JIMS engines are high-performance aftermarket V-twins manufactured by the California-based JIMS USA. The company offers three different Twin Cam engines with displacements of 120”, 131”, and 135”, rated at 125, 130, and 136 HP, respectively.
If you want to find out more about these high-performance power mills, you’ve come to the right place.
We at PowerSportsGuide have compiled all you need to know into this JIMS engine review!
What is a JIMS Engine?
JIMS USA is a well-known name among performance-minded riders. This is no surprise since the company has been in the marketplace since 1967!
JIMS is a California-based manufacturer producing transmissions, performance kits, and complete high-output V-twin engines. These products are primarily designed for Harley-Davidson motorcycles but they are also commonly being used by custom motorcycle builders and racers.
Every part of a JIMS engine is engineered for maximum performance and longevity.
Although they produce a remarkable performance in stock condition, they are able to produce much more! This means that JIMS engines can tolerate numerous performance modifications very well.
It’s also good to know that JIMS Twin Cam engines are available with Evolution motor mounts as well. Thanks to this option, they can fit into any OEM or aftermarket Evolution-style frame.
Besides complete engines, the manufacturer offers heavy-duty transmissions and other performance motorcycle parts.
Whether you are building a custom race bike, just looking for a replacement engine, or parts for your current machine, you can’t go wrong with JIMS products.
Drawbacks?
To the greatest regret of many fans, JIMS engines are marketed as “race engines,” meaning that they are not street legal.
Where are JIMS Engines Built?
JIMS engines and parts are proudly manufactured in the US. You can find the machine shop and the company headquarter in Camarillo, California.
JIMS Engine Reviews
JIMS currently offers three different engine configurations, which are as follows:
- JIMS 120” Twin Cam Race Engine (125 HP)
- JIMS 131” Twin Cam Race Engine (130 HP)
- JIMS 135” Twin Cam Race Engine (136 HP)
The available features and options for these engines are as follows:
- Customizing options
- “Evolution mount” Twin Cams
- One year factory warranty
- Night Train Engine Cover Set
- Diamond Cut cylinder heads
- JIMS thick-walled cases
Let’s get down to the nitty-gritty and talk about these power sources in detail!
JIMS 120” Twin Cam Race Engine Review
The 120” Twin Cam Race is the smallest engine in JIMS’ fleet.
Just like its bigger brothers, the JIMS 120” also features a thick-walled case that ensures outstanding strength. This solid case can accept cylinders with bore sizes of up to 4.8”.
This power mill comes with many advanced features including JIMS Forged Pistons and pressed flywheels, Screamin’ Eagle valve springs, JIMS Powerglide II tappets, and forged 4340 steel connecting rods.
Thanks to these features, the JIMS 120” can put out 125 HP with 121 ft-lbs of torque in stock condition.
The key features of the JIMS 120” are as follows:
- Screamin’ Eagle® valve springs
- JIMS Powerglide II high-performance tappets
- Screamin’ Eagle Adjustable Pushrods
- ARP® Cylinder Studs
- JIMS Roller Rockers
- JIMS Forged Pistons
- Screamin’ Eagle Cams
- JIMS Pressed & Welded Flywheel Assembly
- JIMS Cylinders
- JIMS Engine Cases
- Timken Bearing
Furthermore, the key specifications of the JIMS 120” engine are as follows:
- Horsepower: 125 HP
- Torque: 121 ft-lbs
- Cam Lift: .658”
- Intake Valve: 2.120“
- Bore: 4.125”
- Stroke: 4.500”
- Case Material: A356-T1
- Connecting Rods: 4340
- Compression: 10:1
- Recommended Octane: 91
JIMS 131” Twin Cam Race Engine Review
The JIMS 131” engine is a more advanced, big bore configuration of the 120”.
They share the same stroke (4.500”) but the 131” comes with larger cylinders with a diameter of 4.313”.
Besides larger cylinders and pistons, the JIMS 131” saw some performance upgrades like CNC ported heads for better airflow.
For an adequate oil supply, the engine is equipped with a high-flow Harley-Davidson oil pump, which can be found on OEM H-D Twin Cam engines.
Other features include JIMS Billet Cam Support Plate, H-D hydraulic cam chain tensioner, and JIMS Powerglide II tappets.
The big-bore cylinder configuration combined with these enhancements ensures a performance of 130 HP with 135 ft-lbs of torque.
JIMS 131” engine features:
- Screamin’ Eagle® Adjustable Pushrods
- JIMS Billet Cam Support Plate
- ARP® Cylinder Studs
- JIMS Roller Rockers
- JIMS Forged Pistons
- JIMS Powerglide II Tappets
- JIMS Pressed & Welded Flywheel Assembly
- CNC Ported Heads
- H-D Hydraulic Cam Chain Tensioner
- Screamin’ Eagle Cams
- Screamin’ Eagle Valve Springs
- H-D High Flow Oil Pump
- JIMS Cylinders
- JIMS Engine Cases
- Timken Bearing
JIMS 131” engine specifications:
- Horsepower: 130 HP
- Torque: 135 ft-lbs
- Cam Lift: .658”
- Intake Valve: 2.120“
- Bore: 4.313”
- Stroke: 4.500”
- Case Material: A356-T1
- Connecting Rods: 4340
- Compression: 10.5:1
- Recommended Octane: 91
JIMS also sells a 131” Big Bore Kit separately intended to turn a JIMS 120” into a 131”. The kit contains a set of 4.313” JIMS cylinders completed with a set of 4.313” JIMS pistons.
You can find the same cylinder setup in the stock JIMS 131” race engine.
If you already have a JIMS 120” engine but are considering upgrading it to a 131”, this kit is for you!
JIMS 135” Twin Cam Race Engine Review
JIMS 135” Twin Cam engine is the flagship model in the lineup.
This power source features impressive cylinders with a bore of 4.313” and a stroke of 4.625”.
This big-bore configuration is complemented with many other performance parts including CNC ported heads, a JIMS Billet Cam support plate, an H-D hydraulic cam chain tensioner, a Screamin Eagle Hi Volume oil pump, and JIMS Powerglide II tappets.
Power?
As you might expect, the 135” is the most powerful JIMS engine with a performance of 136 HP and 135 ft-lbs of torque.
Just like any other JIMS engine, the 135” provides excellent reliability and durability.
JIMS 135” Engine Features:
- Screamin’ Eagle® Adjustable Pushrods
- JIMS Billet Cam Support Plate
- ARP® Cylinder Studs JIMS Roller Rockers Arms
- JIMS Forged Pistons
- JIMS Powerglide™II tappets
- JIMS Pressed & Welded Flywheel Assembly
- CNC Ported Heads
- H-D Hydraulic Cam Chain Tensioner
- SE 266 Cam
- Screamin’ Eagle Valve Springs
- SE High Flow Oil Pump
- JIMS Cylinders
- JIMS Fat Tube Pushrod Covers
- Black High Lift Rocker Covers
- JIMS Engine Cases
- Forged Rocker Support Plates
- Timken Bearing
- ARP Case Bolts
JIMS 135” Engine Specifications:
- Horsepower: 136 HP
- Torque: 135 ft-lbs
- Bore: 4.313”
- Stroke: 4.625”
- Cam Lift: .658”
- Intake Valve: 2.120”
- Case Material: A356-T1
- Connecting Rods: 4340
- Compression: 10.67:1
- Recommended Octane: 91
Options and Extra Features
JIMS engines are available with some custom features, including:
- CNC custom lettering: Would you like to display your name on your engine? JIMS can deliver their engines with unique lettering stamped on the cylinder heads.This CNC custom lettering service is a unique way to customize your engine!
- Diamond cut cylinders and heads: JIMS engines are available with a unique patented diamond finish as well. The surface of these heads and the cylinders are covered with hundreds of cuts, which provide an amazing reflection of light. This shine and sparky look gives these engines an unbeatable, head-turning appearance.
- Night train engine cover set: JIMS engines are also available with “Night Train” black cover sets. These sets are OEM Harley-Davidson engine covers that are modified to fit on JIMS engines. Therefore, they can perfectly accommodate JIMS roller rocker arms.
- 10.5:1 compression upgrade: Although the stock JIMS 120” engine has a compression of 10:1, it can be increased up to 10.5:1 as an option.
JIMS Engine Specs Chart
For your convenience, we’ve compiled the key specifications of JIMS engines into one chart:
| Specs | Jims 135″ | Jims 131″ | Jims 120″ |
| Displ. (cu in) | 135 | 131 | 120 |
| HP | 136 | 130 | 125 |
| Torque (ft-lbs) | 135 | 135 | 121 |
| Bore (“) | 4.313 | 4.313 | 4.125 |
| Stroke (“) | 4.625 | 4.500 | 4.500 |
| Compression | 10.67:1 | 10.5:1 | 10:1 |
| Cam Lift (‘) | .658 | .658 | .658 |
| Intake Valve (“) | 2.120 | 2.120 | 2.120 |
Disclaimer: These charts are for informational purposes only! For more information, please check the official factory manuals!
Takeaways – FAQs About JIMS Engines
As a takeaway, we’ve answered the most frequent questions about JIMS engines!
What Size Motors does JIMS Make?
JIMS currently offers three different engine sizes including 120”, 131”, and 135”.
How Much Horsepower Does a JIMS Engine Have?
The HP rating of JIMS engines ranges from 125 up to 136 HP:
- JIMS 120” Twin Cam Race: 125 HP
- JIMS 131” Twin Cam Race: 130 HP
- JIMS 135” Twin Cam Race: 136 HP
Which JIMS Engine is the Biggest?
The biggest JIMS engine is the 135” Twin Cam Race twin rated at 136 HP with 135 lb-ft torque.
Are JIMS Engines Street Legal?
No, unfortunately, JIMS engines are not street legal. This is why these high-performance twins are marketed with a “Race” label.
What Kind of Oil do JIMS Engines Use?
As per the original owner’s manual, the manufacturer recommends mineral-based engine oils for JIMS engines, like H-D 360.
Are JIMS Engines Made in the USA?
Yes, JIMS engines and performance parts are manufactured in Camarillo, California.
Is JIMS a Harley Engine?
Contrary to popular belief, JIMS engines are not made by Harley-Davidson. Instead, this brand produces aftermarket performance V-twin engines that can be a replacement for Harley-Davidsons or the heart of a custom-built.
How do You Know Which JIMS Engine You Have?
You can identify a JIMS engine based on its serial number. Once you locate the number you may want to call the manufacturer as they will likely help you identify your engine.
Is JIMS Still in Business?
Yes, to the delight of many tuners and racers, JIMS USA is still in business. You can find out more by contacting the manufacturer here.
Are JIMS Motors Any Good?
Yes, it’s safe to say that JIMS engines are some of the most reliable and durable V-twin power sources available. These engines produce a remarkable power out of the box, but they are also strong enough to tolerate heavy performance modifications.
This is why JIMS engines are widely popular among racers!
References
