I could hear spark as I was putting the wire back on, gas comes out of the bowl when i loosing the screw.  HELP what else can i try
Thanks

[John U.]

It sounds like another clogged slow jet problem. Try a heavy dose of Techron fuel system cleaner. Give it some time to work, run the bike untill warmed up well then let it sit, then run it some more.
To avoid this problem I use a dose of Marine Stabil in every tank of fuel unless I'll be burning it quickly. I hear Starbright works also but I haven't tried it yet.

[jimnvalk]

been running proguard in it and i use either that or seafoam every tank

[jimnvalk]

also my gas mileage went from around34 to 24 this last tank

[Chrisj CMA]

what does #5 spark plug look like?  That may tell you if its firing, getting any gas to it or what...

[Westsider]

Yes sounds like a bad spark p , have you trried a spare or new one yet....

[Earl in Pensacola]

I'd try the easist things first--Switch plugs with another hole!  See if the problem follows the plug!

[jimnvalk]

i switched out plugs and the problem did not follow the plug, it stayed on cylinder 5,  i did notice something last time, with the plug not on the vacuum it ran better when i plug the vacuum with my finger it started spitting and popping.  it has been desmogged so i only have the cap on that cylinder

[Thunderbolt]

since you switched plugs, and the problem did not move, it most likely is a clogged slow jet.  Try the Techron or Sea Foam first.  If it doesn't help in a tank or two, you would do well to bite the bullet and take the carbs out and clean the slow jet.

[Ricky-D]

If you are using ethanol enriched gasoline the problem you are encountering certainly could be something clogged up, slow jet not withstanding.

I think the consensus on the forum is that Techron and B-12 are stronger and better agents to help in this area. Seafoam kinda follows up behind those two products.

Make sure all the vacuum barbs are covered with caps except the one that powers your gas petcock.

Simply because you feel the no-5 cylinder is not firing properly because of the tests you did, there can be other reasons for the results that you should consider and at the top of the list should be a synchronization.

You say 

"with the plug not on the vacuum it ran better when i plug the vacuum with my finger it started spitting and popping."

 

This says to me that there is no problem with gas supply on this cylinder.  It also indicates to me that this cylinder is not contributing to the idling effort.

So this being the case: I'd say a synchronization is in order.

***

[Patrick]

 "it has been desmogged so i only have the cap on that cylinder"

What does this mean??  None of the other intakes are capped/plugged, only #5 ??

[BudMan]

Hi James,
I think a trip through the ultrasonic cleaner for the slow jet would be my first approach.
The bowls will come off easily enough without removing the carbs completely if you just remove the air box and disconnect the “black boots” from the intake runners.
That will let you get under and unscrew the bowls fairly easily.
Then it is a simple trick to take the jets out and put them in the ultrasonic tank.
I knew mine were easier to get to than yours, and then I remembered why, we weren’t raising each side up while working them. I just secure each side up with a string while doing a bank of carbs.
May not be the “school solution” but it works for me.
Give me a shout if you want to get together and fool with it.
Karen and I are on a short Valk trip this weekend, but will be around most other weekends.

[BudMan]

What does this mean??  None of the other intakes are capped/plugged, only #5 ??

Unless something else has gone terribly wrong from when we worked on it last time, everything is capped except for the #6 line to the petcock.   

[Madmike]

Was this cylinder running lean long enough that you took the rings out?????  Sounds like you have established that you have spark, you may have fuel, do you have air??  A compression test will quickly answer the question and eliminate that variable.

[jimnvalk]

Was this cylinder running lean long enough that you took the rings out?????  Sounds like you have established that you have spark, you may have fuel, do you have air??  A compression test will quickly answer the question and eliminate that variable.

this does not sound good am trying to aquire a compression gauge to check, What is the compression suppose to be on these?

[lucky_1_chris]

Was this cylinder running lean long enough that you took the rings out?????  Sounds like you have established that you have spark, you may have fuel, do you have air??  A compression test will quickly answer the question and eliminate that variable.

this does not sound good am trying to aquire a compression gauge to check, What is the compression suppose to be on these?

AutoZone will lend you a compression tester. If compression is too low pour a little oil through the spark plug hole in that cylinder and check compression again. If compression goes up after adding the oil then you've verified it's the rings. If there is no change after repeating this a couple times you may get out with only work on the heads. Again, that's IF it's low. I hope it's nothing serious. Is it hitting at higher rpm's?

[Blackduck]

To me this cylinder has too much fuel, quote it stops spluttering when I take my finger off the nipple but starts again when I block the nipple.
Suggest adjusting the mixture screw and if that does not work you maybe looking at carb removal to check the needle and seat.
Cheers Steve

[BudMan]

To me this cylinder has too much fuel, quote it stops spluttering when I take my finger off the nipple but starts again when I block the nipple.
Suggest adjusting the mixture screw and if that does not work you maybe looking at carb removal to check the needle and seat.
Cheers Steve

I can see your point Steve, but think there is also the possibility #5 with no cover on the nipple will not hit at all, and can hit some when it is properly sealed.
I've just had jets plug up with little to no warning after setting for a couple of days and then not plug at all after setting for a couple of weeks.  I have had my tank lined and took care of that, but the bad memories are still there!
I've worked on this baike before and she's just in too good a shape for me to think this is anything too serious.

[BudMan]

this does not sound good am trying to aquire a compression gauge to check, What is the compression suppose to be on these?
[/quote]
171 Lbs at 400 RPM

[rangernight]

When I checked mine a coulple of weeks ago with a cheep compresion gauge I had 160 across the entire motor----with 75,000miles.

[Ricky-D]

Just trying to understand what's going on here.

Budman is working on jimnvalk's bike.

Is this correct?

***

[BudMan]

I have in the past, but not lately.

[jimnvalk]

it hit between 165 and 170 on check

[Blackduck]

A question was asked earlier on about the colour of the sparkplugs, particularly on #5, Have not seen an answer. That may give a better indication of what is happening with the mixture.

[jimnvalk]

A question was asked earlier on about the colour of the sparkplugs, particularly on #5, Have not seen an answer. That may give a better indication of what is happening with the mixture.

light gray

[lucky_1_chris]

it hit between 165 and 170 on check

Good news.

[Pete]

Just stating the obvious:

Plug not fouled, color light gray
Compression, 165-170
Plug firing.

two possibles:

No fuel or very lean fuel (low speed jet not working properly)
Spark plug leads switched between cylinders.

[Ricky-D]

Just stating the obvious:

Plug not fouled, color light gray
Compression, 165-170
Plug firing.

two possibles:

No fuel or very lean fuel (low speed jet not working properly)
Spark plug leads switched between cylinders.

Naw, I don't buy that at all.

Reason being that when he covered the vacuum barb the motor started running differently.

That's evidence there is plenty of gas available and negates the theory that the plug wires are switched.

The problem is the carburetors need synchronization.  The last time this was performed on his bike, the job was not accurate enough and who knows,, maybe the synchronization was performed with the vacuum barb uncovered.  I would also bet that the idle mixture screws are also out of adjustment.

***

[Disco]

The problem is the carburetors need synchronization. 

I'm not positive, but I think the carbs were synchronized at our June Wrench Party.  If so, they were done correctly.  Plus, even though I've only been at the Valkyrie party for 4 years, I've never seen carbs that were so out-of-sync that they really even needed it.

It takes three things for that cylinder to run.  Compression, Spark, and Fuel.  If Compression & Spark are present, I'm betting on clogged pilot. 

We should know more by the end of play Saturday.

[Pete]

Just stating the obvious:

Plug not fouled, color light gray
Compression, 165-170
Plug firing.

two possibles:

No fuel or very lean fuel (low speed jet not working properly)
Spark plug leads switched between cylinders.

Naw, I don't buy that at all.

Reason being that when he covered the vacuum barb the motor started running differently.

That's evidence there is plenty of gas available and negates the theory that the plug wires are switched.

The problem is the carburetors need synchronization.  The last time this was performed on his bike, the job was not accurate enough and who knows, maybe the synchronization was performed with the vacuum barb uncovered.  I would also bet that the idle mixture screws are also out of adjustment.

***

You and I are each entitled to our opinion. You saw mine base on his reports.
As for Carb Sync issue, I never saw one that bad, rough yes, completely cylinder miss no.
I have seen many stopped up pilot air jets that caused this exact issue.

[BudMan]

I have seen many stopped up pilot air jets that caused this exact issue.

That is exactly the same issue I had about a year ago, except it was my #3.  It was fine when I shut off the motor, and for the next crank a few hours later #3 was stone cold dead, Wouldn't hit a lick.  We cleaned the pilot jet and Vroom Vroom Vroom! Well, I must admit we cleaned the jet AFTER swapping plugs, then coils, and trying all other exotic vodo fixes. Yep, I learned a thing or two THAT day!

[Madmike]

No fuel or very lean fuel (low speed jet not working properly)
Spark plug leads switched between cylinders.

I agree, keeping in mind that if 2 leads were crossed you would have miss on 2 cylinders and so would be inclined to check out the low speed circuit and air screw.

[jimnvalk]

spark plug wires are not crossed, i am replacing the main fuel lines, pet-rooster, all new vacuum caps, new o-rings on runners, while i have the runner off on number 5 going to pull the bowl and look at jets.  I do not have the ultrasound we used last time to clean them.  The carbs were sinced in November one year ago and was done right. 
I want to thank everyone on here for the information.  I cant tell you how much better it makes me feel to know that I can get help like this, me being basically mechanically inept.

[John U.]

You may want to consider replacing with 38 slows. Of couse you will need to readjust the pilot screws to 1 3/4 turns out and resync. Sudco has the Keihin jets, 35s or 38s.

[Ricky-D]

I don't think the motor was having a complete cylinder miss as stated in a post.

Reasons being: Stating again (1) that when he plugged the vacuum barb the motor reacted in a positive way and (2) the plug showed normal combustion condition exists in the cylinder.

A poorly done synchronization can result in an Ok running motor and even an Ok idling. In Jimn's bike I would surmise that the offending cylinder is loafing and never was contributing to the idling effort.

This, by the way, would be consistent with the suggestion of a lean condition (clogged jet) since the carburetor is effectively closed and the low speed circuit is not functional.

I guess it can be both, but the facts will be found out if there is no change when the jet cleaning exercise has been performed.

Regarding whether or not a synchronization performed is a "good" job well done, depends upon a lot of factors,,,,and way too many, to be discussed in this thread, I would think.

***

[jimnvalk]

replaced all the vacuum plugs with honda parts, replace all the intake o-rings with honda brand, replaced petcock, and hooked it up to sinc machine.  The sink was still good from the last time, and the orings and new vacuum plugs on 1-5 did the trick.  did not get to try it out as much as i would have liked because i caged it to friends to do work. but will find out this week for sure.
Thanks for eveyones suggestions

[RainMaker]

replaced all the vacuum plugs with honda parts, replace all the intake o-rings with honda brand, replaced petcock, and hooked it up to sinc machine.  The sink was still good from the last time, and the orings and new vacuum plugs on 1-5 did the trick.  did not get to try it out as much as i would have liked because i caged it to friends to do work. but will find out this week for sure.
Thanks for eveyones suggestions

The old intake o-rings were not the OEM - they were actually flattened and looked shredded.  Jim put new OEM o-rings on and that, along with the split vacuum caps, seems to have been the biggest offenders in regards to how the bike ran.