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1st has spark, the other 3...

  • Thread starter Thread starter ZakDanger
  • Start date Start date
Z

ZakDanger

Guest
1978 gs750

Cleaned the hell out of the carbs when I got her, put an airbox and a brand new k&n filter on her. Take her out for a spin into the city and had her going pretty good cept she wouldn't top out past 60 till she started backfiring. Died on me halfway home, couldn't start it again.

Took her to the garage, she has spark on #1, pretty weak, no spark on the other 3. I'm thinking points, how do I check those with a multi, and what do you think?
 
I would clean the plugs or better yet, replace them. Then take the points off and take a good look at them for pitting and burnt spots. lightly clean them with a fingernail file and install and regap. Condensors can cause problems as well. If you have some spares around swap them out too. Also, look down into the boots and see if there are "slotted" plug connectors in there. Unscrew them and get rid of those junk ceramic resitor and replace them all with a piece of 1/8 brass rod cut to length. Clean the connections where the coils plug into the harness too.
 
I got everything except for the "look down the boots" part. Also my brush is pretty gross.
 
When you "cleaned the hell out of the carbs", how did you do it?

Did you replace all the o-rings?

Did you bother to check the valve adjustment?

With the engine not running, making sure the brakes work is not so important. :-\\\

Sorry, but there is a LOT more to getting a bike running than just "cleaning the hell out of the carbs".

And, if you didn't clean them properly, you're gonna have to do it again.
icon_shrug.gif


.
 
Pull a plug cap ( boot ) and look down in there. The slotted cap unscrews and there are resistors under them. Get rid of the resistors and youll never have to worry if they are gonna fail again. Replace them with 1/8 inch brass or copper rod cut to the right length. As for plug cleaners..here is the solution. Clean and use air to blow the media off the ends and threads and they are like new again..just check the gaps and reuse...

http://www.harborfreight.com/pneumatic-spark-plug-cleaner-32860.html
 
Allow me to reiterate. I did everything to my carbs that bass told me to. So theyre good as they're gonna get. I know these carbs better than I know my mother. I've also learned a ton about carbs in general. Elec... Not exactly my strong suit. Actually none of it is. Feel like a Neanderthal hitting an engine w a club. Make fun machine go vroom vroom!!
 
Also yes I checked my clearances. Everything is spec as far as tuning goes.
 
Yes pulled points. Nasty pitted. 35 off z1. Might as well. Chuck are you talking about the resistors in my spark plugs?
 
INSIDE THE SPARK PLUG CAPS. Brass slotted thing that grips onto the plug when you shove it down onto the plugs. Flat tip and unscrew them...look at a parts fiche.
 
chuck hahn said:
INSIDE THE SPARK PLUG CAPS. Brass slotted thing that grips onto the plug when you shove it down onto the plugs. Flat tip and unscrew them...look at a parts fiche.
Click to expand...

You mentioned this in prior posts, and I've found it intriguing. I would think those resistors in there would be there for a reason, being resistors they surely would provide a voltage drop. If bypassing them helps, you could just connect the plug wire to the plug directly without the cap to check it out.
I did check the parts fiche and it doesn't show the integral parts of the cap other than the boots top and bottom.
Items 21 & 22 on this fiche. (Spark plug caps are not cheap!)
http://www.boulevardsuzuki.com/fich...y=Motorcycles&make=SUZUKI&year=1978&fveh=2146
 
Only EXPLANATION ive ever gotten for the resitors being there is to reduce noise..like if anyones old enough to remember hearing a hum that changed pitch in the AM radio as you pressed the gas in the car type noise. Dale is actually the person that showed me the bad resistor trick because I had lost spark on a cylinder and did all the other tricks such as trim the wire and reinstall the cap, cleaning all the connections, replaced points and condensors..etc etc etc. The problem was still there and a new out of the box plug still was dead. Took the resistors out and got some brass rod and the magic of spark returned instantly. Now the first thing that happens when i get a new project and i am going thru it is the resistors ALL go bye bye...good or not.
 
chuck hahn said:
Only EXPLANATION ive ever gotten for the resitors being there is to reduce noise..like if anyones old enough to remember hearing a hum that changed pitch in the AM radio as you pressed the gas in the car type noise. Dale is actually the person that showed me the bad resistor trick because I had lost spark on a cylinder and did all the other tricks such as trim the wire and reinstall the cap, cleaning all the connections, replaced points and condensors..etc etc etc. The problem was still there and a new out of the box plug still was dead. Took the resistors out and got some brass rod and the magic of spark returned instantly. Now the first thing that happens when i get a new project and i am going thru it is the resistors ALL go bye bye...good or not.
Click to expand...

Thanks Chuck,
I would think that without the resistors you would not have a voltage drop and get a hotter spark.
 
Dont know about that..Maybe ask Dale to chime in as hes the electrical guru. All i know is that they can and will just drop off at anytime, and that "time" is usually not in the driveway. So it doesnt hurt to straight shot them with the brass rod, so why bargain on a potential breakdown that is totally negateable.
 
Furthermore..why would #1 HAVE spark and #4 not...they are on the same coil. That in itself would point me to the cap and the resistors or a bad plug. But he says he cleaned the plugs and if 1 is firing that also means that set of point and condensor is also working. The process of elimination is pointing toward the caps and the resistors if you ask me.
 
chuck hahn said:
Furthermore..why would #1 HAVE spark and #4 not...they are on the same coil. That in itself would point me to the cap and the resistors or a bad plug. But he says he cleaned the plugs and if 1 is firing that also means that set of point and condensor is also working. The process of elimination is pointing toward the caps and the resistors if you ask me.
Click to expand...

Yeah, maybe he should swap 1 & 4 leads and plugs around and see what happens.
 
chuck hahn said:
Dont know about that..Maybe ask Dale to chime in as hes the electrical guru.
Click to expand...
I wished! I've forgotten so much over the last 40 years...

It appears the resistors are in place to reduce 'ringing' in the coils secondary system. A resistor placed in line reduces the ringing by limiting or reducing the current flow in the coils secondary. A reduction in current flow would tend to reduce voltage 'overshoot' and oscillations.

See... http://en.wikipedia.org/wiki/Ringing_(signal)
Ringing is undesirable because it causes extra current to flow, thereby wasting energy and causing extra heating of the components; it can cause unwanted electromagnetic radiation to be emitted
Click to expand...

and another... http://www.ultralightnews.ca/articles/resistorcapsandplugs.htm
This reduces current flow in the spark and it takes quite a bit longer until the energy in the coil has expelled itself via resistor and spark gap. This results in a longer spark. However the spark is weaker due to energy loss in the resistor.

The scope shows this very nicely and it also gives reason why the resistor helps to suppress RF. With the resistor changes in the rate of current flow are much less resulting in "flatter" edges on the voltage vs. time curve that the scope shows you. This implies less high frequency components of the signal in the cable feeding the spark plugs.
Click to expand...

It's been a long time since I've heard the term 'ringing'... :(
 
rustybronco said:
I wished! I've forgotten so much over the last 40 years...

It appears the resistors are in place to reduce 'ringing' in the coils secondary system. A resistor placed in line reduces the ringing by limiting or reducing the current flow in the coils secondary. A reduction in current flow would tend to reduce voltage 'overshoot' and oscillations.

See... http://en.wikipedia.org/wiki/Ringing_(signal)


and another... http://www.ultralightnews.ca/articles/resistorcapsandplugs.htm


It's been a long time since I've heard the term 'ringing'... :(
Click to expand...


Thanks Dale,
Now could you put that in layman's terms.
Here's what I get out of it.
A longer and weaker spark, don't think that's good.
Could this have anything to do with RF radiation? Could these be used only for the reduction of noise emmissions to a radio?
I used to have to put special stuff on my outboard ignition circuit to eliminate the buzz on my VHF radio.
 
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