Editor’s Note: We’ve worked with JIMS staff for maybe 30 years, maybe longer. Jim Thiessen has one of the most solid companies in the industry. When the custom world is on fire JIMS keeps rolling along. So, when we decided to create something completely nuts for Bonneville in a Belly Tank configuration I discussed it with Jim and he immediately wanted to be involved. JIMS is our first, and so far our largest 5-Ball Racing sponsor behind this endeavor. Second to JIMS is Kent Weeks of Lucky Devil Metal Works, then Paughco.
When I discussed this endeavor with Jim he had just announced his new 135-inch twin cam, a similar engine to the JIMS engine used by Hiro on the salt this year for more records.
I reached out to Paul Platts and quizzed him about the new JIMS race engine sold exclusively through H-D dealerships.
BIKERNET: Tell us a little about the JIMS history of building engines with H-D?
JIMS: JIMS and H-D entered into a license agreement back in 2000. H-D licensed certain twin cam intellectual property so JIMS could build an authentic twin cam motor. Some aftermarket manufacturers prefer to design around a patent; JIMS went the other way and licensed the intellectual property. All JIMS engines use authentic Harley-Davidson product, or JIMS product … They can be easily worked on at any authorized Harley-Davidson dealership.
BIKERNET: How is this engine improved over the 131?
JIMS: The main difference is stroke. The 131 is 4.5 stroke x 4 5/16 bore. The 135 is 4 5/8 stroke x 4 5/16 bore. Other upgrades include JIMS pushrod covers, Multiple cam cover options with black rocker box covers, and the Screamin’ Eagle upgraded oil pump.
BIKERNET: Why did your team pick this bore and stroke configuration?
JIMS: Although these are ‘race only’ motors, It’s very important to JIMS to develop a stroke and bore configuration that can live up to durability in the real world. The 135 was a modest step up from the 131 without sacrificing reliability.
BIKERNET: Where are the cases improved and why?
JIMS: JIMS needed to develop a special case in order to spread out the cylinder head bolt pattern. While doing this, JIMS also added more material in many areas for strength. Every single JIMS engine utilizes a Timken style bearing in the left case.
BIKERNET: What’s the compression of this engine and what is the piston configuration?
JIMS: JIMS engines either come with a flat top piston, and or a slightly dished piston. The compression ratio is 10.67:1, which once again, is designed for many hundreds of hours of reliability. Many customers increase compression after purchasing the engine, but we wanted to keep the compression ratio down for dependability. It is always recommended that JIMS engines use high-octane pump gas.
BIKERNET: What connecting rods do you use in this engine?
JIMS: The JIMS engines incorporates the Screamin’ Eagle I-beam connecting rods. These rods are forged, incredibly strong and proven in thousands of flywheel assemblies.
BIKERNET: Do you change the valve configuration from stock other than the roller rockers?
JIMS: No, the heads used on the JIMS motors are CNC ported Screamin’ Eagle heads with the JIMS bolt pattern machined into them.
JIMS: The pistons used in the JIMS engine are fully machined from a forging at CP pistons. These pistons have been durability tested with zero issues, and have proved themselves over the years to be next to bullet proof. There are proprietary skirt profiles that help with piston wear.
BIKERNET: What will this engine rev to?
JIMS: 6400 rpm
BIKERNET: Does JIMS offer a series of cams for this motor for different applications? Are there mid-range torque cams and top speed cams?
JIMS: No, JIMS offers the engine with the Screamin’ Eagle 266 cam. A very good performing cam that once again … Doesn’t take away from reliability. Many customer change cams after purchasing the motor, but all of JIMS testing is done with this cam.
BIKERNET: Are the engines factory balanced?
JIMS: The flywheel assembly is fully machined on every surface, giving JIMS the ability to balance at the machine center. Yes, all JIMS engines are balanced to spec.
Is there any need to do anything except install it and go for a ride? Like any change, the engine will need proper tune / mapping.
The process goes like this… Install in chassis, tune for break-in period, break in motor, tune for power ~ then go have fun at the track!
BIKERNET: What does JIM recommend for break-in procedure?
JIMS: First 50 miles do not exceed 2500 / 50mph varying speed, next 500 do not exceed 3000 / 55 mph varying speed. Oil change at 50, 500 and 100 miles. Very similar to stock.
BIKERNET: This is a monster. Does JIM recommend any added chassis elements, such as a performance clutch, outboard bearings on a belt drive system, a true track on a touring frame?
JIMS: The added recommendations include: Large intake (As big as possible), performance exhaust (must have larger header tube), performance clutch & S.E. Race tuner.
BIKERNET: We are going to install one of these monsters in our Streamlined Trike Bonneville effort with a carburetor and most likely a D&D exhaust system. We are using a Paughco Rubber mounted frame carriage with the oil bag under the 5-speed transmission. We are thinking about a CCE larger oil tank, massive oil coolers, and perhaps two of the JIMS head fan systems. Would you recommend anything else?
JIMS: You are on the right track for keeping the motor cool! Large oil capacity and fans = awesome!
BIKERNET: Tell us about ordering one of these engines?
JIMS: They are all sold through H-D dealers.
I would note that each engine is built to order. They are custom. The customer can pay for custom engraving on the heads, diamond cut is available, manual or automatic compression releases, night train covers, compression hop up, etc. are available.
We have all Twin Cam cases, early to late, as well as a Evo mounting twin cam, which has the Evolution Mount cast in the case.
These engines come with a 1-year warranty.
