Lull in acceleration after slowing down from 90 plus.

Discussion in 'Carb/Tuning' started by Geoff Lewie, Oct 15, 2019.

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  1. Oct 15, 2019 #1

    Geoff Lewie

    Geoff Lewie

    Geoff Lewie

    2003 MAX @ Continental Divide Supporting Member

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    I have had and modified multiple bikes since I started riding in 1974. I have had three Maxs. First 2 new. The present one is a used 2005 anniversary editon. My second was one too. I had to do a full carb cleaning and rebuild as well as fork seals and other refresh needs. Just put a Supertrapp set of pipes on it.

    Open with no silencer with the engine mods a smoking second gear shift. Runs similar to my 2003 which was a 160 mph beast. Here's the problem. With the silencer discs, 20 each side to allow for engine mods coming off over 100 mph and then speeding back up the Max has a lull like it is running out of gas and then picks back up. Obviously it accelerates more genteelly, but without the silence disks it rages with no hesitation. I have never experienced this sort of lull in pickup on any other except running out of gas. Replaced the fuel pump some time back and diaphragm/slide springs. Cut them experimenting (worked great on my 2003). Obviously the CV carbs with the change in back pressure could have some effect but still have not experienced that before. I have not actually started to test for answers yet. Looking to see if anyone has any suggestions.

    Mods: it has similar to a "stage 2 dynajet carb setup with 155 mains". Stock main is 152; T-Boost, Nology wires, K&N air filter and the pipe. Plus a number of tweeks to improve the handling as I did to my other 2. My 2003 had the same except stock pipes drilled to allow more flow with the cover disk riveted back on and It was a 100mph wheelie machine, (I did not buy a set of headers then because Kerker, my fave, did not allow center stand, others were too loud. Member of VMOA for years and experienced a lot of pipes at ralleys). Now of course this does include 17" rear wheel with z rated tire...

    I appreciate any suggestions.
     
    Last edited: Oct 17, 2019
  2. Oct 15, 2019 #2

    Fire-medic

    Fire-medic

    Fire-medic

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    What's your main jetting, stock? You might try leaning it out 1 or 2 sizes. Make-sure the K&N filter is clean. At 2,900 ft above sea level, you could safely do this.
     
  3. Oct 15, 2019 #3

    Geoff Lewie

    Geoff Lewie

    Geoff Lewie

    2003 MAX @ Continental Divide Supporting Member

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    No, it has stage 2 dynajet kit. Main jet is 155. Needle is set 2 slots down.
     
  4. Oct 15, 2019 #4

    Geoff Lewie

    Geoff Lewie

    Geoff Lewie

    2003 MAX @ Continental Divide Supporting Member

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    Thanks for the suggestion. It is a equivalent to a stage 2 Dynojet kit with 155 mains. Leaning it out would make the problem worse would it not. And as I said, with the silencer plates removed there is no hesitation plus it gains about a 20% hp bump, very responsive and where I want to be there. But with the silencer plates a lull after accelerating off a high speed slowdown. Very strange effect. The optimum is without the silencers, and that is excellent. Just with the added back-pressure of the silencers is the flat spot in re-accelerating. The K&N has very few miles on it since the last cleaning, but perhaps too much oil. I will look at that when I get back on it.
     
  5. Oct 16, 2019 #5

    sdt354

    sdt354

    sdt354

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    With stock header pipes, I'd not venture into so many carb.changes. The 2nd needle groove from the blunt end is kind of lean, if the rest is set up normally. 150 main would be more appropriate. IMO.
     
  6. Oct 16, 2019 #6

    Traumahawk

    Traumahawk

    Traumahawk

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    Can you post a pic of the needles? There is only a stage 1 kit, or a stage 7 kit of the Vmax. I will assume that it is stage 1. With that you should go atleast 150's with needles in the first clip from the blunt end. You might even go 147's.....because the stage 1 needles are richer than stock.
     
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  7. Oct 17, 2019 #7

    Geoff Lewie

    Geoff Lewie

    Geoff Lewie

    2003 MAX @ Continental Divide Supporting Member

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    Thanks all for the info and refresh of old memories. Please excuse me as I am a bit chatty and have lived my bikes for over 45 years. I worked my way through my undergraduate as a Honda certified tech so I have some idea about this. I call it a stage 2 dynajet kit because I did it myself. I have no reason to buy kits. I have for done it myself for over 40 years. I modified these carbs in 2008 and 4 other mods then. One, most people do not know is Nology wires. These are sparkplug wires that were simular to an ACEL ignition coil on a car. They have capacitors in the wires and boost the stark like surface gap plugs in a Kaw H1 or H2. Just using the wires suggest one to increase main jet a size or 2 and change to non-resister plug. They honestly add about 10 horses. They really are a dramatic uncommon inexpensive upgrade, a C-note. Really make a seat of the pants difference accompanying carb rejecting, with exhaust upgrade, K&N, T-boost for relativity a small Investment.

    I did this over 10 years ago this last one. Did that along with numerous other upgrades to the previous two. Some of the settings I am fuzzy on. When I rebuilt the carbs I did not look at the mains. The problem was the slow and idle circuits. Idle was not cammy or cool like the Max is normally. They have gotten gummed up. Replaced the needle jets and seats and the carbs needed a good syncing. I had a set of mercury sticks but the mercury spilled in a move years ago. So I bought some gauges.

    Traumahawk, you are right I would say and they are most likely are 150s; 125.5 are stock. But since I did that I probably have not put 5K on it and for then for 6 years almost never road it due to the ex-wife who sucked the life out of me.

    I will say that since I have rebuilt them with a number other restores and upgrades and the pipes. The Supertrapps are as I have expected. Though things are getting hard to find, I still have a list of resources. Kerker are my favorites, but you loose the center stand, I’ll pass. I have had Jadine, Hooker, and Denco on my Hondas, and Kaws. The Trapps open are a little less robust than the stock modified. The Max is the only bike I have ever had experience with that stock pipes modified to reduce backpressure give almost as much an increase as some UFO pipes a couple of my riding buddies had and the UFOs were soooo loud. Though granted they do not have the tuned curves of the headers.

    Without the silencer plates the Max gave me a smoking second gear after I got the carbs balanced. A new rear Shinko Tourmaster gave change for the better as one would hope. I was happily shocked. This tire is steady up to 135 without any wobble. Much like the 17" Rear wheels I had on my first 2. The Metzler 888 I took off was deadly above 100 mph. Did not bother to go any faster though had plenty left... Nice price too. It pulled a small wheelie shifting into 2nd and I was not trying. Not bad for a Max considering it is not a light weight. I have always started from first and made it into 2nd before letting it down when I was wheeling my previous Maxes.

    As far as the lull, that is strange. Without the silencer plates there is nothing abnormal. It is strong and responsive. But this happened after riding on the highway for about a half an hour at 90 to 100. Backing off coming into traffic and then speeding back up felt it. It lasted for the remainder of the afternoon. I have ridden it about 40 miles since with the silencer and it has not reappeared. Might be bad gas. I will admit that because the environment is so filthy out here in the Permian basin that I have the K&N heavily oiled and that could be a part of the incidence, but as of the moment it has disappeared. Well if it did it once it most likely will reoccur, so checking the plugs, float levels and as suggested cleaning the K&N is next on the agenda…

    Thanks again to you guys for the suggestions. I obviously enjoy talking shop. I will update when I find the culprit.
     
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