20 HP Briggs Engine Miss

gkins · 04-12-2009, 06:17 PM

I have a 20 HP Briggs Intek which has a miss at high rpm. I have checked the spark, which seems good, but when I run at high speeds it has a miss which I cannot rectify. I am assuming I have one bad coil but cannot confirm. Any ideas?

MrChooks · 04-12-2009, 06:22 PM

Hi & welcome to TSF.

Have you pulled the plugs and had a good look at both of them??

See if they both look the same (colour and burn marks around the electrode). You might be able to identify which one is the from the missing cylinder that way.

Have you tried a new set of plugs - sometimes when they get tired they work OK at low revs but when the going gets tough they give up - so a cheap fix would be a new set of plugs and see if that fies the miss

gkins · 04-12-2009, 06:31 PM

I have checked the plugs and they both look good and are gapped properly. They were new at the begining of last summer, but I agree, I need to change them. I put an amp clamp on both plug wires and one show about 8A and the other about 6A, but I'm not certain this is an indicator of anything.

MrChooks · 04-12-2009, 06:34 PM

I doubt an amp clamp around a HT ignition lead would give much indication of anything as the current in these leads is very very low BUT the voltage is often 20Kv +

If the plugs doesn't fix your problem

- have a look at the main jet of the carb and see if it responds to a good clean. Sometimes a small bit of muck can upset the fuel flow / atomisation needed at high engine speeds / loads.

gkins · 04-12-2009, 07:16 PM

I cleaned the carb and put a complete new kit in it. I will try the new plugs and from there purchase a new coil and see what that does.

MrChooks · 04-12-2009, 07:22 PM

gkins - Given that you have the carb clean (and presume you have float level correctly set) if new plugs don't fix this it is starting to sound like this one could be a total PiA

If new plugs don't get rid of the problem - I guess you could look at the coil - BUT I have never had a coil fail partially - they tend to either work or they don't

Also they are not cheap

so before you part with hard earned $s on a new coil - I would suggest you re-check everything in the carb and see how you go with new plugs - coz I am not aware of parts retailers that will allow a return / refund on a coil / ignition parts if you find it doesn't fix your problem

k2skier · 04-12-2009, 08:04 PM

Doesn't it have 2 coils? If it does, there's a shorting (kill) wire that connects the 2 together, and to isolate the 2 coils the wire has a diode (s?) in it. It's possible that one of the coils is bad and or the wire between the coils had a bad diode. Don't forget to check valve lash if none of this helps.

04-12-2009, 06:17 PM	#1 (permalink)
gkins Registered User Join Date: Apr 2009 Posts: 3 OS: XP	20 HP Briggs Engine Miss I have a 20 HP Briggs Intek which has a miss at high rpm. I have checked the spark, which seems good, but when I run at high speeds it has a miss which I cannot rectify. I am assuming I have one bad coil but cannot confirm. Any ideas?

04-12-2009, 06:22 PM	#2 (permalink)
MrChooks Gearhead Join Date: Apr 2008 Location: Sydney, Australia Posts: 613 OS: Windows XP Home SP 3 My System	Re: 20 HP Briggs Engine Miss Hi & welcome to TSF. Have you pulled the plugs and had a good look at both of them?? See if they both look the same (colour and burn marks around the electrode). You might be able to identify which one is the from the missing cylinder that way. Have you tried a new set of plugs - sometimes when they get tired they work OK at low revs but when the going gets tough they give up - so a cheap fix would be a new set of plugs and see if that fies the miss

04-12-2009, 06:31 PM	#3 (permalink)
gkins Registered User Join Date: Apr 2009 Posts: 3 OS: XP	Re: 20 HP Briggs Engine Miss I have checked the plugs and they both look good and are gapped properly. They were new at the begining of last summer, but I agree, I need to change them. I put an amp clamp on both plug wires and one show about 8A and the other about 6A, but I'm not certain this is an indicator of anything.

04-12-2009, 06:34 PM	#4 (permalink)
MrChooks Gearhead Join Date: Apr 2008 Location: Sydney, Australia Posts: 613 OS: Windows XP Home SP 3 My System	Re: 20 HP Briggs Engine Miss I doubt an amp clamp around a HT ignition lead would give much indication of anything as the current in these leads is very very low BUT the voltage is often 20Kv + If the plugs doesn't fix your problem - have a look at the main jet of the carb and see if it responds to a good clean. Sometimes a small bit of muck can upset the fuel flow / atomisation needed at high engine speeds / loads.

04-12-2009, 07:16 PM	#5 (permalink)
gkins Registered User Join Date: Apr 2009 Posts: 3 OS: XP	Re: 20 HP Briggs Engine Miss I cleaned the carb and put a complete new kit in it. I will try the new plugs and from there purchase a new coil and see what that does.

04-12-2009, 07:22 PM	#6 (permalink)
MrChooks Gearhead Join Date: Apr 2008 Location: Sydney, Australia Posts: 613 OS: Windows XP Home SP 3 My System	Re: 20 HP Briggs Engine Miss gkins - Given that you have the carb clean (and presume you have float level correctly set) if new plugs don't fix this it is starting to sound like this one could be a total PiA If new plugs don't get rid of the problem - I guess you could look at the coil - BUT I have never had a coil fail partially - they tend to either work or they don't Also they are not cheap so before you part with hard earned $s on a new coil - I would suggest you re-check everything in the carb and see how you go with new plugs - coz I am not aware of parts retailers that will allow a return / refund on a coil / ignition parts if you find it doesn't fix your problem

04-12-2009, 08:04 PM	#7 (permalink)
k2skier Registered User Join Date: Sep 2008 Location: Oregon Posts: 313 OS: XP Home-SP3 My System	Re: 20 HP Briggs Engine Miss Doesn't it have 2 coils? If it does, there's a shorting (kill) wire that connects the 2 together, and to isolate the 2 coils the wire has a diode (s?) in it. It's possible that one of the coils is bad and or the wire between the coils had a bad diode. Don't forget to check valve lash if none of this helps.