Maruha motors

SST(Special Service Tool): Crank Lock Plate

SST means "Special Service Tool"

SST(専用特殊工具):クランク ロックプレート
SST(専用特殊工具):クランク ロックプレート
SST(専用特殊工具):クランク ロックプレート
SSTCrank Lock Plate
特殊工具 SST クランクロックプレート(分度器対応)2023年1月〜
code:mar23012600 For ALL MODEL

The Lock Tool for loosening the center bolt of Crank Shaft was once discontinued, but its resale with new designing starts this time (in 2023).

The product is not merely cutting from iron plate.
It is made by machining for the base of the optional crank scale plate.

As there are impact wrenches (air tools) in professional garages and repair shops, the center bolts can be loosened easily after making space for using air tools.

However it is not easy for private person to do that.If the center bolts need to be removed by hand without air tools, the crankshaft have to be fixed, but no special tool is available in the market.
In case of only engine unit, it can be fixed by using ring gear of fly wheel, but it would be worried a little bit because the important gear might be broken.
In case, the engine is installed in the body, there is no way to fix it without special tools like ours. It might be useful for even specialty shops to remove lock bolts without taking off radiator in a narrow space.


From this version, optional crank scale plate (entire angle protractor) can be attached.
Please refer to “SST Crank Scale (360° protractor) & Stud Bolts (3 pcs.) set”.

1.Reason why loosen Center Lock Bolts

In overhauling an engine, it should be loosened. For general maintenance (replacing timing belts and water pump), it should be taken off.
For removing timing belt, pulley boss has to be taken off after removing the center lock bolt.

Reason why loosen Center Lock Bolts

2.Handling methods

If you try, Maruha original special tool, Crankshaft can be fixed easily.
・Firstly, Crank pulley is taken off ( Removing 4 pcs. of M6 bolt only).


・After removing Crank pulley, Lock plate is fixed to Pulley boss by using the enclosed stud bolts.


As you can see from the images, without removing the radiator, the crank center bolt can be loosened in a narrow space.

・The crank should be fixed by using something like a closed wrench, then the center bolt can be loosened.

In the image, the rotation of plate is fixed by a closed wrench. Please try to fix well by using your own tools.

クランクプーリーが外れたら、プーリーボスにロックプレートを付属のボルトを使って固定します。The center lock is removed.

・The center blot might be fixed very tightly by rust.
Please be very careful of damage on other parts or injury while working.

3.Advantages and Feature

  • It’s easy to lock the crank.
  • It enables working in a narrow space without taking off a radiator.
  • Loosening and tightening the center bolt is feasible.
  • The optional crank scale can be equipped.


SST(専用特殊工具):クランク ロックプレート
SST(専用特殊工具):クランク ロックプレート

It is suitable for all of NA and NB cars after NA6CE-#127441 (NC and ND are exempt.)

  • Ealy version until NA6 early model (short nose) is exempt.
  • The size of nut welded on the plate is 21mm.
  • The size of center bolt with crank shaft is 21mm.

5.The optional crank scale plate can be equipped.

SST(専用特殊工具):クランク ロックプレート
SST(専用特殊工具):クランク ロックプレート
SST(専用特殊工具):クランク ロックプレート
SST(専用特殊工具):クランク ロックプレート
SSTCrank Scale with stud bolts
特殊工具 SST クランク スケール(360°分度器)&スタッドボルト付き(3本)
  • SST
  • SST

Please refer to “SST Crank Scale (360° protractor) & Stud Bolts (3 pcs.) set”.

We hope you will use our “SST Crank Scale (360° protractor) & Stud Bolts (3 pcs.) set”.

SST (Special Service Tools) related story

Contact us here



Maruha Produce!Engine oil for MX-5 miata
ESTER27 Full Synthetic♪


Maruha Original Crank Shaft For BP New release♪
マルハオリジナル サスペンション♪BCストリート ストロークアップ仕様
BC StreetNB upper Mount