BACKFIRING. I'm shooting flames here!

So thanks again to all who helped me solve my starter chain guide problem.

I removed the oil pan and stripped off the gasket and oil crud using a bit of carb cleaner.

Was that dumb?

Now my bike won't start but when it turns over it backfires once. The first time I got flames and it sounded like a .44 magnum. As cool as it is to have a red, fire-shooting Seca I'm pretty sure the novelty will wear off when the neighbours call the cops.

KAPOW!

What should I do?

As always, thank you ahead of time.

 

Make sure you have the plug wires on the right cylinders.

 

Is it possible you did something to the wires from the pick up coils on the left hand side of the engine? Sounds like your getting intermittant ignition.

 

Having a similar issue here with a new project ... what would cause blowback through the carbs?

 

Plug wires on wrong or coil plugs switched for some reason. Too lean mixture . Valves not sealing. to name just a few.

 

I know it wasn't plug wires or the coil plugs. Those are stock and labeled.

This happened at one point on my xj650 and now another project is doing the same thing. On the 650, it was definitely the carbs. I haven't really gotten into the new project, but just know that is one of its problems.

Lean mixture is a very good possibility in this case.

 

That gives me some places to start.

Thanks rpgoerlich and MN-Maxims. I'm 99 per cent sure the plug wires are correct but will double check tomorrow. I'll also check the pickup coils.

Also thanks tumbleweed_biff. Lean mixture... that means too much air? I'm getting blowback through the carbs as well. Also, I'm not sure if I trust the integrity of the intake manifolds.

The only other thing I did on the left hand side while I was in there was manually turn the crank a few times to dislodge a bit of chain guide. The pickup coils are above and to the right of the crank case, right? I'm pretty sure it's untouched but I'll check that too.

Important to note, it was running fine before I removed the crank case cover, oil pan and exhaust pipes. The last time the bike ran it was also considerably colder outside, like - 15 celcius... i don't know what that is in Fahrenheit. Bloody cold. Maybe need to tighten things up, given cold-hot expansion of rubber.

Thanks all.

AA

 

-15C is a balmy +5F.

Isn't timing the classic cause of backfire through the carb? To get a true backfire you have to have an intake valve open at the time the plug fires. This would also explain the flame thrower out the back phenomenon. An exhaust valve open when one or more plugs fire.

Is it possible you have slipped a tooth or two cam chain on the cam?

Moved a plate associated with ignition timing(help me here guys).

Something to think about anyway.

 

In my case, it wasn't timing as the backfiring in the exhaust as well as the blowback through the carb (which caused a fire once) was resolved when I got the carbs completely spotless and working properly, including being able to "clunck" (which they didn't previously).

The one thing I can think of is that if it is too lean, it doesn't burn fast enough so that it is still burning when the intake valve opens perhaps?

 

Well, looks like I'm not going to have a chance to find out for a while.

I tried swapping the intake manifolds with some new ones I had lying around and busted a bolt on the engine block. I've tried all the tricks and can't get it out. Looks like I might have to go the route of Hellicoil.

Will keep you posted. Anyone have tricks for pulling out an impossibly embedded snapped bolt?

 

Sounds like it will keep cagers from tailgating you at night lol

 

Tricks for getting out an impossibly embedded snapped bolt?

From what I understand, heat it up with a heat gun, then use an easy out - you drill into the end of the bolt then use an easy out - kind of a backwards mandrill bit. Work slowly so the bit has a chance to bite and not slip.

Failing that, you drill through the entire bolt and then retap the threads ...

 

I know it's not typical and a bit crude but... I cut out a bit of the head then used jb weld to fasten a bolt backward, I took my time and made sure everything lined up. This was my only economical route after trying to drill. I find drilling to be tedious as I kept "running" off the hardened steel of the bolt and in to the aluminum, giving me a pretty crooked hole.

Like I said crude..

 

Im with Wamaxim on this one, timing retarded together with over rich fuel mix building up in the mufflers.

 

The Bike might have the wrong Igniter.
It happens.
The Rotor's get bent, too by somebody using it to jack-over the engine.

If the Contact Points retaining ring hasn't been altered ... the Dynamic Timing should not be affected.

Use a wooden dowel or a length of fiberglass rod and Bring the #1 Piston to TDC. Check all the Indicators to see that the Bike IS Timed right.

 

Save your self the trouble of ruining the head. Just pull it now and send it into the machine shop so that it gets drilled staright and the helicoil installed properly. You can not drill that head with a hand drill. It should be put in a head bench and drilled by machine. (like a drill press) One of the other members found out the hard way and have not heard yet but it sounded like by the time it got to the shop it was a mess. Hope it works out for you.

 

Thanks all,

So Wamaxim and XJwizard, what might I do now?

If I've slipped a tooth on the camchain, how would I know? There were pieces of what I believed to be starter chain guide inside. Could more of that be "retarding the timing" as wizard commented? Regarding rich fuel mixture, should I be adjusting with the mixture on the carbs? How else could it be getting too much air?

Thanks all,

Apato.

 

It can be getting too much air if the intake boots from the air box have any leaks/aren't mounted properly. With the engine running, spray some ether/starting fluid around each of the carbs, one at a time. If you get a change in idle speed, you have found your leak.

 

Problem 1

Air leak; Manifolds:

The Manifolds don't act like they are leaking until there is some Vacuum on them.
Spray the Flat Mating Surface of the Manifold to the Head with Carb Cleaner of Starting Fluid.
IF THERE IS A LEAK.
Remove Carbs. Use High Temp Silicone.
Seal the Manifold to the Head by running a Bead all around the Manifold.
If you put some Armoral on a small sponge ... you can moisten your finger on the sponge and the sealant wont stick to you.
SEAL THE MANIFOLD TO THE HEAD LIKE A WINDOW PANE IS GLAZED TO THE WINDOW. CUT-OFF THE AIR FLOW. ALL-4.

Skipping a Tooth:
Not Likely.
Off a bit. Maybe.
Move the Crank to Top Dead Center on the Number-1 Ignition Stroke.
Put a flashlight on the open spark plug hole so you can see the Piston Crown as it rises on the stroke.
Touch the Crown of the Piston with a wooden dowel or a Bic Pen and get the Piston exactly at Top Dead Center.
Look at the Indicators on the Cams.
Those Indicators should be LINED UP PERFECTLY with the Indicator on the Camshaft Thrust Cover Bridge.
The Indicators NEED to Be lined-up [ --><--] = Perfectly.
Not so.
Re-time the Bike.
OK = Not a timing problem.

 

Rick, if the timing is off wouldn't one of ther following scenarios exist?

Timing off one or more teeth. Caused by tensioner not applying tension to chain allowing chain to skip over a tooth on a sprocket which will severely alter timing.

Timing off less than a tooth. Caused by worn out timing chain/sprockets or tensioner not applying sufficent tension to chain causing timing to be off between lower and upper sprockets.

How far off can the timing be before you put a valve through a piston on these engines?

Loren

 

The Crank and Cam Sprockets are rated for beyond 60,000 miles.

The Chain is rated for 60,000 before an R/R.

I doubt that that Timing is really going to be the issue.

 

sooo.... i just cleaned out my carbs and rejetted for the open headers and pod filters... however, the bike backfired like a canon. My ears are still ringing...

The bike was in running condition but after putting on these pods, removing the mufflers on the exhaust and rejetting... somethings happened? Any ideas?

 

Loosed the PLATE that supports the WHOLE Points Assembly.
Move the WHOLE Plate the Width of a Dime --> Clockwise.

Tighten the Screws enough to allow the Plate to be moved with some friction on it.
Keep one screw tight to keep the Plate from "Getting Away"
Start Bike
Loosen Screw.
Use screwdriver tip to move whole plate PLUS -or- Minus 3 Degrees either way until the Bike Idles without backfire.
Test throttles after backfiring is solved.
Advance or Retard the Spark for your style of riding.

 

Here are two responses from another thread that may be of interest to you. One is from the Great Rick, the second is from ZsoltK :

1)I wouldn't exactly say, as Keven does: "Its pretty simple to get it running like a top."
My personal opinion, only ...
There's not anything easy about it and running like a top is out of the question.
You'll have to make a compromise according to how you ride the Bike.

Idle --> Off Idle --> Mid Range --> Wide Open Throttle.

The ideal situation is for the Bike to Idle and be able to get-out of the hole.
Then, accelerate through the Mid-range to Wide Open without suffering a complication in the Mixture that causes a Hesitation or an Unsatisfactory Mixture Condition that might be damaging.

Initially, upon abandoning the stock configuration for Pods the CONDITION is that the Bike is running TOO LEAN. Far too much AIR is introduced to the Mixture to have the Bike run right or run with a Critically Lean condition which would be harmful to aluminum parts.

This sets-up the first re-Jet.
A situation which needs to be corrected by adjusting the FUEL side of the Air~Fuel Ratio to correct an equation for which the:
(X~Fuel + Y,4~Air)= Z~ Ideal Ratio is maintained by Fuel Jets and a Finite (But unknown value) of Cubic Feet of Air per Minute (CFM) drawn-in through the AirBox Inlet and shared by the four Carbs.

Since the CFM is exponentially increased by PODS (along with introducing turbulence and an eliminating the stream shaping of the AirBax Boots which act as Velocity Stacks) a second Compromise needs to be considered.
The INTAKE AIR at each Carb does not have the same effect "Flowing" across the Top of the Emulsion Tube Outlet.
Less FUEL is drawn-up requiring the MAIN FUEL Jet sizes to be increased.
Although the MAIN JETS sizes are very easily altered to ALLOW a greater "Flow" of Fuel ... The Problem is actually getting the increased volume TO Flow up into the Intake Air Stream.

To achieve an Increased "FLOW" ... The Diaphragm Needle Height needs to be adjusted --> ALONG WITH --> an INCREASED Volume of MAIN AIR Surrounding the Emulsion Tube and that Air's ability to be Drawn through the Emulsion Tubes Metering Ports.

Without modifying the Emulsion Tubes and Increasing the Main Air Supply the Air Fuel Mixtures and Jetting are achieved through experimentation and guess work.

Most people who try it are still guessing.

2)Hmmm ... a few weeks ago I started to write my thoughts on pod filters / jetting / aftermarket exhaust. It was a long article then I deleted the whole thing because it was full of too much detail. But in essence, you can't tune your engine properly with the pods. Engine tuning is a compromise but pods are designed for racing.

It's impossible because the whole system was set up to match all the parts. Intake, filters, carbs, rubbers, displacement, back pressure, etc. If you're installing pods then you ruin this fine balance. The result? You can have a kick ass top end (mine is running #132 jets at the moment, but she can live with #136 jets as well) but in this case below 6K she won't perform well.

Or you can have a decent low end and midrange but you will loose power at top. The best main fuel jets for low end / midrange in my case are the #124. Note a thing: I'm talking about 12 jet sizes. Let's try to make the proper compromise.

Not possible. If I don't want her run lean at top, I have to use the larger jet. But in this case she runs way too rich at the midrange. Ok, let's tune for midrange ... then she's running way too lean at top. What can I do? Acceptable midrange with a bit lean condition at top. In other words: I'm loosing some of the potential of the engine. However, it's still more than the original.

On top of this, you have to change the air jets. All the air jets. And you have to change the needles, diaphragm springs, probably you have to drill the vacuum holes in the slides and finally you will realize it can't be done properly. You can achieve a good 80 or 90 percent but not 100. Why?

Because this engine with those carbs are designed for a compromise. If you're putting on pods you push the engine to the racebike territory where low end doesn't matter. Top end, that's the only important thing. But we're riding our bikes every day and we don't using WOT too often. If you do ... go for pods. If you commute on her don't go for pods.

Yep, a stock bike can run with pods without rejetting but in this case she runs lean. No question about it. Did it, seen it.

Well ... one more thing. It is possible to tune them with the pods. But you have to install a fuel injection system on your bike. Otherwise ... those carbs are not able to serve all the needs of those engines when running on pods. Remember, you can achieve a good 80 percent but not 100.