Spark plug wires (HT Leads) and Coils

[Fred1Boot]

I have been experiencing problems at low RPM.  Idle->6K it runs crappy, wants to stall.  I have to feather the clutch and ham-fist the gas to keep the revs up and prevent a stall.  6K + and she runs like a champ.  

Let me give you some history:
A friend bought a new bike and gave me his '92 Bandit 400.  It wouldn't start and I didn't have time (or confidence) to work on the carbs, so I took it to a shop to figure it out (figured it was just dirty carbs because it sat for 6+ months).  They diagnosed the problem as a bad Ignitor.  They replaced it and said they also cleaned the carbs.  

I pick it up and experience the low-rpm issue.  I have my friend ride it and he says that it is not the way it used to run (duh).  I took it back to the shop and they claim they can't find a problem/there is no problem (runs fine for them -   )  They tell me it is a low-power bike and that is just the way it is.  They also said that there was some rust in the tank so they cleaned that out...  So, I pick it up and it is still running crappy...

Next day, after starting flawlessly in the morning, it doesn't want to start when I go to leave work.  Turns over, will even fire a few times, but no sustained running.  I leave it in the parking lot.  Next day I try to start it again and am able to get it to start and run for longer than 10 seconds, but it's running on 3 cylinders, and dies either as soon as I give it gas or as soon as I let off the throttle.  There was also a loud TICK-TICK-TICK sound.  Exhaust pipe for cylinder 1 was not warm while the rest were hot.

Some investigation revealed spark-plug caps for cylinders 4 and 1 were not solidly connected.  When pulling off the cap for cylinder 1, the plug lead fell out/off the coil!  I already had to trim the ends to re-attach to the plug caps, and after reading the ignition problems thread, figured a new set of plug wires was in order.  

A trip to Pep Boys and all they have are generic length , pre-capped kits for cars.

My questions are as follows:  

1.  Are all wires/leads the same?  Are some 8mm and others 9mm, if so, what size do I want.

2.  What about the stuff inside the leads?  Graphite?  Copper wire?  Does it make a difference?  What does the B4 need?

3.  Should I go to a different auto parts store?


Also, the top tower on both coils seems like the plastic shell around the threaded stud was cracked, and someone had used electrical tape on them.  Is that normal?  Should I just buy new coils too?  One of the threads mentioned the Accell coil/wire kit available at Motorcycle Accessories Warehouse   GSXR400Racer mentioned Nology ProFire coils.  What are the specs for the coils?  Which nology coil is the correct one?  PFC-30D???  3.0 ohm, .6 ohm?  

I don't want to buy coils if new leads will do the trick ($$).

Thanks in advance for the help!      

The two threads I am referring to are:

Ignition problems
Bandit spluttering, idling rough

[interfuse]

Something else you might want to check that the shop may have over looked is jet needle / needle jet wear. My bike was running on two cylinders and stalling at low RPM but above 7000 rpm it ran fine. Once I changed the jet needles the problem was solved.

Here are some links that describe what to look for:

http://www.factorypro.com/tech/needle_jet_Mikuni.html

http://66.47.68.116/tech/needle1.html

[PitterB4]

The stock wires are actually 7mm, I believe.  I used this from Dennis Kirk.  It's cut-your-own length.  Comes in a 6 ft section for $3.  It looks just like the oem stuff.

[SRwitt]

Hello all, I'm new here but this thread is almost exactly what I'm going through with my bike.

I just bought a 91 400 a couple of weeks ago, ran fine.
Now it has problems.  I've replaced the spark plugs, halfway cleaned the carbs(pulled off float bowls just to check things) they didn't appear too dirty so i put them back together after discovering a jet had come unscrewed in the far right(sitting on the bike) #4? carb.  I figured that would be the cause of my problem.  It wouldnt idle, smelt very rich/blowing black smoke and wouldn't rev.  After reassembly it would run sounded good but still wouldnt idle or rev hard.

I checked around the engine and found no heat coming off of the #4 head pipe.  I'm thinking its the ignition I checked that the wire and boot were tight and am wondering if anyone knows of simple ways to diagnose the rest of the ignition(coils,and whatever else).  Sorry not trying to steal the thread.

Shawn

[Red01]

...after discovering a jet had come unscrewed in the far right(sitting on the bike) #4? carb.  

Yes, that's #4.

I checked around the engine and found no heat coming off of the #4 head pipe.  I'm thinking its the ignition I checked that the wire and boot were tight and am wondering if anyone knows of simple ways to diagnose the rest of the ignition(coils,and whatever else).  Sorry not trying to steal the thread.

Shawn

Have you checked for spark on #4?

You can swap leads (just at the spark plug end will do since both leads fire at the same time) with #1 & #4 and see if the problem follows. If it moves to #1, chances are very strong it is just a bad lead. If it doesn't follow and has spark, you've probably got a valve sticking open or poor compression in that hole.