wifesviper
New member
I was riding in the U.P today and at 90 mph I started to lose power I checked and had no compression in the center cylinder.I took it apart when I got home and the center cylinder has the front edge of the piston burnt off right down to both rings!!The other two cylinders where running very very light brown I have bender pipes,opticool head gasket, rear cooler.I have 162.5 mains and 52.5 pilots The air box is gutted.I'm thinking I'm too low on the mains but would just like another opinion.It was 28 degrees out and running premium fuel Thanks for any help
IMO:
The Viper Ignition map has a lot of advance up to about 9000 RPM.
The Bender pipes make their power @ 8800 RPM right in the "Meat" of the Vipers ignition curve.
Fuel quality today is questionable[an understatement!!!]
Sounds like you had a part throttle melt down [sleds are usually leanest just off full throttle]
If I had a Bender piped Viper[I like Bender pipes] I would be exploring one of or all of the following solutions:
-run the vents out of the airbox + rejet accordingly...I think this is MANDITORY with Benders
-replacing the Needle Jets with a larger size + raising the needles until I over richened the sled + then lower the needles to get a safe mixture
-installing a 2001 SRX CDI or installing a 2 degree flywheel key in the retard position to back off the timing.
one of or a combination of the above steps may be required to get the sled back to "Bullit Proof"
JM.02c
The Viper Ignition map has a lot of advance up to about 9000 RPM.
The Bender pipes make their power @ 8800 RPM right in the "Meat" of the Vipers ignition curve.
Fuel quality today is questionable[an understatement!!!]
Sounds like you had a part throttle melt down [sleds are usually leanest just off full throttle]
If I had a Bender piped Viper[I like Bender pipes] I would be exploring one of or all of the following solutions:
-run the vents out of the airbox + rejet accordingly...I think this is MANDITORY with Benders
-replacing the Needle Jets with a larger size + raising the needles until I over richened the sled + then lower the needles to get a safe mixture
-installing a 2001 SRX CDI or installing a 2 degree flywheel key in the retard position to back off the timing.
one of or a combination of the above steps may be required to get the sled back to "Bullit Proof"
JM.02c
maybe a little lean on the main and i think maybe lean on the needle .....if it burn on the exhaust side your lean .....
Makes me wonder about how I just jetted for pipes. Just set our sled up with 162.5 mains, 47.5 pilots, needle at 4.0 and screws at 2 1/8 for speedwerx pipes. Have carbs vented to air box like stock. Rest of the motor is stock, airbox isnt gutted. This is on a 2005 Viper Mtn.
Gutted airbox is the worst idea of any bad idea ever invented for a sled.
daman
New member
I'd bet on it....modsrx said:
Waters88
New member
Personally with how many guys I know that have problems with gutted airboxes all around, I wouldn't do it myself. I have heard that a gutted airbox will also lessen the fuel mileage??
mopar1rules
Active member
problem was the jetting. far too lean on the mains and probably needles. i hate venting to airbox. i would suggest this:
vent carbs to atmosphere
50 pilots w/2.25 turns on fuel screws
3.5 needle position
same 162.5 mains for starting out
do you have stock head? if so, try 160 mains in pto and center cyl and 162.5 mains in mag cyl.
i was up there this weekend too and had no trouble w/my modded viper.
vent carbs to atmosphere
50 pilots w/2.25 turns on fuel screws
3.5 needle position
same 162.5 mains for starting out
do you have stock head? if so, try 160 mains in pto and center cyl and 162.5 mains in mag cyl.
i was up there this weekend too and had no trouble w/my modded viper.
mopar1rules
Active member
Waters88 said:
of course it will....you need to fatten the jetting up, to keep/maintain safe fuel/air ratio.
the good news is that a center melt down will rule out a crank seal.
wifesviper
New member
lmodsrx said:
It is almost the same as that one.It even warped the piston lower on the skirt.I was thinking of going up one on the mains and putting airbox back to stock.The surprised thing is the cylinder is not bad at all.I drove it home 30 miles on 2 cylinders!!
There has to really be something wrong for the middle CYL to go out at 28 degrees. Im not sure if changing 1 size on the jets would help that much or solve the problem.
It sounds like you had a combination of problems. The gutted air box was not helping you from the start. The first thing I would look at is the carb for that cylinder and get the air box back to stock.
Your jetting looks pretty good for bender pipes. Post up a pic of the the middle piston.
It sounds like you had a combination of problems. The gutted air box was not helping you from the start. The first thing I would look at is the carb for that cylinder and get the air box back to stock.
Your jetting looks pretty good for bender pipes. Post up a pic of the the middle piston.
dont forget too raised the needle ...
mopar1rules
Active member
tomseal6 said:
not with carbs vented to airbox and gutted box...trust me.
at least put middle shelf back in the airbox and just drill 3--2.5in holes in the top of the airbox and 2--1.875in holes (i think) in between the 3 already existing OEM holes. this is good enough for trail and requires 1-2 main jet sizes more, from an already perfectly jetted sled.
daman
New member
yamaha did there homework on there air boxs, theres nothing there to improve thats worth anything.
daman said:
it improve burn piston
staggs65
Moderator
lmao!
LMAO... That was funny!!!
Gutting the airbox spells trouble.
Gutting the airbox spells trouble.
bufalobob
Member
viper w/ bender pipes:
gut air box
leave vent tubes in air box
needle - middle ( stock )
pilots - 60 accross
mains - 165 accross - mimimum - to 167.5
the air box not gutted is tooo restrictive. needs to be gutted for proper airflow to allow the pipes to make max power.
bob
gut air box
leave vent tubes in air box
needle - middle ( stock )
pilots - 60 accross
mains - 165 accross - mimimum - to 167.5
the air box not gutted is tooo restrictive. needs to be gutted for proper airflow to allow the pipes to make max power.
bob