One cylinder "popping"

josephjhaney · Oct 16, 2014

I have one cylinder that at idle and cruise will pop a bit, and when the bike is warming up, it only really fires occasionally, once the bike warms up it is better, but still not quite right.

When I hit the bike hard full throttle open, it's fine, runs perfect, but on cruising around 2-3k, you can tell that cylinder is still firing and then missing. It's one of the two left cylinders, and I've done zero diagnostics so far, since the bike runs well enough, but it's going to start pissing me off the longer it goes on.

So....

Should I start with some sort of carb cleaner? Or is it just that the carb is out of sync, and I just need to get one of those sync tools and start there? My initial plan was to take it to the local Yamaha dealer this spring and have them sync it all up, but I figure why not check here and see what you all think.

Joe

josephjhaney · Oct 16, 2014

Oh, also, when the bike is warming up, if you hold your hand over the right pipe, you can feel the bike firing on both cyls, when you do the same over the left, you get a POP pop pop pop POP pop pop miss miss feel. It's hard to explain, but you can def tell the left isn't firing every time.

I guess I should check the plug too, could be a fouled plug, but I would think that would hinder the wide open throttle too, and it does not. Really seems like lack of fuel....

Joe

alorio1 · Oct 16, 2014

Try backing your mixture screws out to see if it changes. The shotgun may help also. Here is a link to the website that explains it....and there are LOTS of pics, and if you get lost...or have anymore questions...dont hesitate to ask. Adding some Seafoam to your fuel may help the problem also. It sounds like those carbs have a plugged idle circuit actually.
http://vmax.lvlhead.com/tips/shotgun.htm

sdt354 · Oct 16, 2014

+1, what Joe mentioned is one of our more common issues. I recommend buying a sync tool and doing your own work. Just some basic tools and this forum are enough to get most people pointed in the right direction. Even a good service providing dealer charges a lot of $$. And the work done is questionable at many stealerships. I'm pretty sure their are some members out your way. Getting to know them is beneficial. There's nothing like riding with other Vmaxer's.
Steve

josephjhaney · Oct 16, 2014

Ok, I'll start with a little seafoam and playing with the idle mixture screw a bit. I guess I'm going to need a carb sync tool, amazon has one that has pretty good reviews.

alorio1 · Oct 16, 2014

Carbtune is what most members buy and use, I've had mine for years and no problems. It will pay for itself on the first use, most dealerships will charge more than you will pay for a Carbtune. http://www.ebay.com/itm/CARBTUNE-PR...221576213934?pt=Motorcycles_Parts_Accessories

Traumahawk · Oct 16, 2014

From what i remember on the morgan site....they have a lifetime guarentee. If you have a problem for any reason....get back in touch with them.

Sent from my PB99400 using Tapatalk 2

Mr. Max · Oct 16, 2014

Also check your fuel levels of each carb, might be one carb too high.

Coffinator · Oct 17, 2014

I've had the same issue since i bought the bike. Do you have a stage 7 kit installed?

josephjhaney · Oct 21, 2014

Coffinator said:
I've had the same issue since i bought the bike. Do you have a stage 7 kit installed?

I don't know if I do or not. I bought her used, and while she does have a Voo-Doo 4 into 2 on her, I don't know if the carbs are stock or not. The airbox is stock, and from what I understand that's usually not the case if the bike has been jetted.

Joe

dannymax · Oct 21, 2014

Not uncommon at all to see jetting changes under a stock airbox, normally see a K & N filter tho.

Traumahawk · Oct 21, 2014

Yep....I had rejetted mine, also had stage 1 needles, had a K&N filter with the Y removed.

josephjhaney · Oct 21, 2014

Traumahawk said:
Yep....I had rejetted mine, also had stage 1 needles, had a K&N filter with the Y removed.

Mine still has the stock foam filter, and the Y is still present. Other than taking it to someone who would know and having them tell me, I don't know of another way to tell if it's been jetted. It is odd that he would dump the cash into a voo-doo and not jet to match it.

Traumahawk · Oct 21, 2014

But....first things first....did you do a shotgun....and sync the carbs?

josephjhaney · Oct 21, 2014

Haha, no, I'm running a nice dose of seafoam though it first, just to see if that clears it up. If that fails, then it's on to the next step.

Joe

Fire-medic · Oct 21, 2014

There are posts & probably stickies on the different needle shapes. All you need to do is open 1 carb diaphragm top to compare. A quick look- I think the USA needles do Not have adjustable c clips on them. Only 1 groove. Compare the needle to the online pics. I think I saw one w/stock, Dynojet, & Factory Pro needles in different 'stages' as applicable. Not sure about Morley's needle shape.

TheFleshRocket · Oct 27, 2014

josephjhaney said:
Mine still has the stock foam filter, and the Y is still present. Other than taking it to someone who would know and having them tell me, I don't know of another way to tell if it's been jetted. It is odd that he would dump the cash into a voo-doo and not jet to match it.

Stock filter is paper--if yours is foam, it's aftermarket.

I've got a Voodoo 4-2 on mine as well, but it's jetted with a K&N, and which was misfiring between 5-7K RPM. Shotgunning and tons of Seafoam had no effect. The K&N was over oiled and the extra oil gunked up the pilot air jet (the one accessible from the top of the carb, not the one under the vacuum diaphragm) on carb #2 (left side rear). I augered it out with a carb cleaning tool and that helped a bunch, but recently I noticed that it still wasn't perfect. I ended up pouring K&N filter cleaner down the PAJs while the bike was running. (That stuff cleans the oil off of the air filters super quickly so I figured it would do a good job on carb passages gunked up with filter oil.) That helped noticeably, and the problem is now almost completely gone--gonna get some more K&N filter cleaner and have another go at it.

I've still got a pop at idle, noticeable out of the right side muffler, so it's coming from #2 or #3 (right side front). I figure the popping is unburned fuel exploding in the exhaust, so I probably ought to lean out the idle mixture screw on 2 and 3 (one at a time) and see if that helps. Pretty sure I set them all at 2.5 turns out.

josephjhaney · Oct 27, 2014

TheFleshRocket said:
Stock filter is paper--if yours is foam, it's aftermarket.

I've got a Voodoo 4-2 on mine as well, but it's jetted with a K&N, and which was misfiring between 5-7K RPM. Shotgunning and tons of Seafoam had no effect. The K&N was over oiled and the extra oil gunked up the pilot air jet (the one accessible from the top of the carb, not the one under the vacuum diaphragm) on carb #2 (left side rear). I augered it out with a carb cleaning tool and that helped a bunch, but recently I noticed that it still wasn't perfect. I ended up pouring K&N filter cleaner down the PAJs while the bike was running. (That stuff cleans the oil off of the air filters super quickly so I figured it would do a good job on carb passages gunked up with filter oil.) That helped noticeably, and the problem is now almost completely gone--gonna get some more K&N filter cleaner and have another go at it.

I've still got a pop at idle, noticeable out of the right side muffler, so it's coming from #2 or #3 (right side front). I figure the popping is unburned fuel exploding in the exhaust, so I probably ought to lean out the idle mixture screw on 2 and 3 (one at a time) and see if that helps. Pretty sure I set them all at 2.5 turns out.

Wow, you guys are awesome, that's such a great amount of info! I have narrowed it down I can hear it coming from the left side of the bike, and it's the left muffler that I can feel isn't firing correctly (popping etc) so given that I hear it "chuffing" (for lack of a better word) back into the airbox, and popping out the left hand muffler, both on the left side of the bike, I think I have it narrowed down to the front left cyl (since that's the one that routes back the left side of the bike from the left). Now to just figure out what's up. I have run 1/2 a tank of gas though with the seafoam with no change as of yet, so I'm thinking that particular quick fix might not work with this instance.

I'll keep you all posted! (OH, and it IS a foam air filter, so maybe it does have some jetting....)

Joe

robmac · Oct 28, 2014

I had the same popping, not quite firing issue but on the right exhaust. Got carbs rebuilt by Dannymax and it sorted it (I replaced all the intake rubbers too while I was there). I tried the shotgun and fuel additive and that had little to no effect.

Is the gas coming out of the exhaust cooler on one side?? Mine was at idle but all was fine once the revs rose.

robmac · Oct 28, 2014

In addition to that I got my Morgan carbtune kit delivered today. My carbs were waayyy out of sync. Such an easy job too, every VMax garage should have one.......or access to a mate who does lol

One cylinder "popping"

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