Backfiring into airbox and high idle.

[Kratos]

I just bought an 07 VMAX with only 1000 miles, so it probably didn't get ridden too often. I didn't see any other posts that had all these specific issues.

Issues;

1. When warm, as soon as it fires up, it immediately jumps to 4K rpms and stays there for quite a while. Sometimes it comes back down to 1K, sometimes it doesn't.

2. If/when idle does come down to normal, I can hear it backfiring into the airbox every so often. When this happens, the idle shoots back up again. Sometimes it is a large jump and sometimes it is only a couple 100 rpm.

3. While riding, when I pull in the clutch while coming to a stop, it will again jump up to 3K - 4K rpms. I have to use the clutch to keep the rpms down.

4. Idle speed screw does not seem to effect it much. I am able to turn it a couple full turns without seeing a noticeable change in rpm. I did notice that if I turn the idle screw down far enough, the high idle issue seems to go away, but it won't stay running on its own.

Things I have done so far;

I have made sure the choke is not on.

I have added some B-12 Chemtool carb cleaner to the fuel, I have only been able to put a little over 30 miles on since adding the carb cleaner.


Any ideas???:ummm:

 

[maxcruiser]

Lean condition, probably due to dirty jets/circuits , especially idle circuits.

Have a look in the VMF Links for the shotgun or peashooter procedures to clean them - just hit the VMF Links icon above and you'll find it.

Mike

 

[Thevmaxrider]

+1 Mike!! It does sound like the bike is lean.

 

[dannymax]

Here's what Maxcruiser is referring to. Prolly well worth a try, it did wonders for my bike.

http://vmax.lvlhead.com/tips/shotgun.htm

 

[Kratos]

Will do, thanks for the info!

 

[lankeeyankee]

Pick up a can of Seafoam at your Auto Parts Store.

 

[Redbone]

Pick up a can of Seafoam at your Auto Parts Store.

Yep, just the threat of having a can of Seafoam has fixed many problems from bobbles to wobbles on Vmax's.... and their owners! unk:
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Easy Lankee, I wuz just goofing!:rofl_200:Look at the picture below and count to ten . . . . . . . . . . see there all better now!

 

[maleko89]

Yep, just the threat of having a can of Seafoam has fixed many problems from bobbles to wobbles on Vmax's.... and their owners! unk:
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.
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Easy Lankee, I wuz just goofing!:rofl_200:Look at the picture below and count to ten . . . . . . . . . . see there all better now!

Redboner, went to Hooters and asked if they knew a Redbone. They asked, "Brian"? lol

 

[Redbone]

LOL, I bet it was...umm, you know the girl with the tig 'ol bitties!

 

[Kratos]

:bang head: I now have a set of the slip-on Supertrapp mufflers with 8 discs and open end caps, as well as a K&N air filter installed. Now that I can hear the exhaust, I have some more information about the problem. I have run SeaFoam through the bike and the issue hasn't seemed to go away, it may have gotten only slightly better, but that is probably more of just wishfull thinking.

When the choke is on, it will backfire through the carbs quite a bit and a little through the exhaust. Once I close the choke, it pops and crackles through the exhaust alot, but not as much through the carbs. Sometimes with the choke off, it will backfire through the carbs, then die. Also when I blip the throttle, it hangs up in the RPMs rather than coming down right away. To me, that would indicate a lean condition, but I'm at a loss as to how I can tell which carb is running lean, or if they all are.

I have the fuel mixture screws turned out 3.5 turns. I tried to sync the carbs as best I could, but the bike still has these issues. I did notice when syncing the carbs that when I unplugged the vacuum hose from the right rear carb, there was no change in the engine idle speed, when I unplugged each of the other 3 hoses, one at a time, the bike dropped in idle speed to the point of dying if I didn't get the hose back on soon enough. There was enough of a vacuum on the right rear carb to sync them though, so not sure why that particular one did not effect the idle speed when I unplugged it.

I have not tried any of the carb cleaning methods described in the forum yet. That is my next step, just hoping someone else has had this issue, and can let me know that it is just a matter of cleaning out the carbs. After all, it's a 2007 with barely more than 1000 miles on it, I'm hoping there is nothing seriously wrong with it.:bang head:

 

[maxcruiser]

Sounds like dirty low/idle circuits - try the peashooter or shotgun method of cleaning them - check the VMF Links icon above for the intructions on how to do it - if that does not work - the carbs will have to come out and be taken apart and cleaned manually.

Mike

 

[Kratos]

Thanks Mike, I'll give it a shot.

 

[shawn kloker]

Sounds like dirty low/idle circuits - try the peashooter or shotgun method of cleaning them - check the VMF Links icon above for the intructions on how to do it - if that does not work - the carbs will have to come out and be taken apart and cleaned manually.

Mike

Mike is right.Do the peashooter and shotgun.Get everything opened up again then resync the carbs.

 

[Kratos]

unk:
Yep, that did the trick. Runs much better and the RPMs don't hang after the throttle is blipped. Thanks for the help!

:ummm:
Now the bike pops and crackles quite a bit on deceleration, and is a bit rough when cruising with the throttle partly opened. Full throttle and idle seem to be good. I synced the carbs, but it did not fix the issue. I have removed some of the discs from the Supertrapp exhaust, thinking that 8 discs with the open end caps were causing it to run too lean, but that did not help either. So I am now running the slip-ons with only 4 discs + open end caps and a K&N air filter. I have the fuel mixture screws 3.5 turns out. I wouldn't think just the slip-ons with open end caps and K&N filter would make it run lean enough to need turn the fuel screws out any further, but that is probably what I will try next. Any ideas?:confused2:

 

[Kratos]

Well, I turned the fuel screws out 4.5 turns and the crackling and popping has gone away on deceleration. Still is rough during steady cruising at part throttle, so it sounds like the stock needles are set too low. I have seen on this forum that stage 1 jet kits are a waste of $$$, but appearently I need some sort of fuel change. I would think that if the K&N filter and Supertrapps made the idle and part throttle too lean, I would also need larger main jets. Does any one have this same setup that could give me an idea of what size main jets and needle position to start with? (Dual Supertrapp slip-ons with 4 discs + open end caps, K&N air filter, and air box Y removed).

 

[veebooster]

Just a thought...double check for a leak at the slip on joint. When I had trapps I had to reseal them a couple times. Could always tell when it needed to be done by the snaapping and popping on decel.

Dale #2592

 

[shawn kloker]

You do not need bigger jets. I think that you still have something thats plugged up somewhere. Or possibly that you have a airbox boot,carb or vboost boot that is cracked and sucking air.

I would ride it some more with seafoam in the gas. It could take a little while to clean the gunk out. It also seems like one of your PAJ1 holes is plugged or gunk on the screw tip. Did you blow compressed air and carb cleaner into each one after pulling the screws out?

 

[Kratos]

Yes. I kept alternating carb cleaner and compressed air until I was able to see either the air, or the carb cleaner coming out of all the holes. The Pilot Air Jets did not take long at all to see a strong stream of carb cleaner when squirting it into Pilot Air Jet #2, or visa versa. The idle screw mixture holes were a different story, it took several alternations of air and carb cleaner to see anything coming out of it when squirting into Main Jet Air Bleed, or visa versa.

The bike idles well, pulls pretty hard at WOT, and I was able to sync it easily. I bought the bike used and it has run like crap since I got it. It is a 2007 with only 1K miles, so I imagine it sat for the better part of its life. So since it has never run well, I don't have anything to compare how it runs now to. I know the difference between now and before I cleaned the carbs is like night and day.

The reason I am leaning toward a jet kit, it that in talking with Supertrapp, they seemed to be very sure that by using the open (off road) end caps, it could cause the bike to run lean. I understand why you wouldn't need a jet kit with the closed end caps, but the open end caps create an almost straight through exhaust flow with minimal resistance, compared to stock. The other reason is that, even though the bike ran poorly, it did not have this issue with the stock exhaust and air filter. Steady cruising at partially open throttle was fairly smooth.

 

[maleko89]

Supertrapp is wrong, no jet kit needed. I ran the same setup and the only things I did was smaller main jet, mixture screw adjustment and sync.

Since it was sitting I'm betting a pilot fuel jet is the culprit. Being gas sucks these days as far as quality it doesn't take much sitting to clog those small holes.

 

[COP RUNNER]

Supertrapp is wrong, no jet kit needed. I ran the same setup and the only things I did was smaller main jet, mixture screw adjustment and sync.

Since it was sitting I'm betting a pilot fuel jet is the culprit. Being gas sucks these days as far as quality it doesn't take much sitting to clog those small holes.

maleko89 , IS RIGHT !!!! I RAN SEAFOAM THROUGH MINE & IT WAS LIKE MAGIC ! unk: