Carb synch went bad ?!? Won't start...

Hello everybody. Few weeks back I attempted to sync carbs (bike ran very decently by the way), found that they were out of sync. Then I was missing bunch of springs that keep carbs in sync sooooo I decided to take the whole carb assembly of the bike to get it fixed (or let just say improve because bike was running just fine). Found some springs from junk yard put everything back together (I did empty carburetors though while I was working on it), it was not too hard. Put everything back, bench synched carbs, all looking good, trying to start - nothing. Then first thing, checked fuel supply, fuel pump relay suddenly dead (was previously working though), so I hot wired fuel pump, pumping nice, thinking ok, now it is going to start without a problem - nope, nothing. Question:
1) how long can I crank before I flood the engine?
2)I will check spark plugs, shall I look back at carb assembly (previously was working fine, did not mess with them at all except disconnecting fuel&air lines.
3)air line which connects all carburetors, has an opening to air that does not connect anywhere, right?
Any suggestions? (bike run fine before)
I did adjust valves (following manual). I doubt I made mistake there.

Thanks, greatly appreciated.

Where else to look? Carburetor?

 

Troubleshooting the wrong way

You could start to help yourself by getting the manuals and the RTFM knowledge before you cross wire something and burn your bike up... But i'll give you a few hints anyway.

The "fuel pump relay" is triggered by the dwell pulse for the coil to the front cylinders. The ignitor boxes in the "trunk" pulse the coils. So your problem is that the coils were not being pulsed--the relay was just a side effect of that malfunction. Mr Honda figured for safety reasons that if the coils are not working then you don't need to pressurize the fuel anyway...

So the ignitor boxes could be bad, but then again it could just be a bad pulse generator sensor which sends ignition timing signals to the ignitor boxes.

There is a logical progression to troubleshooting and jumperin' stuff that you don't understand is not it--that sort of scary larry stuff is better left to the squids...

 

Well, not so fast...;-)

I do appreciate your point of view. I do have Honda shop manual and i did some ( not all) of suggested troubleshooting. ( as they state- first check fuel supply, then hotwire pump, then spark and so on). But I exactly don' t have mechanics experience which is where you can get to the core of the problem FAST!!! thanks for your opinion. I probably burned something, should have disconnected the battery when I was working on it (childish mistake) but again, I bought this old bike for exactly that reason - to learn to ride&fix bikes.

 

Bikes are fun to work on and you can get some good experience. i would not be doing you any favors not to warn you about potential hazards--i've seen bikes burn and that is a hard way to get experience. A beautiful RWB VF700 burned this spring due to a fuel-related error by a friend who should have known better...

So let's get it straight--In no place in the manual does it suggest to try to start the bike on a hot-wired fuel pump relay. The hotwire test is only for 5 seconds duration in order to measure the flowrate of the pump, or is used to during voltage checks to verify that the relay is working.

What would you have done if the bike did start on a hot-wired relay--think all is well and take it for a ride? Imagine the horror of making a left turn across traffic and the jumper wire vibrates loose and you stall in the middle of the oncoming lane...just sayin'

[/soapbox mode off/]

 

Update: did some more torubleshooting, have spark !

Ok, I did check spark plugs, I do have spark on all four when cranking starter! Could this be that initially faulty fuel relay, later overflooded cylinder in combination with weaker battery ( not very new, bike had been sitting a garage for a while too and just yesterday was barely cranking) is the reason for not starting? Had happened to me before on older carburated car...I am charging battery over night, try again tomorrow. I will make a permanent connection for jumped relay, to be safe. Thank you for your warning..;-)

 

If you flooded the engine check your oil for fuel smell, change oil if it has fuel in it. After carb rebuild I jump the fuel pump to fill the carbs rather than cranking it over aimlessly. If it don't start put a small amount of fuel down each carb, reinstall air filter, it should run, if it starts and then stops there's no fuel in the carbs, open carb bowl drains to verify fuel/no fuel. If no fuel make sure there's enough in the tank, check pump fuel flow, all lines hooked up correctly? if it didn't run at all pull plugs to see if there wet (flooded). Start with fully charged battery. Good luck!

 

Could be the relay, but

you would have to do the voltage test from the manual to determine for sure.

Since you have spark and you know the fuel pump will run if it is jumpered, so it is pointing fingers at the relay.

Could be bad connections too, check all the spade lugs on the terminals (a good idea for the Rectifier/Regulator, and almost everywhere else on an older bike, too)

 

Thermometer shorting ignition???

Let me tell you guys, troubleshooting electrical problems ain't easy. So I went. Y shop manual, started with checking resistance on severeal different areas and found out following:

1) previous owner put aftermarket ignition wires on that have NO built in resistors in the ignition cap like OEM suppose to, thus resulting in lower overall resistance of ignition wire ( roughly by half measured in Ohms)

2) seems like that bike would run normally, if I just simply disconnect thermometer wire that is connected to thermostat near carbs. Yet the when connected ( bike does not have spark) thermometer gauge seems to be showing/working fine.

Could it be that because of aftermarket lower resistance ignition wires thermometer gauge is possibly shorting ignition somehow?

 

No, check all your grounds, resistors only cut down the RFI.