We use genuine Honda rollers and cages with silver plated thrust washers.

We used to have a supply of genuine Honda centre seals but this has now dried up and we are in the process of having them made. It is quite a tricky seal as its speed rating is quite high. The seal is also made out of two compounds to confuse the issue. We hope to have these in stock very shortly.

The right hand OE bearing made by NTN as you say is very hard to get. We don't use this and use another genuine Honda bearing. This has a locating pin and circlip and is the system used on most of the other GP Honda's. It does however mean a locating notch has to be machined into the NF5's crank cases. We are very careful when rebuilding NF5's that the bearing housing is round and concentric. If they are not then we machine the mating faces and then rebore the main bearings to get a perfect fit.

We've never had any problem with any of the rebuilt NF5 cranks, and a good number of them are now doing the classic/manx TT
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If I have to take the carbs off once more...