One hundred twenty cubic inches!
- Thread starter hulkss
- Start date
I've been running the SE tuner with a dealer dyno tune. Last night I installed the target tune with a fuel moto map on my PV and it is night and day better performance over the dealer dyno tune. I've had to let my PV sit on a bench for a few years because I couldn't find anyone that knew how to tune with it.
Best combination available, IMHO.
I'm not running a dealer dyno tune. I'm running the factory download tune.
I compared the H-D download to the tuning file I got from Jamie at Fuel Moto and they are the same except for the Lambda Table where the Target Tune can run richer at cruise since it has wide band O2 sensors.
The SE Pro Super Tuner has the same base tuning file as the H-D Street tuner for the 120ST. The tune for your R motor is different than the ST due to the cam. Everybody seems to like Target Tune.
I compared the H-D download to the tuning file I got from Jamie at Fuel Moto and they are the same except for the Lambda Table where the Target Tune can run richer at cruise since it has wide band O2 sensors.
The SE Pro Super Tuner has the same base tuning file as the H-D Street tuner for the 120ST. The tune for your R motor is different than the ST due to the cam. Everybody seems to like Target Tune.
Since we are onto the hot weather coming... I got stuck in stop and go for 20 minutes. My 120ST got up to 352 degrees and spark knock on both cylinders off the lights... I'm wondering what 'normal temps' are for stop and go... run around 250 on the freeway
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Define hot weather...
Apples to oranges, but my dyna would average 280 during summer freeway riding. But if I got caught in traffic, it would easily climb to 300+ after which it would never drop until I actually turned it off. Wards fans lowered it 10-20 degrees and she never hit 300 after that. Keeping it cooler definitely helped avoid that 'hot motor sluggishness' and kept me from staring at the power vision and wondering how hot was truly too hot
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Apples to oranges, but my dyna would average 280 during summer freeway riding. But if I got caught in traffic, it would easily climb to 300+ after which it would never drop until I actually turned it off. Wards fans lowered it 10-20 degrees and she never hit 300 after that. Keeping it cooler definitely helped avoid that 'hot motor sluggishness' and kept me from staring at the power vision and wondering how hot was truly too hot
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Thanks for the input...
And yeah.. I cannot compare Reno, NV weather to AZ weather.. I lived in Yuma for 4 years... so yeah... THATS HOT. we are just now pushing 80+ degrees by mid afternoon.
I have looked at those fans in the past, not an option that is a MUST as traffic here isn't really that bad, just caught a rush hour cluster.
I have found myself staring at the PV more and more monitoring temps and front and rear spark knock... engine temps above 280 seem to trigger more spark knocks and the sluggishness you speak of is evident bad above 300 degrees.
This all seems to be more prominent in 2 up as well ( spark knock ) when the the engine temp climbs up.
Gonna be bringing her in for some diagnostics soon anyway..... got some white smoke at times and oil gets dirty quick ( much quicker than it should) and oil drops to a level i am not happy with and is concerning. Did a leakdown test... 5% in the front and 7% in the rear jugs which is within specs. Compression was dang near perfect... so it's gotta be intake valve seals giving me the issues. We shall see....
As I mentioned in another post, my 120ST has developed a bit of cold start piston slap. I guess this is normal but I need a new project for next winter.
I've got all the parts, tools, and supplies on order to rebuild my 120ST into a 113ST.
The first step will be a ride over to Fuel Moto for a dyno tune on September 12th.
1. They will run a baseline on the 120ST with the factory street tune.
2. Install a dynojet-powervision-target-tune
3. Dyno-tune the 120ST with the new wide-band control capability
4. I'll rebuild the engine over the Minnesota winter (plenty of time for a no pressure build schedule).
5. Ride back to Fuel Moto in the spring for a final tune-up and dyno-run (the fall dyno-tune will be close to correct and the Target Tune will have been checked out).
The advantage to the 113 engine is an improved Rod Length-to-stroke ratio.
The 120ST has a 7.575" connecting rod length and 4.625" stroke: Rod/Stroke= 1.637
The 113ST will have a 7.667" connecting rod length and a 4.375" stroke; Rod/Stroke=1.752
A value of 1.75 is considered ideal by many respected car engine builders.
Short ratio (1.637) geometry makes the engine push the pistons hard against the cylinder walls. Combined with the higher piston velocities of the longer stroke, the pistons and cylinders wear more quickly.
SE pistons 22575-07B are 4.070 diameter @ 10.5:1 compression allowing the stock 4.06 bore 120ST cylinders to be re-bored and custom honed to fit the new pistons.
The engine will be the largest possible bore and stroke for long life in the Harley SE engine cases, IMHO. The 120ST cylinder spigots are .090" thick and fit the SE case bore that is already the maximum possible diameter of 4.262".
Over boring the cylinders to 4.125" would make a 117" motor but the reduced cylinder liner spigot thickness is only 30% as rigid as the 113". Not for me, but it has been done by many others.
Thanks for the help with your list of tools. That got me started and saved a lot of time. The attached list is what I have so far.
View attachment Parts Tools Accessories.pdf
The head pipe on the exhaust I have from H-D (high flow exhaust 64800043) has the required bungs near the exhaust ports for wide band sensors and bungs near the collector for the stock narrow band sensors. I have a set of threaded plugs to replace the stock sensors.
