[Johnno SA]

I have a problem with my 1500SE 1990.
when the engine is stated it runs rough, but when I pull #6 plug lead it off it runs smoothly. There is sparking so I do not suspect ignition.
The carbs are balanced at all revs idle to 3000 plus. Compression test is satisfactory. any clues ????

 

[DenverWinger]

Maybe #6 wire crossed with #4?

 

[gumbyredd]

Could be lots of things. Vacuum leak (s), bad plugs, air filter, bad plug wires. Did bike run fine a day ago, and just started acting up, or has bike been in storage for long periods opf time?
gumbyredd

 

[Johnno SA]

The problem is only on #6 .Pull any other plug wire and engine stops. Plugs are new, vacc pipes have been replaced. Clock 68k miles. was running sweet and this suddenly began.
Plug wires are pre shaped and numbered no mix up is easy to do. I am suspecting a sticky Valve, but why have compression? Have put valve ease in tank, so hope that might work.

 

[DaveO430]

I suspect a bad coil. With both wires connected it is too weak to fire both #5&6 but when you pull #6 it is strong enough to fire #5 alone.

 

[redwing52]

When you remove the plug wire from #6 do you pull it back a small amount from the spark plug and it runs smooth or do you pull the wire off completely?

 

[Johnno SA]

Hi Dave and Redwing, I think we are on the right track. I did notice that the spark form #6 was thin . not as strong as I would have expected. I will have to consider replacing coils and cords, what a mammoth of a task as carbs will have to be removed to get to the coils, wow!!! Well I still have my 1100 to ride about.

 

[redwing52]

Hi Dave and Redwing, I think we are on the right track. I did notice that the spark form #6 was thin . not as strong as I would have expected. I will have to consider replacing coils and cords, what a mammoth of a task as carbs will have to be removed to get to the coils, wow!!! Well I still have my 1100 to ride about.

I think you can just loosen the clamps on the insulators and flex the unit rearward to get access to the coils.

Might want to test the coils but it can be misleading. There is no test for internal carbon tracking. Only takes a few minutes to check though. Also , did you try a new plug in that cylinder? Might be shorted to ground causing the same symptom.

That darn Dave is hard to stump. He's pretty cool!

 

[Johnno SA]

Thanks Guys,
I have yet another problem, In trying to test the secondary coils I find no continuity between any pair of leads, !/2, 3/4 and 5/6 at the plug ends, any ideas?

 

[DaveO430]

Probably the resistors in the caps. Inside the cap is a screw, remove it and the resistor and test them.

 

[AZgl1800]

the resistance between the spark plug leads is extremely high, in the meg ohm range.

the primary windings will be in low ohms range, well below 10 ohms

 

[gumbyredd]

Pulling a spark plug wire off of a running 1500 for test purposes is not recommended, and could be part of the problem.
gumbyredd

 

[DriverRider]

I am going to take a different tack. With one spark plug lead removed it will not kill the engine yet you write it does on the other five, so something more going on especially if it started running poorly all of a sudden. The 1500 will start up and idle on three cylinders. If the spark plugs were badly fouled that would make the whole engine run poorly and skew the results your getting. Remove your spark plugs and check the color of the insulators they should be white or light tan, no black. I would be checking camshaft timing too in maybe a belt jumped. Picture of a good firing plug.
Then again too you have been replacing hoses and I imagine the carbs were out, you sure they got seated all the way down into the insulators?

 

[AZgl1800]

I agree, I bought a '94SE that just seemed to be "lethargic". I rode it home about 35 miles and started to check it out.
None of the cylinders on the left side were making power ( determined by using an IR Temp gun )

forget now what the problem was, but when it was fixed, it was a different bike.

 

[Johnno SA]

AZ you are correct I set my multi tester to the right range and obtained readings all within spec.
My problem is definitely mechanical, Fuel and electrical are eliminated.

 

[Bryanlj]

A coil can still be bad even with good meter results as they can short internaly. Having said that in 40 years of working on Hondas i have never known a coil go bad, wires yes and they used to be bonded into the coils(that repair is a whole other story) but not the coil itself.
Dave have you had coils that were bad?

 

[DaveO430]

Dave have you had coils that were bad?

Lots of them, usually a crack causing them to fire into the mounting brackets. Don't think I ever had one test bad by resistance though.

 

[Bryanlj]

Most of my work now is on the old Honda fours and never seen one cracked on them, unless hit with a hammer by the owner of course.