Fresh top end SEIZED

Youllbe2nd

Youllbe2nd

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Joined
Feb 14, 2015
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425
Location
Canada
Rebuilt the top end on the viper. Did a few heat cycles and then took it for a buzz up the road. I was going nice and easy but making sure to get on and off the gas to help break it in. I got a mile and the top end locked up on me. I warmed it up for about 5 minutes. Cooling system was burped and exchangers warm. I triple checked this before riding it. Carbs clean. I can't figure this out. I haven't torn it down yet but there's scoring on exhaust side I can see. The temp light did not come on. Only thing I can think of is cheap *** pistons. They were half a thou tight on the clearance. We just got hammered with snow biggest storm of the year. I'm going to go cry now.

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I suspect it was lean or bad gas. Likely issues in carbs. Many "carb cleanings" do not get the pilots and air jets clean. Also possibly intake boots not in place or cracked. The other possibility is piston and rings not properly sized or installed.
 
Spx pistons. Sled was syphoned dry and filled with premium. The carbs were clean. Taken apart proper and cleaned. New jets installed. Went fatter on pilot and raised needles. Boots were inspected and also clean. No cracks. The rings were file fit to the spx spec. Pistons half a thou tight. One thing I didn't do is bleed the oil. Maybe an airlock in the oil system??

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Spx pistons are not bad pistons. Did you have the engine out when you re built it? if you had the oil line disconnected you should have bled the system.
 
Yep it was out to fix some steering issues. I can't believe I forgot to do this.

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I would lean towards air lock in the oil system. I always mix my first tank after removing oil lines. I'd rather replace plugs than pistons.
 
wildthangci said:
I would lean towards air lock in the oil system. I always mix my first tank after removing oil lines. I'd rather replace plugs than pistons.
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Ya I used to always do that too. A ty member mentioned that running premix in an oil injected sled will lean the air fuel mixture so I stopped doing it that way. It made too much sense to ignore.

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Man that sucks. That's most definitely what happened. Hope there is not too much damage. I bleed the oil line and then hold the oil cable wide open for a minute when I start it for the first time and haven't had any problems.
 
That's probably what caused it then. I run a little pre mix in the gas tank after a rebuild just in case. fill the oil tank to the top and keep an eye on it to make sure the oil level is going down so I know that the engine is getting oil. Once I see the oil level is going down I drain out the pre mix.
 
Youllbe2nd said:
Ya I used to always do that too. A ty member mentioned that running premix in an oil injected sled will lean the air fuel mixture so I stopped doing it that way. It made too much sense to ignore.

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I don't know how it can lean it out. It even says to premix the fuel for break in on the SPI instruction sheet that comes with the pistons.
 
More oil means less gas, so leaner, but not by much. As long as your not doing real long WOT pulls, it shouldn't be a problem.
 
Ugh I'm an idiot. I've been so busy I've been working on this sled for about a year whenever I have time between work and kids and other projects. I meant to do it and I totally forgot. I just ported it too. Hopefully my cyls are OK. She pulled like a bastard for a mile!! Yeesh I'm going to drink a bottle and call in sick tomorrow and cry all day haha damn

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More oil can't hurt anything (other than fouling plugs), but more oil means the gas to air ratio is leaner. I premix my first tank (actually just a couple gallons) until I'm sure the oil pump is working.
 
Youllbe2nd said:
Ugh I'm an idiot. I've been so busy I've been working on this sled for about a year whenever I have time between work and kids and other projects. I meant to do it and I totally forgot. I just ported it too. Hopefully my cyls are OK. She pulled like a bastard for a mile!! Yeesh I'm going to drink a bottle and call in sick tomorrow and cry all day haha damn

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Don't just cry tomorrow. crack that sucker open and see what you're dealing with. Does it turn over now or is it locked up solid?
 
It runs. I've got about 90 psi in all three. I pulled pipes off and middle is bad. Other two don't look too bad. I'll try to find time tonight to open it up and post back

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take some pics, if I read this right you heat cycled it a couple times and then let it warm up for 5 mins before riding it, and then rode it for a mile up the road before a problem, the oilpump would of have already bled itself by then that's at least 15-20 mins of run time.

If it is/was a oil problem all 3 will be damaged the same and the pistons will be scored all the way around.

post some pics and lets see what happened there, will be much better then guessing.
 
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