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1984 XR500R Top End Rebuild


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Well my trusty 500 is finally showing signs of getting worn out. The smoke on start is getting thicker, it does not seem to have the same power it once did, and just feels like it's getting "looser" for lack of a better term. The good news is that it still starts first kick every single time, the clutch and tranny still work great (put in new clutch plates last year), and the chassis/suspension are still in good working order. I can take the head, jug and piston off myself so that will save some cash. Any recommendations on where to send the cyl head for reconditioning? Also, would it be OK to just hone the cylinder and put in new rings? Or do I need to bore it to the next size up? I suspect some micro-caliper measurements are in my future. Any and all feedback will be appreciated, thx in advance. (P.S. I posted here because this 500 is pretty much the same as the 85+ XR600 except for an extra carb and, no rear disc, and 17" rear wheel.)

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If it was me, I'd go ahead and bore it regardless if it was in spec. I just don't see the point of installing new rings on a used piston, especially as long as that one has been in there doing work. But, that's just me. Others would say I'm just wasting money...

Where in CA are ya?

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Measure, measure and measure again. The piston is aluminum, the cylinder is steel. Aluminum is softer, wears out first.

If you didn't get any shit into your engine (no gouges or weird wear areas), and your oil was maintained, the cylinder could be ok with just a hone. Hone it and measure it.

Chances are, your piston is toast. Measure it for sure, but it'll probably be to the low limit or beyond.

You can clean up your head and valves yourself. It's not a race bike, it's an XR. It doesn't need triple angle valve grinds, just relap the things, and clean them up good - reinstall with new stem seals.

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If you're replacing the piston anyway, spend a few extra bucks and bore one size up, have everything nice and new. You'll be happy you did once it's all back together. I just did the top end on my '86 600R and the bore/hone only cost me $25 and was done while I watched. 👍

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I am in Rancho Cordova, about 10 miles east of downtown Sacramento.

I've had the head off before to replace the valve stem seals, hoping this would cure the smoke on start issue. It did, for about 6 months. I did not install OEM seals, maybe that is why. Replaced the head gasket at that time, everything in the head looked real good, including the tc tensioner.

I know what is involved in grinding the valves, but what is relapping?

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Ah..you're about 4.5 hours south of me-I'm in Eureka.

Lapping is using an abrasive compound on the valve seat and contact point on the valve and working the valve back and forth while applying a little pressure to the valve until you get a nice shiny line all the way around the seat and valve contact area.

A friend who has been building these things for years says he has never seen an RFVC head where the valves were lined up properly with the seats.

I brought in a head one time that I thought was fine. He popped the valves out and hit the seats real quick with the cutter and low and behold, every seat was cockeyed! The cutter was touching about half of the seat and nothing on the other half. That made me a believer. Any time I have one of these apart now I have him do a proper valve job.

Don't ever cut on a stock Honda valve though. They only have a hardened coating. If they're bad enough they won't clean up with a lapping, replace them.

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  • 2 months later...
Just wondering if you found a shop local to do the work for you.... i'm south of you in Wilton and am looking for a local shop to freshen up my '00..

The best referral so far is to Meticulous Metals in Loomis, (916) 652-9309, ask for Kelly and tell him Mike Russo sent you. They are familiar with the RFVC engine design and have done lots of top end work on them. I know it's the other direction from Wilton but they are hands-down the first place I would go. Even my local machine shop (who are totally swamped right now and can't help me) said to check them out. Carmichael Honda Motorsports is another option, (916) 944-1318. XR's Only also does fine work, they quoted me $250 for a complete cyl head recondition but you have to ship the parts out to them.

A friend of mine recently graduated from MMI and is coming back from Arizona in September, so I'm going to wait and have him do the work on my bike. Fortunately I have another bike to ride in the meantime.

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I would like to find a local place too. I live between you guys in Vacaville (alot closer to RC though)

I have heard of a place in Santa Rosa but can't recall the name right now.

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Pretty sure any decent machine shop can bore/hone the cylinder and do any shaving/planing needed on the head gasket mating surfaces. The RFVC head itself, that is another story. Will pass on any other information as it comes along, but for now just what's in post #8.

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  • 10 months later...

My friend graduated from MMI last October and finally got his shop all set up and stocked with machines, tools, fluids and parts. So tonight I'm taking the XR500R and YZ400F over there so he can start doing the top ends. Yeah it's too bad we're already into the riding season and just beginning motor work, but I have a third to ride in the meantime (XR400R). I miss riding the 500 and never had a chance to spend much time on the YZF, and I'm really excited that all three bikes will soon be ride-ready! WOOT! :worthy::confused:👍

I'll ask him to take regular photos during the build process.

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I would like to find a local place too. I live between you guys in Vacaville (alot closer to RC though)

I have heard of a place in Santa Rosa but can't recall the name right now.

Not sure about SR, but if it's head/valve work you're looking for check out Engine Dynamics in Petaluma. That's their specialty.

http://www.enginedynamics.com/index.html 👍

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