The infamous lean spot in the triples

milo303

milo303

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So I read a while back about the infamous lean spot in the older triples, but I can't find it with a search.

Could use a bit of help if someone remembers the name of a thread discussing the problem, and a solution.

Thanks
 

In the Vipers the lean spot was middle rpm's while you were just cruising down the trail. Not delivering enough oil i believe or fuel. That's why you really are smarter to blurp the throttle from time to time while cruising down the trail on the Viper -- so oyu don't stick in that lean spot for too long.
 
Super Sled said:
In the Vipers the lean spot was middle rpm's while you were just cruising down the trail. Not delivering enough oil i believe or fuel. That's why you really are smarter to blurp the throttle from time to time while cruising down the trail on the Viper -- so oyu don't stick in that lean spot for too long.
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Thats what happened to me at the beginning of winter with my viper. Cruising at 35- 40mph and it burned up the middle piston. Didn't help i didn't know at the time my head was cut wrong. When i got the sled back home the compression was 115, 85, and 175psi.
 
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It really help to have better cooling on these Vipers also. Either a replacement head with water rail or opticool head gasket. Anything that will allow the engine to stay cooler. The stock heads and head gasket do a poor job of keeping these engines cool. Then when you get into those situations cruising down the trail, everything adds up and catastrophe can strike. I added better cooling and a engine coolant temp guage with the hopes I could catch this if it ever started happening. I also have richened up my oil cable a bit for more oil when I blurp the throttle. :bump:
 
Super Sled said:
It really help to have better cooling on these Vipers also. Either a replacement head with water rail or opticool head gasket. Anything that will allow the engine to stay cooler. The stock heads and head gasket do a poor job of keeping these engines cool. Then when you get into those situations cruising down the trail, everything adds up and catastrophe can strike. I added better cooling and a engine coolant temp guage with the hopes I could catch this if it ever started happening. I also have richened up my oil cable a bit for more oil when I blurp the throttle. :bump:
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I do hit the throttle all the time now since I rebuilt it. I do have the opticool head gasket and a srx rear heat exchanger when it happened. Wasn't my fault it ate a piston up. Im not bashing Bender racing but they cut my head wrong when i sent it in for their head mod. 60 miles later it ate a piston after I put the cut head on. At this time i found my head to be cut way off. Bender did agree with me it was 100% their mistake on my head. I do thank Bender for sticking up for their mistake and making it right with me. Sled runs alot better when the compression is 125psi in all three instead of running 115psi to 175psi.
 
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Is there a way to modify the stock head by opening the water passages in the head? Or is the design so poor that it is just wiser to use alternate heads(SRX- A/M, etc).
 
Sxr700Bandit said:
Is there a way to modify the stock head by opening the water passages in the head? Or is the design so poor that it is just wiser to use alternate heads(SRX- A/M, etc).
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I believe it's the oem head-gasket itself that causes the poor cooling.
 

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So then technically the opticool gasket forces the water to pick up more heat along with re-routing the water instead of letting it free flow.
 
Sxr700Bandit said:
So then technically the opticool gasket forces the water to pick up more heat along with re-routing the water instead of letting it free flow.
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That is also what i was thinking. I have them on all my vipers for the comming winter and moved the needles to the 4th groove per mrviper. Doing what i can to prevent any trouble.
 
More cooling is a band aid way to fix a lean spot.

My waverunner (yamaha GP1200R) has a similar issue. It's a 2 stroke 3 cylinder with a catalytic converter and carburetors. Bad idea from the start, right there. Jetted lean from the factory to keep the cat alive. But even with no cat, jetted fatter, it burned down a second motor on me from cruising in the midrange for too long. Burnt two motors by running ~20 miles at ~3/4 throttle. I guess there's just a weak signal there that you can't really tune out with the carbs. So I just run harder / faster. Not a cooling issue on the PWC because the lake water keeps it plenty cool. Ski runs Mikuni SBN 44's, 3 of them.
 
Depending on how you mean more cooling... More efficient cooling is the way to build a motor and have it live along time. There is such a thing of adding more(to much) cooling and not efficiently being able to transfer the heat to the water (so to speak) and cause all types of problems.
I used to run a Kawasaki JS550 that was built to the hilt and the motor lived through all of the abuse I had put it through. I also ran a different from stock headgasket which was supposed to aid in cooling... So there is a way to help the factory keep their stuff alive.

I was pondering on this since I posted... With watercraft carbs it is imperative that the pop off pressure is set properly to get the right or proper fuel flow, otherwise if your pop off pressure is set to high you will run into lean conditions.

With todays fuels you also have to be VERY careful as the alcohol content corrodes the non ferrous materials that the carbs and jets are made from hampering fuel flow. I have had to replace one weed whip carb this year and have another one to replace as I have rebuilt and tried to clean the passages that I can get to, but the performance still lacks and dont want to have to rebuild/repair/replace the motor on my Stihl whip.
 
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sleeper_dave said:
More cooling is a band aid way to fix a lean spot.

My waverunner (yamaha GP1200R) has a similar issue. It's a 2 stroke 3 cylinder with a catalytic converter and carburetors. Bad idea from the start, right there. Jetted lean from the factory to keep the cat alive. But even with no cat, jetted fatter, it burned down a second motor on me from cruising in the midrange for too long. Burnt two motors by running ~20 miles at ~3/4 throttle. I guess there's just a weak signal there that you can't really tune out with the carbs. So I just run harder / faster. Not a cooling issue on the PWC because the lake water keeps it plenty cool. Ski runs Mikuni SBN 44's, 3 of them.
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Agreed to a point. The viper was built with a poor head design to start with, the opticool helps that but is not a fix all. Also the needles need to be moved up. And most important is MRVIPER said to move the needles so thats all i need to hear. Also run closer to 50:1 with oil.
 
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super1c said:
Agreed to a point. The viper was built with a poor head design to start with, the opticool helps that but is not a fix all. Also the needles need to be moved up. And most important is MRVIPER said to move the needles so thats all i need to hear. Also run closer to 50:1 with oil.
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Whoa whoa, Chris, bro, what is 50:1 with oil? You mean adjusting the pump differently? Premixing on top of that? I know the jets and opticool for extra measure but what's with that? Ive never heard about this... I am only running my vipers oil pumps at stock specs but a touch to rich. :)

Enlighten us brother... :2strokes: :2strokes: :2strokes: :2strokes: :letitsnow
 
SXRider7Hundo said:
Whoa whoa, Chris, bro, what is 50:1 with oil? You mean adjusting the pump differently? Premixing on top of that? I know the jets and opticool for extra measure but what's with that? Ive never heard about this... I am only running my vipers oil pumps at stock specs but a touch to rich. :)

Enlighten us brother... :2strokes: :2strokes: :2strokes: :2strokes: :letitsnow
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No, no. I should have worded that better. Run your oil pump to achieve a 50:1 ratio never premix on top of the oil pump. That comes out to about a quart of oil to a tank of gas to achieve around 50:1 to about 45:1. But checking back on my notes from daman the tought was to get even closer to 40:1. That may be a touch much so i try to stay right around 45:1. But the word was the viper cranks love their oil. Their was a good post on it ill see if i can find it. I always check my ratio after burning a tank of gas to see where im at. Lots of cool ratio calculators on line and phone apps. I have the app. Sorry about the confusion.
 
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