OzVMX Forum
Clubroom => Tech Talk => Topic started by: Freakshow on May 17, 2010, 12:59:38 pm
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Just asking, i can fit reeds in a PRe 75 Cr125 and its legal right ?
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It should be legal Freaky.. you could buy a Gem reed block in 1974 for a 125 and 250 Elsinore but who knows with the rules nowadays.
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freaky
yes you can but must NOT BE V FORCE
a gem is ok
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A GEM reed setup will enhance the CR's low end power but it's a trade off and you may find it'll lose a little off the top ;) I tried a GEM reed on my TM125 when I first built it and that's basically what happened.
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Doc if your tm lost power up top than the reed valve and manifolding are acting as a restrictor, maybe a larger r/valve out of a 250 would give increased flow
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I think the Gem Type interreed, on a TM v's a CR on Alchy will be a little hard to compare, plus it might actualy fix the Cr125 'must run at 60,000 rev or nothing" problem anyway ;D
Been messing with it and its been about the same line drag as the TM 250 on petrol, but against the other Cr's on petrol and Piston port its been 4 sec faster per 30sec laps, so looks to make a big differance in combination. Just wanted to be sure i wasnt crossing the line, i assumed it was fine as other bikes ran Reeds in Pre 75 so basically your just transferring the technology across.
Thought it was just worth checking before i committed to saying it was 110% legal ( i scrutineer on the classic line and dont want to shoot myself in the foot and look like a bigger peanut) :D
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30 second laps :-\..obviously we are talking about flat track where it's a HP thing but the flow problem remains static no matter what fuel you run. I think you'll find the CR will develop more top end power without the reed regardless simply due to the reeds messing with the inlet flow especially at high rpm.
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to get it to work properly you need to get the barrell ported.you cant just bolt a reed valve on a piston port motor and think it will work.
look at the difference between you rt1 and yz to see what i mean.
jim
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Freaky - Jim is right in that it is not just a bolt on. I believe two types were available - mossbarger and Gem. I had the Gem on my 250 but it also needs porting and windows to the piston as well to get maximum benefit. Doc - my well set up 250 absolutely flew with the Gem set up - made a huge difference to stock.
regards
Rossco
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I was actually going to say it isn't as simple as bolting it on but I assumed since the bike was running alcohol that the motor would probably be extensively ported and running a huge carb anyway ;)
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ported with 36mm MUK ;)
i know it works, i just needed to be sure its legal in case people ask questions :)
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moms 18.6.04 c)no reeds valves perrmitted on machines up to and including pre 1970 class
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freaky
yes you can but must NOT BE V FORCE
a gem is ok
There is no restrictions or rules to cover reed cages themselves.
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Lozza - V force by design maybe but not V Force by make ie later? :-* ;)
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You can run a reed cage aa long as it's a period piece of equipment. GEM, Mossberger and even a DT/MX Yamaha reed block welded to the Honda barrel is acceptable. I'm certain you won't get away with later setups unless you're a master of disguising your work ;).
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Sully up in Emerald had what appears to be a yammy reed valve grafted onto a TM125 barrel (quite professionally I might add :o) we assumed at the time this barrel and mod was not legal as the reed was not a GEM or other aftermarket available in the era. Looks like we both assumed wrong :-\ looking for a pic of said reed conversion for some qualified advice as I have no idea what the DT/MX reeds looked like ;)
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okies found it!
(http://boospq.bay.livefilestore.com/y1pECk-RQlPv4OwaYpXKL-1uDfrtj9_T4rvBM0a3Q3UGLnMdtAU384x8izyYDM3euWfVumnPoMS63XoyPV4tpDfp0b6gqpIvPLt/tm%20125%20barrell%20001.jpg)
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doc
i have 1 just like it on my 1973 cr250m it was done in texas usa in the 70s using a yamaha mx 250 1974 reed cage and reeds.the barrell is like swiss cheese holes eveywere.
jim
i have some pics of it at home will try and did them up
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Why cant we see a window i the piston ? or is he trying to use the old Piston port piston in it ?
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freaky
just because the cyl is ported it might not still be ok to put a reed on and run well.i have scored a d&h eng reed valve for my cz400 gen period stuff.all the porting mods for this motor is out the window as different ports will be run to get the best out of the reed set up.porting for piston port and reed valve is different.both my cr250ms will not run piston port any more.must use reed block that the barrell is ported for.you will need to pull the top end and get it checked out. as just bolting the reed no could have the oppersite outcome you are looking for
jim
ps
speak to lozza
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The piston for the TM cylinder does have the windows and the whole deal ran great while it was in place ;)
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also my cr had a window in the piston as well as the 2 bridge port cooling holes on the exhurst side
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JIM you going off trqack, all i asked was why i couldnt see a window in the piston, dont fret about what ever your trying to say, this is a working unit.
I was just curious as to what Doc TM 125 was using as i though i saw the piston in there, now i look at it again its not a piston , its the otherside of the bore..... i didnt see the finger first time.
The question was/is can reeds be fitted to anything pre 75 as it was a period part and/or technology used. I think the answer here is "yes" regardless if it was originally Piston port technology, as anyone could have made a conversion or bolt on versions happen based on at least 2 years knowledge and production models being available on the mx market pre 75.
What im saying is pre 70 is a no go obviously, but post 70 you can do what you like ?
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yes freaky as long as it is period again no vforce or reeds from later bikes
mossbarger and Gem and i have found d&h eng out of ca as well