Loss of power and RPM at high speeds - HELP-

[Valk6 (diaz)]

Good morning all!
This past weekend I went to bikeweek in Sandusky Ohio, it was about 100 miles each way.
I used the turnpike about 20 minutes into the trip the bike started loosing power and rpm’s, I was doing about 75 mph …. so I pulled over turned the bike off and did a visual inspection, checked the gas tank, fuel level was still visible and did not see anything obvious that could be causing the problem.
I started the bike with out any problems and continued the trip, everything was good and then it did it again …. this time I was doing about 70 mph, again I pulled over and turned the bike off  for a minute, it started right up and I continued to my destination. While around town in Sandusky the bike had no issues whatsoever  ….. on the way back same thing happened.  ….. any suggestions and help would be appreciated.

A bit of history, during the off season I did a complete Desmog, installed a Dan-Mark electric fuel shut off (the one that has a built-in filter) and did a Petcock Mod (http://daughertymotorsports.com/howto/Tankvalve/tankvalve.html), the bike has about 63,500 miles, it’s a 1998 standard ….. I have done about  1,000 miles so far this season, though most of the time I stay away from the freeways 

Thanks,  Ride Safe

~Chris

[MP]

Sounds like a typical petcock failure, but you said you changed it to a straight manual valve.  Sooo, am not so sure.  Does sound like a fuel flow issue though, since it only happens when the Valk needs lots of fuel.

MP

[Cliff]

Possibly a restricition (partial pinch off) of the tank vent tube?  Still enough air passes during low speed fuel demad that it can keep up but at highter rate of fuel consumption can't keep up... just a thought.

[Tundra]

 Not a petcock according to your post... That makes it easier. Pinched vent line?
Next time this happens pull over open your gas cap and see if this symptom goes away. If it does, look for a pinched or kinked, maybe improperly routed vent line. Hopefully this will be a real easy fix for you

[Patrick]

I agree that it sounds like a fuel delivery issue..  It sounds like its either a vent line issue or the petcock/ fuel shut-off  modification or installation.. You're not the first to complain of this problem after installing the electric shut-off.. I'm not familiar with this particular shut-off,but, since these engines don't really need that much fuel flow to stay satisfied, I'd suspect the installation.. Some folks have installed these without any problems.. Maybe the fuel line was left just a tad too long and has become kinked/pinched slightly upon assembly.. Just a thought..

[Mr.BubblesVRCCDS0008]

If you have a spare key open the gas cap, just crack it  open and take off for a ride. If you do not have the same problem then it is the vent tube is pinched or plugged.

[Hoser]

It is probly the dan-marc.  If you don't get it mounted just right it cuts down on the fuel flow at higher speeds.  MP had one on his Interstate side car combo, we were heading down I90 and whenever he got up to 70 or more.  It would do it after he got down to half a tank.  Took it off and no more problem.  Hoser  

[John U.]

It could just be that the fuel line is cut a bit too long and has a partial kink in it.

[BonS]

After installing my DanMarc valve I found that the length of the flexible fuel line is critical. After the engine heated up the fuel line developed a kink because it was the slightest bit too long. In my case it was only noticeable on the highway and a half-tank of gas or so. All is well after snipping off about 3/8" of hose in my case. A restrictive fuel filter will do the same nasty trick as other have mentioned. Let us know what you find out.

[X Ring]

It could just be that the fuel line is cut a bit too long and has a partial kink in it.

I agree with John.  Check the simple stuff first.  Fuel line kinked or vent issues.  Then make sure your Dan Marc is installed correctly.

Marty

[MP]

It is probly the dan-marc.  If you don't get it mounted just right it cuts down on the fuel flow at higher speeds.  MP had one on his Interstate side car combo, we were heading down I90 and whenever he got up to 70 or more.  It would do it after he got down to half a tank.  Took it off and no more problem.  Hoser  

Did have the problem, but it was a fuel quick disconnect that I took off.  I left the DanMark on, and it has been working fine since. 

Check also for a kinked fuel line.  Some like to leave the line a little longer than stock, but it has a tendency to get a kink in it as it warms up, and restricts or cuts off fuel flow.

MP

[Valk6 (diaz)]

Thanks so much for the responses!!  What great resource all of you are.   

I went to replace the vent line last night, but there's a T-Joint in the middle that I cant figure out where it plugs in to ?? 
I did not notice any kinks in the fuel line, but as mention it may be happening when engine is hot.   I did order a replacement fuel shutoff from Dan-Mark with out the filter just in case.

I will keep you posted.

Thanks Again,  Ride Safe

~Chris

[sugerbear]

it plugs into nothing, leave it open.
i diagnosed mine with a coffee stir stick latched into the gas cap(don't let it fall in).

got me home so i could fix it. it was a pinch off vent line. good luck

[custom1]

"installed a Dan-Mark electric fuel shut off (the one that has a built-in filter)"

Could be as simple as the fuel filter doing it's job. If you have rust in your tank it could clog up a filter in short order. A partially clogged filter will act exactly as you describe. I have had this happen on a few different vehicles in my lifetime. I dont have a Dan-Mark, but I assume you can change the filter without replacing the shut-off?

[Flat6Valk]

it could be the ignition control module.  That is what cured my '97 two years ago.

[valkyriemc]

Take off the seat remove the tank hold down fasteners and lift the rear an inch or two looking in the very rear of the tank for the small rubber vent line making its way down through the frame. Hopefully its not kinked or miss routed. Open T is good as was mentioned. Nice small bright flashlight is a plus...

[Valk6 (diaz)]

UPDATE: 
Well, I replaced the gas tank vent hose and went for a ride ..... but still doing the same thing 

I got the bike ready so I can replace the Dan-Mark fuel shut off and redo the fuel lines, waiting on parts.


Flat6Valk - how do I test to make sure the ignition control module is functioning properly?

~Chris

[Flat6Valk]

I was lucky and had a spare.  the spare was actually the icm for the bike as an extra part.  It had a dyna in it at purchase.  It ran fine then over a period of months it started to act differently, or so I thought.  After more time, it would run fine at low rpms, short trips, etc then it would seem to labor.  I finally did some research and tried switching the icm, and wa-la........perfect again. 

the dyna icm apparantly has a short life.

[Valk6 (diaz)]

UPDATE:
Got my Dragon Lady back together, replaced the Dan-Mark fuel shut off with one without the built in filter (the openings on the filtered one were smaller than the ones on the one without the filter, maybe that was part of the problem?), also made sure all the fuel lines sat naturally without stress, I did notice that the hose going to the tank was about 1/2 inch too long .... so made sure this time it was not so.

Took my Dragon Lady and her 6 little dragons for a 100 mile run .... and I'm happy to report that all is well, her health has been restored!!!      

Now She's ready for Inzane XI 

Thanks All for the help and suggestions!

[Willow]

the dyna icm apparantly has a short life.

Not by my experience.  Mine has 140,000 and six years on it.  Still works very well.