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Discussion Starter #1
Hi guys,

I have been trawling through the forums to see if my issue has already been discussed. It hasn't.

I have a 2014 Yamah Bolt R Spec, equipped with the V&H Twin Slash exhaust, VO2 Air Intake and the FuelPak LCD (this is the legacy version with various mode settings that you can input based on map). I bought the bike used with all that already on. My issue was that there was pronounced decel pop when going off throttle. This is how it acts; I go off throttle, heavy engine braking (assume due to fuel cut-off), reduced engine braking when fuel is restored, burble, pop, burble, burble, pop, pop, burble, POP! You get the idea. I went to the V&H website and downloaded a map appropriate to my model bike and the exhaust. The map was supposed to work fine with stock exhaust (except to run a little rich), and work perfectly with a free flow air intake. That reduced the popping very slightly. So I wrote to V&H and they sent me another map. I added that, and the bike smoothed out a bit (less jerky throttle response, but very slightly) but the pop was still there. I noticed that it is almost gone when I start my bike in the morning if the ambient temp is low. It comes back when the engine is warmed up and the ambient temp rises. I do not suspect any exhaust leaks as the pipes do not seem to get very hot.

My question is whether the engine is still running lean and if this is bad for it. Noob motorcyclist, btw.

Does anyone have an explanation of what the various mode settings on the FuelPak LCD do?

All help will be appreciated. Thanks in advance.
 

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Popping and backfiring is a very subjective thing.

My 650 has carbs and its all factory stock. I know they set it up to be as lean as possible, and I have not messed with the carbs.

If I wind the bike out and then throttle off, it compression brakes nicely all the way down to about 2000 rpm, then it will pop a little bit. If I crack the throttle open just slightly the popping stops.

Same in all the gears, that last 1000 rpm down to idle speed it sounds like snapping bubble wrap bubbles.

I dont think its really an issue unless the exhaust is loudly backfiring - BANG BANG! like gun shots. The easy way to see whats going on, next time you check your plugs, if its running a little rich they should be a little brown or even slightly black around the edges.

Google the images for spark plug condition - if your plugs look like the 'too lean' photos, then you need to worry about it.

Its hard to get the fuel injection map perfect for every possible riding condition. If the bike feels like its running well, and the plugs look like the 'good' photos, its probably good.
 

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Discussion Starter #3
Thanks KCW. I will try to record the sound. The pops are medium loud usually (louder than bubble wrap, unless you guys have some type of rock concert style bubble wrap heheheh), with a louder one just sometimes (still not as loud as gunshots, unless you use suppressors, hahaha). I will pull the plugs on the weekend to see the colour. I don't have a tach so can't comment on RPM but 2000 or thereabouts sounds more or less right.
 

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there are websites that will tell you what your engine RPM is for any given gear at any specific speed - some already have the drive ratios, so you just tell it what bike you have, and it lists the rpm vs speed table

but the important thing is, on my 650 for example - the compression braking sounds normal from 75mph in 5th gear, all the way down to about 30mph - then it starts to act up and pop a bit.

If it was snapping and popping every time I let off the throttle at 75mph, all the way down to 30mph, then I would be concerned.
 

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It's this just the normal EFI fuel cutoff to the injectors, cause you killed the throttle? There isn't any fuel map that can fix that.

You would be looking into an ECU flash that removes the throttle off fuel cut.
 

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Discussion Starter #6
Thanks KCW and Patrick. I will try to look out for the speed at which which fuel cuts off and when it comes back on. My issue is not the cutoff, it is the pop when fuel is restored.My Harley 883 does not pop like this. However, it has stock exhaust / intake and no fuel controller. I was wondering whether there is a map to modify just the setting when fuel is restored for no decel pop and keep the mixture richer when throttle is opened.
 

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Discussion Starter #8
I found the following instruction on the FAQ page for the FuelPak:

Q. My pipe “pops” when coming to a stop, what can I do to eliminate that?
A. The Fuelpak has a function which shuts off the fuel when decelerating. No fuel=no pop. Obviously the Fuelpak has to turn the fuel back on at some point or the engine would die. Not all popping can be eliminated, but this feature does lessen it. Mode 23 controls the rpm where the fuel is turned back on. Try lowering this by one number and see if it helps you. If you have done this and have gotten to 14 or your bike is stalling when coming to a stop, that is all you can do and you will not be able to lessen the popping without changing the pipes or installing quieter baffles. The popping is not harmful, just annoying.

I checked the setting and it was at 5 already. I can try bringing that number further down, so the fuel is restored at a lower RPM. Alternatively, I could raise the number to restore fuel earlier. Let's see...

PS: A friend rode my bike while I rode his Suzuki M109. He said he enjoyed the popping, heheheh.
 

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Nice work Inspector Baldilocks!
 

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Discussion Starter #10
if the V&H module can't give you a map that corrects out the fuel mixture, then your best options might be to switch it out with something else or get your ECU flashed.
Thanks bevo. I got the whole V&H set already installed on my bike when I bought it. I am getting used to the pop, and some of my friends actually like it. If I manage to confirm that the engine is not being damaged, there is no harm in keeping what I got. I got a good deal actually (for my country).
 

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I lowered my #23 fuelpak setting by one and it helped quite a bit. Maybe try going back up to V&H recommended setting on #23 and try working your way back down?
 

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Discussion Starter #13
not sure i understand this. most popping occurs on deceleration when you completely let off the throttle.
You are correct. The controller cuts off fuel when you close the throttle. After the bike has slowed down and the engine is at lower RPM, the controller starts fuel supply again, that is when the off throttle popping happens due to unburnt fuel in the exhaust.
 

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Discussion Starter #15
I lowered my #23 fuelpak setting by one and it helped quite a bit. Maybe try going back up to V&H recommended setting on #23 and try working your way back down?
So, although the documentation I copied and pasted says 14 as the lower limit, the V&H people sent me a recommendation of 5 for my bike, exhaust and air intake. I lowered it to 3 and here is what I noticed.

Bike started cold in the morning. Reduced engine braking (perhaps psychological), fuel restored earlier, no burble and pop till the bike warmed up.

Bike started in the afternoon when the temperature was about 33 degrees Centigrade (91 F). Immediate burble / pop, but I feel it was somewhat reduced from before. However, I do feel that the engine braking is reduced, which is not really possible as no fuel means no fuel regardless of restore point...

I think I will ride like this on Saturday over a longer distance including hilly terrain and then consider testing by going to 7 or 8, to see how the higher value works.
 

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Discussion Starter #16
It's 4 am and I woke up to get ready for my ride today. So far no takers, I may have to ride alone.

Yesterday the decel pop was back but intermittently. I noticed that the pop is more when hard off the throttle, but just some times. At other times, it would just sort of give the normal rev down sound (gently off the throttle). Let's see how the downhill sections feel like today. I did notice that the engine braking is a bit less on the new setting. As I rely a lot on engine braking on downhill I am curious to how the bike will feel today.
 

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Discussion Starter #17
UPDATE:

Rode up and down the hills in cooler temps. There was less decel pop on the downhill. The pop increased when the outside temperature rose. I haven't changed the settings again. Now that I have installed the KOSO speedometer, I know that the decel pop at mode 23 = 3 starts at 2000 rpm.
 

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This week I decided to fill my bike up with ethanol free regular gas, to see if the fuel efficiency would come up a few mpgs. Most gas here has 10% ethanol. I have another 20 miles to ride before I fill it up again to see how it did, but one thing that I did not expect is the bike runs noticeably better on the pure gas. The engine is smoother and it seems to have a little more power. I also think the bike is popping and snapping less than it use to when fully compression braking.

You probably do not have ethanol blend gas there, but the point is these bikes can be very sensitive to the fuel you are using. if you are filling your bike up at different places, you might be getting very different gas - and that will affect all the things you are trying to correct on your bike.

If you are getting a mix of regular octane and hi octane gas from one station to another, that will affect the fuel map on your engine. These fuel injected motorcycle engines do not correct the mixture based on the O2 sensor, they are almost completely going by the fuel map in the control module, just like a bike with carbs is going totally by the size of the jets.
 

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Discussion Starter #19
This week I decided to fill my bike up with ethanol free regular gas, to see if the fuel efficiency would come up a few mpgs. Most gas here has 10% ethanol. I have another 20 miles to ride before I fill it up again to see how it did, but one thing that I did not expect is the bike runs noticeably better on the pure gas. The engine is smoother and it seems to have a little more power. I also think the bike is popping and snapping less than it use to when fully compression braking.

You probably do not have ethanol blend gas there, but the point is these bikes can be very sensitive to the fuel you are using. if you are filling your bike up at different places, you might be getting very different gas - and that will affect all the things you are trying to correct on your bike.

If you are getting a mix of regular octane and hi octane gas from one station to another, that will affect the fuel map on your engine. These fuel injected motorcycle engines do not correct the mixture based on the O2 sensor, they are almost completely going by the fuel map in the control module, just like a bike with carbs is going totally by the size of the jets.
Thanks for the comment. I am filling up with Hi Octane fuel from various pumps. Another rider told me yesterday not use Hi Octane and 87 octane is enough for this type of engine (low compression). What is the advice on that?

Now that I have a tach, I guess I could play with the setting and see how they affect the rpm at which fuel is restored.
 

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I wouldn't use hi octane, but every pump is different and the rating is just a close avg.

The general method is, if it's pinging you have to low octane, and if it is sluggish on throttle, then the octane is too high. This is how I have always filled my sportbikes up. This being said, I can't really tell the difference between 87 and 89 in my vstar 950, but I have never attempted anything higher than 89.

Engine Pinging
 
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