I'm hoping someone else maybe has had this problem and knows the solution. I have a 107ci with stage II heads, 10.6:1 comp., TR590 cams, D&D Boss pipes. This has been an on going problem that I have spent much money and time trying to solve. Basically it only makes 104Tq/96hp. It starts off strong with between 90 & 95 ft/lbs at 2500 rpm and it hits 100 ft/lbs between 2800 & 3250. After that it just seems like it flattens out and won't make any more power. Gets to 102-104 and thats it. I have tried two different tuners and the results are close to the same. I am currently using a TMax. When I was dynoing today making changes to the AFR it didn't seem to affect the power output to any degree. I'm thinking that it may be a fuel problem. If so, is it electronics or is it injectors? If I replace injectors do I stay with stock or go with 5.3's? Is it possible that there is a broken wire in the harness that is affecting the fuel? I would really appreciate anyone that has had similar problems letting me know how they solved it.

 

Do a compression test on the front a rear cylinders. I cant believe any competent wrench wouldn't think to do this. Who did the build?

Something else to think about, some dyno's don't show good numbers but that doesn't mean the bike isn't running good. Don't get too caught up in the numbers game.

 

Could you possibly post up a dyno sheet? Maybe we could be of more help if we had a little more info. If your injectors are at their duty cycle limits, I would think it would show up as a lean condition on the top end. If your dyno sheet shows the A/F ratio you should see it.

 

Exactly what I was going to say. Was there a baseline pull, and if so what was it? When doing mods like this it's better to compare before and after numbers to see if the percentage improvement looks right rather than just getting a certain number in mind and then wondering why it didn't achieve that number. The real question is how does it ride, is it pulling like a freight train with good, crisp throttle and no flat spots? If so then I'd say forget about the numbers and go enjoy it

 

What size TB do you have? What brand? Have you done head work? What size injectors? Exhaust and A/C? give us all the details so we can help you out.

 

I've checked the compression two or three times, 193 - 195 psi both cylinders. It is exactly what it should be @ 1300 ft. altitude. This is also the second dyno I've tryed, they are with a couple hp of each other. Thanks for the suggestions.
I've got a sheet from the last tuner, I haven't scanned the one from today yet. One thing I did notice is the O2 read on the dyno was showing much leaner than what the tuner was set for. In other words to get a reading of 13.8 I had to adjust the tuner to 13.0. On the other tuner I used there was a richness problem. I'll scan and post a dyno sheet tomorrow.

 

It is the stock 50mm TB TBW with stock 4.3 injectors. 1.9 int / 1.63 ex. D&D Boss 2:1, Arlen Ness A/C w/K&N element.

 

It's been my experiance that the a/f ratio with O2 sensors is usually pretty flat because that is what is managing the a/f mixture. I would think about using the SERT with someone that is very familiar with using it to tune your bilke. My guess is that you need more fuel injector size and a 54mm TB. A friend had a 95 inch, TR600 cam, Baisley heads, larger injectors and 54mm TB, Fatcat D&D and made 105 & 105.

 

I have a 106,see sig. Once you go over the 103 ci you need a bigger tb or it can't get enough air after about 3500 rpm. If your power output peaks near that rpm that would indicate to me it's not getting enough air.
My motor still has stock injectors,58 mm tb,ported heads and a pcv and it makes 107 hp and 115tq. Mine hits 100tq at 2300rpm and stays over 100 til 5200rpm then the engine hits 100 hp and keeps climbing til the rev limit at 6200 rpm.
So I don't think it's your injectors if my stockers can handle it,I think it's not enough air.

 

The injector size can be a little misleading ... it is the amount of fuel that can be delivered during the duty cycle that is key (and there is even a 'bigger' one that delivers less fuel) ...

If you're using T-Max, have you contacted Zippers to check with them whether you're using the recommended base map ...? I had a guy on another forum provide a base map for my setup ... he didn't adjust the fuel curves so much as making some changes to the timing curves ...

Have you done anything with the ignition timing ...?

Just a thought ... it does seem like you should be getting higher torque and HP numbers out of that build ....

R/
'Chop