Hey guys, first post here. Posting for a buddy actually who's not to computer savvy. Did all kinds of searches here and tried all the things I found but his 04 SXViper won't fire on the one cylinder until 4000rpm and up. Tested TPS and adjusted it. (4.68ohm and set to .64 volts) Swapped coil, reeds, wires from another cylinder and same thing. Took carb apart several times, cleaned it, even the screen still same thing. Compression is 125-130 on all three. Put new fuel lines from pump. Checked pump with lines unhooked and pushing tons of gas. Like I said i've done all kinds of searches, even on google which always led me here. He parked it last spring and it was 100%. Put fuel in it this fall and fired it up and the one lung won't fire for no money. What else could it be? Would the ECU do this to 1 cyl? Oh and had the stator out and cleaned it all up too. Also did the TORS bypass thing and no change. Same with unplugging the TPS.
motorhead327
VIP Member
You swapped coils right? There have been guys that have cleaned the carbs 10 times over, but the pilots need to be cleaned GOOD. If you cant see light through them, they are plugged. The hole is the size of a sowing needle or smaller. If that don't fix it, I would check the crank seal.
staggs65
Moderator
change plug caps too. I'd be surprised if there are any origional plug caps out there that still ohm out right.
Devilin AblueDress!
New member
X2 on the above. If pilot is plugges it would be coming off pilot circuit around 4k. swapping coils should have moved problem to other cylinder but plug caps are cheap to rule out. One thing that stands out to me though is shouldnt one cylinder be down on compression like 8-10lbs? Seems I read on other threads 1 cylinder was designed to be lower? Any resonable explanation why they would all be the same?
staggs65
Moderator
very common head mod on vipers is to machine the head to even the compression or change the head all together.
Spark plug wires were swapped around also, as were plugs. Even a new one was thrown around on each cylinder but no diff. Never heard anything about one cyl having less compression than the others, but they are all over 120 which should mean they're healthy. We'll take the carb apart again and clean. I wish we could swap carbs from side to side.
staggs65
Moderator
Vipers have less compression on the pto cyl than the other two. you cant just swap plug wires around its a 3d ignition
check the choke plunger on that cylinder, take a small penlight screw driver and GENTLY push on the plunger, see if it has stuck open, this will make that cylinder super rich.
ADD: another way you can check to see if its flooding out is to take a pair of needle nose pliers and gently pinch off that fuel line, if the cylinder picks up its getting too much gas, so youd be looking at a stuck choke plunger or needle and seat leaking, incorrect float adjustment, sticking float, although usually a float will spit gas out the overflow tubes..
ADD: another way you can check to see if its flooding out is to take a pair of needle nose pliers and gently pinch off that fuel line, if the cylinder picks up its getting too much gas, so youd be looking at a stuck choke plunger or needle and seat leaking, incorrect float adjustment, sticking float, although usually a float will spit gas out the overflow tubes..
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YAMMIEGOD3:16
Active member
check the o rings at the base of your needle and seats. just had same problem with my vmax 800. 3:16 (YAMMIE TONY)
Blue Devil
New member
pull your needle and seat out of the carb that is not fireing its probably pluged same thing happened to mine thought it was fire but it was gas, good luck!