ViperTurboPete
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2022 Expedition Extreme 850
Hey guys,
I bought a 2015 Viper XTX MPI turbo (Yamaha dealer installed with 6000 kms) a few weeks ago. All I have had time to do is turn the key and hammer the throttle. So far so good.
Just wondering if there are any known issues or any preventative maintenance I should do. I am new the turbo game. The only experience I have ever had was dreaming about one.
Thanks for any input you may have.
I bought a 2015 Viper XTX MPI turbo (Yamaha dealer installed with 6000 kms) a few weeks ago. All I have had time to do is turn the key and hammer the throttle. So far so good.
Just wondering if there are any known issues or any preventative maintenance I should do. I am new the turbo game. The only experience I have ever had was dreaming about one.
Thanks for any input you may have.
ViperTurboPete
TY 4 Stroke Master
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2022 Expedition Extreme 850
Also, I hear MPI is no longer selling parts, so again any insight on this unit would be greatly appreciated.


Mike P
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Chain Case. Inspect your chain case at least every 4k miles. Make sure you have an AFR gauge. Let the turbo cool for a moment before shutting off. Always carry an extra belt. Make sure your gears and clutch have been set up foe the increase in power. I'm sure more people will chime in.


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What did they set your Gems too?
ViperTurboPete
TY 4 Stroke Master
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2022 Expedition Extreme 850
Gems lol! This is why I posted my question(s). I have no idea what Gems stands for (I will google). I know lots about sleds and do my own wrenching, but know zero about turbo chargers. Any information on what the "gems" should be set at would be much appreciated. Sorry guys for being so out to lunch on this topic, but I don't know if the Gems controller comes with the machine or if I have to buy one.
AFR...Air Fuel Ratio guage...got it. Just need to know which one you guys recommend to go with.
Getting at the chaincase on this machine looks like it will require a complete tear down! Ulmer recommends a 22 top gear (from 21) to achieve 110 mph. Looking into his clutch kit and machined secondary.
I have been on this forum for many years and on the two stroke SRX TYforum (under a different name) prior to 4stroke. It is hilarious that some people around home think I am some sort of guru by modifying my Yamaha sleds, Waverunners. I am no trained mechanic by any means, but I owe all my knowledge to the members of this forum....you guys are the gurus! It just never ever ceases to amaze me how people help people on here. MrSled, I can't thank you enough for starting it all...
Still have lots of riding here, snow and ice conditions are good. I will be doing lots of reading/researching in the future.
Again, I very much appreciate any input you may have.
Stay healthy, stay home.
AFR...Air Fuel Ratio guage...got it. Just need to know which one you guys recommend to go with.
Getting at the chaincase on this machine looks like it will require a complete tear down! Ulmer recommends a 22 top gear (from 21) to achieve 110 mph. Looking into his clutch kit and machined secondary.
I have been on this forum for many years and on the two stroke SRX TYforum (under a different name) prior to 4stroke. It is hilarious that some people around home think I am some sort of guru by modifying my Yamaha sleds, Waverunners. I am no trained mechanic by any means, but I owe all my knowledge to the members of this forum....you guys are the gurus! It just never ever ceases to amaze me how people help people on here. MrSled, I can't thank you enough for starting it all...
Still have lots of riding here, snow and ice conditions are good. I will be doing lots of reading/researching in the future.
Again, I very much appreciate any input you may have.
Stay healthy, stay home.


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GEMS, is the little box that controls the fuel on that turbo, they should have given you info on what was set. Also you must have boost and AFR gauges to properly tun that turbo. What was installed for clutching?
ateick
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Once you have boost and afr gauges you want to monitor max. boost and afr ranges from idle to WOT to ensure you are in the safe area and that GEMs is working correctly. You would adjust GEMs if you needed to add/remove fuel in low load/med load and high load situations.
AEM makes great gauges but can be pricey
Boost you don't want over 6 psi.
AFR you want:
- Idle 13's
- 1/4 throttle and below 13
- 1/2 throttle 5000rpm 12.5
- 3/4 throttle 7000rpm 12
- WOT 11
AEM makes great gauges but can be pricey
Boost you don't want over 6 psi.
AFR you want:
- Idle 13's
- 1/4 throttle and below 13
- 1/2 throttle 5000rpm 12.5
- 3/4 throttle 7000rpm 12
- WOT 11
ViperTurboPete
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2022 Expedition Extreme 850
Thanks for the input aetick!
I have no idea what the clutching is...the person I bought it from didn't have a clue. All he mentioned that the dealer said primary needed a lot of weight and a Sidewinder spring was installed in the secondary. I hate not knowing what is going on in there so I will be looking into Ulmer Viper clutch kit he offers so I know exactly what's going on. I will be calling the dealer if they have any information. Some dealers don't have a clue (other than replacing parts) in my past experience, so I hope these guys would know. It is a very small dealer so I don't think they sold/installed very many turbo kits.
The previous owner didn't know how many cylinders the engine had...he used it for fishing.
I have no idea what the clutching is...the person I bought it from didn't have a clue. All he mentioned that the dealer said primary needed a lot of weight and a Sidewinder spring was installed in the secondary. I hate not knowing what is going on in there so I will be looking into Ulmer Viper clutch kit he offers so I know exactly what's going on. I will be calling the dealer if they have any information. Some dealers don't have a clue (other than replacing parts) in my past experience, so I hope these guys would know. It is a very small dealer so I don't think they sold/installed very many turbo kits.
The previous owner didn't know how many cylinders the engine had...he used it for fishing.
Last edited:
rbell14
TY 4 Stroke Guru
Fishing?? ha ha, that's classic! 180HP fishing machine.
ViperTurboPete
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Its true lol! My buddy's father in law is his neighbour. He used it a lot for fishing was always hauling a sleigh. No different than me I guess. I used my SRX's to go high performance ice fishing as well (without a sleigh).
ateick
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Oh and your XTX has 21/41 gearing I believe which is what most people want to change to in order to max top speed on these Vipers. I for example have 24/50 stock on my RTX. You may want to save money and stick with what you have.
ViperTurboPete
TY 4 Stroke Master
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2022 Expedition Extreme 850
Correct 21/41 gearing, but the XTX has 8 tooth drivers vs your 9 tooth.
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