Mag side cylinder is not firing on VIper-Help!

SledBoy

SledBoy

VIP Member
Joined
Sep 22, 2003
Messages
204
Age
62
Location
Stillwater,MN
I have an issue on a triple piped viper. Just installed a Peak Performance Billet Head and Mag side (cylinder #3) is not firing. I 1st notice when idling, that one pipe exhaust had more smoke (not complete combustion) and that pipe was not hot as I refilled the coolant. I Checked spark, changed plug & it's getting gas. So I'm stumped :o| and we are supposed to get a lot of snow starting on Sunday! Help! Now I'm wondering if the mag cylinder was firing before Installed the Peak Performance Billet Head as it was not running crisp before. My compression is good at 120psi on all 3 cylinders with a Peak Performance Billet Head and with 22cc domes.
Update=> Swapped coils between Mag and Center cylinder and now it moved to Center cylinder. During idle engine warm-up, the center cylinder pipe would not get hot just like the original mag one did with that coil-plug wire assembly. What I don't fully understand is that the non-firing cylinder's pipe did get hot (measured with a infra-red temp sensor) when I took it for a spin around our pond. this may be a engine temperature related intermittent failure! I assume this points to the $$$ parts==> CDI or Stator??? :o|
 
Last edited:
Mag side (cylinder #3) is not firing...My compression is good at 120psi on all 3 cylinders with a Peak Performance Billet Head and with 22cc domes. The Mag cylinder is getting spark when I hook the plug wire to a plug and set it on top of engine for ground.
 
OK,
Swapped coils between Mag and center cylinder and now it moved to center cylinder. During idle engine warm-up, the center cylinder pipe would not get hot just like the original mag one did with that coil-plug wire assembly. What I don't fully understand is that the non-firing cylinder's pipe did get hot (measured with a infra-red temp sensor) when I took it for a spin around our pond. this may be a engine temperature related intermittent failure! I assume this points to the $$$ parts==> CDI or Stator???

Possible Cause of cylinder not firing- current status
1 - bad spark plug -checked out OK
2 - bad coil or coil wire-Maybe or one channel of 3 in CDI
3 - faulty spark plug cap-Maybe
4 - poor/low/or no compression-all are at 120 PSI
5 - plugged carb circuit[make sure you check the filters under the float needle + seat]- took apart cleaned, checked all jets, used compressed air too
6 - plugged or stuck float plunger; If the needle + seat is worn or not seating it will allow the float bowl to overfill and flood the cylinder as the fuel pump will happily pump as much fuel into the bowl as it can.- took float & needle out, looked OK
7 - fuel pump issue[remember each carb has a separate feed from pump]- unplugged and turn engine over, all 3 lines pump gas!
8 - incorrect float level on that cylinder- checked out within spec.
9 - wiring harness rub through- re-did about 3 years ago.
10 - stator or pickup[ these can fool you sometimes they test OK yet they are toast]
11 - CDI or Stator- have not rules out yet, but hope not! $$$
12 - Reed Valve Petals: broken, chipped, worn out => run Rich-looks good
13 - choke plunger on that carb is sticking or has something in it do you ? Or out of adjustment ?-looks good
14 - the pilot circuit also flows out the fuelscrew orfice in the throat of the carb when you spray carb cleaner thru the hole where the pilot jet screws in..right?- OK
15 - Power Valve- need to check!
16 - Fuel Filter- need to check
17 - gas tank air vent-- need to check
18 -Fly wheel-???
 
I know this sounds dumb but did you make sure the main jet was tightened all the way. I have see this before.
 
I have a coil and plug wire on order and yes the jets are tightened. Thanks!
I can't imagine the problem not being the coil and plug wire since the non-firing cylinder during warm up followed the coil and plug wire when I switched them between Mag & Center cylinders. I hope this is the case! Thanks again!
 
first thing I would check is to see if the flywheel magnet is all rusted up, you can shine a light down by recoil and see. If the spark problem moves when you swap wires, then its either the flywheel magnet rusted, bad coil or bad cdi.
 
remove recoil, use sandpaper to remove rust from magnets, blow out stator area with compressed air, then wipe down flywheel with a light oil, reinstall recoil.
 
You must log in or register to reply here.


Back
Top