cNw Specialized Modifications

cNw Breather Modification

Development:  Comstock Engineering

Manufacturer: cNw

Description:  We are very excited about offering the most efficient breather modification for Commandos on the market. This kit is developed and designed for maximum performance. We have operated this through a variety of circumstances and rpm ranges and how found it to actually pull a vacuum in the crankcases up to about 4000 rpm. From there to red line it’s virtually running at 0 pressure. The benefits are many and the idea of reducing the excessive pressure in the crankcases that, due to the parallel twin design, will free up the engine and actually create some horse power. It will also virtually eliminate any and all leaks associated with the pressure in the cases. You will notice this where there is a gasket, seal or a material joint. Because of additional modifications that we do in the timing side case to further increase the performance of the breather we are also lowering the operating temperature of the engine oil.

In order to install this kit the engine needs to be completely stripped down as we mill a mounting surface on the lower backside of the drive side case half. We also modify the timing case half.

The above mentioned results are of course directly related to how the engine is built as piston clearance, cylinder bore, piston ring quality, head work, gasket quality and much more will all play a part in how well the engine breather will operate and what kind of results you will experience.

  • Experience an increase in engine performance
  • Eliminate persistent leaks at gaskets, seals, tach drives, head, crank case joints and more
  • Lower the operating temperature of the engine oil
  • The valve can operate consistently during a far higher rpm range than the Commando engine can ever reach
  • The valve is not affected by oil contamination and can perform even if submerged
  • The valve will actually aid in returning the crankcase oil back to the oil tank in case the engine has wet sumped
  • The valve housing is CNC machined out of high quality billet aluminum
  • The valve has an indefinite service life and will not have to be replaced
  • Turnaround time for service is 7 days

cNw part # 0500-08

Price $ 265.00

This includes:

  • Milling the drive side case half
  • Modifying the timing side case half
  • Breather assembly
  • All parts necessary to install the breather valve

Special order – Please contact us for information  (not available through online ordering)

Note:  If you have a 1972 engine case, you do not need the machining done. You can install our bolt up version of the valve available in the parts catalog in the Engine category

cNw Oil Tank Modification

Modification:  cNw

Description:  Send us your old oil tank and we will do a number of upgrades and modifications to improve on the original design. The original upper mounts fail and when the lower mount gets over loaded it will fracture the tank. If you are fortunate it will only create hairline cracks and the tank will just leak, if you aren’t so fortunate the entire mounting boss and part of the oil tank will come off and the oil will pour out (on your rear wheel to make it all worse) and in a matter of seconds your oil tank will be completely empty. Your sweet old Commando engine is now running without oil and it won’t do that for very long


  • The oil tank gets completely boiled out to remove any sludge and build up. This also strips all paint off.
  • The lower tank mount gets cut off and a plate is brazed over the area to ensure any hairline cracks are covered up.
  • The rear mount is beefed up for added strength. This rear mount is also shaped to give it a better fit with the thicker than stock mounting rubber
  • The spigot to the chain oiler (if equipped) is closed up
  • The oil tank is finished in a gloss powder coat
  • The finish is removed to bare metal where it is needed to ensure proper sealing when installed.
  • Included are two rubber mounts that are far stronger than the original.
  • Stainless steel hardware to mount is included.
  • A high density foam pad to install between the battery cover and oil tank is included

Note:  All the modifications are done to the tank you send us. We do no longer offer an exchange service

We do these oil tanks in batches in order to make sense out of the service and keep the cost down. This will allow you to plan ahead as well. Here’s how its works:

  • Each batch is scheduled to start the 1st week of each month
  • If you tank is here on the 1st, it will be included in that batch, completed in the 3 rd week and shipped to you before the end of that same month
  • Regardless when we get the tank during the month, it will get included in the next batch that starts on the following 1st
  • We need the tank only, no attachments

Note: This service is not available for the central mounted oil tank used on the 1970 machines. The tank design in the image below is the one we can do the work on

cNw part # 1201-03

Price $ 169.95

cNw Transmission Seal Upgrade

Machine Work:  cNw

Description:  Modify to outer transmission cover to allow proper seals to be installed


  • Send us your transmission cover and we will machine and install a kick start seal and a shift lever seal to replace the o-rings that are prone to fail and leak.
  • Service includes all parts and machining
  • optional service includes a full prep, sand and show polish.
  • Turnaround time for service is 4 days

Note:  Many of the alloy Commando parts and the Transmission covers in particular have a lot of casting flaws that show up like little dimples (porosity). These will not disappear with the polish. The cover will be as perfect as it can get given the core quality

cNw part # 1201-01    Machining and seals

Price $ 89.00

cNw part # 1201-02    Machining, seals and a full prep, sand and polish

Price $ 164.00

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