Runnipng Rough

[NZ FJ Rider]

Hi all. Had several cracks at putting this up it keeps becoming a novel so :-) going for the shortest version.
86FJ ex US.  Cuzzie (retired bike shop owner//mechanic) had her for 10 years. No major issues. Serviced properly etc...was his pride and joy now mine almost 18 months.
Running issues started about a year ago with the occasional miss at speed. .... then came intermittent loss of power, to the point where I even got passed by a Harley.Long story short, now goes extremely well or 10-15mins...then doesnt. Any request for power (even just a little bit to get over 30mph) is met with stutter and missing, and a hill will result result in death under power almost as if 2 cylinders cut out.....pull in clutch and rev....back to 4.....let' out clutch....dies.. that results in over heating on one and the start to loose clutch (since adjusted clutch) Have done carbs (cleaned checked ... then a reconditioned bank. Plugs, caps, coils, tested and swapped, swapped primary coil ..tested outputs, ( all within spec).
New TDI don't start from cold then but didn't change result after 15 mins.
Initially rode for 30+ ks with Fuel cap open...no difference....
Have access to testing gear from cuzzies time as a mechanic...so it's not guess work. Stumped.

[movenon]

Have you got a vacuum controlled petcock ?
George

[FJmonkey]

Have you got a vacuum controlled petcock ?
George

If his 86' is still stock then yes he has one. And that means he needs to perform the "Suck Test", follow the link.

http://www.fjowners.com/index.php?topic=10019.msg96039#msg96039

[Pat Conlon]

Yes he does.
It sure sounds fuel related. The 3 most common issues on gravity flow FJ's (84-87) are
1) improper fuel line routing: as the single line leaves the petcock, this line should run *under* the 2 branch lines which feed the carbs. This is critical. If the fuel line incorrectly runs over the 2 branch lines, when the fuel line warms up and gets soft, the fuel line will pinch, impeding fuel to the carbs.
2) the petcock opens and closes based on a vacuum signal off your #1 cylinder intake manifold. Double check the condition of your vacuum line. Make sure the connections at both ends (petcock and intake manifold) are snug.
3) the petcock diaphragm not holding a vacuum thus causing a interruption of fuel flow. Do the suck test.
Connect a piece of tubing (hopefully clean) to the vacuum port on your petcock. Now lightly suck, you should hear your petcock click open, you should not be able to draw air thru the tubing...if so your diaphragm leaks...also while you suck, block the open end of the tubing with your tongue, you should be able to hold a vacuum in the line, if not your diaphragm leaks.
The solution is a new petcock from RPM.
2 options on a new petcock :
a) a new expensive 86/87 petcock that has the electric reserve or
b) a less expensive 84/85 petcock that has no goofy reserve switch but does have a 'prime' setting which will get you home in the event that, if in the future, the vacuum function stops working.

We have yet to find a suitable rebuild kit for our petcocks. Our only option has been to buy a new oem.

Hope this helps.  Pat

[NZ FJ Rider]

Hi Pat ....and thank you. Sadly have tried the suck test.. also replaced the vac line to #-1 just in case.
Cuzzie had replaced the petcock.. has a 1100 petcock with prime. Have tried with both options. And with tank cap open. -
Due to the length of the saga and the number of timess I have related the issues I feel like everyboldy has heard the tale of woe....sorry omitted a few such details. The replacement carb bank has required adjustment to fuel Line as there is only one entry point in the centre of the bank. Cuzz has assured me. There was sufficient gas getting to bowl. Metered testing and balancing did tend to confirm that. .....equally everything tends to point back to that area.

Have also enclosed line in "non crush" at critical points to try to alleviate that or kinking as an issue. We have been concentrating on electrical then fuel.....back to electrical....back to fuel.....

[NZ FJ Rider]

Have you got a vacuum controlled petcock ?
George

Hi George. Yes. But it does have prime....:-)

[racerrad8]

So, just to confirm...

The bike has the missing problem when it is operated with the petcock in the "prime" position as well?

Randy - RPM

[FJmonkey]

It could still be fuel line routing/pinched issue.

[Pat Conlon]

Ooooh, this is a good mystery....

Brian, when the bike studders and misses....are the plugs wet or dry?

If dry, then it's fuel...if wet, then it's spark...

Occasional miss followed by a more constant miss could be electrical....if your coils are ok, how about the voltage to the coils? Check the point to point ohm resistance? Have you cleaned and sanded all your electrical connections? Why not try the coil relay mod, it can't hurt.
How about the coil signal from the ignition pickup? Good ohm readings on the signal wires?

[Pat Conlon]

It could still be fuel line routing/pinched issue.

If he has the center feed fuel pump carbs (no branch lines)  I don't see how the fuel line could pinch.
Based on my experience, I do know that on the fuel pump models (89-94) when the pump fails you can bypass the pump (in a pinch) and run the bike on gravity flow to get you home...but when the tank empties down to below 1/2 full and the head pressure drops on the fuel line, the bike can start running poorly....
Does the center feed carbs contribute to this condition? Could be...

Come to think about it....I'm not sure the fuel pump carbs (center feed, small float seats)  and be run reliably with a gravity flow system.

[movenon]

You beat to the 88-93 1.2 Needle and seat fitment Pat 

I don't understand what is being said here.  "New TDI don't start from cold then but didn't change result after 15 mins." ?

Does it start every time now ?
George

[FJmonkey]

If he has the center feed fuel pump carbs (no branch lines)  I don't see how the fuel line could pinch.
Based on my experience, I do know that on the fuel pump models (89-94) when the pump fails you can bypass the pump (in a pinch) and run the bike on gravity flow to get you home...but when the tank empties down to below 1/2 full and the head pressure drops on the fuel line, the bike can start running poorly....
Does the center feed carbs contribute to this condition? Could be...

Come to think about it....I'm not sure the fuel pump carbs (center feed, small float seats)  and be run reliably with a gravity flow system.

I missed that he changed over to center feed like the FP carbs. So he now has one 6MM hose vs. two 10MM hoses, I don't see how that could be a problem.  If he did not keep the larger needle seats then there is one more restriction that Pat suggested.

[NZ FJ Rider]

So, just to confirm...

The bike has the missing problem when it is operated with the petcock in the "prime" position as well?

Randy - RPM

Hi Randy. Yes. goes fine for the first 10mins either way....... on vac setting or prime....outcome is still the same around the same set test course. Up till 10 mins (15 mins max) will  rock up to. 80 mph no issues Then starts playinng up/ when asked to do a hill or accelerate above 35mph.... once that happens the missing and farting is continuous and will eventually die as she feels likes she seems to drop cylinders.

[NZ FJ Rider]

You beat to the 88-93 1.2 Needle and seat fitment Pat 

I don't understand what is being said here.  "New TDI don't start from cold then but didn't change result after 15 mins." ?

Does it start every time now ?
George

Yes starts every time with old unit....

The new TDI is a kiwi made replacement that has an electronic advance. It will start the bike if it is warm but not from cold. I had both tdi temp on bike.... the vacuum sys (original) starts her first time and fires up immediately from cold with choke. When warm I switched over to the new electronic version to see if the original was at fault causing the missing when warm.. they both performed the same...... didn't matter what one was used.....10 mins sad face.

Ooooh, this is a good mystery....

Brian, when the bike studders and misses....are the plugs wet or dry?

If dry, then it's fuel...if wet, then it's spark...

Occasional miss followed by a more constant miss could be electrical....if your coils are ok, how about the voltage to the coils? Check the point to point ohm resistance? Have you cleaned and sanded all your electrical connections? Why not try the coil relay mod, it can't hurt.
How about the coil signal from the ignition pickup? Good ohm readings on the signal wires?

[NZ FJ Rider]

So, just to confirm...

The bike has the missing problem when it is operated with the petcock in the "prime" position as well?

Randy - RPM

Yes Randy....either vacuum or prime...same result