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.