Concours Owners Group (COG) Forum

Motorcycle Talk => Other Motorcycles => Topic started by: Rogue Booger on August 07, 2017, 02:06:11 pm

Title: Stump the Coggers also known as: I have this old bike (SOLVED I THINK)
Post by: Rogue Booger on August 07, 2017, 02:06:11 pm
I have a 1993 Yamaha Virago 535. It unfortunately sat for a year without being started, so it wouldn't start. I've cleaned and reassembled the carbs, drained the tanks, put in fresh gas. The bike will not start without the help of starting fluid but runs ok after that. Sometimes the idle rises on its own, but will slow to normal after twisting the throttle. Although it returns to normal idle slowly. No smoke, no back fire. Any thoughts on why it won't start with out starting fluid?

Let it run a while with say - sea foam - to clean out any crud I may have missed?

I belong to a Virago Forum but as fewer of these bikes exist it can be a long time before anyone chimes in.

Any thoughts are greatly appreciated.

Phil
Title: Re: Stump the Coggers also known as: I have this old bike
Post by: WillyP on August 07, 2017, 02:10:54 pm
Vacuum leak.
Title: Re: Stump the Coggers also known as: I have this old bike
Post by: works4me on August 07, 2017, 02:33:06 pm
Vacuum leak.

^^^This. Check for cracks in the intake manifolds.
Not uncommon at this age, especially for a bike
that has sat. Any vacuum hoses would also be suspect.
Title: Re: Stump the Coggers also known as: I have this old bike
Post by: connie_rider on August 07, 2017, 02:41:58 pm
Does it crank after it is warmed up?

Do the carbs have an enrichener circuit in them? {Instead of a choke}
If yes, you may have a problem in that circuit. {Blocked passages, or rubber on plungers not sealing}

Ride safe, Ted
Title: Re: Stump the Coggers also known as: I have this old bike
Post by: Rogue Booger on August 07, 2017, 07:23:28 pm
Bike has a choke. I spray something on the vacuum lines to find a leak right?
Title: Re: Stump the Coggers also known as: I have this old bike
Post by: Rogue Booger on August 07, 2017, 07:54:16 pm
Bike has a choke. I spray something on the vacuum lines to find a leak right?


I'll look it up online. Thanks!!
Title: Re: Stump the Coggers also known as: I have this old bike
Post by: connie_rider on August 07, 2017, 07:59:11 pm
WD-40 sprayed on the lines etc will cause the motor to smooth or rev up a little if you have a vacuum leak.
I've heard of folks using brake clean or even Ether too.   (OMG  :-[)
But brake clean/etc can go bang if there is a spark...

Ride safe, Ted
Title: Re: Stump the Coggers also known as: I have this old bike
Post by: MAN OF BLUES on August 07, 2017, 08:26:30 pm
WD-40 sprayed on the lines etc will cause the motor to smooth or rev up a little if you have a vacuum leak.
I've heard of folks using brake clean or even Ether too.   (OMG  :-[)
But brake clean/etc can go bang if there is a spark...

Ride safe, Ted

Please.... DONT use BrakeKleen....not for fire risks, but because when it is exposed to high heat, or burned in the combustion process, it produces phosgene gas....
Deadly, and at the least very extremely harmful to the body, in the most minute amount.... one whiff is enough to do damage, permanent health damage...


When trying to find an intake leak, use a simple propane torch, don't light it, just pass the end so the gas cam be sucked into the probable leaks... done outdoors, its simple, and safe, and you will not risk anything.. just turn it off when finished....

In addition, intake leaks really don't manifest themselves by "having to spray starting fluid in".... the common symptom on an intake leak is the bike, once started (a bike with CVK carbs) will not return to low idle speed correctly...
There is more to this than a vac leak..
Title: Re: Stump the Coggers also known as: I have this old bike
Post by: MAN OF BLUES on August 07, 2017, 09:06:32 pm
Bike does NOT have a choke, its an enrichener circuit.... just like a Conni...

You have a combination of issues....
Incomplete "cleaning" of the passages for low speed circuits, probably mal adjusted float level....
Improper air screw adjustment on build, throttle plate stop mal adjusted, not allowing proper low speed and enrichment from occuring, basic starting points...
Those carbs are a bit more "complex" due to that manifolding inside the carb float area also, which does require attention, and everything inside does require sealing correctly once cleaned.....
So, stop spraying starting fluid in there... you will be buying main slide diaphragms shortly if you keep doing that....

Here's some basics...

http://youtu.be/tuva-EdPvZE (http://youtu.be/tuva-EdPvZE)
Title: Re: Stump the Coggers also known as: I have this old bike (SOLVED I THINK)
Post by: Rogue Booger on August 07, 2017, 09:57:57 pm
I failed to tighten the carb boots when I put them back on with the barrel bands. It seems to work ok now. THANK YOU EACH AND EVERY ONE.

AND thanks for the heads up on the brake clean!
Title: Re: Stump the Coggers also known as: I have this old bike
Post by: Grant on September 01, 2017, 10:31:37 am
WD-40 sprayed on the lines etc will cause the motor to smooth or rev up a little if you have a vacuum leak.
I've heard of folks using brake clean or even Ether too.   (OMG  :-[)
But brake clean/etc can go bang if there is a spark...

Ride safe, Ted

Please.... DONT use BrakeKleen....not for fire risks, but because when it is exposed to high heat, or burned in the combustion process, it produces phosgene gas....
Deadly, and at the least very extremely harmful to the body, in the most minute amount.... one whiff is enough to do damage, permanent health damage...


When trying to find an intake leak, use a simple propane torch, don't light it, just pass the end so the gas cam be sucked into the probable leaks... done outdoors, its simple, and safe, and you will not risk anything.. just turn it off when finished....

In addition, intake leaks really don't manifest themselves by "having to spray starting fluid in".... the common symptom on an intake leak is the bike, once started (a bike with CVK carbs) will not return to low idle speed correctly...
There is more to this than a vac leak..
I have an old cheap propane torch that I removed the air mixer tip and installed a 3' section of 3/8 fuel line on just for this purpose.
Title: Re: Stump the Coggers also known as: I have this old bike (SOLVED I THINK)
Post by: ConcoursKZ on September 01, 2017, 10:45:09 am
I have used wd40 many times for this type of situation. Carb boots get old, hard and cracked. They look good but but are not.