OzVMX Forum
Marque Remarks => Honda => Topic started by: b490 on February 20, 2011, 08:50:06 pm
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Hi all ,
I am in the process of doing up this big lump of an engine out of my '82 XR500
Discovered reed petals are not fitted & NLA.
Anybody know what might fit ? ( reed cage all there & ok)
Regards ,
Steve
(http://)(http://i604.photobucket.com/albums/tt127/scm00/S7300060.jpg)
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Reed petals on a 4 stroke?? That's why they have valves.. ;)
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I think that is an '83 RFVC (Radial Four Valve Combustion or Really Fugged Valve Configuration - which ever way you want to look at it) XR500 motor . They had dual carbs which I think carried through to the first XR600 model in '85 . They did have a reed valve set up and a chamber cast into the side of the head . I can't remember if it acted like a boost bottle or a means of equalising pressure between the two inlet tracts. I still have one of these motors buried somewhere deep in my shed .
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yes they have reeds. try genuine honda and ballards.
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They do I have to pick up my 82 xr500 if you check a parts diagram you will see the reed valves. ;)
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It is not an RFVC engine .(1983 XR500 on)
My bike is 1982 model
Engine basically same as '79 -82 XL 500 models , main difference being '81/'82 XR500's had intake port reed valve set up.
Tried Honda ; no longer available .
Will try Ballards .......just need to speak to somebody there who is old enough to remember them ;D
Regards ,
Steve
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thats an 82 motor. rfvc is clearly stamped on the side shown on those models.
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The reed valve was to allow bigger overlap on the intake cam lobs. The will run OK for MX without them but loose a bit down the bottom end.
Back in 81 we hotted up a XL500. Big cam bigger carby and porting. Suffered very poorly off the bottom. The cam we used was about 2 degrees (from memory) more than the XR's but they had a very responsive bottom end.
It's all about keeping the fuel going the right direction all the time.
By the way, I actually saw something very similar on a old Holden 6 in a hill climb car. With a very radical cam and no reed valves (on triple carbs) the thing would not pull low down (lots of spluttering back through the carbs). With the reed blocks just under the carbs the thing idled and screamed.
Peter B
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Yep Thats pretty much the reason they fitted them back in the day.... to gain improvement bottom end response, as I am led to believe .
Bike runs fine without them ....(rebuilding to cure the old girls appetite for oil ;D ) but I would like to (eventually) see if there is a noticeable improvement with reeds fitted.
Regards
Steve
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You should be able to get a set of aftermarket reeds for it....boyseen perhaps (did I just say that?) ;D
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Hello, I have 2 1981 XR500R, one from new back in the day. The stock steel reed valves tend to break (ask me how I know). I have had fiber valves from a 1980 125 Husky for 30 years, they are still fine. Boyesen makes them, not cheap.
At worst, you can simply remove them, or one of the sides, leave the box or take out completely, you will hardly notice a difference in normal use.
Personally, I like them because they are an oddity :)
Some used to replace the whole box with a spacer shaped to direct the mixed gases better. See one of those aftermarket bits under
https://picasaweb.google.com/ericf318/XR500RReconstruction#5499563946887404098
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Boyesen do XR500 reeds. Part number is #606
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Thanks for the info Gentlemen .
Great pics Eric318
Would love the Ohlins rear shock ;D
I know these are big heavy bikes when compared to most all of the big bores back in the day but I
remember riding a mates older brothers (new)' 82 XR500 I was about 15 . Loved it, but couldn't afford one back then
Finally got one in 2010
Regards ,
Steve
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Ah, finally figured how to post a pic.
Here is the aftermarket replacement piece for the reed cage.
(https://lh4.googleusercontent.com/_AouLVMAxNLQ/TFJgRZHE2kI/AAAAAAAAO2k/c0WlFC81DKI/s640/IMG_20100729_204411.jpg)
(https://lh4.googleusercontent.com/_AouLVMAxNLQ/TFJe-z7yOdI/AAAAAAAAO14/puM0mZk7ok0/s640/IMG_20100729_204434.jpg)
Here is one of the 2 XR500R. This one is the tricked one. Got it as a non-runner but it had on it no less than:
- Simons fork
- Ohlins rear shock
- White Bros swing arm
- unknown aftermarket exhaust header
Could not say no... Was an easy restoration. Goes like a dream. I now took the Simons off and fitted a 1982 Kayaba.
(https://lh4.googleusercontent.com/_AouLVMAxNLQ/THRw_Q2Kk2I/AAAAAAAAPp8/8fFvBRxSSLo/s640/IMG_20100821_183653.jpg)
Since you are asking about the Ohlins, cannot resist that pic after rebuild at factory:
(https://lh6.googleusercontent.com/_AouLVMAxNLQ/S3mJjd0rFvI/AAAAAAAAL4s/jrcMY3lphGQ/s640/268.JPG)
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i removed the complete reed cage from my 82 xr 500 and it made a big increase in power all over. the problem is that it kick backs real bad the kickstarter when starting it! but worth it for sure.
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Then there was something wrong with your reed cage. Good move. Good luck with kick backs... :)
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Steve, Give SERCO a ring they do blank reed sheets from Carbon Tech. Cost is approx $100 easy to cut them out, have done it seveal times on odd-bod bikes. I think they do them in 2 different thicknesses too
Bill.