1997 blackbird poor idle, running rough on 3 or less cylinders.

matthew

matthew

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Hi Everyone,

I'm having issues with my new to me, 1997 Blackbird.
I noticed that it was surging while I was riding on the highway, this seemed to happen regardless of speed, fuel level or RPM (from what I can remember). Also, a few times on start up, it was runnin on 3 cylinders. A few quick throttle blips smoothed this out and it was back on 4.

I figured it was time to change the plugs as I'm unaware of the prior maintenance of the bike.
I removed the plastics, tank, airbox and spark plug boost. Old plugs come out, new plugs go in. They're the correct plugs for the bike.
Ever since then the bike has idled rough, back fired and ran on 2 or 3 cylinders. A few times it has started up strong but ends up losing a cylidern

THe coils have low resistence, I checked them with a multi meter. The plugs are getting spark, I grounded them to the frame. THe carbs seem to be in working order, the diaphragm slides well.

Originally I had the coil wires in the wrong order, I now have it 2/3 on left, 1/4 on right.

It's still running rough, with weak idle.

I have to start it on full choke.

I'm in desperate need of help and I'm open to suggestions
 
Plugs weren't gapped, I'll check them when I get home tonight

Caps were tight.
 
SLaP said:
Just to be sure, did you gap the plugs correctly?
Caps on tight?
Click to expand...

matthew said:
Plugs weren't gapped, I'll check them when I get home tonight

Caps were tight.
Click to expand...

NGK or any good plug mfg will supply plugs - pregrapped.

Since its a honda - and I am sure the blackbird would also be using the special honda plug with the shoulder. pre-gapped at 0.9mm.

If it is iridium - do not gap - they are pre-gapped and shouldn't be adjusted.
 
Last edited:
Is it always the same cylinders that are sick? use a wet cloth on the headers to see which cylinders are firing. Try swapping coils between a working and non-working cylinder and see if the problem moves.
 
Gas in the tank is new. I had it out for 500km not too long ago, ran fine.

I'll double check to see what pipes are hot and see if that correspondes to a coil and then i'll swap coils.

dieelectric grease shouldnt be necessary, i had some on already and no difference was noticed
 
matthew said:
Gas in the tank is new. I had it out for 500km not too long ago, ran fine.

I'll double check to see what pipes are hot and see if that correspondes to a coil and then i'll swap coils.

dieelectric grease shouldnt be necessary, i had some on already and no difference was noticed
Click to expand...

"surging while I was riding on the highway, this seemed to happen regardless of speed, fuel level or RPM" fuel pump priming and flowing? Have you checked the flow rate?

Have you checked the voltage at the battery to rule out the lack of electrical power? (it should run fine until about 8-10v of battery power).
 
frekeyguy said:
NGK or any good plug mfg will supply plugs - pregrapped.

Since its a honda - and I am sure the blackbird would also be using the special honda plug with the shoulder. pre-gapped at 0.9mm.

If it is iridium - do not gap - they are pre-gapped and shouldn't be adjusted.
Click to expand...

Pre-gapped or not, I check them. I have seen pre-gapped plugs that were off. Use of a Spark plug gapping tool is recommended.

If Iridium, just be more careful when checking/adjusting the gap.
http://www.densoiridium.com/installationguide.php

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqpregap.asp
http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp#gapping
 
what did the old spark plugs look like ? where they wet or dry looking ?
you may not have a ignition related problem, could be fuel.
 
old plugs were dry, looked old, but not oil or grease covered

pipes 3/4 weren't as hot as 1/2. those pipes aren't controlled by one specific coil


at times the bike would run on 4 cylinders perfectly, but die when i took the choke off


other times it would run perfectly without choke, rev up strong but not get past 5k rpm


i swapped the coils, no difference in results
 
SLaP said:
Pre-gapped or not, I check them. I have seen pre-gapped plugs that were off. Use of a Spark plug gapping tool is recommended.

If Iridium, just be more careful when checking/adjusting the gap.
http://www.densoiridium.com/installationguide.php

http://www.ngksparkplugs.com/tech_support/spark_plugs/faqs/faqpregap.asp
http://www.ngksparkplugs.com/techinfo/spark_plugs/installation.asp#gapping
Click to expand...

I'd like to add, be careful gapping iridium plugs. The small wire at the tip can break off if you're not careful. I prefer not to touch them.


If I was Matt, I'll run seafoam thru it. Plus what Greyghost said was excellent advice.

If bad comes to worse, I'll assume something got stuck in one of the jets.
 
Problem Solved:

Vacuum line was hooked up to the bottom of the fuel shut off valve, which apparently does nothing. Everything is fine now

Thanks everyone.
 
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