Hi all - First post from a long time lurker. Looking for some tuning or troubleshooting help after a cam install.

A friend recently got a S&S 465 cam put in his 2020 107 Street Glide. After getting the bike back from the shop, the bike has an issue where the rev's hang when the bike is warm. Bike runs great cold, but once warm rev's hang between 1,300 and 1,700 RPM. I have a bit of tuning experience, so I offered to take a look. This is a tough one.

Here is what seems ok:

• Engine temp and Intake temp sensors reading ok.
• MAP is around 32kpa at idle.
• Motor idles as expected when cold.
• Motor sounds good and tight. ie: no exhaust leaks, no misfires, coughs, sneezes, chirps, clicks or clacks.

Here is what is odd or not right:

• I can see the ECM command a lower idle RPM as the bike warms up, but the motor does not respond and rpm's stay high.
• Throttle grip reads 0%, but the throttle blade will walk down from 3% down to 1% as the motor warms. It does not reach 0%.

Some questions:

Do these M8's have IAC valves, or does it use the throttle blade to regulate idle speed?
Should the throttle blade ever reach 0%? Or alternately is 1% perhaps too low, indicating that the ECM is trying to compensate for an intake leak?
A throttle-position reset was done twice, no difference in behavior. (4 ignition cycles, 10 seconds on, 10 seconds off)

Map tooth settings: IVC = 38, IVO = 19. Unsure if this is right, but other than this problem I don't think I have any reason to suspect it's wrong.

The bike is currently running a Dynojet provided map in a Power Vision. Owner just switched from a Fuel Pack, which was behaving the same way. Bike is running a closed loop map. Fueling seemed to be pretty rich during our testing, but motor ran great otherwise and cam provides a noticeable performance improvement. I understand the top end was taken apart during the cam install, but I don't have details as to how far down it was taken. I mention this to bring credit to a potential intake leak.

My next steps: I'm considering writing an open-loop map to hopefully determine if the condition is triggered by a switch to closed-loop, or if its simply engine-temp related. I also want to investigating for intake leaks.

Anyone have any thoughts on what else to check? Any troubleshooting ideas?

Thanks!

 

It's hard to fathom that they would take the top end part to just swap the cam... But anyway, have you verified that the throttle hand grip isn't sticking?

 

Thank you for the reply - the bike was taken to (what I believe was) another shop, where it was found to have a cracked intake manifold. Replaced, and bike is up and running great.

The shop doing the work said the air cleaners backing plate and/or its mounting screws caused the crack; likely from being over-tightened at some point.

 

Sounds like an intake leak. They have been known to crack.

 

^ Nailed it!

I didn't realize it was a common problem.

 

Right exhaust and tune once it is fix . he is going to love that $^% in a 107.