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Falling flat on it’s face

2K views 18 replies 5 participants last post by  One1 
#1 ·
Got myself an issue. See the video. Basically it falls on it’s face above 4k.





front plugs were wet so i thought maybe a coil was failing, but after cleaning them the haven't been wet since so idk. I have fuel in the carbs. Voltage of the bike is great. I have all the mods done.
 
#2 ·
I've never been able to play a video posted on this site. It always says an error has occurred.

So, without seeing/hearing the video: Perhaps pull the main jets and clean them well. They can be reached while the carbs are still installed. 4K is about the rpm where they would kick in. If they're clogged it would run fine below 4K but crap at and above 4K.
 
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#3 ·
I agree. What threw me off was the wet plugs in the front cyl, but I haven’t seen them wet since so I’m working on it from fuel for now. When i drained the carbs to pull the main jets today the front cyl was low on fuel in the bottom of the bowl. Probably 1/2 what it should have. I didn't Have any clogged jets as best i can see, so if it’s still acting up tomorrow when i finish putting it back together and i see low fuel volume in that carb I’m going to have to pull them and check the float system.
 
#4 ·
I can't see the video either. But if you mean the engine cuts out above 4,000 RPM, it is almost certainly a carburetor issue. If you have pod filters and a gutted exhaust, it could simply be too lean.
 
#8 · (Edited)
I changed the diaphragms on the coaster area and they were moving. Since it cuts both cyl now i have to assume it’s before the carbs. When it first started only 1 cyl sounded like it was cutting. Now both cut completely off when i twist the throttle. It will idle all day long and run fine at partial throttle, which makes it very hard to figure out since it has everything it needs to run just not enough of something. Voltage is very strong though. That Ricks stator is awesome and is driving nails. I may need to check the VR output on each pin just for kicks, but at the battery it’s regulating at 14v strong.

When it first started i felt like it could be a clogged carb. It acted like it was running out of gas with one cyl cutting out. I eliminated poogs by opening the gas cap lid. Then the next day it ran great for a day, then both cyls cut out from then on.

Since i have the coil mod I’m going to check the relays output, but i don’t think anything is going on with it. It’s clean as new inside.

First thing though is to swap the brain box from a stock VN i have to this one and see what happens. I think between all my mods I’ve mostly bypassed the fuse box, but just to be sure. I’ve bypassed the headlight, relay on the coils, shaved pickups, and everything else.

Oh and there is something I can’t see in the manual which is in black and white..... which color goes on which coil for the rear ign coil? I can’t tell with my bikes because i have new wiring on them. It appears as though green is on top.
 
#9 ·
Not the junction box. It really feels like it’s running lean. You know how if you are lean and crack the throttle it’ll spit and putter out? That’s what it feels like. I’ve swapped several things between these two VN’s and nothing has worked yet. The problem is that nothing has changed on the bike by my doing. It’s ran perfectly for years.
 

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#10 · (Edited)
The plugs aren’t lean though so that’s not it.

Edit: the only clue I’ve had so far about anything is that with the choke off it breaks up at 3k and with it full on it breaks up at 3800. So it’s making a difference but not sure if related or just coincidence.
 

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#11 ·
Checked the sidestand, clutch and neutral switches?
It will cause this same action if you are out of neutral with the clutch released and the sidestand down. Was running the bike through the gears on the center stand and found this out.
 
#12 ·
All right folks I’m back I had to take a week and get some stuff straight. I got back to working on it today and I figured out the issue. I’ve never had any problem running that vacuum line from the carburetor to the air filter on the right hand side like you’re supposed to do in fact all of my bikes have it in that spot because that’s were it’s supposed to be, but for whatever reason this one has decided it does not like that spot anymore so once I pulled the vacuum line out of the air filter Inlet the bike ran like a charm. There was apparently enough negative pressure coming inside that air housing to bias the carburetors
 
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#13 ·
Yep. Right here. Something is amiss, but long as she runs....... whatever. I would have fixed this on the first day but i knew it was supposed to be there. When i had checked everything i started doing things wrong for a reaction and this was what made it work.
 

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#15 ·
The hose passage doesn't go inside the air filter housing, its just a cleaner location to vent air than hanging loose in the engine area. Bottoming the hose is the same as plugging it, thats why performance suffers, the bowl can't fill/drain.
 
#17 ·
Correct. However this issue wouldn’t be relevant to that solution. It’s actually exactly how it should be and is on all my other bikes. The problem wasn’t with it not flowing, it was flowing too much. Exact opposite issue. For some reason it was being super sensitive to negative pressure. Nothing changed (position wise) so no idea why. Long as she runs I’m good. I actually had some time on one of my other VN’s I don’t use much and gained some perspective on how my main VN is running. It could be “quicker” (peppier) so I’ll have to do some maintenance like different plugs. It’s getting up there a little (36,000 miles) and the closest other one is 19k so i can see the difference in how it runs.
 
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