2000 yammy 100 4 stroke with no mid range

vanislehunter

Active Member
Good Morning Everyone.

I have a 100HP yamaha 4 stroke from 2000. It's carburated. It starts and idles beautifully and runs WOT beautifully. I have almost no midrange though. From about 2100RPM to ~3000RPM it shutters, and if you try to push through that range too fast, it dies. Thoughts?
 
Good Morning Everyone.

I have a 100HP yamaha 4 stroke from 2000. It's carburated. It starts and idles beautifully and runs WOT beautifully. I have almost no midrange though. From about 2100RPM to ~3000RPM it shutters, and if you try to push through that range too fast, it dies. Thoughts?

Could be your VST filter.
 
Clean the carbs and make sure your sync them using the syncing tool, buddy had a 50 4 stroke carbed motor did the same thing cleaned the carbs used the syncing tool and runs like a top at all ranges now. Ethanol in the fuel is killer on carburetors especially if they sit for any length of time.
 
Clean the carbs and make sure your sync them using the syncing tool, buddy had a 50 4 stroke carbed motor did the same thing cleaned the carbs used the syncing tool and runs like a top at all ranges now. Ethanol in the fuel is killer on carburetors especially if they sit for any length of time.
The syncing tool is called a Manometer. I am happy to be corrected, but unless they are way out of wack he symptoms would most likely be a loss of performance, not stalling, no?
 
Gummed up carb would be causing the stalling. Out of sync carbs would still run and the syncing will make it run and idle smoother. My motorcycle has four carbs so I’ve gotten dialed in on syncing carbs haha.
The syncing tool is called a Manometer. I am happy to be corrected, but unless they are way out of wack he symptoms would most likely be a loss of performance, not stalling, no?
No it stalled going into gear could have been the gumbed carbs tough to say as he did both at the same time.
 
You can sync outboard carbs without any tool. One carb is fixed and you just lossen off the linkage on the others so that they all match the fixed one.
 
Most likely gummed up carbs/sync issues like the others have said, but the F100 also had a TPS that they used to control the timing, very specific and finicky setting for it and impossible to adjust without the proper breakout kit and a mulit-meter. Typically this being out would show up more at idle and not mid range but if it's way out it could be delaying the advance causing your shuddering/stalling.
 
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