Anyone a motorcycle troubleshooting guru?

[Iamero]

Hey guys, just made a profile over on Hondashadow.net as well and hopefully will get some answers once I get my lost count up, but figured I would check here too.

I took an old 1985 Honda Shadow VT700C and converted it into a bobber. Rebuilt the carb when I got it and got all sorts of crap out of there and the bike started and ran like a dream (just a little backfire on decel after I put new pipes on).

Well I ran it 4 days ago with no issues whatsoever. Fender and taillights came in so I mounted the fender and wired in the turn signals. All of that checked out good, but when I went to start it yesterday I couldn’t get her to fire. I assumed it was a weak battery from having the key on a lot during testing and wiring the tail lights.

I charged it up, turned the choke on full and then half, and finally got it to fire up after several attempts. Problem is it wouldn’t stay running even on choke. If I turn the choke off then it won’t even fire up or stay running whatsoever.

I pulled the carb again, soaked it, blasted it, to no avail.

Fuel pump is still spitting fuel, opened the drain plug on the carbs and it’s draining fuel so carbs have fuel, but it won’t hardly stay running. If I try to rev it up it stalls instantly.

Any idea what might have happened in the last 3 days that made it go from flawless to not being able to stay running? Maybe something electrical?

 

[Mike Casselton]

Pull the carb, remove the idle jet and make sure the passage though the carb is clear. Small monofilament line or wire should clear the blockage that's probably there.

 

[adeakins]

Are you using a dry or oiled type foam air filter?

 

[Iamero]

Not 100% sure on the air filter. All I know is that it desperately needs a new one after I pulled it to clean it. I tried running it without a filter in case it was running rich.

I pulled every jet I could get out (3 total) and I can see through every one. I used a guitar string to run through every hole. The pilot jet was my first thought which is why I took it apart, but I haven’t noticed any difference since reassembly. Think a little bit of funk got in there and plug something in the circuit?

 

[Badfinger]

Did the problem start after you changed fenders and lights? Make sure you didn't pinch or short a wire changing fenders etc. Did you have the gas tank off? If so check under there too.

 

[Spblademaker]

I’d say carbs also. Have an 85 VF700F. 4 carbs on mine. Like stated above. Pull them. Clean them out. Clean fuel lines, tank and filter.

 

[Badfinger]

Did you put LED lights on the bike?

 

[Quarter Horse]

How old is the fuel? Depending on the state you are in, you can sometimes buy fuel without ethanol at a Stihl dealer. Get a fuel additive and swap out the fuel.

 

[Iamero]

Yea put LEDs on there. I don’t see any wires pinched. Whatcha thinking?

 

[Basher]

I'd recheck the carbs. Maybe do a carb dip, and then use an aerosol carb cleaner to blow the passages out. Check the diaphrams for any pinholes that would affect their function. Check the floats to make sur you don't have a leak, and set float height. Drain all the old fuel, and replace with new after checking to be sure the tank isn't rusted. Replace the fuel filter and the fuel lines, if it's been sitting awhile. Verify that none of the adjustment screws have changed their settings due to vibration, etc. Replace the air filter.

All of these are things I'd start with after a bike sat for a good while. How do the plugs look after running it?

 

[Iamero]

Plugs are looking pretty good. Perhaps a little lean but when I just pulled one there was some gas on it so it’s not completely dry.

I disconnected the LED taillights just in case I screwed something up with the circuit but that made no difference.

I just attempted to start it again and it almost sounded like it was running a little better but then had the same symptoms and stalled.

I pulled the line off the pump and it “spurts” gasoline every few seconds and isn’t a constant flow. Not sure how pumps work on bikes, so is that normal? I noticed when I had it down the road and idling the other week that there was a weird “tick”. I thought it was a valve or something hitting but upon closer inspection I realized the sound was just coming from the pump. It would make a loud tick every time it spurted the fuel out.

When it first fired up it sounded halfway OK but quickly starved which makes me think its lean in getting fuel delivered, but not sure. I also noticed this time that it’s getting a little “hiss” out of the rear cylinder which on the virago bobber I did was a result of crap carb boots. Think that would cause these other issues with it running or just add to it?

 

[sirhrmechanic]

If you are using Ethanol Fuel... those pre-ethanol bikes are full of plastic and rubber things that do not do well in Ethanol-land.

Also, if the tank has old varnish and scale in it... that does fine with fuel. But when you run ethanol fuel in it, it dissolves all the old crud and fills up the carb and everything else with a nice, stick candy-apple coating...

Before doing anything to carbs... check condenser(s). They are the $5 part that screws everyone over. Until ignition is perfect, don't touch carbs. So condenser is always a first thing to check.

But I concur carb stuff. Maybe ethanol-caused. Ethanol and 1980's plastic and rubber do not mix.

Cheers,

Sirhr

 

[Iamero]

Might be a dumb question but where is the condenser typically located?

 

[sirhrmechanic]

Attached to the wire between the coil and the points... somewhere. Not sure on a Honda. But there has to be one somewhere.

Might be integral with the coil... Something tells me that bikes might have done that...

Cheers,

Sirhr

 

[Basher]

Attached to the wire between the coil and the points... somewhere. Not sure on a Honda. But there has to be one somewhere.

Might be integral with the coil... Something tells me that bikes might have done that...

Cheers,

Sirhr

A google search shows the '85 VT700C has a transistorized igntion system, so no points.

OP, have you confirmed you're getting good spark? I'd wager on a fuel issue of some kind, but as you're aware, you need fuel, air, and source of ignition to run. Never hurts to make sure. If they're wet, either it's rich (doesn't sound like it) or you're not getting reliable ignition. You may be facing a variety of issues here.

 

[Iamero]

I pulled the plugs and checked their spark. Definitely plenty there and bright blue. What I can’t get over is how it was running like a top 3 days ago.

 

[Basher]

I pulled the plugs and checked their spark. Definitely plenty there and bright blue. What I can’t get over is how it was running like a top 3 days ago.

Doesn't take much. Coils can break down quickly, especially if they're old, and obviously a blockage in any of the carb's circuits can happen in an instant. Likewise, any old rubber components can break down or swell up in a short period of time, causing blockages or air leaks.

But allow me to say that diagnosing anything over the web/phone is an exercise in frustration and futility, in most cases, haha. We're all just grasping at straws in the dark here!

 

[Badfinger]

Yea put LEDs on there. I don’t see any wires pinched. Whatcha thinking?

I was a Harley service manager for a while and I don't know why but we had several bikes towed in from guys who tried to put LEDs on their bikes. Somehow it screwed up their electrical system. Disconnect them and try the bike.

 

[Iamero]

I disconnected them and capped the wires and it didn’t make a difference on this one. I’m going to get new coils, boots, and fuel lines and filters and see if anything happens.

 

[whatsupdoc]

Take the plugs out squirt a little gas in the plug holes and see if it fires, if it does its a fuel issue if it does not its an electrical issue.
You do need to put the plugs back before you try.

 

[thejeep]

Pull out voltmeter and check leucy system. Stator, rectifier, regulator, what ever it has. If it ran then you messed with electric thats where my money would be.