Here we go again...

[Cable810]

Here we go again....

My viper is back to stuttering.... I can't tell if it's either a fueling issue or a spark issue.

Found two boost leaks and fixed them. Thought that was my over all issue but apparently not... went for a short rip and its still stuttering...

Seems to be typically around 5200 to 6200 rims.

Here is a youtube video when it's stuttering.

Also here is my first post relating to this issue.

Viper Miss/Stutter. Wont fire on .02 Gap

After the first ride of the season I'm left with trying to get the sled running right... 2015 Viper MTX Mpi turbo. Between 5100 and 6200rpms there's a stutter and sounds like a miss. 0lbs of boost at around 40-45mph i get a constant stutters and sounds like it's missing as well. Once I get...

ty4stroke.com

Had it fixed and ran great but unfortunately ended up back in the same spot...

I've got new coils on the way cause why not. I have one coil that's Ohm reading a touch different than the other 3 coils. New plugs this year gapped at .020.

I'm also in touch with Ulmer

 

[Cable810]

Tested sled with new coils nothing changed. New inline fuel filter nothing changed. Put old tune back in no change. Afr reads perfect at idle and low cruise speeds. As soon as I get on it and it starts to stutter the afr jumps to 19-20....

Fuel pressure at idle was within spec next is to try and see what pressure is at when it stutters

 

[Cable810]

E-mail I sent to Ulmer tonight

Took it for a spin tonight and I decided to change the belt. Saw a slight change still stuttered and AFR hit 19-20.
Robbed a 8dn Belt of my friends Nytro(3 bolts on the back were removed) adjusted the belt where about 1/16th was above the sheave and saw a significant change! Still stuttering but much better than before! AFR still hits 19-20

I'm beginning to wonder if my Clutching is off in comparison to the PC6 tunes. I had changed the clutching the year after(Oct,'23) I had bought(Dec,'21) the sled from whatever was on the sled to Schmidt Brothers MotorSports stage 2.

I seem to be around 7K when it really wants to build boost and where the stutter or lack of fuel is happening... I have a feeling that my fueling is not matching my RPMs?!?!?!

I could just be going down a rabbit hole with this that is going to lead me nowhere.... I just found it weird that a simple belt change and adjustment changed my issue. I'm going to give Thunder Products Clutching in Cedarville a call tomorrow and talk with them and see what they think.

Thanks to @yamahaguy for letting me pick his brain/helping me come to the possible conclusion to my issue!!

 

[Cable810]

Well I am pretty sure I have finally have the issue narrowed down!!! I'm going to go for a decent ride tomorrow to make sure and I will report back!

 

[Cable810]

Well as a hailmary I decided to throw my GEMS back on the sled Tuesday night after trying another Map modification I received from Ulmer for my PC6 which sadly didn't fix it....

Well the GEMS fixed my issue!!! Something must be up with my PC6. Still in touch with Ulmer regarding this.

After a long 5 frustrating weeks of trying to figure this out I can safely say she is fixed!!! I probably just jinxed myself but guess I'll know Saturday when I meet up with @yamahaguy!!

 

[yamahaguy]

With the miles we put on I think your really close to 95% fixed. I think you said your injectors have been upgraded by a previous owner so maybe the gems setting from Yamaha/MPI need fine tuned a bit to compensate for the different injectors? Just a idea

 

[Cable810]

With the miles we put on I think your really close to 95% fixed. I think you said your injectors have been upgraded by a previous owner so maybe the gems setting from Yamaha/MPI need fine tuned a bit to compensate for the different injectors? Just a idea

You are probably right it needs some fine tuning. For the time being I'm not really going to worry about it.
DynoJet sent me instructions to "Reset" the PC6 not sure if I should go through with it or not. I'll just wait to hear back from Ulmer.