Engine loses power and bogs under throttle..

[madmax-im]

Every so often i am riding on the local hwys and i will be cruising in 5th @ 70 mph ...plenty of gas...and all of a sudden bike starts losing power and engine is shuddering if I downshift to 4th ...in 5th trying to accelerate and it bogs completely...so after continuing to ride with these symptoms for a few mins > decide to exit onto local roads...At that point then everything comes back to life...so i go back out onto the bypass hwys and continue along...It does feel like maybe 2 cylinders arent firing but i cant stop to test the header pipes to see if they're all hot...This has happened several times in the past 2 years...not a high occurance of frequency but still is this indicative of a failure waiting to happen with the coils?
I have been told this is or could be a coil issue...Interested in hearing what you all think...?

[MPittma100]

Bogs

Hi Ben,

Sounds like it is running out of fuel. And it could be only on two cylinders. Take a look at your fuel lines and look for any kinks or pinched sections. Also make sure gas cap vent is not clogged.

[BA80]

sounds a lot like a clogged has cap vent.

[madmax-im]

Everything was just reassembled so i doubt its the vent...but.I'll check..Thanks..

[JeffH]

....... This has happened several times in the past 2 years...not a high occurance of frequency but still is this indicative of a failure waiting to happen with the coils?

I have been told this is or could be a coil issue...Interested in hearing what you all think...?

Ben,

Question: does it seem to happen after 5 miles of steady 4,500 rpm operation or 10 miles or 30 miles. Just wondering 'how long' at 70 mph before the (seemingly random) issue materializes.

btw: Did it happen at all Sunday on your 250 mile ride from Asheville back home? I'm sure a lot of that was steady at 4,500 rpm to 5,000 rpm or more. Any issue then?

Odd that it would come & go unless the driving conditions / temp / rpm / duration of time are similar when the problem pops up.

As guys say, sounds like fuel starvation but if it is you should be able to manifest the problem each time you hit that time duration / temp / rpm point.

Just fishin' for data.
Like 100 degrees at 75 mph for 35 minutes it acts up. But if you just drove 250 miles on Sunday in HEAT then who knows. What about that fine-fine netting in your standpipes. Is that crapped out? Mine were. Wouldn't pass gas well so got new ones (standpipes - Net, Filter 1
1J7-24514-02-00). Not cheap but it fixed my problem. New petcocks are cheaper than those nets unless you go with Pingel.

Hopefully you can figure out the cause with too much hassle.

Jeff

[madmax-im]

Ben,

Question: does it seem to happen after 5 miles of steady 4,500 rpm operation or 10 miles or 30 miles. Just wondering 'how long' at 70 mph before the (seemingly random) issue materializes.

btw: Did it happen at all Sunday on your 250 mile ride from Asheville back home? I'm sure a lot of that was steady at 4,500 rpm to 5,000 rpm or more. Any issue then?

Odd that it would come & go unless the driving conditions / temp / rpm / duration of time are similar when the problem pops up.

As guys say, sounds like fuel starvation but if it is you should be able to manifest the problem each time you hit that time duration / temp / rpm point.

Just fishin' for data.
Like 100 degrees at 75 mph for 35 minutes it acts up. But if you just drove 250 miles on Sunday in HEAT then who knows. What about that fine-fine netting in your standpipes. Is that crapped out? Mine were. Wouldn't pass gas well so got new ones (standpipes - Net, Filter 1
1J7-24514-02-00). Not cheap but it fixed my problem. New petcocks are cheaper than those nets unless you go with Pingel.

Hopefully you can figure out the cause with too much hassle.

Jeff

Always happens within 15 miles of setting out...it has only happened locally...
Sat and sunday bike ran great..nary an issue
was not excessively hot...air temp was in the low 90s
havent yet timed the duration of the "event' but it lasted about 5 mins each time..
as for the netting in the petcocks...kurt was just in there so maybe he can shed some light there. I am sure that if he saw something wrong he would have mentioned it...
I will tell you one thing ...coming home sunday i waited until i was about to get onto I40 to completely fill the tank and run it until it hit reserve...i wanted to see if that transition from ON to RES worked better than it did previously... and to see if my tank range had changed drastically with the addition of the fairing..@ 129 miles the engine sputtered and I pulled off onto the shoulder to switch to the RES position and the engine stalled...it would not restart after severeal tries ...so I sat for a few mins wondering if i should call for assistance...but eventually i tried to start it again and it did restart...but this was the worst transition I have ever experienced on any XJ or XS11..so from now on the petcocks will just stay in the RES position...odo readings and my dead nuts accurate fuel gauge will tell me when to start looking for more petrol...But I wonder now about those nets...

[BA80]

Now that I think of it I've had a similar issue and Tod says he has too. I seems to run out of gas but I know I have plenty. I turn the petcocks to reserve and it snaps out of it then I can turn them back to on and it's fine.

It doesn't happen often but it happens.

No clue why.

[skids]

Try putting the left petcock on prime if you have a standard. The pickup coils don't move while under constant speed unless you throttle-up/down for hills. I have two standards that have issues at highway speeds and both are immediately remedied by switching the left petcock to prime. Yes...fuel starvation and perhaps the vacuum has issues with operating the automatic petcock for flow.

[skids]

PS, for standards, there is an option available to route the petcock outputs together in a plenum-fashion and tee-off to the carb inputs. That way, if one petcock starts acting-up, or if one side of the tank is running lower than the other, you will still have fuel supply. I am lazy and haven't done this yet!

[JeffH]

Always happens within 15 miles of setting out...it has only happened locally...
Sat and sunday bike ran great..nary an issue
was not excessively hot...air temp was in the low 90s

havent yet timed the duration of the "event' but it lasted about 5 mins each time..
as for the netting in the petcocks...kurt was just in there so maybe he can shed some light there. I am sure that if he saw something wrong he would have mentioned it... WOULDN'T SEE IT - CAN'T SEE IT


I will tell you one thing ...coming home sunday i waited until i was about to get onto I40 to completely fill the tank and run it until it hit reserve...i wanted to see if that transition from ON to RES worked better than it did previously... and to see if my tank range had changed drastically with the addition of the fairing..@ 129 miles the engine sputtered and I pulled off onto the shoulder to switch to the RES position and the engine stalled...it would not restart after severeal tries ...so I sat for a few mins wondering if i should call for assistance...but eventually i tried to start it again and it did restart...but this was the worst transition I have ever experienced on any XJ or XS11..so from now on the petcocks will just stay in the RES position...odo readings and my dead nuts accurate fuel gauge will tell me when to start looking for more petrol

Exact problem I had with my bike. Nets LOOKED fine. Brown and stained but LOOKED / Appeared just fine. Intermittent issue. Finally cut the tops off the standpipe so I had fuel. Unfiltered of course but I had inline filters. Fixed the problem.

Before the snip cut my Low fuel draw call it less than 1/4 tank wasn't good. Reserve fuel draw was about impossible (duh, mesh was too old & brittle; gas wasn't going through) but after the cut / snip 1/4" from the top THEN with full or 1/2 tank down to 1/3 tank at least the problem stopped.

...But I wonder now about those nets...

Guys have that scotch bright pad fix for the cap breather. Something you can easily check and replace.

But yep, I'm wondering about those nets. If they are 37 years old and PO had rusted tank and bike sat and ..... and ...... and ..... well you get the picture. They LOOK FINE but is adequate fuel really getting through.

I rode 2 years after cutting the top off -then- to improve my Reserve Fuel draw I spent the bucks for new ones. Bike runs great down to about 1 quart of petrol.

You say this has been happening for a couple years so whatever is causing it has been around for a long time. I'd look at those net filters but new ones are like $35 each.

BUT, with your case it doesn't happen all the time. Mine didn't either which was odd.

Maybe SKIDS has nailed it. Vacuum ....................

My vote is check that. What skids says. Logic would dictate that like with my Nets, if the Cap Vent breather was clogged then how did you drive down I-40 for 250 miles at high speed without a problem? Some oddity for you to discover about your bike. Sounding like a gremlin that's been lurking for a few years.

Jeff

[JeffH]

btw: you sure didn't seem to have a fuel flow problem when you were trying to follow me on Porter Springs Rd last Saturday that was a hoot.

Or on the ride up from Atlanta to the mountains, but that was a lot off On-Off the throttle so Vac & Flows & Fuel level you think would re-balance.

I especially like the curves and terrain on that road.
but i was cheating. Hardly opened the throttle.

Jeff

[madmax-im]

btw: you sure didn't seem to have a fuel flow problem when you were trying to follow me on Porter Springs Rd last Saturday that was a hoot.

Or on the ride up from Atlanta to the mountains, but that was a lot off On-Off the throttle so Vac & Flows & Fuel level you think would re-balance.

I especially like the curves and terrain on that road.
but i was cheating. Hardly opened the throttle.

Jeff

You got that rightPorter Springs road was a hoot n holler...I was doing 80 just to keep you in sight...hardly opened throttle..yeah right..ha ha
Sunday morning Vinny and i headed to blairsville for breakfast and taking GA19 that is the main road...its a wonderful never ending fast sweeper type of twisties ..we were out there @ 7a.m. and the mountain air was cool and quite refreshing...and nary another car or bike on the road besides us...just a nice 25 mile wake up ride to brekky..if you like good breakfast and you're in Blairsville head to the "Hole in the Wall" ..Great folks n food too...

[ViperRon]

Not sure of the routing of the fuel lines to the Carbs but I have to run mine a certain way like diagram cywelchjr made up. I think it is in the helps section. Just like the vent in the gas cap the routing can cause the same issue. This can be enhanced by the type of filter put on the bike. Heat can change the situation also especially if you have a sharp bend. You can also have an issue with the pick up coil wires or electrical connector going to them that also will come and go with heat. Just some other issues to look into. A clear gas line where it goes into carbs can help identify if its fuel flow. Any bubbles or streams in lines not full of fluid identifies a problem. As well a quick metering of the wires and reseating of the wiring plugs can identify if its the pickups.

If I am ridding and it runs empty I typically switch to prime first get bike running and then switch to reserve because I have had issues when it was hot getting bike restarted when carbs went empty.

[madmax-im]

Thats interesting Ron...In all the years i ran my XJ I never once had any problems with the transition from On to RES and on that bike it would barely miss a beat from the switchover... Swampthing before the petcock rebuild would still run after the switchover but it did gag and gasp and stumble for a min ot two before it would smooth out...but it never did what just hapened last sunday...
Ok I got enough stuff to look at for a while...

[GLoweVA]

It has happened to me a few times on my H. Switched petcocks to prime cleared it right up.