Ignition coils

[rideordive2ss]

So my spark is pretty weak and when I pull my plugs clean reinstall run it for a bit and check the #1 plug I can tell she works but seems like part time.  While at idle I cam pull the plug wire and more Often then not (but not always) there is no change to rpm. Some times it changes   and seems at high rpm it is deff firing. I'm going to replace the coils as they seem to be original. Now I've got to ask. Should I go OE or aftermarket?   The bike I bought after a 907 kit was done so I wonder if I need higher primary and secondary resistance ohm. So with that thought is there a better and around the same price tag coils that I should use?

Any and all responses welcomed and appreciated 

[DAZ]

Try checking the plug wire , if it's only one cylinder its probably not the coil as each coil fires two cylinders... Can you check the resistance with a multi meter or swap leads around 

Edited April 24, 2023 by DAZ

[TonyGee]

you didn't say what bike ? is the plug getting sooty ? you get them symptoms with a leaking float valve, lumpy at low rev's but no problem at higher revs.  

[Gixer1460]

New or old plugs? If new don't bother cleaning as fouled plugs rarely 'clean up' or function correctly - also they could be fakes if NGK / Denso ! ! !

Std coils in good working order will fire plugs in most things - high CR, Nitrous and Turbo applications will test their limits. For a 'normal' engine a std. 3.0 ohm coil will be fine. Most times 'electrical' problems are usually carb related!

[rideordive2ss]

11 hours ago, DAZ said:

Try checking the plug wire , if it's only one cylinder its probably not the coil as each coil fires two cylinders... Can you check the resistance with a multi meter or swap leads around 

I'll be doing an ohm check today or tomorrow   I was going to swap them around but hadn't gotten around to it.  It very well could be missing like 1 on 3  just hadn't pulled the tank to get to it to verify 

[rideordive2ss]

3 hours ago, TonyGee said:

you didn't say what bike ? is the plug getting sooty ? you get them symptoms with a leaking float valve, lumpy at low rev's but no problem at higher revs.  

91 gsxr750 with a 907 kit

 

  I just had the carbs out so maybe but all seemed well enough when I inspected and reinstalled. Yes the plug does foul up   same with 3 now that I think of it  but I was working on the carbs and had many hard starts before I got it right   so when I cleaned them all (sand blasted) reinstalled  I've only checked #1 and 4 since then  and 1 is more so worse off but like I said at higer rpm I can tell all 4 cyl are working  it's just at idle sounds off and when I pulled the wire no change but some times it would sputter when pulled..  I put a plug in the boot and grounded it and shit for spark 

[rideordive2ss]

9 minutes ago, Gixer1460 said:

New or old plugs? If new don't bother cleaning as fouled plugs rarely 'clean up' or function correctly - also they could be fakes if NGK / Denso ! ! !

Std coils in good working order will fire plugs in most things - high CR, Nitrous and Turbo applications will test their limits. For a 'normal' engine a std. 3.0 ohm coil will be fine. Most times 'electrical' problems are usually carb related!

New plugs  but when I was having hard start issues I had to pull them all and sand blasted them. Cleaned up well. They are ngk.  Fake from the auto dealer???   I'm being told since I'm running a 907cc kit I should upgrade to better coils anyways and I figured if and when I run an ohms check if it is in fact the coil as they are OE it looks like they must be old a weak by now... but I'm interested in this could be a carb issue. Hadn't really thought about that. Another guy here said leaking float Valve... how do I go about checking that?

[TonyGee]

3 minutes ago, rideordive2ss said:

91 gsxr750 with a 907 kit

 

  I just had the carbs out so maybe but all seemed well enough when I inspected and reinstalled. Yes the plug does foul up   same with 3 now that I think of it  but I was working on the carbs and had many hard starts before I got it right   so when I cleaned them all (sand blasted) reinstalled  I've only checked #1 and 4 since then  and 1 is more so worse off but like I said at higer rpm I can tell all 4 cyl are working  it's just at idle sounds off and when I pulled the wire no change but some times it would sputter when pulled..  I put a plug in the boot and grounded it and shit for spark 

I would still look into the float valve though, when they leak it runs very rich at idle and low revs and fouls the plug giving a misfire, giving the impression of loosing the spark. but at high rev's the extra fuel is used and runs better. seen this many times.   

[rideordive2ss]

20 hours ago, TonyGee said:

I would still look into the float valve though, when they leak it runs very rich at idle and low revs and fouls the plug giving a misfire, giving the impression of loosing the spark. but at high rev's the extra fuel is used and runs better. seen this many times.   

Forgiven my ignorance, how do I test this

[TonyGee]

6 minutes ago, rideordive2ss said:

Forgiven my ignorance, how do I test this

by doing a bench test.  I have a home made stand that I hang the carbs on using my vice. they have to hang straight and level. then hook up a dummy fuel tank above the carbs and let the fuel flow to the carbs. then leave them for a while. a bad leak will show up straight away but a small leak will take longer. if a float valve is leaking you will see fuel coming out of the carb venturi (where the air flows through from the airbox) 

[rideordive2ss]

4 minutes ago, TonyGee said:

by doing a bench test.  I have a home made stand that I hang the carbs on using my vice. they have to hang straight and level. then hook up a dummy fuel tank above the carbs and let the fuel flow to the carbs. then leave them for a while. a bad leak will show up straight away but a small leak will take longer. if a float valve is leaking you will see fuel coming out of the carb venturi (where the air flows through from the airbox) 

Ugh   I just had them out..lol pain in the ass getting the oe airbox boots back on.. but for sure I'll try this out. Thank you for the info.  If I do find seap/leakage, is there an adjustment to be made or replacement needed.

[TonyGee]

if the valve is leaking then it'll need replacing. 

[slayer61]

2 hours ago, rideordive2ss said:

Ugh   I just had them out..lol pain in the ass getting the oe airbox boots back on.. but for sure I'll try this out. Thank you for the info.  If I do find seap/leakage, is there an adjustment to be made or replacement needed.

I found it's way easier to get my Mrs. to do that part. She has much smaller hands than me!

[rideordive2ss]

35 minutes ago, slayer61 said:

I found it's way easier to get my Mrs. to do that part. She has much smaller hands than me!

I showed my ol lady and she laughed at me and said nope babe   I just ride on the back and keep the bitxhes away, the rest is all you.... smh

[rideordive2ss]

49 minutes ago, TonyGee said:

if the valve is leaking then it'll need replacing. 

Copy that