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Discussion Starter #1
As posted earlier I am doing a magazine article on the RC-51 and I am looking for your input on what the top weakpoints of the STOCK bike are. Either SP1 or SP2. Please tell me which bike you are speaking of and also what you did to address those weaknesses.



Thanks



Don



PS Remember I am still searching for HIGH res, good photos of your RC-51 for the article. So if you have some please email them to me at
[email protected]. But they must be made from a 5 megapixel camera or better. 1200x800 will not cut it for a print magazine.
 

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Discussion Starter #3
A 6 megapixel camera will shoot 3000x2000 at max resolution and then make sure you use FINE resolution etc.

And please email them directly to me with your info, name, city state, mods etc.

Thanks

Don
[email protected]
 

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I can only think of two weak areas.
Weight of the bike, and cams.

The bike was designed to handle any stress expected from World Superbike racing, so it's overbuilt for average street use. But then that's a positive point for me.
You can substitute parts to lighten the bike, but it'll never be as light as today's I-4's.

The engine uses spur gears to drive the cams, and all those gears are heavier than belts or chains, but they are totally reliable and accurate. And I consider that a huge plus.

About the only real weak point of the whole bike is the cams.
They are cast nodular iron as opposed to steel as in the RC30.
If you weld and re-grind them for higher lift and duration, they are known to crack in two.
The only way around that is to replace with billet cams, and they cost a fortune, if you can find them at all.
Otherwise the engine is incredibly durable and reliable and will last practically forever with routine mainteance.
My bike is going on 7 years old with almost 40K miles with no issues.
 

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Over geared as standard and the fuelling is a bit glitchy at low revs. Er that's it.

I can send you a higher res version of this if you wish:
 

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SP1 issues

About the only real weak point of the whole bike is the cams.
They are cast nodular iron as opposed to steel as in the RC30.
If you weld and re-grind them for higher lift and duration, they are known to crack in two.
Can you tell alittle moore about this? My bike has run for 100K km and yesterday I spotted light damage to the cams lobes tops. Im going to regring them (not welding) but I really dont want an engine brakedown during driving due to the cams have broken..... Is it a "normal" thing that they brake in two?

To the main thread:
I have a SP1 2000mod and my two problems (except the cams) are the dampers and the vibration. The vibrations and sound is a big + i think but nuts and bolts tend to get loose. I have to check/retighten bolts and nuts and use locktight to the treads in importent places(like inside the airbox...) I have lost some parts on the street during driving due to this..

The dampers on the SP1 are crappy, but I fixed this by fitting SP2 front and forks and replace the rear damper with a good one from ohlins.

To reduce weight I installed carbonfibre wheels from Blackstone. This is allso good for inertia.

The stock bike have a flappervalve inside the air intake to reduce noise, this is bad for engine power/performance. Remove this valve!

Stock bike allso have a PAIR system for enviromental purposes. But this system gives some engine/exhaust issues. Remove this system to avoid these problems and allso reduce some weight.

Thats for now:)
 

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The stock cams are made from cast metal.
They are perfectly fine for normal use.
However if you try and increase performance by welding and regrinding with a more aggressive lift with accompanying stiffer springs, the camshafts can't handle the increased torsional loads on the outer lobes.
They then usually shear in half somewhere in the middle.
Reportedly, the Moriwaki cams were no better as they were also cast.

The cams for the RC30 were made of chrome-moly steel and had no such problems.
Why they didn't use that material on the RC51 can only be answered by Honda accountants.

You can buy billet steel RC51 cams, but they are very hard to find and very expensive.
Around $2000+ for a set I've seen.
And with other mods, the engine may then put out 150 HP.

Better to use that $2000+ for a down payment on a Ducati 1198 or KTM RC8.
They have 160-170 HP stock.
 

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All right, Thx.
Im not going to do anything about the indexing of the cams, only remove some material around the entire lobes so the damage on the noses dissapears. The timing of the valves will be the same as stock. So I dont need to worry about broken shafts than.

Its nice bikes you are listing there, but Im a little bit conservative when it comes to bikes.. Its allway Honda and allways(for the moment..) RC51...
 

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I believe those cams lobes are case-hardened, so don't remove too much material.
If they're bad off, you may need to replace the camshaft.
Is the bucket damaged/worn as well?
 

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Yes the cams should be chillcast(case-hardened) so the depth of hardeness is at least 3mm. The damage is little so I will remove less than 1mm of material. So I believe Im on the safe side.. For now Ive only inspected the buckets with the shafts in situ. So what Ive managed to see with a powerfull lightsourse they're looking fine. I think Ive decided to use the cams for now, reinspect mid-season and hopefully I can wait to the autumn before sending them for regrind.
 

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I can allso mention that it doesnt look like wearmarks. If I clean the lobe noses and use a good light I can spot that there is some surface defects. To me it looks like an early stage of surface corrosion(pitting) and if I use my nail I can feel irregularitys on the surface. The one million dollar question is why..
 
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