back firing

[Tenman]

Went to take a ride yesterday. Fired my gen 1 up cold and it was back firing and idling erratic. I rode it 90 miles and everything was ok the rest of the ride. Killed it a bunch of times and it fired right back up. I went to take a ride today and it was doing it again. Bad. One cylinder was cutting in and out. It hasn't been washed or anything done to it since the last flawless ride. Any idea what parts to throw at it. There's no decent motorcycle shop within a 100 miles of me.

 

[Bill_C]

It could be a lot if things, but if I was going to start somewhere I'd pull the ignition coil and test the resistance between the pins, be sure to write them down. Then compare the readings across all coils. You're looking for one with lower resistance. That would be the one failing.
Ignition coils can fail slowly and almost always result in misfires in my experience. If you find one going bad, replace the lot because the others aren't far behind.

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[Tenman]

checked coil resistance Ok. In in the middle of spes. I didn’t really think that was going to be it though. One of my cylinders sounded like it wasn’t firing at all occasionally. It had 2 plugs per cylinder. I’ve ran it with one coil I forgot to connect before. It didn’t pop and backfire like it does now. It was just sluggish. Maybe it’s the wiring recall I haven’t done. But I haven’t seen anyone post there’s doing what mine is doing for the recall. Thanx for the recommendation though. I learned something.

 

[Squibb]

Clearly the wiring harness needs doing, if only to eliminate this as a potential cause of problems in future.
Presumably there are no codes showing in 'diag' mode.

Otherwise, can you identify which cylinder has the problem, maybe with an IR thermometer testing the headers. Then swop the coil sticks to see if the misfire moves to the other cylinder.

Then a few thoughts .........

When were the valve clearances last checked?
When were the plugs last changed?
Is the cap on the TB leaking when cold, then healing up with heat? They can perish with age.
Just to clarify, are we talking backfiring in the exhaust, often caused by an air leak in the system, or spitting back into the air box?

 

[Jlq1969]

How did you check the resistance of the coils?….did you do it with the coils out?…if you did it with the coils on, you should take them out…clean the contacts with the spark plugs and clean (if any), rust on the metal part around the coil pencil. If the resistance is fine, (it only means that the coil has the ability to accumulate and multiply energy), it does not mean that the discharge is coming out of the spark plug. If the discharge does not find a "clean" path to the spark plug, the discharge will be towards the engine, through the metal part that is in the pencil of the coil....perhaps the rust started a long time ago and ended for become resistive now….
If you decide to remove the plugs for inspection/cleaning…..DON'T PUT THEM BACK….just throw them away and put in new ones. Remember the nickel/zinc bath of the thread, the pressure of the washer, the position of the electrode towards the intake valves, depending on the washer and the tightening torque, spark plugs stuck in the thread and broken when trying to unscrew it, etc. , etc etc…..

 

[Bill_C]

As someone stated, it could be a vacuum leak at the throttle body. Could also be the wiring harness, as you stated. The fact that it only happens when cold eliminates a lot of possibilities.
You're in for a lot of visual inspections, unfortunately. Vacuum leaks could appear in a few places.
Personally, I am not convinced it has anything to do with valves. If they were too tight you'd know because it would be overheating from pre-ignition and pinging. If they were too loose you'd probably see it in the form of blueish exhaust. Of course, there are always exceptions to this rule and if you skipped your last adjustment or are quickly approaching your next one, it wouldn't hurt to check.

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[Tenman]

Looks like one of my coil wires ptobably wasn’t fully clicked on. I’m healed. Thanx for the replies.

 

[Bill_C]

Glad you got it sorted

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[Tenman]

I just took a 1 mile ride. It's back. It's missing on the left cylinder. Fixin to swap the coils around and see what happens.

 

[Tenman]

I swapped the coils. Still back firing bad and running on the left cylinder now (barely). I pulled the wires off one at a time with it idling. It had no effect until I pulled the far left one off and it died. I rechecked the coils with my dollar store multi meter. All n spec. Plugs look fine. Hmm. When I parked it a week ago. It was running fine

 

[Sierra1]

I swapped the coils. Still back firing bad and running on the left cylinder now (barely). . . .

So, coils got switched, and the problem stayed in the left jug?

 

[Jlq1969]

Start by checking the (+) of the coils with the multimeter. These are always hot when the key is in ignition. The signal (-) is the one sent by the ecu to discharge the energy in the spark plug. By having 2 coils per cylinder, you can disconnect 1, check the (+ permante in ignition), and you can connect a 12v lamp to the plug….and thus know if it arrives (-) from the ecu….I don't know if the cables will arrive , but you could exchange the plugs between the coils of the same cylinder….and thus rule out possible failures (is it the coil?…is it the plug?….is it the spark plug?….is it the harness?….is it the ecu?)

 

[Tenman]

Strange how things can go to shite sitting on a porch a few days. I took the coils out to check them. When it was idling. I pulled each plug wire off from right t to left. No difference until I pulled the far right one off. Got a little shock from that one before it died. It appeared to be the only one keeping it running. Im going to take it to have the recall done and a valve clearance check. I got 71k miles. They were in spec at at 26k

 

[Tenman]

I just got a call from the stealership. The guy told me I had 20lbs of fuel pressure and I need a fuel pump. Over a grand for a fuel pump replacement. I told him to hold up on that. I've cleaned the tea bag before. I think it took me a couple of hours to get the pump in and out. I called another dealer. He told me the book lists fuel pump replacement @ 2 hours and the valve adjustment would be $600. They wanted $571 a year ago. I called the original stealership back and told them to leave the fuel pump alone and do the valve adjustment. He told me I don't need a valve adjustment because it runs too good. He also told me. He can't do a valve adjustment unless they change the fuel pump first. WTF! I was quoted $564.30 a year ago. It's $940 now. I told him to do the wiring recall only.

 

[Bill_C]

Well, we call them stealerships for a reason. That sucks though.

I just checked yamahapartshouse.com (my go-to for OEM Yamaha parts) and a new fuel pump is $547... highway robbery.

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[Tenman]

$330 partzilla. Got one on the way. The stealership told me they replaced my plugs. They were allegedly fouled. I had just checked them. They looked fine. edit $465.67

 

[Tenman]

I see just the pump motor for $74.98 with a lifetime warranty Thinking about going cheap. Anybody done it?

 

[Mr. BR]

"Over a grand for a fuel pump replacement."
"He told me I don't need a valve adjustment because it runs too good."
"He can't do a valve adjustment unless they change the fuel pump first."
That's three strikes and they're OUT... meaning the OP should never return.... sheesh.
Mr. BR

 

[Tenman]

He said as of now. I owe them $161 For the diagnosis and spark plugs. They had me down for the gold star treatment. Not sure what that means. Oil, air filter and plugs? I told them specifically that I needed the recall and a valve adjustment. That’s it. It’ll be interesting to see how much more they want for the recall. I had my valves checked there 5 years ago. When I got there to pick it up. They wanted $150 more than the price I got on the email they sent me. I had to show it to them. Loewer Powersports in Alexandria La. Stay away. If you have a good mechanic. Count your blessings

 

[Reno]

There was a recall on the Gen ones with the wire connector that it gets wet it can shut it down and make it misfire. You might check your year and go to the Yamaha website under recalls and see if it’s in there. Yamaha will fix it for free under the recall