Loud poping noise in engine

[Kopfjaeger]

 

[racerman_27410]

i dont think the engine could jump timing by backfiring unless the cam chain tensioner was out of the engine.

put the plug wires back on correctly and start looking at cleaning out the carb float bowls and jets.


KOokaloo!

[Travis398]

I agree with Frank, I find it hard to believe you could jump the timing by mixing up the plug leads. But it wouldn't be hard to check. Line the crank shaft mark to TDC and check the cam alignment marks. (the holes in the cam caps) It's really not any harder than a car with over head cams and a timing chain or belt. In fact it is probably easier.

[carsick]

It's really not any harder than a car with over head cams and a timing chain or belt. In fact it is probably easier.

Speaking as a recovering ASE master tech, yup the FJ is quite a bit easier! Don't have to remove the belts, alternator, AC, PS, cruise control, fuel lines, vacuum hoses, motor mounts, assorted bracketage, wheel, ABS wheel speed sensor, inner fender, coolant, radiator hoses, upper and lower timing covers, and crank pulley. Note that I didn't mention the easy to remove valve cover, because the marks are only on the belt pullies for many.

[irishluck]

well let me explain the situation of what happened a little better and see if it makes since any more.

Got the whole bike back together and it started up fine(this kinda pertains to the second post i have about the running problem) but then it would die and so forth.

So i thought that the 3 and 4 wires were mixed up, so i reversed the two, tried to starting it and then heard big pop noise, tried to crank again and some weird noises came from inside.  Tore the head cover off and the cams aren't broke, still cranks, i know the crank is fine, and bearing sound fine, From the looking off the cams and the timing chain it does look like it had to of jumped timing, the tensioner was tight and all on the engine.

And from knowledge working on cars, usually if something has jumped timing it wont start right, But cars and bikes are a little different, so after reading this what do ya guys think

[irishluck]

i dont think the engine could jump timing by backfiring unless the cam chain tensioner was out of the engine.

put the plug wires back on correctly and start looking at cleaning out the carb float bowls and jets.


KOokaloo!

Oh forgot to ad, the carbs are freshly rebuilt, cleaned with new jets and all

[FJ111200]

Maybe i've missed something but, have you tried to run the engine since all this happened?

[irishluck]

yes and no, ive tried to crank and after cranking for maybe 10 seconds it makes a weird noise.

Im kinda afraid to keep cranking until i find out whats going on

[FJ111200]

So this weird noise, is it a popping or something different like a fizz-click or crunch or clatter? 

[irishluck]

its been 2 days since ive messed with it so if I member right id say a  popping noise

[Travis398]

Got the whole bike back together and it started up fine

So i thought that the 3 and 4 wires were mixed up, so i reversed the two, tried to starting it and then heard big pop noise,

It sounds like it was running fine before you changed the plug wires. maybe you should change them back, and the noise will go away.

it will pop if the timing is 180 off.  remember one coil does 1-4. and the other does 2-3.

[irishluck]

It sounds like it was running fine before you changed the plug wires. maybe you should change them back, and the noise will go away.

it will pop if the timing is 180 off.  remember one coil does 1-4. and the other does 2-3.

well i did that and it wont start now and still pops ha

and as you say, 1-4 and other does 2-3, welll we might have another problem then....


and the reason why i switched them in the first place was cause it sounded like it was getting enough power like it really wouldnt rev up

[andyb]

Quick visual check time.

Did it backfire through the carbs and pop them off their mounts?

Cam timing is super easy if you don't have slotted sprockets.  The dots line up, or they don't.

Original problem was dirty carbs, dirty plugs, bad HT leads, or the like, most likely the first.

[irishluck]

no did not backfire through the carbs cause thats an easy issue, it didnt backfire at all, it just made a big popping noise, like something snapping

now heres another issue ive came across checking the cams and the timing chain.

book says to line the crank up to position number 1, ive done that.
Its says that cylinder one, which im assuming is when your sitting on the bike its on the far left of the engine, if so then i have an issue, the book says that the cam lobes should both be pointing outwards, mine are both inwards and the far right cylinder which im assuming is number 4 is pointing outwards.

2nd when i align the crank into position number 1 it says in the book that the in and the ex will align with the top of the cylinder head well in in is actually a tooth or 2 higher than the head and the cam is about 1 or 2 teeth lower than the cylinder head

any advice would be great here


edit:
the book also states that on the top of the cam there are 2 holes in the right side on the engine, and when in position 1 that the cams have a punch in them that line up to those holes, the EX cam lines up fine but the IN cam looks like also a tooth off or so.

[RichBaker]

If you are at TDC on the compression stroke, the lobes should point up, away from the piston.  Sounds to me like you're on the exhaust stroke.....  And you are correct in cyl numbering, left-most cyl is #1.