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machman

XR650L cam question: HRC vs HotCams

14 posts in this topic

I hear the HRC is totally hardened as compared to the HotCam Stage 1 cam which is only surface hardened.

Is it true that if you go to the HRC cam you must also go with hardened rockers?

I haven't heard anyone from XRsOnly recommend the HotCams cam.

Two questions:

1) what's the downfall of not using hardened rockers with the HRC cam?

2) why doesn't XRsOnly recommend the HRC cam?

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Well I am waiting on XR's only new cam that wont require you to have hard faced rockers. Should be about $180 or less. As far as the othe cams you mentioned I think I would call the MFG of the cam in question and get that info straight from the hroses mouth.

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The difference in the surface hardening of the Hot Cam vs. the full hardening of the HRC cam is in wear, longevity, and price.

If, for instance, you had a slight oil viscosity breakdown, this could cause premature wear on the cam surface where the rockers are moved by the cam. With a cam that is only surface hardened, once this thin layer is worn through, the cam will wear and flat spot VERY rapidly. With a cam that is fully hardened (such as the HRC cam) , this effect is minimized as the entire cam is composed of the harder material. This was important for Honda when the HRC cam was developed for the 600R and their 628 kits in Baja. The extra high oil temperatures found on the air-cooled XR motors could lead to oil breakdown on the long SCORE races.

For price, to simply surface harden (not that it is all that simple) a part is much less costly than to fully harden a part. Depending on manufacturing tolerances, if machining must also be done following the hardening treatment, much more expensive tools must also be used on a fully hardened part driving the cost up even further.

As for using hardened rock arms, I would take an educated guess and say that you would not want to use them. By having a softer face on the rocker, you will induce wear on the rocker well before the cam. With wear on the rocker face, you can compensate for this with valve clearance adjustment. Your cam timing will not change. If you use a hardened rocker and wear into the face of the cam, you will alter the cam timing, lose power, and pretty much have a junk cam.

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This is all very logical. Thanks guys.

If this is the case though, why does XRsOnly not recommend the HRC cam without hardened rockers?

Is it because they're not a licensed Honda dealer and can't sell the part?

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I'm sure that it is a reliabilty issue on their part. If someone's rockers wore real fast after they put the cam in, I'm sure that individual would cry foul. There are any number of reasons for them not recommending using the stock rockers, and I'm sure that they have theirs. XR's Only primary purpose is to build race bikes that get run HARD. Sure they sell parts to everyone, but they sell race parts and expect the harshness of a racing environment for their products. They actually have really impressed me with this aspect of their company. They almost refused to sell me the full competition exhaust system for my XR650R due to it's noise level. My dealer had to promise them that I would only use it for racing purposes and NOT trail ride with the pipe before they would ship it. With that history, I just expect that they are covering all of the bases and trying to make to consumer aware of is possible. I would think, however, that with dilligent oil changes and a non-racing environment, the hardened rockers would not be a necessity.

The easy way to tell is to find someone that still has the original 628 Power-Up kit literature from HRC. Since that kit came with the cam, if it also came with new hardened rockers as well, I would say you should probably use them. If it didn't, then HRC did not see it as a requirement and you are probably ok with the stock rockers. I'd like to think that HRC knows what they are doing, and the full HRC motor kit I have had in my 650R since 2001 is a testament to that.

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I'm sure that it is a reliabilty issue on their part. If someone's rockers wore real fast after they put the cam in, I'm sure that individual would cry foul. There are any number of reasons for them not recommending using the stock rockers, and I'm sure that they have theirs. XR's Only primary purpose is to build race bikes that get run HARD. Sure they sell parts to everyone, but they sell race parts and expect the harshness of a racing environment for their products. They actually have really impressed me with this aspect of their company. They almost refused to sell me the full competition exhaust system for my XR650R due to it's noise level. My dealer had to promise them that I would only use it for racing purposes and NOT trail ride with the pipe before they would ship it. With that history, I just expect that they are covering all of the bases and trying to make to consumer aware of is possible. I would think, however, that with dilligent oil changes and a non-racing environment, the hardened rockers would not be a necessity.

The easy way to tell is to find someone that still has the original 628 Power-Up kit literature from HRC. Since that kit came with the cam, if it also came with new hardened rockers as well, I would say you should probably use them. If it didn't, then HRC did not see it as a requirement and you are probably ok with the stock rockers. I'd like to think that HRC knows what they are doing, and the full HRC motor kit I have had in my 650R since 2001 is a testament to that.

Hey Eastric nice to hear some comments on the HRC kits for the 628 of which I have one.

I have the literature and there was no need for hardened rockers. I installed the kit on my beloved XR628HRC electric start engined fun machine.

IMG_4054.jpg

IMG_4048.jpg

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That is a great looking XR air-hammer!!!

I like the addition of the Showa Twin-Chambers on the front end. Very clean with the use of OEM clamps. Great job!!!:cheers:

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The difference in the surface hardening of the Hot Cam vs. the full hardening of the HRC cam is in wear, longevity, and price.

If, for instance, you had a slight oil viscosity breakdown, this could cause premature wear on the cam surface where the rockers are moved by the cam. With a cam that is only surface hardened, once this thin layer is worn through, the cam will wear and flat spot VERY rapidly. With a cam that is fully hardened (such as the HRC cam) , this effect is minimized as the entire cam is composed of the harder material. This was important for Honda when the HRC cam was developed for the 600R and their 628 kits in Baja. The extra high oil temperatures found on the air-cooled XR motors could lead to oil breakdown on the long SCORE races.

For price, to simply surface harden (not that it is all that simple) a part is much less costly than to fully harden a part. Depending on manufacturing tolerances, if machining must also be done following the hardening treatment, much more expensive tools must also be used on a fully hardened part driving the cost up even further.

As for using hardened rock arms, I would take an educated guess and say that you would not want to use them. By having a softer face on the rocker, you will induce wear on the rocker well before the cam. With wear on the rocker face, you can compensate for this with valve clearance adjustment. Your cam timing will not change. If you use a hardened rocker and wear into the face of the cam, you will alter the cam timing, lose power, and pretty much have a junk cam.

I realize this is an old post, but feel I must comment on this.

Camshafts are typically surface hardened using either carburizing, or induction hardening. Either treatment method will produce a case depth deep enough, that by the time you actually wore through it you would have other serious problems. We are not talking about a couple of thousandths here, much deeper then that. You may be thinking of a different type of case hardening, such as that used on titanium alloy valves, which is in fact very thin.

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I realize this is an old post, but feel I must comment on this.

Camshafts are typically surface hardened using either carburizing, or induction hardening. Either treatment method will produce a case depth deep enough, that by the time you actually wore through it you would have other serious problems. We are not talking about a couple of thousandths here, much deeper then that. You may be thinking of a different type of case hardening, such as that used on titanium alloy valves, which is in fact very thin.

He is talking about hard welding. The same is done to all re-ground cams. Material is added to the cam or rocker by welding on the surface. The weld is then re-ground to provide more lift or duration in the case of a cam. It is the mismatch in hardness between the two surfaces that causes problems in some cases.

I have been running Hot Cams for 10K miles with the stock rockers and have had no problems.

MGS

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He is talking about hard welding. The same is done to all re-ground cams. Material is added to the cam or rocker by welding on the surface. The weld is then re-ground to provide more lift or duration in the case of a cam. It is the mismatch in hardness between the two surfaces that causes problems in some cases.

I have been running Hot Cams for 10K miles with the stock rockers and have had no problems.

MGS

He is? Neither the HRC cam or any HotCams cam is a re-grind.

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He is? Neither the HRC cam or any HotCams cam is a re-grind.

The HRC "copy" that XRs Only used to sell is a hard welded regrind, to which my statements hold true. The copy is what I thought he was referring too. If not, my bad.

MGS

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The HRC "copy" that XRs Only used to sell is a hard welded regrind, to which my statements hold true. The copy is what I thought he was referring too. If not, my bad.

MGS

I gotcha. I am assuming he was talking about an actual XR600R HRC cam.

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