Trying to get my bike started - Kawasaki Vulcan 750 Forum : Kawasaki VN750 Forums
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post #1 of 4 (permalink) Old 03-12-2019, 01:07 AM Thread Starter
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Trying to get my bike started

Hi guys I am new here. I picked up a 2004 Kawasaki Vulcan 750 about a month ago and it was on faith that it would start and just needed the carbs cleaned out. I only paid $500.00 for it so not a huge gamble. I managed to get it started with starter fluid a couple of weeks ago, and it even restarted after it was warm without a problem. I opted at this stage to start to put some tlc into it in order to get it back on the road reliably, it did backfire a few times before it started initially, so I counted it to just because it was sitting for a while. I opted to start with taking care of the fuel that was in it and am running some fuel with treatments added to it in order to at least get something working towards the positive before I start tearing into each section and formally cleaning things up from the inside out, the whole it's actually started and ran and I was able to put it around my yard as well showed it was not in absolutes needing a complete redo of the carbs and the rest just to get it to fire up, and new used rigs, be it bikes or cars I would rather address what is immediately showing up and work my way into upgrades/fixing up the already shown components.

I am used to cars and finding there are more nuances to the bikes that you don't have to deal with, with them. I have the symptoms from my end, along with those from the original owner from years ago and the one that just sold it to me to be putting into the troubleshooting mix here. The original owner mentioned it was bogging out on power, he knows nothing along mechanics so I couldn't really get much from him. The last owner told me he always had to use starter fluid or roll start it in order to get it going, it would turn over but just not fire up on it's own.

I go from there, to now, where I took out the spark plugs and replaced them "they were desperately needed there even if they were working due to their age", ruling that part out, so now here is what it's doing.

I can turn it over, I here some bubbling from the engine trying to start and an alternative of exhaust backfire and carb backfire, nothing else. I pulled the spark plugs and turned it over, I am not getting spark to them for some reason now. Did I just win the ignition coils failing lottery? There is the kill switch to look at ruling that out, how do you disable it? It started while the kickstand was down, I tried with it up too just to make sure there was not a kill switch for that too, but it didn't change anything.

I am ruling out fuel since it would only start before and then backfired only when I tried using starter fluid, with the new fuel it just stays at that level which shows it's getting plenty of fuel else there would be nothing to actually use to com-bust to backfire. I am ruling out compression for that same reason, it has enough compression to backfire without getting spark, so that is good. I am trying not to go through too many rabbit trails, ie. the battery is new and is in good shape, this was also additionally tested for the people that insist upon some expensive battery recommendation for additional beyond OEM levels since it fixed their personal problems, by also jump start/assist with my full size regular truck battery, not installed in my truck atm in case, you don't connect the leads and jump start a bike from a car or truck while it's running because it will fry the electrical on your bike. That gave me superbattery capacity of sorts, and it did not change, so that is ruled out too.

When I had the bike running, after turning it off, after an hour I started it up again, and it did so on it's own without needing any starting fluid, it was cold on the outside of the engine, so it wasn't some sudden bump or something in the last time I turned it off. I know it's damn close and I should not need to essentially replace every part on this thing from tip to tail and stumble across the spot that actually fixes it, which is what I predominantly see going on with most answers and advice. I might as well strip it down to it's last nut and bolt and rebuild it from the ground up if I am going that route, which I am not going to do.
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post #2 of 4 (permalink) Old 03-12-2019, 01:46 AM
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Sounds like you might have a mish-mash of problems.

Carbs might need to be pulled and cleaned. If the starter is cranking but the motor isn't starting, you may be starved for fuel if the pilot jets are clogged. However, you also said you got it to fire up without issue at least once, so that may not be a problem. Bogging at speed may mean a clogged main jet. There's a vent hose that causes bogging problems at speed as well, but that may be a diagnosis for later.

There are a couple things to check with a no-spark situation. Bad kill switch (not really a common failure point), bad ignition switch (tail lights failing to come on is a dead giveaway. Should have continuity between white and white/brown wire on the smaller of the junction box connectors when unplugged), bad interlock switches (@kickstand, neutral gear, & clutch lever). The interlock on this bike can be the source of some gremlins, esp. when the kickstand switch gets sticky. You can bypass that switch easily if it is problematic. Bike is designed to not start when clutch is engaged and transmission is in gear. Bike is designed to kill the engine if the kickstand is down when the clutch is engaged and the transmission is in gear.

What am I leaving out, guys?

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post #3 of 4 (permalink) Old 03-12-2019, 02:27 AM Thread Starter
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Thanks for the input, much appreciated. Any pointers on circumventing the interlock the better so I can rule that one out.
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post #4 of 4 (permalink) Old 03-12-2019, 07:02 AM Thread Starter
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I ended up getting spark, flaky battery ground issues upon. Same results as before, so on to fuel and timing. I will see if I can get it to com-bust dripping a little bit of gas into the pistons via. two of the spark plug holes, and it only needs to sputter to tell me if it's fuel delivery, if not, it's looking at timing, and again, the car background, there is not distributor or the rest to figure out, so going cold based upon what I dug up so far. I see why it passed to three hands or more at this stage, something a bit more needs to be looked into.
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