84 FJ1100 dies after 10 minutes/miles

[KNyffeler]

I bought a "barn find" 84 FJ.  Totally went through the whole bike; 145 PSI compression on each cylinder, new plugs, carbs completely carb soaked and all jets cleaned out, gas tank and screens cleaned, wiring checked out, new battery, alternator OK, etc.  When I first put it back together, it ran great.  Then one time it started missing then just died cold after a 30 minute ride.  After cooling down for about 45 minutes, it started right up and ran fine.  It now does the same thing every ride, only sooner and sooner.  The last time I rode it, I could only go about 10 minutes.  If you leave it set for 40+ minutes it will start right up every time.  Before that amount of time passes, it won't fire at all.  Since all cylinders die, I assumed it was the ignitor unit.  I replaced it and it does the same exact thing.  Any ideas before I start throwing coils and crank pickups at it?

[RPM - Robert]

I'm not 100% sure if the 1100s have the same setup as the 1200 gas caps as they are a bit different but next time it does it pop the cap and try to start it back up. Father Pat will have the answer to this as he has had his 1100 for a couple years now.

[FJ_Hooligan]

When it dies, what are the symptoms?

Does it sputter to a stop like it's running out of fuel?

Or does it instantly shut off like the ignition stopped working?

The more descriptive you are with the symptoms, the better help you will get.  Sound like a fuel delivery issue.  Check routing of the fuel lines, check operation/integrity of of the vacuum petcock, verify tank venting, and try riding with the petcock in the PRIME position.

[Pat Conlon]

Pinched fuel line from incorrect fuel line routing..
All is well when cold but...as the bike heats up the fuel line gets warm and pinches, voila, no fuel to the carbies.

The single fuel line from the petcock outlet should be run *under* the two branch lines that go to carbs 1/2 and 3/4

[balky1]

Pinched fuel line from incorrect fuel line routing..
All is well when cold but...as the bike heats up the fuel line gets warm and pinches, voila, no fuel to the carbies.

The single fuel line from the petcock outlet should be run *under* the two branch lines that go to carbs 1/2 and 3/4

Yes, this and possibly the petcock also. Try running on PRI (or turn on PRI when it dies). I had a similar problem with my 'barn find'.

[KNyffeler]

I am running the petcock in "prime" position.  The gas cap is actually broken and doesn't close all the way.  The bike doesn't just die, like being shut off, but sputters and dies fairly quickly.  If it is a fuel problem, why would it run for 15-20 minutes, then have to sit for 45+ minutes before it runs again?  However, I will check the carbs for fuel the next time it dies.

Let me know what other ideas you have, else thanks for the tips.  I'll try to troubleshoot it better next weekend.

Here is a picture of how it turned out.

[FJmonkey]

The fact that it runs again after a short wait seems like a restriction. The fuel can still flow and fills the carb bowls. Just not fast enough to keep them full when running at speed. With a restricted flow, the fuel is filling the bowls, just slowly. So all you have to is ride much slower. Easy fix. All done now, move on. 

[TexasDave]

The fact that it runs again after a short wait seems like a restriction. The fuel can still flow and fills the carb bowls. Just not fast enough to keep them full when running at speed. With a restricted flow, the fuel is filling the bowls, just slowly. So all you have to is ride much slower. Easy fix. All done now, move on. 

Ride much slower......             

[Urban_Legend]

It is sounding like a fuel flow issue to me (Been known to be wrong before)
If after checking the fuel line is no pinching and everything looks ok, next thing to check it the filter. With the 1100 it has a filter attached to the fuel tap inside the tank. If it is blocked up with crud, that will restrict the flow and give you the symptoms you describe.

I think RPM (or possible YAMAHA dealer too) sell a replacement fileter for this. If not, here is the link for new petcock with filter attached.

http://rpmracingca.com/proddetail.asp?prod=M%2FC%3A36Y-24500-01&cat=34
Mark

[Tuned forks]

I agree with Mark but didn't know if the gravity feed 1100's had a filter.

Joe

[Urban_Legend]

Just re read you earlier post. You say you have the tap in "Prime" position. this will allow fuel to flow weather the bike is running or not. If you pull the fuel hose does fuel run out like a Texas oil line or does it dribble out like an IV drip?
For normal running the tap should be in the run position, which is vacuum operated by a hose from the No.2 inlet boot. To put it simply if the bike stops, then the fuel stops. It is a safety item....but should not affect the actual running of the bike.

Back to my point. with the tap in the prime position, pull the hose. If only a little dribble of fuel, then you have a blockage in the Tap/Filter area. If it flows free then it is down stream in the fuel line or carbs (the least likely thing...at the moment.)

Mark

[Pat Conlon]

 If it is a fuel problem, why would it run for 15-20 minutes, then have to sit for 45+ minutes before it runs again?  

If routed incorrectly, the soft fuel line pinches when it gets hot (and it gets hot under the tank) only to return to shape when it cools down.

Filter vs screen.
The gravity flow bikes (84-87) didn't have a fuel filter per se, but only a screen inside the tank (as part of the petcock)
The screen catches the big stuff but let's the small rust/varnish/dirt particles thru to the carbs.
A common mistake is to put an actual fuel filter on the 84-87 fuel line. Only to find that with the new restriction in the flow, and as the tank gets to ~1/4 full, the head pressure pushing the fuel lessens to a point where the carbs starve for fuel.
Gravity flow bikes do not like fuel filters. Fuel screens are fine, not filters, and as such, gravity flow bikes do not like dirty or rusty tanks.

A real benefit the fuel pump FJ's (88-95) have over the gravity flow bikes....they can use an actual fuel filter to keep their carbs clean.
Something to think about as our 35 year old steel tanks get older.

[Firehawk068]

As Pat has said, it is absolutely crucial that you route the fuel supply hose correctly on these gravity-feed FJs, or you will have a restriction.


Make sure it is routed exactly like in the following picture, or it will get pinched when you lower the tank down on top of it.

[ryanschoebel]

I'm 99% certain mine isn't routed anything like that

[Pat Conlon]

That's a great picture Alan, thank you. Worth 1,000 words.

I have a favor to ask, this fuel starvation symptom has come up a few times this year, so Alan, how about posting a write up along with this picture over in our Maintenance Files Section? To guarantee continued future access to the photo, if you could import your photo to the Gallery (Misc.Photos) that would be great.

That way in the future, when this comes up again (and it will) would be easy to just post a link to the Files.

This fuel line routing is counter intuitive until you see how low the petcock outlet sits once the tank is lowered into position.

Good job laddie!