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2003 ACE 750 Deluxe
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Discussion Starter · #1 ·
Hi all, as an extension of this discussion: 2003 Honda ACE 750cd backfiring not starting without throttle | Honda Shadow Forums , I thought I would break it down into the moving parts. I recently determined that I definitely had a weak AGM battery from the PO even though he said it was one year old. He neve rode. It was dead and I mistakenly charged it at very high amps so it was probably crap for one of those reasons. Stock exhaust came with bluing headers.

I bought a factory activated Wolftech AGM that is supposedly made by Yuasa in China . It tested weak but they said its fine. Voltage dipped to 10.5 on starting so I ditched it. Don't recommend these. Bought a freshly activated Genuine Yuasa at three times the price 2 days ago. I charged it and gave it a good run at 80-100kmh for 40 minutes. The resting voltage is 13volts and hits 14.4 when revved. My stator tested up to 60 volts when revved, and continuity tested fine. This side seems a lot better.

Question is, could the weak old battery have caused the brand new NGK DPRea8-9 to carbon foul after a few hundred kilometers? Once fouled, would they cause the gently burbly "backfire" I am hearing on decel in lower gears even with the new battery in place?

My working hypothesis is weak spark, combined with a possible lean condition. These are factory lean and I'm 99% sure the bike is still fully stock, including intake and carb wise. New HiFLo Filtro air filter. I thought I would eliminate the weak spark/ignition side before diving into intake and carb.

If I clean the plugs with carb cleaner and wire brush (regap if necessary) will that assist in diagnosis, or must ditch fouled plugs to get an honest diagnosis? The PO's old standard OEM Denso plugs were perfect looking, but misfiring. I recall that Denso's might be hotter firing that the equivalent NGK. Is it safe to put in hotter NGK DPR-ea7-9 now that the cooler temps are here if I can't easily find Denso's.

Have a great riding day and looking forward to anyone's input!

P.S Where the HELL can I buy a spark plug socket that actually fits down the hole! I bought 2 18mm plug sockets that are too fat, and a tool from Royal distributing that is too short.
 

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2001 Shadow Spirit 750
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"Where the HELL can I buy a spark plug socket that actually fits down the hole! I bought 2 18mm plug sockets that are too fat, and a tool from Royal distributing that is too short."

As far as the plug socket...if you have the original tool kit on the bike, the one in there works the best. Good luck with the other issues.
 

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Where the HELL can I buy a spark plug socket that actually fits down the hole! I bought 2 18mm plug sockets that are too fat, and a tool from Royal distributing that is too short.
As far as the plug socket...if you have the original tool kit on the bike, the one in there works the best. Good luck with the other issues.
You have to get a thin wall socket.
 

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My bad battery on my Ace made it have a dead spot in the power band due to fuel pump not having enough voltage to run also the starter would definitely crank slower compared to a new battery
 

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Where the HELL can I buy a spark plug socket that actually fits down the hole! I bought 2 18mm plug sockets that are too fat, and a tool from Royal distributing that is too short.
As far as the plug socket...if you have the original tool kit on the bike, the one in there works the best. Good luck with the other issues.
Best to make your own .. mine was turned down on my lathe to proper O.D. first one was ground down with a bench grinder ...
 

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Hi all, as an extension of this discussion: 2003 Honda ACE 750cd backfiring not starting without throttle | Honda Shadow Forums , I thought I would break it down into the moving parts. I recently determined that I definitely had a weak AGM battery from the PO even though he said it was one year old. He neve rode. It was dead and I mistakenly charged it at very high amps so it was probably crap for one of those reasons. Stock exhaust came with bluing headers.

I bought a factory activated Wolftech AGM that is supposedly made by Yuasa in China . It tested weak but they said its fine. Voltage dipped to 10.5 on starting so I ditched it. Don't recommend these. Bought a freshly activated Genuine Yuasa at three times the price 2 days ago. I charged it and gave it a good run at 80-100kmh for 40 minutes. The resting voltage is 13volts and hits 14.4 when revved. My stator tested up to 60 volts when revved, and continuity tested fine. This side seems a lot better.

Question is, could the weak old battery have caused the brand new NGK DPRea8-9 to carbon foul after a few hundred kilometers? Once fouled, would they cause the gently burbly "backfire" I am hearing on decel in lower gears even with the new battery in place?

My working hypothesis is weak spark, combined with a possible lean condition. These are factory lean and I'm 99% sure the bike is still fully stock, including intake and carb wise. New HiFLo Filtro air filter. I thought I would eliminate the weak spark/ignition side before diving into intake and carb.

If I clean the plugs with carb cleaner and wire brush (regap if necessary) will that assist in diagnosis, or must ditch fouled plugs to get an honest diagnosis? The PO's old standard OEM Denso plugs were perfect looking, but misfiring. I recall that Denso's might be hotter firing that the equivalent NGK. Is it safe to put in hotter NGK DPR-ea7-9 now that the cooler temps are here if I can't easily find Denso's.

Have a great riding day and looking forward to anyone's input!

P.S Where the HELL can I buy a spark plug socket that actually fits down the hole! I bought 2 18mm plug sockets that are too fat, and a tool from Royal distributing that is too short.
Bluing of headers is a sure sign of a lean condition .. also the pop on decel. New battery may help , but check fuel tank venting , carb venting , float height , fuel delivery ....
 

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1983 Honda vt750 Shadow
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If the plugs are carbon fouling and black sooty, that is not lean but too rich. Are you using the bare minimum of choke to get it started?
Sounds like the battery and charging system is all good now.
So it boils down to fuel supply or choke use fouling the plugs.
Clean them and re-use them to see if the problem persists.
They are your mixture feedback.
You might turn each mixture screw in gently til it stops and count the turns.
Then back them out 1 1/2 turns as a starting point.
 

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2003 ACE 750 Deluxe
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Discussion Starter · #11 ·
If the plugs are carbon fouling and black sooty, that is not lean but too rich. Are you using the bare minimum of choke to get it started?
Sounds like the battery and charging system is all good now.
So it boils down to fuel supply or choke use fouling the plugs.
Clean them and re-use them to see if the problem persists.
They are your mixture feedback.
You might turn each mixture screw in gently til it stops and count the turns.
Then back them out 1 1/2 turns as a starting point.
I can barely use any choke at all to assist at the beginning. and after 30 seconds or it stalls. The conundrum of fouled plugs and blue pipes is the challenge. Obviously two things are wrong. I thought I'd first isolate things that don't involve taking the tank and air box out first i.e ignition. That's why I was wondering if a weak battery could have caused the fouling via weak spark. It could barely hold a charge. 10 seconds with the key and headlight on and it probably wouldn't start.
 

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1983 Honda vt750 Shadow
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If the battery got too weak and the ignition too, the spark would fail and the engine would die.
Probably not enough run time to foul the plugs. Unless it is running very rich.
Are you sure the pipes are factory? A picture would help.
They are usually double wall pipe from the factory and have less bluing.
Does it run very smooth at idle? A vacuum leak may be in the mix also.
 

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2003 ACE 750 Deluxe
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Discussion Starter · #13 ·
If the battery got too weak and the ignition too, the spark would fail and the engine would die.
Probably not enough run time to foul the plugs. Unless it is running very rich.
Are you sure the pipes are factory? A picture would help.
They are usually double wall pipe from the factory and have less bluing.
Does it run very smooth at idle? A vacuum leak may be in the mix also.
Swifty, the pipes are definitely 100% stock. I even purchased a 2nd mint set for the future. Don't have a closeup of the bluing, but I put the bike in my Avatar. After a month of buying sockets, I finally got an OEM so I can pull the other two plugs finally. Little victories!

Anyway, I'm thinking next steps are to pull all four plugs this time to check for spark and fouling levels. Then clean them with carb cleaner and a tooth/wire brush, regap to minimum spec. Then pull them again to see if fouling was just the old bad battery. How long to drive before I do that?
 

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1983 Honda vt750 Shadow
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Take it for a good hard ride for 10 miles and see what color they are.
Another way to clean fouled plugs.

 
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Melting the elcctrode and grounding strap just does'nt look like something for me . Soda blasting and carb cleaner is more my style ...
 

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'83 VT750C
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Huh? The temperatures that plug will see in the chamber will be WAY higher than what a small propane torch can heat it up to, even if it was held to the plug for a while.
 
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