I have identical 2003 SX Viper Mtns, SLP pipes w/EGT's, opticool head gaskets, Holtzman ATACC. They've got about 1800 miles. I'm running 165 mains, 47.5 pilots, needles @ 4.0, 1.75 fuel screw. This setup has worked very well for years for both sleds. One sled has sat for 3 years, so I pulled the carbs and gave them a thorough cleaning. I cleaned and adjusted the power valves, changed coolant. Took it out for a run and it just felt flat and the plugs were all wet, so I pulled the carbs again, soaked the parts in carb cleaner over night and blew out with compressed air. I took the choke plungers out and verified they were clean then reassebled and made sure the choke plungers had free play when not engaged. Took it out for another ride and it was much better, but not quite as snappy as my other sled. The mag and center plugs look good, but the PTO side is still wet looking. EGT readings support the rich plug: 600F (PTO), 950 (cen), 950 (mag). It does make good RPM's and snaps to 9000 pretty quickly, but not like the other sled. Compression is 110 (PTO), 125, 125. I'm thinking about swapping carb racks, then maybe ignition coils. Any ideas would be appreciated. Here's the plugs from my 65 mile ride: left is mag, right is PTO.
mod-it
Member
I'd try removing the cap on the PTO side, trim the wire back a bit, and twist a new cap on the end first. Or swap with one of the other ones and see if problem follows, but make sure to trim the wire a bit.
If that didn't do it, then I'd try coils next, and then carb racks last. I have seen a slightly blocked main cause fuel to dribble in instead of a nice mist and cause a rich condition rather than a lean one...I assume you looked through them to verify they were fully clean? I think you're on the right track, but don't overlook the plug caps.
If getting 9k rpm I think the power valves are opening fully in all 3...
One other thing, I've seen jets get bored out too big if a torch tip cleaner is ran through them (too big of one or too aggressive). Just a thought if you used one to run through the jets. A friend did that, although it was a pilot jet, and the sled ran pretty rich on one side until we threw a new one in it.
You must ride a lot lower elevation than I do! I have SLP's and the cold air flo-rites in the dash, as well as all underhood air blocked so it only takes the cold outside air. I'm running 152.5 mains, 3.0 needle, stock pilots, 3 turns out. Average 3500' to 6000' elevation.
Hope its as simple as a plug cap.
If that didn't do it, then I'd try coils next, and then carb racks last. I have seen a slightly blocked main cause fuel to dribble in instead of a nice mist and cause a rich condition rather than a lean one...I assume you looked through them to verify they were fully clean? I think you're on the right track, but don't overlook the plug caps.
If getting 9k rpm I think the power valves are opening fully in all 3...
One other thing, I've seen jets get bored out too big if a torch tip cleaner is ran through them (too big of one or too aggressive). Just a thought if you used one to run through the jets. A friend did that, although it was a pilot jet, and the sled ran pretty rich on one side until we threw a new one in it.
You must ride a lot lower elevation than I do! I have SLP's and the cold air flo-rites in the dash, as well as all underhood air blocked so it only takes the cold outside air. I'm running 152.5 mains, 3.0 needle, stock pilots, 3 turns out. Average 3500' to 6000' elevation.
Hope its as simple as a plug cap.
spark plug boot is good advice
Yeah, baseline jetting is for -20F and 1000 ft here in MN. I re-baseline to your setup when I go to Cooke City. The 10,000 ft elevation change at some of the riding peaks out there is too much for the ATACC to accommodate if your looking for performance. I first experienced the powder bog when I piped my '93 exciter LT. Took me a couple days to figure out it was the steam of the pipes creating an instant rich condition that'd cause the sled to fall on it's face. Fashioned some ducting out of an antifreeze bottle and duct tape to only take in outside air to get me through the rest of the trip. Forgot about it until I piped my Vipers and had the same thing occur.
mod-it
Member
I'm sure glad I don't have to ride in -20F! I average more 15f to 25F.
Change that plug cap and let us know.
Change that plug cap and let us know.
Trimmed the coil wires back 1" and installed new boots. Installed new reeds as the ends were chipped and not sealing at all especially on the PTO cylinder. We lost all our snow by the time my parts arrived, so I haven't had a chance to test it out. One thing I did find was my flywheel was extremely rusted, so I took the dremmel with a brass brush to it. The target strips pertaining to each cylinder for the pickup coil on the flywheel are quite long. Does anyone know if the 3D ignition algorithm uses the length of time that the pickup coil is sensing the target to calculate when and for how long to fire each coil? In essence I'm asking if the pickup coil isn't sensing the target for the whole duration of the strip due to rust build up, would this potentially change the ignition timing enough to cause inefficient combustion and foul plugs?
A couple of bucks
VIP Member
A corroded flywheel might just have been 1/3 the issue of the incomplete burn. Reeds ... 1/3, plug caps... 1/3. Did you seal up the bare steel on the flywheel. I use battery post protectant.