I have a friend that just bought a 2012 SG with the 103 and he did the V&H's power duals, 4" Rienharts sllip on, highflow intake and the HD Screaming Eagle Race Tuner.

He had it dynoed and i could tell instantly that the bike wasn't right, so I recomended the guy that has dynoed my bike and several friends and as far as I can tell did a great job. So he had it dynoed again and now we are seeing a issue that the dyno guy is saying normal...

He can cruise at any rpm and snap the throttle and it cuts out for a split second and then takes off just fine. We took it back and the dyno guy told us that it's due to the factory cams on the 103 not being big enough. He is basically saying that with the bike setup with a damn near perfect AFR and he snaps the throttle it is dumping so much fuel and there is not big enough cams and that is what is causing the lag.

Anybody got any ideas?

 

What happens when the power is rolled on instead of "snapped" on? Cams not big enough, doubt it. I haven't ridden a TBW bike but suspect that part of the snap/lag is due to the TBW, not the cams.

 

It sounds like the power enrichment where dumps more fuel on the se tuner you can not adjust this. This would be somehting to ask Brian from Valley Racing or Doc from hdmm tuning. To great tuners

 

I don't think it is his TBW unless there is something that is actually wrong with it. I have a 11 SG that has all the same setup except mine is a 96" motor and I used the same dyno guy and you can snap the throttle and there is no lag at all.

 

Thansk I will try and find their info and give them a call and see what they have to say.

 

http://docsperformancetuning.com/ Doc is a great guy as well as one of the top tuners in the country.

 

The dyno guys I use are a race shop mainly working big Jap bikes for endurance racing. They also do a lot of work on street tuning big Jap bikes and apparently they get a big improvement in throttle "snap" on street tunes by adjusting the FI potentiometers (or something) because basically these big bhp motors are slightly de-tuned in the factory to make the throttle response less sudden as some riders could otherwise get into big trouble quickly. They think that HD have done something similar possibly to prevent crank twisting. I'm only passing on hearsay but it might be something to look into.

 

There are many things that can be adjusted when tuning. One issue withthe TBW bikes that is hit and miss from bike to bike is the throttle "lag" from when you twist the throttle to when the engine actually responds. On the newer bikes the throttle progressivity is set as such that you do not get full throttle opening, even with a full twist of the wrist until about 3000 rpm. This can be adjusted. Another is that the amount of fuel being dumped when the throttle is snapped open may be too much or too little. This too can be adjusted to provide a small shot of more fuel or less fuel at the time the throttle is activated. Without actually knowing whether it is too much or too little it is hard to say what needs to be done, but usually you will get lag if not enough fuel, and you will get a "stumble" when too much fuel. Really hard to describe in writing, but an experienced tuner will know the difference. I am betting that it is more of a fuel lag, and needs a bit more fuel immediately upon throttle opening.

It is definitely not the cams, you can tune this out.

 

Maybe not but it could be and just something to check and eliminate as the source. As Dalton points out, this can be adjusted by the tuner. That TBW lag setting may be different on your bike than the OPs. The OP describes the anomoly as a "cut out"; does that mean a lag or a stumble as Dalton make reference to? A competent tuner will know how to deal with the anomoly; it's definitely not the cams. The OP needs to find another tuner.