still wont start...

:evil: I just rebuilt my bike (81 xj650 with a 750 motor on it), put a new motor in, changed all fluids, cleaned the carbs and changed to 750 jets, new air filter, new fuse block, replaced main switch, changed to correct 750 TCI box and oil level sender, ... and the starter FINALLY spins...

But the bike wont start.... doesn't even try to turn over. I could hold the button down and nuke the battery and id still get nothing.

havent checked for spark, but the plugs were new when i received the engine from the shop. they ran the motor once on those plugs before shipping it to me. What gives?

I guess I'll check for spark and test my coils... but the coils were good before the old motor died and it hasn't been ridden since.

Any suggestions?

 

Start with the basics - make sure you get spark - make sure you are getting fuel. Did you try prime and make sure the bowls filled?

If it ran for the shop it should run for you.

 

no shit. just looked at the plugs and they were fouled, so im gonna get fresh ones to do the tests with. will update asap.

 

" doesn't even try to turn over."

what does that mean?

 

Not going to get much help with that attitude - you asked for ideas - I gave you a couple.

 

Have you tried starter fluid on it yet?

If it doesn't fire up with the fluid its your ignition. If it fires up but doesn't stay running its your fuel.

This might be an over simplification of things, but it help me narrow things down quickly.

That's how I started checking after 18+ yrs in storage.

If you can elaborate on the "doesn't even try to turn over" I think it will help with these more experienced cats diagnosing this problem.

 

This has me confused.
Is the Engine turning-over but fails to start ...
-or-
Is the Bike dead; and nothing happens?

 

my fault for being unclear. Bill, I wasn't being ungrateful for your help, I was laughing at my mistake, which was not looking at the basics before coming for help. sorry if I offended you

After replacing the fouled plugs and checking for spark, which was present, I tried to start the bike again. Charged the battery also.

The solenoid clicks, the starter turns and seems to engage with the starter clutch (instead of sounding like it spins freely) . the bike sounds like it's trying to start, and with new plugs i even get a cough of exhaust, but the bike will not run. When i take my finger off he start switch, the bike is not running. If I'm using the terminology correctly (which might not be the case) the engine is trying to turn over but will not start. I have spark, fuel, and air. Fresh oil, clean carbs, new gas, new fuel, oil, air filters. As i mentioned, the engine ran for the PO.

I'm going to check the mixture screws on the carbs tomorrow, just in case I forgot to reset (2.5 out?) one or more of them after cleaning the carbs.

The only possible vacuum leak would be on the airbox side of the carbs... The boots don't fit as snugly as they should. would this cause the problem?

Haven't tried starter fluid yet.

Tried on prime, carb bowls filled, still no dice.

Again, Bill, sorry if I seemed ungrateful/negative nelly-esque

 

When you say the solenoid clicks is it a single click when you turn the ignition on and off or is it a rapid repeated clicking after a couple of seconds of holding the starter. If it's the latter your battery may not be up to scratch.

 

Boots not fitting snuggly will affect the start. It will have a hard time drawing or pushing the fuel into the enigine. If there is a leak it will draw air only. The filter, other than to filter air, is there to create a back pressure or a vacuum to draw the fuel from the fuel line. Hit it with starter fluid.

I believe you are having trouble fuel delivery issues. Even if the adjustments are off there should be some life to the engine albeit some sputtering or a short lived start. Before you start messing with all the adjustments make sure you have the basics covered.

You have to have everything fitting snuggly on it or then you will have to make adjustments in the carbs as if you were putting those pods on it and then it will require rejetting. Stick to the 3 basics fuel, fire and air. If it ran fine for the PO then no adjustments should be required.

 

No problem Moon a baffling problem for sure. I have to agree with the starter fluid idea - will tell you if it's a fuel issue.

If I understand it right you purchased a running rebuilt engine. Only difference is it is now on your bike with your airbox and electronics. When you try it do you get gas on the plugs? The loose boots could be an issue but you should at least be getting some fuel.

 

I can see fuel entering and exiting the inline fuel filter, plus the carb bowl on cyl. 1 is leaking, so there must be fuel.... but i will try some starter fluid.

if i follow, i should squirt a little starter fluid into the carb boots, and if the bike runs but wont stay running its a fuel problem, if it won't run at all its ignition? correcto?

bill, you understand correctly. the engine wasn't even rebuilt tho, it came off a bike with a busted front end (forks and pipes bent, PO didn't want to replace) and it ran at the shop before they removed it from the other bike. 140 psi on all cylinders too.

The only other changes i made from stock 650 is i put the 750 TCI box on the bike to get correct spark advance curve (i think thats what its called) and rejetted carbs to stock 750 jets. other than that everything is normal.


So im going to go buy some starter fluid and try that. if the bike starts but wont run, ill start trying to cuss the carb boots back into place. Anyone have an idea why they seem too short or how to get them on properly? i have about 1/4 to 3/8 " gap between edge of boot and proper alignment on carb body.

 

Pictures of your boot with carbs would help.

 

Try shooting the starter fluid into the airbox before the carbs directly. It doesn't take much more than a squirt to get things spinning. Too much and you can do damage.

 

The 650 and 750 use different Ignitors.

The 650's were CDI Bikes. 750's got TCI's.

I think you need a another box!

 

i replaced that. got a functioning 750 TCI box on the bike now. when i checked the plugs for spark, i got good spark across all four. this should mean the coils, battery, cables, and plugs are fine, right? New battery, fully charged w. trickle charger overnight.

the bike started instantly and repeatedly with starter fluid. didn't even need "choke." didn't keep running, however.

so, fuel problem? not getting enough vacuum due to loose carb boots? issue with leaking #1 carb bowl?

the carbs are freshly cleaned, haven't sat around with gas in them at all.

I'm at a loss.

 

sounds like it's NOT lack of spark; it's obviously getting AIR, so there's only one leg of the triangle left and you're already on it---fuel delivery and/or mixture, either too much or lack thereof.

 

All you have to do is turn-on the gas of your Propane Torch and stick the Nozzle right down into the Airbox Intake Inlet.

Get some Propane Gas collected in the Airbox and try to start the Bike.
IF it fires-up on the Propane Gas ...

You have a FUEL Related Problem.

 

what steps should i take to make sure that fuel delivery and mixture is OK?

as i said, i can see fuel being pulled into the carbs on vacuum.

I think I'll try and snug those boots on tighter, replace the leaking carb bowl gasket, and see how she fares from there. I guess ill twiddle the idle screws also. 2.5 turns out, correct?

any other suggestions?

IM SO CLOSE I CAN TASTE IT!!! too bad its winter and i can go out for a spin once i fix all this.

one more quick question: I haven't replaced the exhaust pipes -to- head gaskets yet. could an exhaust leak prevent it from firing correctly?

 

Don't worry about the Hot Side of the Head.

Your problems are on the other side.
Get this thing going.

 

soudns good. ill post again after i try a few things

 

OK. SO. There is fuel in all 4 carb bowls, so the fuel delivery system is working (right?). The bike hasn't been run for a looong time (months).

All the electrics work and i have good solid spark.

Starter motor is A OK too, and mixture screws are set at 2.5 turns out.

Push button, nothing besides starter spinning. squirt a lil starter fluid, get some coughing which stops after a few strokes.

Keep doing this, eventually the coughing is persistent WITHOUT fluid and when i squirt fluid i get a stronger attempt at firing up.

The bike will not turn over/run/start at all; ie. not even with starter fluid will it go. Hopefully this makes sense.

I looked at the airbox-carb boots, and, despite them not being fully connected they are connected and there are no leaks (checked using starter fluid sprayed at the bad join.. didn't get a reaction.

I'm stumped.... what gives?

 

I suspect a weak battery and not so solid spark, or a serious vacuum leak somewhere. I have had my 550 SPINNING fine but fiddly little weak spark. Try this: FULLY charge the battery and install NEW spark plugs. When it happened to me the '83 WOULD NOT START but would spin fine and occasionally sputter. But it ran when I parked it. Charged the battery up fully and installed new plugs. It fired IMMEDIATELY. And I know my carbs are goofy, been PO'ed upon and I haven't ripped into them yet.

 

Pull the Seat
Pull the Airbox Cover
Pull the Air Filter
Have someone hold-open the Throttle
Check Kill Switch
Try to Start Bike
Shoot Starting Fluid right at the Inside Connections of the Airibox Boots

If it don't "Pop" or act like it wants to start ...
Investigate Ignition Related Issues.

 

New battery, fully charged, new plugs

spark possibly not as strong as it could be... white and not super bright... should it be blue and bright?

will try that rick, just to make double sure... have a buddy here right now so maybe i can cajole him

 

My xj550 would turn over but did not start - had spark, fuel etc.

Then I unscrewed the throttle preload e.g. the rack butterfly screws (the ones used for synchronization).
The throttle shaft was almost dead ... butterflys were closed.
Backed the idle mixture screws out another turn.. to 4 FULL TURNS anti-clockwise (left).
This move is temporary until its running.
FULL CHOKE
PETCOCK on PRI
Hit the starter button and it just coughed, Sprayed a little fluid and then Viola! it started!

Keep after it ... persistence pays.

 

Plug wires switched around so sparking at the wrong time?
<edit> or coil or pickup connections, same outcome?

 

erm.... i wouldn't know how to check if the spark is off time... the cables are all hooked up correctly..... ill search for how to test coils and post results.

should the spark be bright and blue-white or relatively faint and white?

 

Since you swapped in a bunch of parts, please verify that the right side (when sitting on the bike) coil is connected to the gray wire for its two pin connector and has its spark wires running to cylinders 2 and 3.

If you have a timing light, then you can remove the timing cover on the left end of the engine and check that, with the timing light connected to #1, the ignition is firing when the marks on the reluctor are near the TDC tab.

Another mark of being 180 degrees out of time would be occasional backfiring when trying to start it.

Have you checked spark on all four plugs, or at least on one each of 1/4 and 2/3?

FWIW, when I was doing my initial fuel injection work, I found that my bike would fire up and run nicely for a good five seconds off a squirt of starting fluid.

 

i checked spark on all four, saw white spark that wasn't very bright.

I haven't checked the wiring situation, so I'll do that manana.
I didn't swap the coils, the only thing i swapped was the 650's CDI box for the 750 TCI box. does this house/is this involved in the wiring you're talking about?
I don't have a timing light, and i have no idea what a reluctor is... back to the archives...

I'm charging the battery overnight, we'll see what happens tomorrow.

 

Here's the reluctor:



But you'll need a timing light. The TCI unit certainly ties in with this wiring. I'm not sure whether everything in the harness is the same, so things could well have gotten swapped around between the mix of 650 and 750 parts.

 

Yeah, it wouldn't take much of a difference in the harnesses to get the cylinders flip-flopped.

 

my bad fuse box caused similar symptoms. The starter ran and got a couple pops, but the engine wouldn't run. I *could* push start it easily, so that was my clue (that, and the fuses being soldered in place!). Replacement fuse box solved the problem. I guess it all comes down to the definition of "weak spark" which seems a little subjective to a non-expert like me -- I wouldn't have a standard of comparison.

 

ok... now that i see the pic i know where its at and vaguely what it is....

doing some tests today will post back with results

 

alrighty. Checked wiring, etc. on coils and other ignition components... everything is A-OK.

Pulled plugs before i tried to start it, and plug 1 is DARK, super rich but not fouled (probably coz i have the enrichment circuit on full blast when i try to start). this is the same cylinder as the leaking carb bowl.

plugs 2-4 are CLEAN AS A WHISTLE!! barley wet, no signs of any tarnish whatsoever.

Put a new plug in 1, tried to start. Got it to actually turn over and run for a bit off starter fluid.

This leads me to believe, based on previous suggestions, that this is a fuel issue.

How do I troubleshoot/test? I know all four carb bowls are getting fuel. is it a Vacuum leak? Im a little lost here. I can't understand why i have air and spark and SEEMINGLY have fuel in the carbs but no ignition.

What should I do? How can i check for a vacuum leak when the bike won't run? why would the cylinder whose carb bowl is leaking and has a mediocre seal on the airbox boots be running rich? why are all 3 other cylinders damn near dry and plugs are bright shiny white? the air-to-carb boot on 4 has the best seal out of all cylinders. What is preventing me from getting fuel to these cylinders?

i can't wait until i actually understand what is going on with my bike. I feel like such a nOOb right now. oh well.

 

You are about at the point where you are going to NEED to hook-up to a Manometer to "See" if there is Manifold Vacuum.

If you have a Leak at the Head, Gasket or Manifiold ... The Manometer won't show that there is Vacuum present at the Manifold.

If you aren't generating Intake Vacuum because of a Air Leak at a Manifold ... the Manometer will show you that there is None or very little present.

 

But on the bright side you'll be so proud of your running bike and know it inside and out.Atlest thats how it went for me and the months it took to get running just like i wanted

 

gotcha rick. EDIT: dumb question, wasn't thinking. I'll check fuel level in the bowls while im at it.

maybe i'll get into the starter too to see if the brushes are worn and causing the weak spark.

EDIT (to shorten the thread):: checked vacuum across the rack. un restricted vacuum gauge was attached to the manifold nipple then start button was depressed. wildly swinging needle as expected, went up to about 8 or 9 "Hg" as it says on my gauge (mm or cm i have no idea), for all cylinders.

This would show that I have no leaks in the intake system, correct? if there was a leak the needle would not move, right?

Didn't check the bowl fuel level because i don't have enough clear tubing to do so, nor do i have the "fancy ruler thingy".

why would three out of 4 plugs be completely white while the other is a "too-rich brown"? there was a bit of moisture on the plugs, but they were not wet. this includes colored plug.


so many questions, sorry. complete newbie... trying to figure out something way over my head atm.