1986 fj1200 driveability issues

[weber1]

Hello, I recently bought an 86 fj1200 which had a hesitation on accell from stop unless choke was slightly pulled. Even then it sputtered and bogged unless I throttled it and then it would come alive. Rough idle with backfires thru exhaust. Drained fuel tank and found fuel breaking down. Removed carbs and found jelled fuel in bowls. I used Carb cleaner and light air pressure to clean any ports and fuel pick up tube to bottom of bowl, I did not take anything apart or adjust. I replaced fuel hose from tank to split off. I also replaced plugs. After reassembly the bike barely runs. Ran OK at first with a slight bog on take off but had to walk bike back after 3 mile ride. Feels like it ran out of gas. Will start but has very little if any throttle responce. Stalls on any type of accell. Low choppy idle. I inspected hoses to air box and intakes. All good. Any ideas? I definitely feel its a fuel issue or lack of. Plenty of volume thru hose to carbs. Same problem with fuel tank cap open. Thanks for any help, Rob.

[racerman_27410]

its very common for people to replace the fuel line from the gas tank to the carbs and leave the line a bit too long.

it will cause the line to kink once the tank is bolted back down ... making the carbs run out of fuel.


also it would be best to thorougly clean the carbs and all jets.... just rinsing out the float bowl is not going to be good enough.


there is a great carb cleaning/tuning doc right here.....


http://www.fjowners.com/index.php?topic=655.0


KOokaloo!

[Pat Conlon]

Yep, +1 what Frank said, a pinched fuel line.

On the gravity fed FJ's ('84-'87) fuel line routing is most important.
There should be a diagram on your air box showing the correct route.

If you don't have this diagram, let me try to explain: As the fuel line leaves the tank petcock, this line should run *under* the two branch lines which feed each pair of carbs. It seems weird, but when the tank is installed the line will route properly.
What happens if you run the fuel line above the two branch lines is this, it forms a kink in the fuel line. When the bike is cold (on start up)  the fuel line is still hard and it lets a little bit of gas flow thru to the carbs and the bike runs.... but when the bike warms up and things get hot under the tank, the fuel line softens up and the kink closes off the fuel flow. If you replaced the single fuel line before the 'Y' then chances are the new harder fuel line is pressing down on one or both of the softer oem Yamaha fuel lines.
Again, run this single fuel line *under* the two branch lines and I suspect all will be well.

It's a right of passage for the owners of the older gravity fed FJ's to figure this out.... It has happened to a lot of us.

Also check your vacuum line which opens the petcock, the same thing could be happening to the vacuum line. A pinched vacuum line will close off the petcock. This happens only rarely, most often it is the fuel line that's the culprit.

If pinched fuel line(s) are not the problem (doubtful) then it's time to once again remove your carbs, disassemble them, and properly clean them. Pay particular attention to all those little holes on the main jet nozzles (aka emulsion tubes) and your pilot jets and tiny air jets.

Oh yea,  safety wire that petcock while you are under there! http://www.fjowners.com/index.php?topic=3265.0

Hope this helps.   Pat

[flips]

Hi weber1

+1 to what Frank and Pat said.My oem fuel lines were in pretty poor condition and I replaced them with thicker 5/8 stuff from my local auto shop and off course ended up with kinking problems.I found this thread which cured my kinking woes.Getting rid of the oem airbox and fitting uni pod filters also helps.(more room and easy carb servicing )Thanks mr blackstock......

http://www.fjowners.com/index.php?topic=4411.msg38941#msg38941

Hope this helps

Cheers

Jeff P

[moparman70]

An interesting item I found on my parts bike was the fuel lines.  The previous owner used copper tubing for the curved bend. So off of the T-joint he had a small piece of hose that lead into a curved copper tube that wound around that bracket and then another piece of hose clamped onto the end that would attach to the petcock.

It looked hokey but it I like the idea after all the issues that I've had in this area ( not only kinking but cracks too that go undetected ).

[weber1]

Thanks guys, I will check all the things mentioned out. I did replace the fuel line with a harder line and cut to same length but on reinspect i found it kinked and not routed as mentioned. I will remove the carbs this week and do a thorough cleaning. I did not notice any vacuum line to petcock or fitting for one. I removed petcock assembly and inspected screen, all good. The amount of responses and the knowledge shown is greatly appreciated, Thanks. Rob.

[weber1]

On the petcock issue, it may have been replaced. It's just a basic 3 position valve, off-reserve and on. Also,after I get the bike running correctly I will be changing fork seals. Until then, is there a way to check oil levels and add if needed add without removing front suspension? It feels strange asking asking what are probably basic questions. I have been in my field for 25 years as a senior tech with Ford Motor Co. but this is a new area for me. Used to ride alot as a kid and when I lived in Florida. Now that I'm older and a few of my friends ride I decided to go for what I like instead of the typical  Harley guys my age are buying. I wanted aircooled inline 4 long low and mean. Thanks again.

[Arnie]

Weber1,

The fork oil height (or amount of trapped air) is one of the variables used to adjust fork action.
While the manual gives you only a volume measurement for fork oil, the better and much easier way is to set fork oil height.  This is with the springs (and preload spacers) out and the fork fully compressed.
Standard is about 160mm from the top of the fork tube.  Having the oil higher will give you a more rising spring rate as the fork approaches bottoming due to the trapped air being compressed.  I have my fork set at 130mm, but that is personal pref.
You can check fork oil height with the fork in place, but you'll have to remove the handle bars, and the fork caps to remove the springs and preload spacers.  So, find a way to support the front of the engine first.  Then remove the bars, caps, spacers, and springs.  Have a helper raise the front wheel fully and use a dipstick to measure the distance from the top of each fork tube to the oil.
A 20mm hypodermic syringe with a tube on the tip and an O-ring around the body can be used to set the height quickly and accurately.

HTH,
Arnie
 

[weber1]

Thanks Arnie, I noticed alittle oil on left side fork. Suspension feels alittle soft to me. I will do it all the right way when I replace the seals.    Back to the driveability issue. I put the right hose on and routed it the correct way. Plenty of fuel going to carbs now. After letting it warm up for a few minutes I have a dead spot on an accel off of idle,will stall. I have to feather up the throttle. On road test it goes from nothing to warp drive, no real medium. I am taking the carbs off tonight to thoroughly clean them. Is there anything else I should look at while I am there? Thanks, Rob.                                                     

[andyb]

The fork oil height (or amount of trapped air) is one of the variables used to adjust fork action.
While the manual gives you only a volume measurement for fork oil, the better and much easier way is to set fork oil height.  This is with the springs (and preload spacers) out and the fork fully compressed.
Standard is about 160mm from the top of the fork tube.  Having the oil higher will give you a more rising spring rate as the fork approaches bottoming due to the trapped air being compressed.  I have my fork set at 130mm, but that is personal pref.
You can check fork oil height with the fork in place, but you'll have to remove the handle bars, and the fork caps to remove the springs and preload spacers.  So, find a way to support the front of the engine first.  Then remove the bars, caps, spacers, and springs.  Have a helper raise the front wheel fully and use a dipstick to measure the distance from the top of each fork tube to the oil.  

When you take the fork caps off, be quite careful.  The fact there's "preload spacers" under them should be a tipoff... they're spring loaded, and you can quite easily shoot yourself in the face with them if there's enough tension.  You'll need a very good grip on your tools and a bunch of downforce while unscrewing them to prevent surprises.

As for the latest in drivability, clean the carbs quite well before you start making too many adjustments.  If it keeps doing this most recent behavior after they're known to be good and clean, you could try adjusting the float height / fuel level a bit.  Also before making carb adjustments, do check the stupid easy stuff, like  the condition of the spark plugs and air filter(s).

[weber1]

Will do. Hopefully the cleaning will do the trick. Plugs are new as is the airfilter. Thanks.

[racerman_27410]

when you pull the carbs apart dont forget to remove the emulsion tubes and clean all the little holes out   (the main jets screw into the emulsion tubes)

a proper balance (synch) is also going to be required for the carbs after you clean them.


KOokaloo!

[weber1]

I cleaned the carbs last night, jets and float screens. I only saw one pin hole in emulsion tubes. Cleaned every hole, port, you name it. I installed the carbs with each adjustment screw at 3 turns from fully seated. After warm up the bike runs 90% better. It still has what feels like a miss or stumble on initial snap of throttle. I am going to sink carbs friday. I did not feel comfortable trying to remove the tubes so I cleaned them best I could. I would like to know what the spark plug gap should be set at and if, because of age, should ignition wires be changed? Thanks, Rob.

[simi_ed]

Weber. the emulsion tubes are a piece of cake to remove.  After you have the tops & float bowls removed, along with the slides.  Loosen the main jets 1-1/5 turns, then tap them.  This will force the tubes up from the carb body.  Reach inside the carb throat & remove the tube.  Clean until spotless, reassemble.  Also make 100% sure the pilot system is clean.  I use carb cleaner, sprayed into the air jet in the inlet side of the carb, then remove the adjustment screw, and spray some more, making sure that the cleaner exits from the air jet, the pilot jet and then the downstream hole in the carb body (after the throttle plate).  Next, make sure the pilot jet is 100% clear.  I had 1 jet that was perhaps 10-20% blocked, and it effected the running.  Reassemble and sync, adjust mixture and you're done.

[weber1]

Well, I will probably pull carbs again Saturday and clean the emulsion tubes as recommended. Runs alot whole lot better already, just don't think that hesitation is safe. Thanks for all the advice.