XJ550 Wont work - about to set it on fire!

The thanks:
Hey guys, new to the forum but had been reading posts and gathering information, you guys are great!

The bike:
1983 XJ550, the bike was bought basically in pieces. Wires everywhere, plenty parts missing, been standing for unknown amount of years, the engine turned over that was about it (no compression). The exhaust completely cut out, ends roughly by the centre stand and no muffler in place.

The journey:
Complete carb rebuild (Temple of clean) roughly 6 times, float height set, new orings etc, new pistons (old rings seized), valve clearance done, compression test within range, coils and sparks okay, plugs new.

The problem:
I managed to get the bike to start up with a tiny bit of starter fluid. It runs okay when the rev is set slightly higher else engine dies. When choke is used it seems the rev wants to go up but alot of bogging. The main problem is that cylinder 1 is not firing (confirmed using Colortune). When I rev the throttle slowly the exhaust bogs and pops from what seems like cylinder 1 too but i did manage to get some "orange" in the Colortune as I do this.

The thought:
My primary concern is that i messed up the timing when i was putting the head back in? But if thats the case cylinder 4 which is running on the same coil as number 1 should be running equally as bad which its not? Secondly maybe because the exhaust were cut out so the jets are running too lean and causing the popping noise, but then why are cylinders 2-4 idling fine and just 1 is not running?

Need help:
Im really running out of options, I bought the bike thinking that it just needed a tuneup but in fact i had replaced everything that i touched and its still not working fine.

Any input welcome!!

Thanks folks

 

How many turns from soft bottom do you have the mix screws set at?

Gary H.

 

Hey @rocs82650 thanks for the reply,

Started with all 4 screws 2.5 turns out, while the colortune was in i then went from full in to full out, lots of spark on the plug but no flame.

 

2 things to double check
Small brass tube that goes into float bowl and the passage in the bowl feed idle mixture screws
This is 650/750 carb but many carbs have this feature

 

Hi @Toomanybikes

I will seriously consider opening up the carb AGAIN if no better solution comes up.
I did clean the carb thoroughly including both of the above enrichment circuit passage and the pilot jet passage.
I used a compressed air can to blow through each circuit allowing one exit only at a time i then compared the sound and airflow against all carbs assuming the circuits are free of debris.

When i do again will try shoving a thin wire through these openings and see if anything changes.

On a side note when i set the float height the carb was on a stand, the front and rear of the carb was basically parallel to the ground. I noticed that after the carb had been installed its actually tilted slightly upwards at the rear, will this be an issue in terms of float level and cause a leaner mixture?

 

If you had a clear float bowl you could see the affective level in center of carb were the main jet sits would be nearly identical as with carbs parallel to the ground.the slight tilt forward I imho is to take into account acceleration forcing fuel to rear of carb.

 

have you ohmed out the ignition system??
do that before you burn the bike.

 

Hey @XJ550H

I couldnt get the meter to read anywhere close to what the manual said, so instead i switched the connectors, and then the wires for 2-3 to 1-4, problem stayed with cylinder 1 and did not change with the coils.

 

When you did carbs did you do a bench synch? And a running synch?

 

bad spark plug?

check the timing .

what readings did you get when you checked the ignition resistance

 

Swapped coils and still no spark = Bad plug! Swap plugs to check.

~Ghost

 

Those readings are with the spark plug caps removed from wire. And check the reading of caps separated from wire

 

When you said timing after re-assembly, I presume you are concerned that you messed up the valve timing? What are the valve clearances, intake and exhaust, for each cylinder?

 

for quick test you can leave plug caps on and add 10 K ohms.

cap plugs can have a resistor intermitant fail and apear good
I replaced mine with new caps from chacal and got the spark plug nuts to adapt to them

 

that little hole and brass tube are for the enrichment circuit.
Tuckpuck, spring for a new set of plugs

 

Maxim or Seca?

Might help you decide when to strike the match!

..just kidding Maxim owners

 

@Jetfixer Bench synch done, didnt see the point of doing a running synch before i get cylinder 1 firing?

@XJ550H Any ideas how i could check timing on these engines? Plugs are new and i could not get an accurate reading on the coils but the faulty cylinder should fire when i tried switching the coils, their coils but problem stayed with the same cylinder?

@MiGhost Plenty spark but no flame in the colortune, plugs are new.

@DrewUth Yes valve timing is what im scared of, im scared that the timing is off and causing some kind of detonation/preignition. Would the valve space matter if they were in check? Cant remember where i kept the recordings but if its important i will open up the valve cover again.

@XJ550H Same issue here if it were the plugs, plug caps, wires or coils, the problem should move to another cylinder when i did the connector/coil swop?

@Polock Will definately check that, looks like on your carb that little hole sends fuel to another compartment where the brass tube is getting fuel from? No sure if theres such function on the 550 carbs?

@a100man Im getting close

 

i've seen a bike with the cam chain off one tooth and that one spit fuel back out the intake of the carb like mad but yours could be off one tooth the other way then i don't know what happens.
a compression check would tell you real quick

 

If you think for an instant that something in there could be wrong, it would be a waste of time to do anything else. Imagine if you spent hours diddling with carbs only to find out the cam timing was off...I would absolutely go back and double check the work if I was in doubt at all.

 

valve timing


do you have a repair manual?

if your problem is with coils and plugs it should follow the parts when swaped

ignition timing is done with timing light which requires spark on plug 1 at 1200 rpm

 

Finally got some time to do some work on the bike.

Measured clearance again cylinder 1 intake 0.13mm (0.11-0.15) and exhaust 0.18 (0.16-0.20)
Managed to get all four cylinders to get up to a pressure around 135psi and all within 5% difference.
Took the valve cover off and rechecked the dots on the cams align with the T-mark on the timing plate.
Took the carb of and cleaned enricher circuit bowl and pilot circuit again for the problematic cylinder.

Got the bike to start up, same thing, lots of spark through colortune window on cylinder one but no flame while idling.

This did start occurring thought: As soon as i open up the throttle even just slightly i did see some orange in the colortune but almost at the same time, lots of popping and bogging coming the exhaust of the problematic cylinder, i also did notice some kind of a backfire or backpressure of some sort which was coming out of the carb.

Any ideas? @XJ550H @DrewUth @Polock @Toomanybikes @Jetfixer @rocs82650

 

While its idling play with the mixture screw on that carb and see of it changes
The bowl on that carb may have a blockage in this passage preventing fuel from getting to idle circuit

 

Did you confirm float level?

Did you confirm size and placement of jets?

Confirm the jet at the bottom of the well in the bowl is clear?

What did your mixture screw setting end up at on the other carbs?

 

I will check the passages again, i sprayed carb cleaner and canned air and they sounded ok when i last checked.
I tried the wire method too but couldnt get anything to go pass, or rather bend in the passages, any ideas?

Jets are the same across the carbs and compared ti the service manual
Jets are all clear and float level checked

 

is the bike warmed up while you're getting the bogging and popping? you can't set the carbs on a not hot engine. get that colortune thing out of there and use new real plugs. did you try switching the coils around, see if the no spark follows it. might be a bad plug cap