jlacey
New member
Hi I have a question and hoping I haven't made a blunder. I just bout an 03 Viper ER with 914 miles, looks like it just came off of showroom floor. Thats the good part. The bad part is when I tested the compression cold & I got 95, 100 & 100 pis (starting clutch side). I check my guage and it is low ~5psi. I added oil to cluthc side cylinder and still got 95psi. Warmed up sled and got 85, 95 & 95 psi.
I am hoping there is some trick to testing compression on this sled that I over looked. My test procedure was to pull sled over by hand 5 pulls with throttle wide open and ignition off.
Any feedback would be appreciated.
Thanks
Joe
I am hoping there is some trick to testing compression on this sled that I over looked. My test procedure was to pull sled over by hand 5 pulls with throttle wide open and ignition off.
Any feedback would be appreciated.
Thanks
Joe
dirtjumper895
New member
The viper has a lower compression cyclinder, so you do not have to run staggered jetting. I am pretty sure the low comp cyclinder is the PTO side.
Your numbers seem low, BUT, I am thinking your guage reads low. The biggest reason I use a compression guage is not to measure compression, but as a comparison of compression between cyclinders.
Your numbers seem low, BUT, I am thinking your guage reads low. The biggest reason I use a compression guage is not to measure compression, but as a comparison of compression between cyclinders.
Waters88
New member
I agree with dirtjumper895, I think your compression tester just reads low. I have seen compression testers that read a 20 PSI difference from one tester to the next, so I would guess yours just reads low. Your numbers are all close, so that is a good thing.
youll find alot of just std automotive type testers will show low because of the hose length, and the thread adaptors.
you also only pulled it over 5 times, usually takes about 10 pulls to reach max compression because when you pull it over the rpm is much much slower then with it even idling.
looking at your readings, I would think there isnt a thing wrong with it with only 5 pulls,and all the redings are correct, the PTO cylinder will be lower due to the larger head volume in that cylinder(yamaha thought it was important to be able to use all 3 the same jets)
you also only pulled it over 5 times, usually takes about 10 pulls to reach max compression because when you pull it over the rpm is much much slower then with it even idling.
looking at your readings, I would think there isnt a thing wrong with it with only 5 pulls,and all the redings are correct, the PTO cylinder will be lower due to the larger head volume in that cylinder(yamaha thought it was important to be able to use all 3 the same jets)
jlacey
New member
Thanks for the input guys, I hope your right as the rest of the sled is perfect and I am dying to ride it.
Joe
Joe
dirtjumper895
New member
As they say up here in the UP, just give er.
I have also read to warm the sled for about 30-45 seconds and then pull plugs for a compression test. Is there any truth to this?
I have also read to warm the sled for about 30-45 seconds and then pull plugs for a compression test. Is there any truth to this?
ridergonwild5692
Member
im pretty sure the motor needs to be room temperature to get a good accurate reading out of it.
Snowsnake
New member
Should be at operating temp.