pitz0022
New member
I thought you guys might be able to offer some insights. I'm rebuilding the engine from the bottom up anyhow, but I thought it might be reassuring to get some opinions on what the root cause of the meltdown was. Things to note are that the center cylinder was missing two exhaust manifold studs. the PTO motor mount was broken off and the carbs were a little dirty meaning they had green junk in the bowls. The Mag side had a partially plugged pilot jet, I could see light through all the other jets. Keep in mind that when I checked the carbs the sled had already been sitting since February which is when it blew up.
Here are some pics of my pistons. Top is mag side on both pics.
Here are some pics of my pistons. Top is mag side on both pics.
Attachments
Jetting on mag side is a little rich (unless you cleaned the piston crowns) center was ragged edge lean for some time causing flashing of the piston. Lean could have been from anything from bad gaskets to plugged or bad set up on the carbs. Looks like some foreign material may have been bouncing around as well.
pitz0022
New member
I didn't do anything to the pistons except pull them out, so they are just as they came out of the engine. I'm assuming the "Bouncing material" you mention is detonation.
Last edited:
Have a real good look at the centre crankshaft rod bearing as it also looks to me like some metal has been pounding the piston crown. Damage to the crank rod bearing from heat, lack of oil or foregn materia ect can be missed only to cause another rebuild shortly after the first one and usually its more catastrophic! I definately got that T-Shirt!
JM.02c
Bob
JM.02c
Bob
pitz0022
New member
sideshowBob said:
It didn't take a real good look.... the crank was shot. Center rod broke where it comes around the bottom of the bearing. Pieces got pinched between the crank and the case and ground holes in the bottom of the case. At least two crank bearings surrounding the oil gear are shot.
I bought a new crank here and found a case at haydays. I assembled the bottom with new seals last night. Also rebuilt the water pump.
It should be like a brand new engine when I'm done, but I want to make sure I find out what caused it if possible. I'm going to put new main jets in it because I can't read the numbers on them. I've got a whole new top end, and gaskets. I'm going to keep putting it back together and just monitor everything closely during breakin.
Sounds like you are doing everything the right way...cutting corners never pays.
Once its put back together to all stock specs...good fuel,clean carbs, and good oil with a proper adjusted oil pump and rear cooler[SRX ones the best] should do the trick.
I am assuming this is your Viper so also check into the "opticool' head gasket. lots of info on this if you do a search.
Bob
Once its put back together to all stock specs...good fuel,clean carbs, and good oil with a proper adjusted oil pump and rear cooler[SRX ones the best] should do the trick.
I am assuming this is your Viper so also check into the "opticool' head gasket. lots of info on this if you do a search.
Bob
Last edited:
pitz0022
New member
I got the Opticool Head gasket if that's what you are referring to. I was ordering parts from an aftermarket retailer and he had them for $40 so I had him throw it in. I'll probably put an SRX cooler in it eventually, but I'm running a little tight on budget and time right now. I've got a few hunting trips this fall I need to save for. I should have time before the snow flies though.sideshowBob said:
Yes Opticool head gasket is what I meant...LOL...time to reengage my sled brain!...I will go back + edit my post so I dont mislead anyone...I have a couple SRX rear coolers kicking around PM me if you want one...we could work out a price that works.
Bob
Bob
Last edited:
Bluemonster2
New member
I believe the other two cyl may of been running hot as well just not as bad but pretty big black spots on the bottoms of those pistons. I know this spare redhead parts motor that I bought has a blown center as well but only has a little black spot on the bottom of that piston the others look fine.
I think you may of been running hot hard to say I know on my bikes its a sign of lean jetting/too little oil. Cr250 that I ripped down running on 50-1 had marks like that from the oil searing to the bottom of the piston but when it was torn down again properly jetted/ 30-1 it had no black marks. I know lots of people are having problems with vipers the last couple seasons, I know people suggest tuning oil pump 50-1 but I would suggest more oil when you get it back together.
I think you may of been running hot hard to say I know on my bikes its a sign of lean jetting/too little oil. Cr250 that I ripped down running on 50-1 had marks like that from the oil searing to the bottom of the piston but when it was torn down again properly jetted/ 30-1 it had no black marks. I know lots of people are having problems with vipers the last couple seasons, I know people suggest tuning oil pump 50-1 but I would suggest more oil when you get it back together.
ottawaair
New member
I sounds like there were a few things leading to the burndown. Loose manifold bolts causing exhaust leak could contribute. What went first, rod bearing or piston. Like the chicken & the egg. Make SURE you put the base & head gaskets on the correct way as the water jacket ports are different sizes. The base gasket should have a notch between 2 of the cyl's & flat across the other side. This notch goes between the PTO & center cyl. & to the front of motor. Better look to make sure, but i'm 98% that how it goes. Also look into using a SRX base gasket, especially if you have tripple pipes.
pitz0022
New member
Fantastic advice guys. Thanks. Do I run 50:1 oil mix in my gas tank for break-in as well? I already bought a viper gasket kit with the addition of the opticool... what does the SRX gasket do over the Viper base gasket? Now I wish I would have just bought my gaskets piece-mail.
Thanks for the tip on installing it... I remembered reading that these gaskets had an up and a down. It's my first engine rebuild so I appreciate all the advice I can get.
Thanks for the tip on installing it... I remembered reading that these gaskets had an up and a down. It's my first engine rebuild so I appreciate all the advice I can get.
pitz0022 said:
Those pistons are lean. You have carbon on them in center only because of the oil, the dry smoke color (and barely any of it) tells me you need more fuel. I would raise the needles some.If it was running in the sweet spot the piston tops would be all covered evenly and show shiny bare aluminum wash marks at the rear, and some will show bare aluminum on outside edges but with a satin wet sheen, yours are bone dry and dull.(not counting the center one with detonation pitting)
As for the inside of the dome, if its in the good spot, it will be hershey bar choclate brown about a nickel sized, if its a dry flaked up carbon, its either too much oil or it can also be from excessive rapid crown temps from being lean. You wont always get dry "death ash" unless its been run for a long amount lean and usually a burn down happens quickly and will leave some carbon on bottom. You cant rely on the bottom to determine a lean rich mixture, but it is a excellant source of information on when you think you have the perfect set up to check your consistant crown temp(choclate brown and satin sheen).