DRZ400 Engine Rebuild

This article follows the process of a DRZ400 engine being rebuilt after running a bottom end bearing. It starts at the very beginning with cases apart. Because of running a bearing and potential metal contamination throughout the entire engine, the goal is to remove and replace all crankcase bearings. Following that it will be a process of dissemble, clean, inspect and measure every part subject to wear or that could potentially be harbouring contaminants.

This isn’t a comprehensive rebuild article with exact assembly sequences, torque specs etc, however it shows the majority of the steps and provides anyone interested in rebuilding a DRZ400 an excellent insight to the process.

Washing up and cleaning surfaces of the left hand crankcase in the wash bath.

Both crankcase halves all washed up, all spic and span.

Crankcases wrapped and set aside ready for installing bearings.

Oil Pump

After cleaning up the cases the transmission was next but I was waiting for new input and output shaft circlips so it was onto the oil pump. This was disassembled, washed, inspected for wear and then reassembled.

DRZ400 Oil Pump

Washing up all of the oil pump parts.

Inspecting oil pump parts for wear with a positive result of all parts being in good condition.

Oil pump lubed up, new circlips and assembled.

Bagged up and ready for assembly.

Transmission

With a parts delivery from Mr Suzuki which included the transmission shafts' circlips it was into the wash bath, clean, inspect, measure and reassemble.

Washing up the output shaft and gears followed by the input shaft.

Cleaned, inspected and measured. All was within spec.

Lubed, assembled with new circlips and ready to roll.

New Engine Bearings

With a package arriving with the set of engine bearings, it was onto installing them. The cases were heated to 80 degrees C and the bearings cooling to 5 degrees C so the combination of respective expansion/contraction provided minimal interference and easy installation.

Engine cases fitted with the new engine bearings.

Although I have genuine Suzuki bearing removal/installer sets I opted to machine up my own set. This installer handle and set of attachments fits all the DRZ400 engine bearings plus the entire DRZ400 swingarm and linkage bearings. With a 12mm diameter hole these attachments can be used with either the punch handle or the Suzuki threaded bearing rod tool to press the bearings in.

DRZ400 Crankshaft

With the complete set of engine bearings in, next up was the crankshaft. The first task was to throw the crankshaft in some V blocks and check if the web to web measurements were within spec. This is really a test of, did any of the freighting companies drop it before it reached my doorstep! Following that it was the DTI test to check crank run-out.

First up was the initial check with some digital callipers. The Suzuki spec measurement to look for is 62.0 with a +/- of 0.1 mm. The measurements were within spec at 62.05 and consistent spanning around the webs.

Following this was the task of double checking the web to web with a micrometre. All the micrometre measurements agreed with the digital calipers.

The final test was crank run-out. In V blocks, the outermost ends were checked with a 0.01 DTI. The Suzuki max service limit is 0.08 which this crank breezed in at 0.015

Using a crank installer, the crank was pulled and seated into the crankcase bearing.

Seated crank.

Next up the input and output shafts were carefully slotted into place.

Following that was the gearshift cam and shifting forks. A quick test was performed to ensure the gearbox was operating normally before sliding in the counterbalance shaft.

Counterbalance shaft in place

Author of this article: RMOTO