K75 2V hesitates when starting from idle

[Laitch]

Please forgive me if you have already answered this.   Is this a new to you bike?  Did it run properly for you in the past, or did this problem come with the bike?

The bike was pre-flogged by others before he plopped down cash for it, Gryph. He's had it a few weeks.  Some of the sordid details can be found in his first post.

[The Mighty Gryphon]

Is it fair to assume that the bike hasn't ran properly for a long time and that is the reason(among others) for the incredible price?

If so, my recommendation is to go through the entire bike front to back getting everything right before taking it out for a ride.  This is a  bike with a troubled past and there is nothing you should take for granted. 

If the bike has sat unused for an extended time, the old fuel has probably built up a lot of varnish in the injectors.  You can take them out and send them to be cleaned, or possibly dump a bottle of Techron fuel system cleaner into the tank.  Run the engine for a couple minutes to circulate and mix the Techron throughout the system.  Then let it sit for a few days and restart the engine.  Depending on how bad the varnish is, it may take a couple weeks of doing this to get things loosened up.  If they still don't work after two weeks of circulating the cleaner, you will need to send them out to be professionally cleaned.

If you haven't drained the tank of old fuel, do it now and replace it with two gallons of no corn premium mixed with a bottle of Techron.  An easy way to drain most of the fuel out of the tank is to pull the return line hose from it's spigot on the tank and put it into a container so it can't spray and splash all over the place.  Start the engine and let it run until all the gas is pumped out and it quits.

Since this is a "new" bike, when you have the tank empty, you should remove it and use the opportunity to do any service that requires the tank to be off the bike.   This includes cleaning all the connectors under there, especially the ground connections on the frame backbone.  Then you can drain the cooling system and put in new coolant.  It will also be a good time to do some improvements like an Eastern Beaver headlight relay harness and a manual fan switch.

Tank removal can be done without removing the main fairing.  The hardest part is disconnecting the fuel lines which should be replaced anyway.  You don't even need to remove the seat, although it isn't very difficult, and makes tank removal even easier. 

Once you've done the under tank stuff, get the tank back on and start circulating the Techron fuel mixture while you address everything else.

[johnny]

if this was my moto it would be no corn ethyl and 4 bottles of techron till near empty... then 3 bottles of techron then 2 bottles of techron then 1 bottle of techron then just no corn ethyl... that would be 1000 miles and my heap would me spinning like its 420...

[brichbk]

Is it fair to assume that the bike hasn't ran properly for a long time and that is the reason(among others) for the incredible price?

If so, my recommendation is to go through the entire bike front to back getting everything right before taking it out for a ride.  This is a  bike with a troubled past and there is nothing you should take for granted. 

If the bike has sat unused for an extended time, the old fuel has probably built up a lot of varnish in the injectors.  You can take them out and send them to be cleaned, or possibly dump a bottle of Techron fuel system cleaner into the tank.  Run the engine for a couple minutes to circulate and mix the Techron throughout the system.  Then let it sit for a few days and restart the engine.  Depending on how bad the varnish is, it may take a couple weeks of doing this to get things loosened up.  If they still don't work after two weeks of circulating the cleaner, you will need to send them out to be professionally cleaned.

If you haven't drained the tank of old fuel, do it now and replace it with two gallons of no corn premium mixed with a bottle of Techron.  An easy way to drain most of the fuel out of the tank is to pull the return line hose from it's spigot on the tank and put it into a container so it can't spray and splash all over the place.  Start the engine and let it run until all the gas is pumped out and it quits.

Since this is a "new" bike, when you have the tank empty, you should remove it and use the opportunity to do any service that requires the tank to be off the bike.   This includes cleaning all the connectors under there, especially the ground connections on the frame backbone.  Then you can drain the cooling system and put in new coolant.  It will also be a good time to do some improvements like an Eastern Beaver headlight relay harness and a manual fan switch.

Tank removal can be done without removing the main fairing.  The hardest part is disconnecting the fuel lines which should be replaced anyway.  You don't even need to remove the seat, although it isn't very difficult, and makes tank removal even easier. 

Once you've done the under tank stuff, get the tank back on and start circulating the Techron fuel mixture while you address everything else.

Thanks Gryphon for the recommendation.  I don't have much time to work on it this week so I'll start with the Techron advice.  I can take a few minutes to start it once every few days.  Dos it matter how much gas is in the tank?  The gas light is currently on so it has less than a 1/4 tank of gas.   Then I'll move on to removing the tank and cleaning the connections. 


Yes you are correct in that I bought the bike with this issue.   So I am trying to undo something that might have been a long standing issue.

[Laitch]

Dos it matter how much gas is in the tank?  The gas light is currently on so it has less than a 1/4 tank of gas.     

Techron isn't engine fuel; it's detergent. It matters. Now if instructions matter—only the weak follow them and besides, Standard Oil is part of a pervasive, profit-driven evil that only Armageddon can eliminate—here's what the manufacturer recommends:

Q: Can I use a full bottle of Techron in smaller fuel tanks?          
A: If you use Techron in smaller engines, such as a motorcycle, don’t use the whole bottle. The recommended treatment rate is one ounce per gallon, so in a four-gallon tank, use four ounces of Techron.

Only j o and a select few are able to operate successfully outside these earthly and arbitrary constraints. It's unlikely you are one of them, yet.     

[The Mighty Gryphon]

My engines run fine on rich Techron mixtures.  2-3 gallons of gas with half a bottle, a full bottle in a full tank.   Or a half bottle in a full tank.   How much I put in depends on how much I have and whether or not I want to empty the bottle so I don't have it hanging around.     

 When I got my K100RS it was running pretty rough so I was hitting the system pretty hard with the Techron for the first 2000 miles until it started to run like my other bricks.  My bikes are running pretty good now, so I am dialing it back and just doing it as preventive maintenance.

[johnny]

greetings...

always follow the mfr directions...

with that being said... the most i have used is 6 bottles... have used 4 bottles a few times... use 2 bottles often...

its bogof at advance auto parts right now...

j o

[brichbk]

Update on my progress.  I decided to check the vacuum hose from the throttle body to the fuel regulator.  So I took out the air box and cleaned up all the little gravel, dirt, and crud that had accumulated under the air box.  The vacuum hose was a little hard and dry so I replaced it.  I cleaned the connections for the AFM while I had the air box apart.  I put everything back together and decided to ride down to the gas station for a bit more gas to help run more techron through.  I felt like the bike ran a little better.  I still have to clean the rest of the electrical connections, but so far I think its moving in a good direction but its still not quite there.

[brichbk]

Update part 2:  I decided to check my plugs that I just installed and have less than 10 miles on them. I wanted to check #3 since it was the worst when I replaced them. So I pulled #2 and #3 to compare. Here is what they look like. Should I be concerned that 3 looks worst than 2?

[Laitch]

Should I be concerned that 3 looks worst than 2?

#2 looks good. #3 doesn't look good. What about #1? Does it fit into your numerological maintenance scheme?

[Scott_]

Have you done a compression test?

Looks to me like you might have either ::
1, leaking injector on #3, or
2, bad/week coil/wire for #3.

[Laitch]

2, bad/week coil/wire for #3.

+1

Replace all the secondary leads and help the economy. 100K miles was good enough out of the originals.

[brichbk]

#2 looks good. #3 doesn't look good. What about #1? Does it fit into your numerological maintenance scheme?

#1 looks the same as #2.

[brichbk]

Any suggestions on where to get replacement ignition coils?  Do I have to replace all of them or can I replace just the one I think is bad?  I'd rather replace them all but bikebandit lists the cost at $165 per coil!


Suggestions for replacement spark plug wires?

[The Mighty Gryphon]

I got three ignition coils as spares on eBay for $65.  I bought a complete engine with coils for $75.  sold those coils for $20.

They're out there...

[Laitch]

Do I have to replace all of them or can I replace just the one I think is bad?

How did you determine the coil was faulty and not its lead?

[brichbk]

How did you determine the coil was faulty and not its lead?

I don't know that it is the coil necessarily.  I did the test from the book and using both the #1 and #3 lead all 3 plugs give off a nice blue spark. 


Most of the reason why I was thinking of replacing the coils was based on my experience with a similar issue with my '82 nighthawk where it kept dying when I would pull in the clutch (much like my K75 is doing right now).  I replaced the coils and it fixed the problem, of course I could buy two coils for $15 for that bike so it wasn't much of a risk.


I am looking into getting new leads since the ones on the bike are OEM and probably original.

[brichbk]

Update:  I installed new NGK spark plug wires today.  Unfortunately it didn't fix the issue.  So now I'm going to get a used set of coils and then hopefully I'll be zooming down the road.

[KIWIDON]

Before spending money on coils, I would suggest swapping #3 injector with #1 or #2 and see if plug rich symptom transfers. Looks like injector spray pattern poor or leaking.

[brichbk]

I got 3 coils from beemer boneyard today in the mail.  I replaced my old ones and the bike is running like a bat out of hell.  The throttle is much more responsive, the bike warms up very quickly, and doesn't seem to have the hesitation that it had before.  I'll be taking it out tomorrow to get a better feel how it runs but it is running much better.  Thanks all.

Before spending money on coils, I would suggest swapping #3 injector with #1 or #2 and see if plug rich symptom transfers. Looks like injector spray pattern poor or leaking.

  I might try this in the coming weeks.  But for now it seems to be running good.