Eric and Rich

John K · Apr 18, 2003

A mate and I have just installed a genuine HRC kit to my bike. It is the Australian variant that comes without the primary drive and jetting kits. I had the choice of a White Bros. 1650 camshaft or the HRC kit camshaft, we consequently went with the WB option as it physically appeared to be a more aggressive unit. Our assesment of this was basically done by doing a side by side visual comparrison, hence noting that the WB unit had sharper ramps, and I'm led to beleive that both have similar lift as they allow use with standard springs, retainers, and guides. Some time ago Rich mentioned having run a cam doctor over the HRC unit, any chance of those results Rich?

It was also suggested that 40thou shims be used under the large valvesprings in place of the originals to preload the large springs. Is this a common mod or should I look at just buying some R&D or aftermarket valvesprings?

Lastly, the stock carb is currently being used and we're going to start at the suggested 65,165 jetting and go from there, however I have heard that HRC had a different/modified needle, and in addition to this Scott summers is reputed to have moved material from the centre flat section of the needle to fatten up the mid range some, any thoughts on this?

Thanks.

Rich Rohrich · Apr 19, 2003

John - I had a hard drive die a while back that held all my Cam Doctor data, but I'll see if I can dig up a hard copy of the run and post it out here. FWIW, I was pretty impressed with the HRC cam overall, and when I showed the original run to a cam designer friend he likewise thought it was a very good design. Good area under the curve without getting too aggressive with the valve acceleration.

The shim setup is a common way to increase seating pressure but it puts you at risk for coil bind problems at higher lifts. IMO it's a poor way to do it. I'd suggest contacting KibbleWhite and getting a good spring kit from them http://www.blackdiamondvalves.com/pdfs/spring_kits.pdf

I never tried the Summers mods so I can't be much help. I always preferred using FCR carbs anyway :)

cujet · Apr 19, 2003

Rich, I have learned that a failed hard drive can sometimes be brought back to life by putting it in the freezer for a few days. Of course put it in a plastic bag first. I would like you to know where this information comes from so it is not dismissed as ridiculous. My boss (a computer billonaire) has a number of super smart geeks working for him. I became friendly with them and they helped me recover 3 hard drives.

Chris

John K · Apr 24, 2003

Hard drive in the freezer!! wow, never expected to read about stuff like that in Dirt Bike forums! I've had heaps of drives fail over the years, and I've got one here that belongs to a mates dads compute, I might give it a try.

Rich, thanks for your reply and info, it would be cool if you could find that cam doctor data for me.

cheers, John K.

Swiss · Apr 25, 2003

Honda was pretty smart when they designed the HRC kit for the 600 rfvc engines. They knew that the valve train wasn't happy with a lot more rpms, so they basically built a nice torker engine out of the mods. Back in about '91 some friends were looking for some extra power to run down in Baja. They were running XR600s out of the shop and had one that was a couple of years old here in the area that had a number of miles on it (as in several hundred). They asked me to build up a pipe for it to see how it would run and I did. Figured that it couldn't run too high in revs, but could raise the power peak a bit so I ran some short 1 1/2" head pipes to a 2" collector and then through a 4" max diameter meg that started in front of the swingarm pivot area and finished it with a Supertrapp system muffler with about a 2 1/2" core. Well a few months after they got this one back from me, I was told that they ran it up against a fresh new XR628 factory kit with one of the recommended pipes from CA. The 600 pulled pulled even with the 628 until they hit about 95-96mph, where the 600 walked off from the 628. Other than the pipe, the 600 was stock. Honda had good reliability with the 628 kits, as they pull pretty well down low but typically don't run out hard on the top end. Problem with the pipe was fitting the meg past the shock and the rear frame loop support tube. Both engines were using rejetted stock carbs. Stock small head pipes and straight secondary keep the power from building in the upper rev ranges.

Swiss

LJW · Apr 28, 2003

Originally posted by Swiss
I ran some short 1 1/2" head pipes to a 2" collector

Swiss,
Are these dimensions ID or OD? How did you deal with the port to pipe mismatch? I am planning to build a pipe for a '83 XL600R. This is the old short stroke configuration (100 x 75). Motor has great low - mid range, but is flat by 7100 RPM.

Swiss · Apr 28, 2003

OD dimensions. It is the lengths that are the important part. It is also possible to run dual pipes, but getting it past the airbox and chain clearance on the left side is tough.

Swiss

LJW · May 1, 2003

Swiss,
Contact me at wiechman@inwave.com
I'd like to get your thoughts on the pipe I am building.

Swiss · May 2, 2003

LJW,
I sent you an e-mail.

Swiss

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