Power drops/cuts after engine warms up 10 minutes 1994

Hi All,

Bike just got out of the shop.

Carbs done 6 months ago - Dirty tank caused no start
Sat in shop 5 months (long story)
Carbs just redone and I get it on the highway for a long trip- here are the symptoms.

First two hours ran PERFEct - acceleration all through the gears and powerband were great.
Then
Felt as though it were either starving fuel or bogging- when driving at speed. First the throttle would feel heavy then speed would start to drop and the throttle would be very very sluggish without load. It would want to cut out if rmps dropped below 2k.
At this point- it drives for 10 minutes (until hot) perfectly. Feels good accel. great etc. Once warm, same thing until it cuts. If you let it sit for 5 or 10 it runs perfect again. Rinse and Repeat over and over.


Any ideas from the ThinkTank?

Mark

 

does it have a fuel pump?? my yami did that and turned out to be the fuel pump..

 

Check the petcock for crap building up in it, sounds like a partially plugged petcock. Yes I said twice, petcock.

 

I concur with toe on this one. Hopefully it is that simple. I went through a carb rebuild on my 97 Shadow. I replaced and cleaned everything except the fuel lines themselves. Unluckily, there was still some crud in the lines that broke loose and clogged one of the jets after a few thousand miles and I had to pull the carbs to clean them again.

Heh, Toe said petcock.

 

Well, the fuel pump was just tested..which may or may not mean anything but I am ruling it out because it only happens when hot. Sound reasonable?

Petcock- I shall check my, uh hum, petcock and see if it is clogged.... Would that effect if hot though?

Also note- once it shuts of I can get it started again with the choke but still runs like crap till I shut it off and let it cool.....

 

With a clog in the fuel line it may still pass fuel but not enough to run after time and a demand increases, as large debris tends to bind up and relax after demand is lost.Bugs and large rust flakes cause this most often in my experience.Bugs may sound crazy but if you leave a tank open bugs tend to love to collect in fuel and their bodies hold up well and clog things up.

 

I also had a similar issue on an 89 Ninja and found that they had replaced one of the lines and as it warmed up it would kink so I had to shorten the line to prevent it... Not very common but might see if a line can kink.

 

other things to check:

Fuel Filter could be clogged
Venting in tank could be clogged (vapor locking-like symptoms)

see if it will run from raw fuel into the fuel lines just north of the carbs and work backwards... lines, filter, pump, petcock, tank

 

Ahh,
So it may not actually be the increase in HEAT, it may have to do with the TIME running, where it is continuing to draw particals into a blockage until it "clogs".

 

Again, it runs PERFECT for around 7-10 miles.

I could always run it on idle for an extended time to bring up the heat and see if it want to cut out or run funny. That would rule out/in heat or time running at speed being the key factor.

 

Sure your choke cable is not stuck and keeping partially on ??

 

Before you spend huge amount of time troubleshooting your fuel system, I'd check for spark. That sounds suspiciously like a pulse generator failure. Unless the fuel cut relay is triggered by spark, it won't allow fuel to pump. So some types of ignition failure can actually seem more like a fuel system failure.

Buy one new spark plug, throw it in your pocket and next time it fails immediately check for spark on one of the rear and one of the front cylinder coils.

 

here hee hee hee he said petcock three times in one breath

check you tank vent line? it maybe plugged as well as your petcock

 

How old are the gas lines?? as they age they can collapse (weakened over time)

 

If its the vent Line...

Just pop the gas cap, next time it starts to die.

:crazy:

 

Today I will get the chance to try all suggestions.

History_
Stored in a shed for 7 years prior to this ride. Was a home to several rodents nesting in the V of the engine.
Lots of electrical soldering and mending needed to be done-squirrel damage.
Tank was mildly rusted so it was acid washed and lined.
Carbs were throughly done 2x in 5 months.

I did open tank after having to stop and it did not appear to have any pressure in it.

Plan today-
Pull fairings and tank
Check integrity and connection of all hoses
Change out all coils and wires (have newer spare set that I wanted to fit anyway)
Make certain of all electrical connections
Test drive.

Thanks

 

I suggest you figure a plan to troubleshoot the failure next time it happens. Go on a 'troubleshooting' ride.

 

Because of the time sitting I think I will be very slow and methodical.....

I am starting to think about the integrity of the hoses and seals. It has been a very long time since any of these things were heated to operating temperature.

Careful I will be, Check all I shall.....

You guys are awesome. You have really given me a laundry list of things to go over....I like them all except the head gasket and carb problems