Here's my dilemma.

I have a full detailed, lap history of my NXA. I have printed out all the practice laps and race laps for every race John rode the bike and the Oliver's Mount meetings i have even have it verfied by the circuit and been given an electronic scan of a signed pic that resides at the circuit office.

Anyway the bike has done 1069 miles from new and of these miles John did 579. No doubt he wasnt riding it like he was off down the local sunday cafe for a bacon sarnie and a cup of tea!

The other 490 miles is me pussy footing about like the doddery old git i am becoming ... (at a rate of notts i would rather ignore ).

The cylinder bores look amazingly good and under my ownership all top end parts have been replaced before 300 miles with OEM HRC and i have no doubt Clive P has not skimpt on the comsumables as he prides himself in the reliability of his bikes.

So the question is .... As Ever....

How far do i push the Cylinders and the Crank at this stage?

I know somebody with a CMM so i could get the cylinders accurately measured but what exactly am i looking to measure?

I see loads of bikes with 'spare cranks' that are pulled before full mileage BUT in reality who in their right mind is going to put a crank back into one of these things that hasnt quite reached its HRC Manual mileage? Why not just do the whole mileage and then some ... then lob it in the bin?

Does that make any sense to anyone?

Simon

I do everything at or even before mileage, much to some peoples annoyance. Keeping an eye on things often gives you good warnings of impending doom.

For that reason I would pull it apart. Not however just to replace things on a whim. Quite often you can take a component out that has had its service life, replace it with new only to have the new one fail.

Case point, old cranks are often perfect and just need new cages, seals etc to bring them back to spec or in many cases better than new spec.

I would strip your engine down, spend an evening or two measuring pistons to bore clearances, crank tolerances etc and decide what if anything you feel needs replacing. You'll soon get a feeling as to what goes and doesn't.

We build cranks for a guy that races an NF5 at the manx yearly, after rebuilding a number of cranks for him and his friends at mileage we said he should go longer. All his cranks were always in very good shape. As I recall we were rebuilding his every 1200 miles. We doubled that without fault as we had good experience with the F-III cranks which are very close to the RS's and knew they could take the pain.
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If I have to take the carbs off once more...

I was unser the impression ... no ... I was told the NXA Cranks could not be rebuilt?

To be honest i would not have a clue where to start with checking what you have suggested Steve, i am a simple person in a complicated world, at lest in here

I do have a new Crank and a pair of new barrels and all associated seals, i just wanted best value out of the ones in the bike ... without an impending crank case replacement or even worse ..... A highside on the left hander of Craner .... That would be more costly than money can be held responsible for

simono wrote:I was unser the impression ... no ... I was told the NXA Cranks could not be rebuilt?

I've been told that none of them can be rebuilt, so interested to know the reason why this is the case.
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If it ain't broke, fix it until it is.

Honda say none of the RS cranks cane be rebuilt, however we are able to supply all the bearings and seals for the NF5 range and a good number of parts for the NX5 and NXA. Things like big end rollers, seals, cages and bearings etc can all be replaced and serviced rather than buying new cranks.

We can often true the cranks to even smaller tolerances than HRC supply them new. In the passed we've even had Arrow rods made for some NSR/RS cranks.
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If I have to take the carbs off once more...

StephenRC45 wrote:Honda say none of the RS cranks cane be rebuilt, however we are able to supply all the bearings and seals for the NF5 range and a good number of parts for the NX5 and NXA. Things like big end rollers, seals, cages and bearings etc can all be replaced and serviced rather than buying new cranks.

We can often true the cranks to even smaller tolerances than HRC supply them new. In the passed we've even had Arrow rods made for some NSR/RS cranks.

So if i supplied you a used crank, you could refurb it for me? PM me with a cost as this is the first time anyone has said it can be done.

Cheers

Simon

Simon, the cylinders should last you ages, providing you get the piston ring gaps and piston to cylinder bore clearances right, and you warm the bike up correctly and run at right operating temp (no cold seizures) and you don't run lean.
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Rich
MC21 Track Bike / RS250 NF5 'Spencer', NX5 'Cadalora' & NXA 'Aoyama' / RS500 / Two Brothers Racing RC30

StephenRC45 wrote:Honda say none of the RS cranks cane be rebuilt, however we are able to supply all the bearings and seals for the NF5 range and a good number of parts for the NX5 and NXA. Things like big end rollers, seals, cages and bearings etc can all be replaced and serviced rather than buying new cranks.

We can often true the cranks to even smaller tolerances than HRC supply them new. In the passed we've even had Arrow rods made for some NSR/RS cranks.

Hi - your statement above that Honda say RS cranks cannot be rebuilt and that you are able to supply all of the required bearings & seals...and that big-end rollers, cages etc can all be replaced rather than buying a new crank has me very, very surprised and intensely interested.

Just so you are aware - Honda (HRC) used to have a crank-rebuild service for all RS model owners where you could send them your used cranks and it would be returned to you fully rebuilt and balanced! I have personally used this service for an RS250 and RS500 triple. I admit it was quite some time ago and Honda ceased the service after 5 years as at the time, the Japanese Yen was not competitive against most currencies so it was more cost effective to buy a crank rather than have it rebuilt.

Due to the extreme shortage of NF5 cranks, I have been researching crank parts availability for quite some time now (5+ years). RS250 cranks can be rebuilt and rods, big-end rollers and the bearing on the ignition side can be sourced but the main issue is sourcing the inner labrynth seal as well as the next-to-impossible to obtain, primary drive side outer bearing pictured below.

My research finally took me to the primary Japanese supplier of bearings and seals to most of the Factories. They have a significant amount of 'surplus to requirement' bearings and seals that suit the NF5 range of bikes but here's the choke-point........
The parts are made under license so they cannot release them for retail sale until receiving authorisation from the Factory. I managed to get a reply to many letters sent stating it would require legal department consideration but I've yet to get any further reply regardless how many times I chase it up..

So may I please ask......Are the parts that you source OEM or after-market? Can you source the clutch side bearing that has the orange nylon insert (Pic below)? If you are not using this bearing - are you experiencing bearing 'skip' in the cases?

Your assistance in giving me some indication of parts and availability would be greatly appreciated and also provide me with some closure on many quiries I have been chasing.
Thank you!

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...

Thank you for the detailed reply - I'm very appreciative! You have identified a major issue with using an NF5 bike on a regular basis and have come up with a good solution - well done!

I have a dismantled crank that I pulled apart to inspect for wear. Honda cranks are well built particularly the rods which are high quality. After crack testing the rods, I would certainly risk running them again for at least 1 rebuild without replacing (Only caveat to this is you would need to know the complete history of the crank since new eg - any over-revs, type of oil used, time spent sitting idle and total mileage since installation)

Please let all forum members know when you have all the required parts in stock. I for one will send you at least 2 cranks so I have additional spares for my 2 bikes.

As you will need to machine the cases meaning, I would need to send over 2 cranks and a set of cases - do you have a cost estimate for the complete job? I won't hold you to it but an approximation of cost will assist O/S customers who have to combine freight into the complete cost.

Many thanks again!

MarkR wrote:
I've been told that none of them can be rebuilt, so interested to know the reason why this is the case.

HRC supply the main bearings, part numbers

91001-NX5-003
91003-NX5-003

Crank rebuilds start from £500.00 inc VAT up to £800.00 and include parts. Most crank rebuilds come in at around the £600.00 mark though depending on the parts and condition of the crank to be rebuilt.
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If I have to take the carbs off once more...

Hi All, yes just to confirm, the NF5 cranks built by Stephen are top notch. My bike has done 3 Manx GP all at top speed with no Problems. It managed 142 mph down sulby, thanks

Hello Malc,

Long time no see. Glad they are still performing for you. Maybe you could come to the NSR-W day at Donington in July?
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If I have to take the carbs off once more...