Popping and hard hot start - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 17 (permalink) Old 08-07-2008, 05:35 PM Thread Starter
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Popping and hard hot start

My 1990 has developed constant popping on the left side on deceleration. It has also become hard to hot start and backfires when trying to hot start. Starts fine when cold don't even need choke. No mods all stock. Thanks for sharing your wizdom.
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post #2 of 17 (permalink) Old 08-07-2008, 07:58 PM
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The first thing that needs to be determined with hot start issues is, what kind of battery do you have?


AKA: Tim & 'The Adventure Cycle' VROC #24567, NEVROC, SteelCity VROC


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Aim for the apex."

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post #3 of 17 (permalink) Old 08-07-2008, 09:43 PM
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Check out the threads on a Maintenance Free or MF battery. This has solved most hot start probs.

Jim W
93 VN 750 "Ursula"
Moved R/R 08Sep06
R/R rewire 17Feb07
New R/R, Installed 14Jun08
New Stator installed 10 Jun08
Maintenance Free Battery 12Jan08
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VROC #8542
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post #4 of 17 (permalink) Old 08-07-2008, 10:50 PM
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Yep! Our bikes don't like a weak spark from a non MF battery. Leaves unburnt fuel in the exhaust that ignites when it finds some air, (with a boom!) and sends the lady types and small children running.

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Kyle, TX VN750.com member #707 VROC#19556
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Spline Lube Procedure, with photos, R/R Relocation and Coil Mod
Rusty Tank Cleaning!
Electrical Fault Finding Flowchart
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post #5 of 17 (permalink) Old 08-08-2008, 09:20 AM Thread Starter
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It has a one year old wet cell. But why does it fire it right up even after sitting a week or two. But if it runs for 5 min and I shut it off its a bear to restart. Wait 20 -30 min fires right up again. I think its some other problem. Also what happened prior to these MF batteries?
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post #6 of 17 (permalink) Old 08-08-2008, 09:55 AM
 
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the constant popping only on the left side would make me think that the carb may need cleaning or adjustment. i may be wrong though because i dont know much about the electrical system.
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post #7 of 17 (permalink) Old 08-08-2008, 10:34 AM
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Quote:
Originally Posted by engine89 View Post
It has a one year old wet cell. But why does it fire it right up even after sitting a week or two. But if it runs for 5 min and I shut it off its a bear to restart. Wait 20 -30 min fires right up again. I think its some other problem. Also what happened prior to these MF batteries?
I can't explain the theory behind it, but that's how it goes.
Might possibly be the R/R?

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Originally Posted by dutter View Post
the constant popping only on the left side would make me think that the carb may need cleaning or adjustment. i may be wrong though because i dont know much about the electrical system.
That's likely. The air mix screws may need adjusted. But if no mods, could just need cleaning


AKA: Tim & 'The Adventure Cycle' VROC #24567, NEVROC, SteelCity VROC


"When life throws you curves,
Aim for the apex."

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Last edited by hyperbuzzin; 08-08-2008 at 10:43 AM.
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post #8 of 17 (permalink) Old 08-08-2008, 04:22 PM Thread Starter
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Marbled it this morning and adjusted mix to 3 full turns. Popping went away but hot start problem still remains. Will get a new battery unless someone has other thoughts thanks.
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post #9 of 17 (permalink) Old 08-08-2008, 07:35 PM
 
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I read somewhere else about the hot start problems, and the suggested fix was adjusting the pickup coil magnet gap - reducing the gap, I believe. I think I read it in the exhaust forum. Try a search. Good luck!
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post #10 of 17 (permalink) Old 08-09-2008, 10:45 PM
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The hot start problem is weak spark when the engine is hot. There are multiple things you can do to solve it, but I prefer to do three of them. I've done two to mine. 1. MF battery. Yes, it does make a difference. You'll have more voltage even when the engine is hot to create a better spark. This alone could solve the problem. I had hot starting problems with my bike when I first bought it. Same as you describe. I already had an MF battery. I did the coil mod and installed the Iridium plugs at the same time. I've never had the problem since. So, I don't know which solved it, and I did the coil mod just to see if it would work on our bikes, which it did, and it's an easy thing to do so I'd suggest all three. I've heard several talk about the pickup coil gap solving their hot start problems, but my experience was that the above solved it so I've never fooled with the pickup coil mod.

By the way, I still have the same MF battery in my bike, which I've had for nearly 2.5 years, and it wasn't a new battery when I bought the bike. So I feel like the coil mod might have had more effect than I might have imagined.

Fergy
Kyle, TX VN750.com member #707 VROC#19556
2002 VN1500 Classic
Spline Lube Procedure, with photos, R/R Relocation and Coil Mod
Rusty Tank Cleaning!
Electrical Fault Finding Flowchart
SEAFOAM JUNKIE!


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