FJ600 - Trouble starting.

Hi guys.

New member, so i hope this post is allowed since its an FJ600.

Bike is a FJ600 from 1990, US/Canadian import is my guess, but the bike is now in Europe.

It was bought as a running motorcycle, but had been standing since november of 2020 heard it running, but had servere starting issues, and would not idle, or accept any throttle what so ever, and was only running on 3 cylinders.

Since then i did a few things to the bike, carbs has been cleaned, rebuilt and bench sync'ed, float level set with the clear tube method, new spark plugs, new battery, new airfilter, new fusebox it has spark on all 4 cylinders.

Here is the trouble, i had the bike started before swapping out the plug caps, started on the first push of the button, only running on 3 cylinders, found out 3 of the sparkplug caps was bad, so i decided to call it quits and leave it until new plug caps would arrive, a few days passed and now it will not fire, cranks fine, has spark on all 4, but gives no indication what so ever about firing, no popping, nothing, all 4 carbs has fuel in the bowls, and fuel is fresh, feed from an auxiliary tank, so direct feed.

The new plug caps are NGK VD05F 5k, i think the OEM is supposed to be 10k, but i cant imagine that would make a difference since it was running with 3 caps with no connection what so ever.

It has compression, spark, fuel, and air, everything says it should be running, only thing i can think of is a weak spark.

Can anyone shed some light on this bike, season is soon - and it would be nice to enjoy it on two wheels.

Regards
Ronni

 

Does teh spark look weak? Did you try trimming a little off the HT leads (10mm or so) before fitting the new caps. If your caps are resistor AND the plugs also resistor type
maybe that's too much resistor.. Did you try any 'Start ya bastard' or whatever they sell in Denmark ;-)

 

Older XJ's are battery sensitive and don't like to start if the battery voltage drops below 10V when cranking. You mentioned a new battery, but a full charge and load test while cranking would be a good idea.

 

Have you checked the valves? Must want to make sure that has been looked at.

Starting fluid has it firing on all 4?

 

Plugs should be standard to the bike, NGK DR8ES, i did trim around 10mm of the plug wires before fitting new caps, spark is clear blue and strong will jump 1 cm without the plug cap, it fires of on brake clean, and will keep running of the fuel in the bowls.

Battery is new, and fully charged, i do however seem to have a voltage drop when measuring directly on the TCI unit, it drops to around 9 volts during cranking, did clean the grounds, and battery terminals, and fuse box is new, so not sure where the problem is located.

Still need to check the valves, it does seem to run on all 4 on brake cleaner, and on the fuel in the carbs when the RPM's gets high enough.

 

9 volts is nowhere near enough juice. Get a good strong battery

 

Brand new yuasa yb12a-a, fully charged, there is a voltage drop, but not sure where - engine cranks strong, light is bright.

 

Blocked pilot or choke (enrichment) circuit in carbs? These carbs need a deep thorough clean - nothing else really cuts the mustard.
Its a hateful job pulling them on and off but sometime you have to bite the bullet (again). +1 on valve clearances too.

 

Well, if there’s a voltage drop, then you’re STILL not getting near enough juice...
Check your starter or starter brushes......

 

thats the same bike ,and engine as my xj600 , plugs are correct, and yes the Haynes does state 10K plug caps ,but i've been using the same 5K caps as you, for 10 years
without any problems.
clean up the earth wires, theres one on the back of the engine, on the RH side ,on one of the crankcase half, bolts ,
and another underneath the battery tray, on the frame , also the battery terminals

 

Voltage drop is around 1 volt between the TCI and the battery, lets say battery is showing 10v while cranking, then TCI will show 9.

I had them off around 5 times now, just did another clean with brakeclean and compressed air, nothing seems to be plugged, but if they keep acting up i will split them and throw them in the ultrasonic.

 

Ground wires and battery terminals are already cleaned. And yes, it should be the same bike, except the FJ600 is called 3RC in the VIN, not 51j or 3km/3kn.

 

Is the well and jet at the bottom clear and clean? Brakleen and compressed air alone may not do the job.

 

Yes, 100% clear, carbs has been torn apart and cleaned thoroughly.

 

If you only have 10 at the battery when cranking the 9 at the TCI is fairly typical with losses along the way through switches and connectors. 10 would be low for a new fully charged battery.

I know my XJ750 will not fire up cold unless the bowls are near full, it's like the enrichment circuit requires full or near full bowls to function correctly. I have also had issues with auxiliary tanks particularly in conjunction with an on off valve in line - the gas will flow but not completely fill the carb bowls before it stops. So, if you just verified gas in bowls go one step further and use the clear tube method to make sure they are all filling to the correct level.

Yes on the enrichment well being clean, but it would be more convincing if you said yes I used a flashlight down the well to see the pinhole at the bottom of the bowl, or I nearly shot carb cleaner into my eye when I verified they were open and flowing.

Measured?

And yes valves as suggested

 

I must admit i got lazy and only checked compression on the "non" running cylinder, it sits at around 155 psi, so i would call that a good compression, will check the remaining 3.

Guess its time to troubleshot the electrical system a bit more, maybe try and run a constant powerfeed to the TCI bypassing all the switches and connectors.

Float levels has been set using the clear tube method, they are within 1mm of the correct setting, so that should be perfect according to my manual, and no i did not shine a flashlight to check the enrichment, but i did spray carb cleaner through, and verified it came out of the other end.

I will recheck the float level before refitting the carbs.

 

Ahh, the problem here is that the jet may be slightly open. Use a flashlight towards the bottom of the bowl and peer down the well. Make sure you see a nice round hole lit up. If not round it will not be thoroughly cleaned out. You know how wrong sized jets (and clogged jets) perform, I assume.

 

Done and done, just finished another clean of the carbs, enrichment circuit is open, checked with a flashlight.

I am not positive its a carb issue, but i will keep my options open.

 

Back to running, well sort of, it still only runs on 3 cylinders, or 3,5 maybe, since the sparkplug in cylinder 4 is getting some color, i guess next step is to check the valve clearance.

Also swapped sparkplug and plug wire between cylinder 1 and 4, no difference, so it is not a ignition issue.

Compression numbers are:
1: 160 psi
2: 155 psi
3: 153 psi
4: 150 psi

And fuel level on cylinder 1 looks like this:

 

And its not a valve problem.

Back to the carb.

 

Diaphragms in good order?, sticking float needle on trouble carb? Take a look when its running on three - you may need a mirror - and see if the slider is moving on the throttle opening you should also be able to see the fuel spray (or not)

 

It has new needle and seat, does not seem to stick, diaphragms are good, i am suspecting leaky shaft seals, since they most likely are OEM, and 32 years old.

Carbs are off the bike again again and again.

 

In your very first post here you said you rebuilt them......

 

Throttle shaft seals are a common reason to remove carbs yet again, because people don't think they can or should break the rack initially. Usually if there is leakage it produces a lean condition with possible revving.

 

I did, just not the shaft seals, guess i am paying for that now.

I will order at set, somebody told me Suzuki # 13651-51010 should fit, and they are a lot cheaper than the Yamaha version.

 

Carbs are split, that was super easy and i feared the worst about removing the screws holding the butterfly valves, old seals are pretty sloppy, will order new seals, and new screws.

And while i am waiting for parts i will drop the carbs in my ultrasonic.

 

I'll be interested to learn if that fixes it...
..I'm not sure.

 

Same, i hope it will be a confirmed fix, but i doubt it, because why would it only affect one cylinder, and not the other 3, all the seals are bad.

But i am running out of ideas, so everything goes right now.

 

Try starting it off a car battery.

 

The seller did that when i bought it, was only running on 3 cylinders, also tried with battery and booster, still only running on 3.

 

Have all the ignition components been tested and verified within spec? Coils, wires, caps, plugs

 

Plugs and caps are new, and checked, used 5K caps instead of the 10k oem, but that should make no difference.

Did not check wires or coils, but i did swap wire and plug from cylinder 4 to cylinder 1, and no difference, cylinder 4 is running.

 

If it’s not carburetor/fuel issue, then it’s either electrical or mechanical.

electrical-TCI, wires/connections, coils/leads/caps/plugs, grounds

mechanical - did you do either a compression test or leakdown test, check cam for a bad lobe, etc....

 

I did not do a leak down test, but compression is at 160 psi, and valve clearance are in spec, lobes looked fine.

All ground connections has been removed and cleaned, there is plenty of spark on cylinder 1, a faulty coil should also affect cylinder 4, since its a wastespark system, and plug wire has been moved from 1 to 4 without any change, sparkplug in cylinder 1 is getting some color, so it is running, at least a little bit, its not stone dead.

 

If #1 is not stone dead, maybe it is just super lean?

I just re-read the thread and I didn't see anything about pilot mixture adjustment.

Also, is there any difference when you use the enrichment/choke?

If it is firing occasionally, it kind of reminds me of when you are using a colortune and bottom out the pilot adjustment screw so it is super lean - it will fire occasionally, but not much.

 

Pilot mixture screws are set at 2.5 turns out, it does not seem to do much difference when adjusting it on cylinder 1, when using the choke enrichment bike idles higher as it should, but the exhaust on cylinder 1 is still cold compared to the other 3.

 

How weird.

Since we are grasping at straws, what about some sort of obstruction in the intake or exhaust? Like somebody stuffed a rag in the intake to keep dirt out while working on the carbs and never removed it - seems like something I would do. Or perhaps an obstruction in the exhaust - maybe a family of mice moved in while it was sitting??

I know it may not be inexpensive, but would it be possible to get another rack of carbs? Seems like it would be a small victory to either confirm that the problem in is the carbs or rule them out as the source of the problem.

 

I did actually order a spare carb set, just for testing, still waiting for it to arrive, bike was complete when i bought it, had been standing for around 1 year, was last on the road in november of 2020, intake is clean, did not check exhaust.

Looking on the exhaust headers it looks like its been on 3 cylinders for quite some time, there is a visible difference between 2-3-4 and 1, i dont hope the engine is hurt.

 

Did you try swapping coils 2/3 for 1/4 yet?

 

That is always a good thought on a dead cylinder, particularly at lower speeds. Aside from defective carburetors, the Intake Manifold gaskets as well as the Intake Manifold itself leaking can cause that.

I don't know if just a butterfly shaft seal leaking a bit would make it that extreme.

 

I did not, but will give it a shot when the parts for the carbs arrive.

No i have the same thoughts, leaking shaft seals will make problems, but keeping a cylinder from running, i doubt it, i did spray the intake boot with carb cleaner without any effect.

 

Seems like about the best next step in the troubleshooting process. Thanks for being a good sport @RonniN .

 

Carbs ultrasonic cleaned, rebuilt, new throttle shaft seals, new o-rings, new screws for the butterfly valve, and plenty amounts of loctite to make sure the screws are staying in place.

Still need to bench sync them, and then reinstall on the motorcycle, i am hoping it will make 3 cylinders become 4.

And yes, Suzuki seals fit, and they are a lot cheaper than the Yamaha version, partnumber can be seen on the picture.

 

Good info. I guess if they're are both Mikunis there's no reason why not. Fingers crossed - this is intriguing

 

Come on Ronni - we're waiting!

 

Fowlers have these seals, anyone know if they are the same?

https://www.fowlersparts.co.uk/parts/4273175/-0/carburetor-model-h-e18?noredir=1

SEAL
13651-51011-000
Replaces 13651-51010-000
Share this part
IN STOCK
£2.74 inc. VAT

 

Yea me too, been pretty busy lately, but hoping i soon will get back to it.

I think they should fit, if you look on my picture its the same part number.

 

Yes good price for them too.

 

Back to working on the FJ.

Reinstalled the carbs, airbox, connected fuel, and turn the key - started right up, on 3 cylinders, did a bit of tweaking and 3 cylinders still, and noticed fuel dripping from the bottom of the carbs, shut down the motorcycle, and pulled the carbs - again.

Morale of the story, is when you rebuild your carbs, replace the friggin fuel inlet T.

The good news is i am pretty sure i found out why it runs on 3 cylinders, or 3.5, decided to check the bolts holding the intake boots on the head, and surprise the two on number 1 could be unscrewed with the fingers, the remaining 3 cylinders was good.

And no, i did not tear the gasket, it looked like that when i removed the intake boot.

 

You have some gasket paper? Or I think someone on here uses cereal boxes with good results...no kidding.