Yamaha XJ 550 4V8 Trouble Starting Motorcycle (Philipp's ongoing troubleshoot)

Hey there people,

Just a quick introduction before I get to the actual dead end I'm finding myself at:

My name's Philipp, I recently bought a rather neglected Yamaha XJ 550 and I'm currently in the process of breathing some life back into it. Even though it's been sitting for only a year or so, the previous owner did not treat his motorcycle with the same tender love as I'm used to, so there are a lot of small things to repair/replace.

Also, as a kind of quick disclaimer: I'm actually German, but because the German equivalent of this XJ forum is dead and I can't even register because I'd have to be accepted by an administrator ( ), I'm turning towards you guys for help. Since English is not my mother tongue and I haven't figured out all the English technical lingo yet, I'd appreciate if you could, should motorcycle specific terminology arise, use the most general expression for it so I can look up the German equivalent. Also, please try to spare me with acronyms, I'd only have to waste your time even more by asking you to elaborate


So, now that that's done, here's where I'm at:

The foremost problem (of which I'm sure there'll be plenty more for you guys to enjoy helping me with ) is that the engine just won't start. I can have the starter motor turn the engine as much as I want (in intervals of course, wouldn't wanna melt the starter motor), it just won't fire.

Now, even when I'm turning the engine until the battery runs out of juice, the spark plugs stay dry as bones. To me, that means that the fuel/air mixture doesn't find its way into the cylinders, eh?
I can only see two reasons for that:

1. There's a vacuum issue between the cylinders and the carbs that prevents the gas to be sucked into the combustion chamber
2. Something with valves and stuff.

I feel like this is the point where I should mention that I did work on run-down motorcycles before, but I never had to deal with valves and valve adjustment. I know that there are intake and exhaust valves, and if I understand it correctly, misadjusted intake valves could be a reason why there's no fuel going to the combustion chamber even if all other criteria for a successful start are met. Does that sound about right?

I am going to measure valve clearences as soon as I can and get back to you with the results, but I want to get as much input about possible issues as I can, so that I can check them off the list.

A few other things I already tried/took into consideration:

- Disconnected air filter box from carbs
- Tested all spark plugs for spark, all there (even though I can't evaluate if the spark is 'good' or 'strong' enough for the engine to fire)
- Even when using... starting spray (proper expression?) while turning the engine, there's not even the slightest pop
- Pulled and cleaned the carbs twice by hand (with the help of break cleaner) and replaced the jets
- Fresh fuel is going from the tank through a filter to the carb bowls without a problem, so gas availability shouldn't be a problem
- intake manifolds aren't the prettiest, but nearly not hard/brittle enough for vacuum leaks
- The engine is turning; after pulling the spark plugs, you can feel the air pressuring out from all four spark plug holes while turning the engine
- Didn't have the chance to check compression yet, but I ordered one of those testers and I'm going to update you once I know more. Still, as far as I know, even bad compression should be enough to at least make the engine cough with the help of starting spray
- I ordered an ultrasonic cleaner (always wanted to have one, found a 10l cleaner for a bit over 100€ ), I will clean the carbs again, this time properly


I hope that gives you a general overview about my situation. I was trying extensively to look up similar problems online, but I couldn't quite find any other approaches as the ones already mentioned.
Again, the only possibilities I was able to come up with are vacuum leaks, possibly a weak compression, clogged carbs or troubles with valve adjustments.

Are there any other things that come to your mind that could cause this/ that I should try?


Thank you all in advance for taking the time and for actually reading through this all, I know it's all rather unorganized but it's hard getting all the things that I already tried and the things that I found online in order

If there's anything else you need to know, please do ask. Also, I'm always happy to learn, so if there are any misconceptions about all this on my end, please feel free to correct me!


Cheers and Danke,


Philipp

 

y ou own a 82 XJ550 euro version.

first thing to test is your battery. do a voltage drop test. hook volt meter to battery and crank the starter if voltage drops below 10 volts bike will not start. Transistor Controled Ignition (TCI) needs 10 volts to fire ignition.

ohm out your ignition system Ignition coils , spark plug caps (caps unscrew from plug wires) and pick up coils.

the ends of the spark plug wire may be corroded so trim 6 mm off each end.
spark plug caps may have a screw inside where spark plug goes tighten it if needed.


do the spark plugs get wet when you try to start bike?

it should fire with starting fluid or at least back fire.

do you have glass fuses? you should replace with blade style fuse block or inline fuses.

enrichment circuit may be clogged and the wells in the carb bowls that the tube goes into if you are not getting any fuel

 

intake manifolds can be coated with Black RTV fuel resistant gasket sealer. this will eliminate them as a issue

 

Yes, re do the battery health, first, even a GOOD XJ electrical system can have a somewhat 'weak' spark.....

You could even try a truck/car battery.....repalce your XJ battery leads temporarily with 'jump start' leads from a known good ( heavy duty) battery....I always take my XJ battery out of the equation completely,( disconnect leads) to use this method, then use 'jumper cables' from the car directly to the disconnected leads + and -

Are you able to see ANY sparks, when grounding out the plugs to the head ( night is best, obviously)

It does sound like you still have NO fuel getting though though, although with copious amounts of starting fluid, you should at least get a 'backfire' ( its not really a backfire, but you know what I mean)

Are you able to 'drain' your carburetor float bowls ( screws) to make sure you have gas/petrol in them??

 

Hey guys,

Thanks for the input.
I tested my batterie, after fully charging it and putting it in, it breaks down to about 9,5 volts while turning the engine for an extended period of time (about 7-9 sec).
It might be worth buying a new one, but I know that my current battery must be working because a friend of mine put that same battery in his bike, and that one fires.

The ignition coils, pick up coils and spark plugs along with the caps have been replaced, and there is a visible spark coming off of all spark plugs when grounding them to the cylinder head.

Even if the spark wasn't strong enough, as I said before, the spark plugs remain dry even after cranking the engine for a long time. They should be soaking wet eh? I feel like that's the bigger problem I gotta tackle first.

The float bowls definitely get gas, I checked that.

I'm going to use my cars' battery to take my bikes battery out of the equation, just to get that off the list.

I hope I can work on the bike today, I'll get back to you with the results.

Any other things that come to mind?

 

550 is harder to start with a low battery. if battery works well in another bike. you want to clean ground cable from battery to motor and frame.
clean the positive cables from battery to solenoid and to starter. your starter may be drawing to many amps. starter may need to be rebuilt.

did you bench sync the carbs when you cleaned them?
set mixture screws to 2-1/2 turns up from soft bottom?
did you check the wet fuel level?

Setting the fuel levels

dry spark plugs


Bigfitz's AIRHEAD VALVE ADJUSTMENT with Pics - parts I & II

 

Sorry for the late reply.

I have yet to try starting the motor with a car battery attached, but I did manage to check valve clearances. Here's what I found:

According to the manual, Intake Clearance should be 0.11 - 0.15 and Exhaust Clearance should be 0.16 - 0.20.

Cylinder: 1 2 3 4
IN 0.04 0.05 0.05 0.03
EX 0.06 0.07 0.06 0.04

All valves are obiously way too tight, so that's something I need to address. The question is though: Could that be a reason for why the bike won't start, even when spraying a bit of brake cleaner into the intake (cylinder side) ?

@ kerriskandiesinc : I'm gonna try that with my car's battery, but I somehow want to address the issue of the dry combustion chamber first...

@ XJ550H : I didn't sync the carbs, I'm gonna have to take care of that as well at some point. Also, I might be horribly wrong, but... is it possible that my set of carbs doesn't have any mixture screws?

 

Yes, if those valve clearances are correct, as posted that could make her a lot harder to start......basically, she can't breathe properly

 

I'm actually glad to hear it. I feared it might have been something worse.

By the way, I forgot to mention that I checked the compression. It's about 95-110 psi for all cylinders. Not great, but not bad enough for the engine not to fire. Adjusting the valves should improve the compression, right?

There's a special tool in order to get the current shims out, right?

 

compression should go up with new shims. 10 psi is a nice tight spread between cylinders
we have a thread on shim check and replacement there is the tool way the wire tie way and house wire way

Bigfitz's AIRHEAD VALVE ADJUSTMENT with Pics - parts I & II

the tool that is sold needs a little grinding on the sides to fit properly unless you find a yamaha brand tool

 

Amazing guide, thanks a lot.


I still can't quite wrap my head around it. With a very tight fit like that, shouldn't the lobes open the valves even more than they're supposed to? If so, then why is there no fuel going through?

 

open more and maybe not letting them close enough

 

Alright I'm gonna try adjusting the valve clearances, it's gonna take me a few days to get all the materials.

 

Fuel might be getting sucked right back out!!, before compression/spark has a chance......you still might have other problems, but, 'fix' one at a time, and then see how she responds

 

Will do, thanks!

 

Just lurking some threads trying to figure out my own starting problem. How'd it go with the valve adjustment? Did that help with starting?

 

I can't tell yet.

I adjusted the valve clearances and tried turning the engine over, but my battery was pretty dead, it was cold outside and there was no gas in the carbs, only some starting fluid fume.

I'm gonna try it properly some time next week and get back to you with the results.

 

on your carbs there are small discs covering the screws have mixture screws up on top front of carb
cut away of carbs
http://www.xj4ever.com/inside your carbs.pdf

 

also can be seen in this link for maxim x carbs
Cleaning your Mikuni carbs

screw driver is in the hole

 

Philippe,
The site won't let me respond to you in German, but I'll try using PM.