55mm HP Inc Throttle body question

[BrianM]

Hi Mike, I need some guidance on figuring out why my bike wont idle when cold. I just built a 98" kit with flat top pistons and the R&R heads, basically the same exact build as "Sledman" who told me about you and this forum. He brought his bike to you from Idaho. Anyhow, I had my bike tuned at RC Cycles in Hayward and it runs great but when I start it for the first time of the day it will fart back through the air cleaner once or twice and die unless I constantly jockey the throttle. Once it is warm it runs great but even shutting it down for 20 minutes will sometimes have the problem return. At the tuner's suggestion I tried raising the warmup enrichment field since he always pulls fuel out in that table but it is still happening. Do you have any suggestions on where to look? Thanks, Brian

Here is my build:
2006 FLHXI Street Glide
98" GMR kit
585/615 cams S&S Gear Drive
R&R Cast heads with raised port
55mm HP Inc throttle body for 2006 models
25 degree HD injectors
S&S teardrop AC
FULLSAC true dual kit - Fullsac muffs
SERT
Rev Perf roller rockers

[BrianM]

Anyone have any suggestions on what to check or where to look? I heard you may have run into this problem before on the HP throttle bodies... I sure would appreciate it if anyone knows what I should check,

Thanks

Brian

[Mike]

Apologies for late reply. It may be the IAC steps are out of sync or near min or max. You can go to Data Monitor in SERT Data Mode and view in real time the IAC step counts. They should be within 5 of the IAC steps table in tuning mode, be sure to check engine temp so that you are comparing the same point on the table. You can adjust this by turning the throttle stop screw on the front of the throttle body. Turning the screw in (opening the throttle plates) will decrease the steps and turning it out (closing the throttle plate) will increase the steps. It take the IAC a few moments to catch up with the adjustments and very little makes a big change. Do just small adjustments at a time and let the IAC stablelize after each. You'll have to remove the air cleaner backing plate to make these adjustments, the bike should be at least at 64-80c and idling.

Another possibility is that your idle rpm may be set too low. Motors with performance work often require idle settings higher than normal to maintain good idle and prevent dying. We routinely set ours to 1050 or even 1100. Even with this target the motor may actually idle slightly lower than the set rpm because the cams may not allow for smooth idle.

Let me know if this works out. Mike

[BrianM]

Mike,

That's exactly what it was... THANK YOU!!!

The problem I had is that I did all the build work myself and took it to this tuner and they dyno'ed it for me but I didn't find out about the cold start problem till I got it home. They said they have installed plenty of HP Inc TBs but they should come pre-adjusted from the factory and they never have to adjust them. Finally he adjusted the stop and I could see the difference immediately. As soon as he turned the screw the idle RPM went up until the IAC reset and then it smoothed out and idled correctly. He had it hooked up to the data mode on the SERT so we could get the steps perfect but we didn't end up checking the voltage. I let it sit for 45 minutes at their shop and then restarted it and it ran perfect and didn't cough or sputter.

I rode it home through a monsoon (it was fun) and the next morning I went out in the garage and pushed the started button and it ran for over a minute without touching the throttle... just like it's supposed to.

If I ever get up your way I'll stop in and buy something,

Thanks, Brian

[Mike]

Always glad to hear things work out.
Mike