1 engine sputters on throttle Mon Apr 09, 2012 6:48 pm
kringb
Silver member
I am usually pretty good at troubleshooting but this one has me stumped. I am not sure where to look. I'm not even sure if it is an electrical or fuel problem.
First some background;
It is an 85 k100 with about 90k miles. I rode it for most of those miles doing the basic maintenance and it rode well but slowly the problems began to creep up on it. When it hit 90K I debated trading it in versus rebuilding it and chose to rebuild it. I had the head rebuilt, replaced the engine block with a younger used one, replaced the clutch, , cleaned the injectors, changed all the seals and generally cleaned everything up. In doing this most of the problems were cleared up and it now runs great except for the one problem that remained.
There are two symptoms to the problem. I am not sure if they are related but guessing they are. They are exactly the same as before the rebuild.
1.) when you start the bike and it is in neutral, if you give the throttle a quick twist it chokes and sputters. It is not responsive and seems to trip over itself. When it is warmed up it is less so but still evident. If it is very cold it may stall but usually catches itself and then powers.
2.) This one is hard to reproduce. In 4th gear at about 4500 rpm it chokes. It is as if it is not getting gas. It will choke, the rpm will drop and then catch itself and regain power. Sometimes it chokes repeatedly. Sometimes just a few sputters. Sometimes giving it more throttle can seem to blow past it and sometimes not. It does not always occur and is difficult to reproduce. It does seem to generally occur at the same point on my way to work. At about 10 miles in on the freeway on a very slight downgrade. Not sure if that is a helpful clue or not.
When the second problem first occurred before the rebuild I tried to solve it and read that it might be the fuel filter. I replaced the fuel filter and it seemed to help but the problem returned after not too long. Then I replaced the filter again and it did not seem to help. Because the problem is not consistent it is difficult to tell if there was any small improvement but I don't think so.
With the first problem I thought it might be the clutch or splines. On the rebuild I replaced the clutch and the splines looked good. There was no change.
I am hoping it is not a electronic control problem. That could be expensive. Maybe a vaccuum leak but where should I look or begin to trouble shoot it? I replaced that S shaped breather hose that is always cracking. I also red about the connections on the fuel sensor connector causing problems.
Any ideas?
First some background;
It is an 85 k100 with about 90k miles. I rode it for most of those miles doing the basic maintenance and it rode well but slowly the problems began to creep up on it. When it hit 90K I debated trading it in versus rebuilding it and chose to rebuild it. I had the head rebuilt, replaced the engine block with a younger used one, replaced the clutch, , cleaned the injectors, changed all the seals and generally cleaned everything up. In doing this most of the problems were cleared up and it now runs great except for the one problem that remained.
There are two symptoms to the problem. I am not sure if they are related but guessing they are. They are exactly the same as before the rebuild.
1.) when you start the bike and it is in neutral, if you give the throttle a quick twist it chokes and sputters. It is not responsive and seems to trip over itself. When it is warmed up it is less so but still evident. If it is very cold it may stall but usually catches itself and then powers.
2.) This one is hard to reproduce. In 4th gear at about 4500 rpm it chokes. It is as if it is not getting gas. It will choke, the rpm will drop and then catch itself and regain power. Sometimes it chokes repeatedly. Sometimes just a few sputters. Sometimes giving it more throttle can seem to blow past it and sometimes not. It does not always occur and is difficult to reproduce. It does seem to generally occur at the same point on my way to work. At about 10 miles in on the freeway on a very slight downgrade. Not sure if that is a helpful clue or not.
When the second problem first occurred before the rebuild I tried to solve it and read that it might be the fuel filter. I replaced the fuel filter and it seemed to help but the problem returned after not too long. Then I replaced the filter again and it did not seem to help. Because the problem is not consistent it is difficult to tell if there was any small improvement but I don't think so.
With the first problem I thought it might be the clutch or splines. On the rebuild I replaced the clutch and the splines looked good. There was no change.
I am hoping it is not a electronic control problem. That could be expensive. Maybe a vaccuum leak but where should I look or begin to trouble shoot it? I replaced that S shaped breather hose that is always cracking. I also red about the connections on the fuel sensor connector causing problems.
Any ideas?