My 120ST on the Fuel Moto Dynojet 250i with Target Tune

[hulkss]

I finally got around to tuning up my 120ST. I took it to Fuel Moto in Wisconsin and Jamie did the tuning. Jamie said the engine sounds normal and runs like it should. I was worried about a little cold start piston slap, but I guess that is normal for big bore forged pistons in air cooled motors.

My 120ST crate motor is bone stock P/N 19221-15. It has the the H-D high flow dual-cat exhaust P/N 64800043. I'm using an S&S Stealth air cleaner P/N 170-0164. The H-D SE A&S Clutch Kit P/N 37000026 held the torque no problem.

Fuel Moto installed a Dynojet Target Tune wideband O2 sensor system and tuned the bike with a Dynojet Power Vision tuner. The bike is really running sweet now.

 

[NGOT8R]

Looks like it's running good hulkss. Are you still planning on building the FM 113, or are you going to shelf that project until a build is absolutely necessary?

 

[RuknRole]

Buck twenty all around! Nice!

 

[hulkss]

I have all the parts so I will see if I can get my hands on a video bore scope and have a peek inside. If the cylinder walls look good, I will put in all the new valve train parts and not do the flywheel/rod assembly and pistons. All I will need to remove is the rocker covers and cam chest cover to get at everything. I'll check out the compensator too.

Jamie at Fuel Moto strongly recommended changing to AV&V Beehive valve springs and better lifters (I have S&S Premium lifters on hand with their new cam plate and 3 element oil pump). He has seen two messy OEM lifter failures that ruined the engine cases. The stock valve springs are stiffer than needed for the SE259E cam I am using and some say are loading the lifter rollers more than necessary.

 

[hulkss]

Buck twenty all around! Nice!

I REALLY LIKE the flat torque curve. The engine pulls hard through the gears and does not lose torque as the revs build.

 

[Designflaw]

Hulk,
Now that you've had it a bit how does it compare $$$ to Butt Feel? Using just round round numbers, 120 with proper set up 10-12,000 vs. 103 to 107 or 110 for less than half? This is all hypothetical. This winter I may try cams and head work. I think that is about as far as I will go.

 

[hulkss]

Hulk,
Now that you've had it a bit how does it compare $$$ to Butt Feel? Using just round round numbers, 120 with proper set up 10-12,000 vs. 103 to 107 or 110 for less than half? This is all hypothetical. This winter I may try cams and head work. I think that is about as far as I will go.

Cost wise:
120ST @ MVP price (15% off) $4841.
Sell used motor on eBay for $1500.
Everything else: exhaust, clutch upgrade, tune. You already have exhaust and tuner. You need the clutch with any upgrade.
So if you do the work yourself, and it is easy because there are no precision parts to handle, it can be done for about $3500 net.

Cams and head work without new pistons usually ends up lacking compression ratio. If you mill the heads, then your valve to piston clearance is affected.

Feel wise, this is like driving a 6.2 liter LS3 Chevy. Yes, I would do it again for sure. Best improvement in a bike I have ever done.