View Full Version : 1996 Shadow VT500 won't start when warm
07-09-2006, 01:10 AM
I bought a 1996 Honda Shadow last year. It came with a peculiar problem. It starts and runs fine when the engine is cold. However If it warms up for a couple minutes or more then turned off it will not start until it cools off. (Exception: It used to start up again if I tried within 20 seconds of turning off.)
When the problem occurs the starter can barely turn over the engine. It is like there is a huge vacuum or blockage of some sort keeping the engine from turning over easy. I haven't tried compression start when trying to start. I have tried using ether to get it moving as a fuel diagnostic step but starter could only turned over a few times and ether appeared to do nothing.
I am thinking that it is vapor lock issue of some sort in the fuel line. Unfortunately I have no idea how to diagnose, isolate, and/or fix the problem. (I had someone tell me to insulate the fuel line, but that doesn't seem very feasible given tight tolerances.)
I will note that this model has a spiffy fuel on/off/reserve switch that is also has a vacuum hose connected to the engine head. Fuel won't go through the switch unless the engine is turning over.
Related story: The vacuum gas shutoff feature caused me some brief pause when I opened sediment bowl and turned fuel ON to drain tank… only to find no gas would come out. When I turned over engine it actually started (with sediment bowl off!) making me seriously wonder why my motorcycle will only run when I have sediment bowl off :o. Of course the sediment bowl was draining gas well (into a turkey roasting pan) but it was still hilarious after having problems starting with everything hooked up but running fine while pouring gas out. I closed bowl and drove around the block a couple times. I had several big pauses when trying to accelerate but otherwise ran fine… until I returned home and turned off and tried turning on again. I have since drained gas and put in 1.5 gallons of fresh gasoline. No change in warm start problem :-).
I need to find and purchase a manual for this vehicle (and a road tool kit since it has none). I feel pretty ignorant about how this motorcycle works and steps to maintain and fix it right now. I also need someone's kind help to get me past this warm start block. Please reply!
Thanks in advance! -Zephan
If you wanna make sure it isnt a vapor lock, run it, carefully, without the cap on the tank, or so loose that it wont stop gas from spilling out. If it runs better and restart, buy a new gas cap for it. If that doesnt stop the problem, may want to try a different set of coils, not sure if your local honda shop has a way to check em.
07-10-2006, 02:11 AM
Hi Mute. Thanks for the reply and suggestion. I've actually opened the gas cap after the motorcycle has warmed up but it did not affect the real hard starter turnover condition. Perhaps running with gas cap open would do different (I haven't tried this yet).
Someone gave me another theory that merits consideration. I was told that a defective starter motor can increase resistance when hot. This would exactly match my symptom which is starter trying really hard to barely turn over engine when motorcycle is warm.
Vapor lock symptom would be "out of gas" even when gas tank has fuel. Unless someone tells me that vapor lock or other problem can induce a vacuum or blockage that would overwork the starter motor I am going to pursue the faulty starter theory. Please post if you have heard of this or have any helpful comments. My next task is to get price quote from local Bent Bike for starter, find out if it is a DIY project for novice mechanic, and go from there.
FYI: Ran my kids around the block today several times. My Shadow ran perfectly until I was done and turned it off for the evening... then tried starting it just to confirm the warm start problem. Yup, still there.
Yep, didnt even think of the starter being the culprit. Im so used to havin no mechanical problems on the metrics.. lol. You whould be able to change it yourself, all you need is a pretty good memory if you have to remove other stuff to get to it.
07-22-2006, 03:21 AM
You may want to try replacing the battery cables also. When they get hot the resistance goes up and current cant flow through them fast enough to turn the starter.
08-08-2009, 01:55 PM
Hi Zephans, I've got exactly the same problem with mine, did you ever get yours sorted, if so, what was it thay sorted yours please ? Regards, Andy
08-08-2009, 02:22 PM
can you push start it? if so it is most likley either battery, battery cable or starter.
08-08-2009, 03:33 PM
No, reason being if you wait long enough the bike starts again. When it's hot the starter spins the engine over quiet slowly and the bike will not start. As it cools down the starter will spin the motor quicker and eventually it will start. I usually have to wait 10 minutes after a five mile run and 40 minutes after a 30 mile run.
08-08-2009, 07:29 PM
i understand that, but you can narrow down the problem as to either the starter or battery or a cable that are temperature related by push starting it when the starter doesn't work. Then you know it is not engine related but something else.
08-10-2009, 09:02 PM
the problem might also be the choke that prenvents your bike from starting.
or just your sparkplugs.
my xs does that too when it's too humid in montreal.
08-11-2009, 02:32 PM
Thanks for the replies, I've done the following in the last couple of days.
Had the battery checked by an Auto Electrical dealer, they say it's good.
Reterminated (soldered) the connecters on the wires from the alternator (the old ones just pulled of in my hand). The battery now shows 14.5 V with the engine running.
Cleaned up the wiring and connecters on the battery, starter solenoid, the big lead to starter motor, the main earth where it attaches to he motor.
Balanced the carb's
Adjusted the choke.
And still I'm getting the same problem. It spins over but does not start, I tried bumping it but again this did not start it.
When it's going it runs beautifully, it's just the restarting it.
I'll pick up another set of plugs tomoprrow
Any other ideas are welcomed.
08-11-2009, 02:58 PM
Did you attempt to push start it when it wouldn't start? If so did it?
08-11-2009, 03:07 PM
Yes I tried push starting it a few times when it would not start on the button & it would not start.
08-11-2009, 03:28 PM
if that's the case then you have eliminated the Starter, starter wiring, and most likely the battery.
You need to look elsewhere, when it doesn't start do you have spark?
08-11-2009, 03:38 PM
That's going to be my job for tomorrow. I'll take it for a run and assuming I have the uual problem I'll pull a sparking plug out, see if I'm getting a spark. & I'll let you know. Thanks for all the assistance so far.
08-12-2009, 10:50 AM
OK, here we go.
Before I started the bike I measured the battery voltage
I checked for a spark at the plug.
There was one there
I fired the bike up from cold.
It started OK.
I checked the battery voltage with the bike running (to make sure the alternator was OK)
I went for a 10 mile run.
When I got back I checked the battery voltage with the bike running
I stopped the bike and checked the battery voltage.
I went away for 10 mins,
When came back, I checked the battery voltage
I tried to start the bike & it would not start.
I checked the sparking plug & again there was a a spark there, it looked as good as the one I saw before I started.
So, I'm beginning to think the battery / electrics / ignition isn't the problem & perhaps I need to start looking at the carb's.
08-12-2009, 12:15 PM
when you turn it over when it will not start does it turn over like it normally would and it just doesn't start? Or is it obviously turning the motor over way to slow to start.
08-12-2009, 12:45 PM
The motor spins over at the normal speed (all the while the battery has a decent charge in it). You can hear it try to start but it doesn't quite make it until the engine cools down.
08-12-2009, 01:46 PM
if you have good spark then you either have no fuel (carburetor issue) or possibly compression issue. things get hot they expand which would cause fuel not to be drawn in. Valve issue, again heat issue from a valve not seating thereby causing loss of compress thereby causing fuel not to be drawn in. Can you check compression when the engine will not start?
08-12-2009, 02:14 PM
Don't know about compression test. I'll see if I can pick up a tester in town tomorrow. The fact that it runs OK up until when I stop it makes me think the compression can't be to bad. For the same reason I assume fuel is getting through the tap OK, and there ought to be enough in the float chambers to start it anyway. I've only ever worked on Amal carb's up until now. The bike has been standing a couple of years, is there anything in a CV carb that could perish over time ?
08-12-2009, 02:26 PM
cannot help you with that. i know little about cv carbs.
08-12-2009, 02:57 PM
Me neither, wih me luck. Thanks for all the help.
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