VT500c only starts when jumped, only revs in neutral - Honda Shadow Forums : Shadow Motorcycle Forum
 
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post #1 of 6 (permalink) Old 05-25-2012, 03:12 PM Thread Starter
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VT500c only starts when jumped, only revs in neutral

Hey all, I was wondering if anyone can offer some insight into my bike rebuild. I have a 1986 vt500c, already put a lot of work into it.

It will start when jumped by a car and it revs beautifully when in neutral, there is absolutely no hesitation or coughs. The exhaust does heat up very quickly. Within one minute, the exhaust starts to smoke and will burn the hell out of my fingers (ask me how I know ), but the engine temps are still good.

When I put the bike in gear and try to run it, the bike needs constant throttle or it will die. It will barely move under it's own power. I drove it into the street just to see how it will run, ended up dying just before the ramp to my driveway. I jumped it again and was going full WOT just to get it to creep up my driveway, and having to play with the clutch to keep the revs up enough to where it wouldn't die.

I am 90% sure it has nothing to do with the carbs. I just rebuilt them and they are clean as a whistle, factory spec. I did have problems getting all the boots to sit right, could it be a problem there that would effect things this much?

I have a new rectifyer from Rick's Motorsports on order, I figure that might be the problem with starting it, since my battery is checking out okay. I'm not sure that explains the bogging down when in gear. Would the stator have anything to do with that? Pulse generator?

Plugs have been replaced, and when I pulled the old ones, they were ashy white, indicating a lean mixture, right? I've checked my fuel supply thoroughly, and float bowls definitely fill with gas. I did put an aftermarket fuel filter on the bike, but the problems remain whether it is on or off.

I would appreciate any insight you all may have to offer! I'm definitely a beginner mechanic, but I've learned a lot already working on this thing. I'm not afraid to learn a little more, I love this bike and will not stop until I get it running like it should!


Last edited by VoluntaryistDude; 05-25-2012 at 03:17 PM.
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post #2 of 6 (permalink) Old 05-25-2012, 04:14 PM
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if it wont start with out a jump the battery is toast. 12 volt does not always mean a battery is GOOD. What the voltage with the starter button pushed?

Stator supplies the electricity to run the bike. The pulse generatoris the sensor that tell the ignition when to fire. BOTH could be part of the issue. But i'm betting it the battery. It's not that the battery is used to run the bike, the stator does that. But if the battery is weak (Low amperage), the battery can draw enough power away from other things, like the ignition, to cause issues you describe. You have to fix the startering issue first. Might also fix the power issue by accident.

IF NOT
When you say REBUILD how detailed do you mean? Rebuilt from what to what?
NEVER assume you got the carbs cleaned, re-assymbleed, adjusted and installed correctly. I have been rebuilding my carbs on VWs and Bikes for years. I mess up something almost every time. If you had issues with the boots they might be leaking? What is the compression?


93 VT1100C Sleeper, VH Exhaust, Saddleman Seat, Baby Apes, Metzlers, 2mm sleeved and bored (1150cc),10.5:1 comp, Modified Heads, Valves, Cams, Adjustable Timing, Bored Carbs.
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post #3 of 6 (permalink) Old 05-26-2012, 09:46 PM Thread Starter
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Quote:
Originally Posted by 93gc40 View Post
if it wont start with out a jump the battery is toast. 12 volt does not always mean a battery is GOOD. What the voltage with the starter button pushed?
Battery is okay, drops down to 10volts when started.

Quote:
Stator supplies the electricity to run the bike. The pulse generatoris the sensor that tell the ignition when to fire. BOTH could be part of the issue. But i'm betting it the battery. It's not that the battery is used to run the bike, the stator does that. But if the battery is weak (Low amperage), the battery can draw enough power away from other things, like the ignition, to cause issues you describe. You have to fix the startering issue first. Might also fix the power issue by accident.
I understand that so much better now, thanks! Don't think it's my problem though, as it turns out...

Quote:
IF NOT
When you say REBUILD how detailed do you mean? Rebuilt from what to what?
NEVER assume you got the carbs cleaned, re-assymbleed, adjusted and installed correctly. I have been rebuilding my carbs on VWs and Bikes for years. I mess up something almost every time. If you had issues with the boots they might be leaking?
Rebuilt as in rebuilt the carbs. I know my carbs aren't the problem. I swapped them out with some old carbs I had. Still doing the same thing.

Quote:
What is the compression?
I think that's the issue. Didn't have a gauge so I didn't check my compression. I got one today.

Rear cylinder is at 165psi
Front cylinder is at 45psi

Crap.
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post #4 of 6 (permalink) Old 05-26-2012, 10:19 PM Thread Starter
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I just ran the compression test again, this time I put a little oil in the spark plug hole to see if it was my valves or my cylinder. For anyone that searches this topic (that's how I gained the little knowledge I have), this checks if your valves are bad or your cylinder.

With a bad cylinder, if you put oil in the spark plug hole, it should seal the gaps in the bad cylinder and you'll hold more compression.

If you have bad valves, there will be no change in compression once you add oil. Check your valve clearances and that should clear things up.

Of course, once I added oil to the spark plug hole, I held more pressure. It went from 45psi to 120psi. Meaning...my cylinder is bad.

Crap again

I'm looking at purchasing another motorcycle now. I'm just not sure I'm capable of tearing down an engine that much, or how expensive the tools I would need are. I'm going to be reading the manual to determine that. I'm on a limited budget, so if I do decide to tear it down rather than scrap it, I will try and post pics of the entire process.

Last edited by VoluntaryistDude; 05-26-2012 at 10:24 PM.
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post #5 of 6 (permalink) Old 05-27-2012, 12:54 AM Thread Starter
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I decided to go for it. Quick question though, I realized when I was starting to take things apart that the choke cable on the right hand side of the carbs was not screwed in. Would that affect my compression test? I don't see how it would, but thought I'd check before I got too into things.

Last edited by VoluntaryistDude; 05-27-2012 at 08:30 PM.
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post #6 of 6 (permalink) Old 05-31-2012, 05:35 AM Thread Starter
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Well, here's the problem!



When I got to the piston and touched it, the rings just crumbled with any pressure. Some fell down within the engine compartment, whoops! The piston itself crumbled like a cookie, and was coated with thick carbon deposits. Same with the valves.

Just have to find a new piston and ring set, and hopefully I'll be good to go! The piston is kinda hard to find since they are discontinued now.

I am going to open up the other cylinder to take a look at it and make sure everything is up to spec. It won't hurt anything if I just change one out, since the other cylinder's compression was good?

Got a couple weeks till I can order parts, what does everyone use to clean the inner components? Kerosene? Regular gas? Degreaser?

Last edited by VoluntaryistDude; 05-31-2012 at 05:40 AM.
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