Perplexing problem - can anyone help?

[Shuriken]

I started discussing this problem here:
http://www.vmaxforum.net/showthread.php?t=4518

I'm bringing it up again because I don't know that it is a carb problem.

Basically, my Max just started running like absolute crap from about 60 percent throttle to 100 percent (full) throttle. I haven't done anything except spray sea foam in the vboost manifold ports about a week or two ago. That was the day the problems began. Feels like the bike is running on 3 cylinders when you try to wind it up. There is no difference after 6500rpm.

I have tried 2 different sets of replacement plugs. Carbs have been synched multiple times. Vboost cycles on startup. Replaced fuel filter a few months ago. Also completely cleaned the carbs at that time, after which the bike ran great.

I *did* discover that the electrical connector at the vboost sensor was disconnected (vibration?) so I reconnected it. I hoped that would fix the problem but it did not.

Anybody have any ideas? Anyone had this problem before? I really don't want to tear into the carbs again, especially if it is not a carb problem...

 

[shawn kloker]

Are you positive that the air box boots are on the whole way?Sucking air in will screw it up big time with stock carbs.Too much air for them.Try opening the choke to see if it gets better by richening it up some.?????

 

[RVAVMAX]

May need to clean the carbs, if it happend when you sprayed the foam one of the ports could be gummed up.

 

[Shuriken]

Are you positive that the air box boots are on the whole way?Sucking air in will screw it up big time with stock carbs.Too much air for them.Try opening the choke to see if it gets better by richening it up some.?????

Thanks for the idea about the choke. I didn't think of that. I will wind it up till it starts to sputter and then I will choke it. If it takes off or if it runs even worse, I will assume the problem is not electrical and off come the carbs. If it does not take off or if there is no noticeable difference, I will assume electrical.

 

[Neil-3446]

What is your elevation??? I think Shawn already knows your problem, and is trying to diagnose it with choke (richen).

Electronics will make no difference in the rpm range, unless you have a random spark (weak pickup, cdi, or ht coil breaking down).

At those rpms, something is sucking air and not breaking down on the electrical side.

How many times have you had the carb stack off???

Neil

 

[Shuriken]

Now things get interesting.

The choke has no effect on performance when the bike is flubbing. I've tried opening the choke at the moment the flub starts. Also tried running the bike on choke the whole time.

So for the experts out there, what now?

If it were a compression problem, why would the bike seem to run ok on low RPM? If it were a fuel problem, operating the choke would cause some kind of noticeable difference. If it were an intake leak, the choke would also produce an effect. If it were a spark plug problem, changing the plugs would have produced some effect. If it were a carb sync issue, the fact that I synched the carbs twice would have produced an effect. If it were a v-boost sensor problem, I would have noticed a difference when the electrical connector is unplugged and when it is connected. If it were a v-boost servo issue, I don't expect that I'd hear it operating.

Coil or ignition module?

 

[RagingMain]

Electronics will make no difference in the rpm range, unless you have a random spark (weak pickup, cdi, or ht coil breaking down).
Neil

Does it do it only when hot???
The electronics on these bikes gets weird when the bike gets hot. Grab a multi meter and follow the sticky in the electrical system to find out if you have a problem.

My reasoning for this is I had a bad stator. It would run fine when not producing a lot of voltage at idle. When I wound it up, when hot, voltage would start to "leak" between windings in the stator. The resistance checked fine when cold but when it got hot the problem showed up. The faster the engine spins the more voltage produced, greater chance something is not right. Especially since he has gone through the carbs a million times. Just changing the plug wont fix an electrical problem.
Cheers

 

[RVAVMAX]

Now that I read into your issue a little more, it seems you are having about the same isuess I am... Does it backfire out of the carbs at all? Does it feel like a missfire or just lack of fuel when it's hot? I checked my mixture screws this morning and seated them all the way, one at a time (Tightend) while the bike was warm AND running. I took them all 2.5 turns out and then gave them and extra quarter of a turn. Mine were all 4 turns out. The bike seems to be running a lot better and isn't heating up as fast! I HOPE this is the fix or maybe it will help if you haven't already tried that. If you have does this already you just wasted a minute of your life reading this that you will never get back.:biglaugh:

 

[Shuriken]

Does it do it only when hot???
The electronics on these bikes gets weird when the bike gets hot. Grab a multi meter and follow the sticky in the electrical system to find out if you have a problem.

My reasoning for this is I had a bad stator. It would run fine when not producing a lot of voltage at idle. When I wound it up, when hot, voltage would start to "leak" between windings in the stator. The resistance checked fine when cold but when it got hot the problem showed up. The faster the engine spins the more voltage produced, greater chance something is not right. Especially since he has gone through the carbs a million times. Just changing the plug wont fix an electrical problem.
Cheers

Unfortunately, it does it hot or cold.

I agree with you about spark plugs not fixing an electrical problem. I like to start out with the easy stuff first to eliminate little things. I once had a problem with an old XS11 where when I turned on the key, it would blow a fuse. I checked every dang thing there was. Even went along the harness to try and find a short. Just as I was about to give up, I decided to disconnect the horn. What'dya know... problem was in the horn.

Nearly yanked the carbs again yesterday but had a hunch it might be electrical. Now I'm thinking it almost has to be electrical.

 

[RVAVMAX]

I would guess that it would have to be somewhere in the ignition though... Hopefully you won't have to do much digging to find it.

 

[Shuriken]

Will a coil crap out only at high revs? Is there anything on this bike that knows about throttle position or does the ignitor unit just read RPM and vacuum?

 

[gleno]

Unfortunately, it does it hot or cold.

I agree with you about spark plugs not fixing an electrical problem. I like to start out with the easy stuff first to eliminate little things. I once had a problem with an old XS11 where when I turned on the key, it would blow a fuse. I checked every dang thing there was. Even went along the harness to try and find a short. Just as I was about to give up, I decided to disconnect the horn. What'dya know... problem was in the horn.

Nearly yanked the carbs again yesterday but had a hunch it might be electrical. Now I'm thinking it almost has to be electrical.

I would say the problem is electrical. I've looked at your posts to try to understand the sequence of events leading up to the problem.

Why did you spray seafoam in the v-boost manifold? Were you having a problem at that time? Did you remove the carbs when you did the seafoam thing?

Removing the plugs can be enough physical movement to show up faults in the lead and coil connections.

You should have a big, fat spark. If the spark is pale, thin and thready you may have (in order of probability):

1) Bad connections between the spark plug lead and the spark plug boot. You can use a resistor to check. Normal resistance values are in the specs section of the workshop manual. Disconnect, clean and re-seat these.

2) Bad spark plug leads.

3) Bad connections between the spark plug lead and the coil. The connection pin. You can use a resistor to check. Normal resistance values are in the specs section of the workshop manual. Disconnect, clean and re-seat these.

4) A Dud coil. Check resistances.

5) Bad flywheel ignition pick-up sensor. Check resistances.

 

[COP RUNNER]

i had an xs1100 that started not being able to go over 7,000 rpm's day's later it would'nt go over 6,000 rpm's & so on , untill it would'nt go over 4,000 rpm's , it was a bad ignition box ! Put a new one on , it ran like a raped ape !

 

[Shuriken]

The bike produces a fat blue spark on all 4. I verified that this evening. I also cleaned connectors as good as I could and reconnected them. Didn't get to the front coils to check resistance and connections, but the rear coils look OK. Didn't have a manual but I measured resistance between the two input wires of each coil and got 3.7 on the 200 ohm scale. Measured between the two metal flanges that the screws mount through and got 0.8 on the 200 ohm scale.

Did not have a chance to test the bike due to rain storms, though, but I really doubt that I did anything that will solve the problem - yet.

I'm going to order new velocity stack boots, carb manifold boots, and vboost boots. While the carbs are off, I'll go through them again.

I wondered.... last time I repaired the v-boost computer, I had to remove the silicone sealant from the board. Wonder if it's possible that water could get in there and short that out.... but if that happened, I shouldn't hear the vboost cycle, right?

CopRunner.... I've repaired a couple of those XS11 TCI boxes and then finally got a spare replacement. That and pick up coil wire problems really caused intermittent spark problems on that dang bike.... but the XS11 was easier to work on.

 

[gleno]

The bike produces a fat blue spark on all 4. I verified that this evening. I also cleaned connectors as good as I could and reconnected them. Didn't get to the front coils to check resistance and connections, but the rear coils look OK. Didn't have a manual but I measured resistance between the two input wires of each coil and got 3.7 on the 200 ohm scale. Measured between the two metal flanges that the screws mount through and got 0.8 on the 200 ohm scale.

Did not have a chance to test the bike due to rain storms, though, but I really doubt that I did anything that will solve the problem - yet.

I'm going to order new velocity stack boots, carb manifold boots, and vboost boots. While the carbs are off, I'll go through them again.

I wondered.... last time I repaired the v-boost computer, I had to remove the silicone sealant from the board. Wonder if it's possible that water could get in there and short that out.... but if that happened, I shouldn't hear the vboost cycle, right?

CopRunner.... I've repaired a couple of those XS11 TCI boxes and then finally got a spare replacement. That and pick up coil wire problems really caused intermittent spark problems on that dang bike.... but the XS11 was easier to work on.

Well that eliminates some issues.

Have you tested the input and output of the pressure sensor which controls the ignition advance.

1) Check rubber vacuum line to make sure it has no leak.
2) Check input and output as per service manual.
3) check its connection to the ignitor unit.

 

[Shuriken]

Well that eliminates some issues.

Have you tested the input and output of the pressure sensor which controls the ignition advance.

1) Check rubber vacuum line to make sure it has no leak.
2) Check input and output as per service manual.
3) check its connection to the ignitor unit.

Thanks for the info. I will get to this tomorrow hopefully.

I need to check the pick up coils. The manual says they are located under the right hand crankcase cover. What are they talking about? The right hand side has the clutch and water pump covers, right? On my XS11, they were on the left hand side.

If I tested the pickup coils connector correctly (at the left side of the bike near the left metal VMax side cover), I've got some issues. All of the readings except one tested at 248 ohms and only one was within spec. If this was the correct connector (the wire colors matched the manual), resistance is much higher. This would lead me to believe the coils are shorted somewhere.

But if the pickup coils are shorted, I should have problems at low RPM too, right? This sounds like a spark advance problem, which would point to the pressure sensor and/or TCI. Was going to ask how bad this bike will suffer without spark advance?

Also rode the bike up the street without the airbox installed. Definitely sounds like electrical cut out above 60% throttle.

 

[gleno]

Thanks for the info. I will get to this tomorrow hopefully.

I need to check the pick up coils. The manual says they are located under the right hand crankcase cover. What are they talking about? The right hand side has the clutch and water pump covers, right? On my XS11, they were on the left hand side.

If I tested the pickup coils connector correctly (at the left side of the bike near the left metal VMax side cover), I've got some issues. All of the readings except one tested at 248 ohms and only one was within spec. If this was the correct connector (the wire colors matched the manual), resistance is much higher. This would lead me to believe the coils are shorted somewhere.

But if the pickup coils are shorted, I should have problems at low RPM too, right? This sounds like a spark advance problem, which would point to the pressure sensor and/or TCI. Was going to ask how bad this bike will suffer without spark advance?

Also rode the bike up the street without the airbox installed. Definitely sounds like electrical cut out above 60% throttle.

Those resistance readings are way out of spec. If not completely shorted a faulty insulator around the coil windings will break down at higher sustained loads.

If you want to rule out the vacuum advance sensor just unplug it and block off the manifold inlet. That will pretty much tell you what affect that pressure reading has on timing advance.

p.s. we have something in common. I'm an ex XS-1100E owner.

 

[maleko89]

Make sure you use the black wire as common when measure p/u coil resistance.

 

[Shuriken]

Those resistance readings are way out of spec. If not completely shorted a faulty insulator around the coil windings will break down at higher sustained loads.

If you want to rule out the vacuum advance sensor just unplug it and block off the manifold inlet. That will pretty much tell you what affect that pressure reading has on timing advance.

p.s. we have something in common. I'm an ex XS-1100E owner.

I agree they are out of spec. Did I get the right connector? The connector for the pickup coils is on the end of the wire that comes up near the left foot peg and up near the VMax side cover?

So then, to get to the coils to check them, do I have to remove the left crank case cover? Manual says they are under the right side....

Nice about the 11. Loved those bikes, just needed more power....

 

[Shuriken]

Make sure you use the black wire as common when measure p/u coil resistance.

Could you explain in more detail what you meant? I think what you are getting at is to make sure you don't get added resistance in the tests by using some other ground?

Manual states to measure between the orange wire and each of the others.