So first off the sled is a 2002 viper sx 700. The first real issue i have is i had lent it to a friend and he brought it back telling me it was overheating.So i filled the coolant tank back up cause it had steamed over .Then i attempted to bleed the system by lifting the back and opening the bleeder screw on the crossover pipe. At first i couldn't get any coolant what so ever thinking the water pump was broke. But after a while it started to come out bubbling ect. So after it streamed out i figured it was ok checked the other heat ex-changer and it was getting warm.Then i went for a small ride didn't even make it 2 blocks from home and again over heating!! took it into my shop there was air yet again at the crossover pipe. bled the line and still over heating. i also opened the small screw on top of the head that's above the carb heater on/off switch nothing came out of there. is that not another bleed screw?also did a pressure test afterwards of cooling system held 15psi no problem no leaks. Then i did a compression test only getting 70psi on the PTO side 100middle 105 Mag side. not great in my opinion. Am i right to think that this is a head gasket issue? I think air is being introduced into the coolant system because of bad gasket? anybody advice would be great.
Youllbe2nd
New member
Your compression is way low. It is possible you have a bad gasket. It's definitely time to pull the head off and have a look at very least
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do you have a lot of snow as if you ride a viper with the stock crossover tube in marginal snow they overheat easily.
yes there is a ton of snow. Also am not concerned with the stock crossover tube in the rear .Had this sled for over 3 years rode it here in these exact conditions and have never ever had a problem. there is a a heat exchange on both undersides of running boards and also one in the front of the tunnel. When it works its works very well for cooling the machine. This is a new problem thats causing it to overheat Mr viper7000.
but what is causing the overheating? No point in rebuilding the top end if i cant figure out what the original cause of the overheating is.
there will be bubbling in the overflow bottle at idle if the headgasket is bad, run it at idle with the cap off and observe.
if no bubbling, then next remove the thermostat housing top and look at the thermostat see if the center pin on thermostat is wedged in sideways or bent crooked.
if no bubbling, then next remove the thermostat housing top and look at the thermostat see if the center pin on thermostat is wedged in sideways or bent crooked.
Youllbe2nd
New member
Is there any coolant in the exhaust? If you have a bad gasket your plugs and piston wash will be very clean looking. Chances are there will be coolant in the motor and in exhaust. It would smoke like a bastard. Can you rule this out? Otherwise it could be a dozen things causing over heating. There could be sludge jammed up somewhere in the system causing blockage. Thermostat ****ed. You running the right plugs? The bleeder in the head is useless don't bother with it. Elevate the front of the sled so the coolant bottle is the highest point and run it with the lid off to burp the air out.
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your gonna need to relax and be patient, nobody here can see your sled so we have to ask questions and you do the leg work to answer them to solve the problem.
super1c
Super Moderator
Caleb MR viper knows more about these Sled then we will ever know. I would pay close attention to his advise. These Vipers are very prone to overheating and always have been. Even the octain level in the fuel can effect overheating. It is highly recommended to put the rear heat exchanger on regardless. I have done this to all mine. You have no idea what really wennt on as you lent it to a friend. I highly doubt this is a head gasket problem. Compression numbers mean nothing it depends on a million things. Key is center and mag are close. The PTO should be lower as viper has started comp, but 70 seems a little low. How do plugs look? How do domes look? Bleeding from rear is all that's needed, front one never worked. Start with what MR viper stated and report back.
super1c
Super Moderator
Caleb MR viper knows more about these Sled then we will ever know. I would pay close attention to his advise. These Vipers are very prone to overheating and always have been. Even the octain level in the fuel can effect overheating. It is highly recommended to put the rear heat exchanger on regardless. I have done this to all mine. You have no idea what really wennt on as you lent it to a friend. I highly doubt this is a head gasket problem. Compression numbers mean nothing it depends on a million things. Key is center and mag are close. The PTO should be lower as viper has started comp, but 70 seems a little low. How do plugs look? How do domes look? Bleeding from rear is all that's needed, front one never worked. Start with what MR viper stated and report back.
Yes im taking mr vipers advice. IM just uncertain why he thinks im running my sled with stock crossover tube in marginal snow. i stated it has a rear heat ex-changer and i never mentioned snow conditions in my post. I will also be following his suggestions how to diagnose. All is appreciated guys.Ps maybe im not using the proper term to describe the "crossover tube" i was just referring to the tube thats tucked in the back of the tunnel thats between both rubber hoses, it has a bleeder screw on it"
sorry for any misunderstanding guys im trying to solve this on my own up till now.ill report back my findings in the morning
sorry for any misunderstanding guys im trying to solve this on my own up till now.ill report back my findings in the morning
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super1c
Super Moderator
You say you stated it has a rear heat exchanger in one sentence and a crossover tube in another. I'm assuming you have the tube. Almost everyone replaces this tube with a heat exchanger. Easy to find from a old Srx. With this added it helps the viper run cooler which it struggles to do on its own. He didn't assume you were running in marginal snow he simply asked if that was the case as low snow and no rear heat exchanger overheating will occur. The crossover tube is NOT a heat exchanger
Alright thanks super1c got what you and mr viper was saying thanks
Update: removed thermostat checked pin it was straight up and down. tested it in hot water and it also open and closed properly . next i removed the head to visual inspect. Found center piston damaged, pitting on both head and deep scoring on cylinder walls. It appears the valve looks pretty chewed up also. Any thoughts next what could have caused this ? Possible that the valve went in to far and contacted piston? And im still at a lose for what caused the original over heating.What's the next step to locate the over heating boys?
hard to say with overheating because you didn't check to see if there were bubbles in overflow tank when idling ,lending information to a bad headgasket or not but unusual to find that in these sleds.
If the piston is all burned up its either been run on junk gas(low octane) or the carbs were dirty. If it were to be caused by overheating youd have warped the head and all 3 would be damaged from the excessive heat. Being only one cylinder is hot I would have to say the reasons stated already. If you can take some pics of the tops of the pistons can diagnose the problem better.
Vipers need to have the needles raised from stock, so if your buddy rode it for a prolonged period cruising speed say 40-50mph your running on the needle circuit in the carbs. The advanced ign. timing in a viper makes then run lean at that spot. If he used low octane fuel it furthermore advances the damage.
vipers didn't come with the rear heat exchanger but the crossover tube that's why I asked about low snow as they were common to overheat. Yamaha knew about it and in 03 came out with a service bulletin to add the rear heat exchanger to address the overheat problem. As you said.. if its good snow, no problem but marginal snow and or icy conditions where theres not a lot of powder dust to cool they would overheat.
If the piston is all burned up its either been run on junk gas(low octane) or the carbs were dirty. If it were to be caused by overheating youd have warped the head and all 3 would be damaged from the excessive heat. Being only one cylinder is hot I would have to say the reasons stated already. If you can take some pics of the tops of the pistons can diagnose the problem better.
Vipers need to have the needles raised from stock, so if your buddy rode it for a prolonged period cruising speed say 40-50mph your running on the needle circuit in the carbs. The advanced ign. timing in a viper makes then run lean at that spot. If he used low octane fuel it furthermore advances the damage.
vipers didn't come with the rear heat exchanger but the crossover tube that's why I asked about low snow as they were common to overheat. Yamaha knew about it and in 03 came out with a service bulletin to add the rear heat exchanger to address the overheat problem. As you said.. if its good snow, no problem but marginal snow and or icy conditions where theres not a lot of powder dust to cool they would overheat.
super1c
Super Moderator
Pic's of the piston will help a lot in finding out what happened. Not sure about the valve as it has stops to prevent the valve from comming in contact with piston but has happened. I would guess its pieces of metal from piston that damaged valve, but pic's are worth a thousand words. It overheated due to the meltdown (have to find why. Bad gas, plugged jets, ?PV?), not melted cause of overheating.
super1c
Super Moderator
Posted as i was typing! LOL!
alright perfect guys i will take pics and post within next hour. Also Mr viper i did check for bubbling in coolant tank prior and there was none forgot to mention in post. Going to get a long bolt downtown to make a "piston pin puller " lol .
super1c
Super Moderator
The long bolt with washers is my go to tool. LOL! Works great! The only way ive ever done it.
Youllbe2nd
New member
Are you running stock plugs??
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