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Restoration update of my Legendary Yamahas: Engine work on the RZ 350

11th March 2025, 18:02 by Kanad Kalasur

So, as we tackle and resolve one issue at a time , we can just pray that we don’t encounter any further surprises and we can fire the engine asap..

BHPian SnS_12 recently shared this with other enthusiasts:

Expect the unexpected

The engine on the RZ is one thing we were not going to touch from day one and this was supposed to be more off a cosmetic rebuild than a mechanical and though the engine would have run in the condition it was in I for sure wouldn’t have a sound sleep especially after seeing the state of the right piston. This bike was last owned by a passionate collector and the surprises we have come across in the last few months is something you don’t expect from a bike like this and especially when it was part of such a collection. So, in the end it’s not just the owner but the mechanic who has done the work on the bike that equally matters.

Coming to the engine the progress in the last week has been slow as I had mentioned the blocks require shappering especially to remove the rough and sharp edges around the ports. That, work is yet to be completed and then we wound out the blocks and head needed lapping as well as the surface was not even thanks to the previous mechanic who had manually tightened the head and block and not as per factory torque specifications. Small details like this is what defines a good and proper rebuild. And, since this is a liquid cooled engine and unevenness in the head can lead to the coolant entering the compression chamber and we can say goodbye to the engine. Also, the woodruff key has had its fair share of contributions to the issues we have faced with this engine. Whoever, last put this engine together had cut the woodruff key and that had created a groove on the magnet which was holding it from coming out and that is what led us to ultimately cut the inner holder of the magnet. Further, while installing the new magnet the replacement woodruff key that I got from Yambits was bigger in dimension and had to shaped to size to fit in correctly and that process took an entire day.

So, as we tackle and resolve one issue at a time , we can just pray that we don’t encounter any further surprises and we can fire the engine asap..

Pictures of small but significant work done while we wait for the engine to be assembled back…

Lapping of the head. Done over a piece of plain glass as it has a uniform surface with water and abrasive material. A slow and tiring process but much required

The head surface was quite uneven and required the most effort.

You can see the centre portion still doesn’t have the smooth surface like the other portion of the head. So, a few more lapping sessions are required.

Trying my hand on lapping the block, which got done quickly

Now to finish the shaper work

The face of the blocks are now even

The minute edges near the water jackets will be sealed by the gasket

New brake lever and master cylinder top cap. The OE one with kanji lettering will be sent for sandblasting along with my 125 parts and later for powder coating. So, till then this one will do its duty

The bottom portion has been painted as well

There was a tape covering the lens, which now has been removed.

New clutch lever

Old will be sent for sandblasting as well followed by powder coating.

The seat alignment has been fixed. The centre portion was heated with a heat gun and locked into place and has now taken its natural shape again

The seat cover will be replaced and all these gaps and alignment will be addressed then

Perfect alignment at the back though

From rear angle

Side angles

The rear fairing has been bolted on with the old bolts a d once the rear grab rail arrives will be fitted with the correct bolts

Top angle

The shape and height of the seat foam needs to be corrected too

All rubber mounts and caps have been fitted to the coolant reservoir and 2t tank

Finally sat on the bike for the first time since I bought it. I was hoping to kick start it today but I have waited patiently for so long so can do another week as well to hear it roar again with the correct engine internals.

The spare Daytona key which was missing the top plastic holder.

Tony made the cap out of brass and looks classy next to the RZ key for comparison. Key ring hole still needs to be made though. A side hole or a centre hole is the dilemma…