My VMax backfires a little

[Easydrifter]

I have a 2001 with a Kirker 4 into 1. I don't know any of the history on the bike but my suspicion is that they never rejetted the carbs after they bolted on the pipes. I will do a compression test and check valve lash when I get around to it but just want to ride it for now. It has 27,000 miles on it.. It's not too bad, the pops are not very loud more like a sputter at certain RPMs. Not looking forward to pulling the carbs and messing with them or paying some else to do it with unknown results. If I do find it necessary I'll wait till January when I won't be riding much anyway. Maybe just cleaning the carbs would help but how could I recognize if a jet kit has been previously installed? And what kit would be a match with the Kirker and stock air box? I'm not looking for more power (it has plenty for me already) I just want it to run as good as possible.

 

[DreamV4]

Exhaust popping should be probably called "forward firing" and exhaust leak is a common reason. Usually happens when you close throttle fast.

 

[Easydrifter]

Well it's not popping then, it backfires out of the exhaust pipe and not while rapidly decelerating. More when accelerating or running at at steady rpm in the midrange. Haven't been able to detect any exhaust or vacuum leaks although I wouldn't completely rule that out. Thanks for the input.

 

[02GF74]

At what mileage was the last service, namely new spark plugs, air and fuel filter?

What is the inside of the fuel tank like and colour of the fuel filter (only applies if it is transparent plastic).

 

[Easydrifter]

I changed the plugs and air filter right after I got it, a week ago. The plugs looked good a tan color, no black at all (maybe running lean). Haven't gotten to the fuel filter yet or peered into the tank with a light. Will be doing that soon. I got an oil filter for it will be changing that soon too. Meanwhile I'm having fun riding it in the hot Arizona sun.

 

[Fire-medic]

Remove a CV cap, then the slide, and compare the needle to these, which do you have?



I don't see the oil return hose to the crankcase filler, so I suspect you do not have the Dynojet Stage 7 jetting kit. You can use a pair of straight-jaw Vise-Grip pliers to remove the one security screw on each CV cap, you can buy a set of security screw tips from Harbor Freight, you can use a Dremel tool to cut a slot in the security screw head for a slot-head screwdriver (ensure the slot and the screwdriver are a snug-fit). Replace any carb screws you remove with same-sized allen-heads.

Security Bit Set with Case, 100 Pc. (harborfreight.com) $10

Carburetor overhaul experts from the forum, I've done business with all of them and they're worth every penny. OEM parts are what they use.

dannymax [email protected]

Sean Morley [email protected]

CaptainKyle [email protected]

 

[Easydrifter]

Thanks, I'll do that when I get a chance. The covers were off of the idle mixture screws but I suspect that's all they've done to the carbs. It will be interesting to compare my needle to the ones in your photo.

 

[Easydrifter]

The backfiring problem pretty much went away when I replaced the little cover on top of the air cleaner (it was missing when I got the bike) and put a new fuel filter on.