OzVMX Forum
Clubroom => Tech Talk => Topic started by: Momus on February 14, 2015, 07:20:50 pm
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Guys, I know the commercially available GEM reed kits are being used on 125 Elsinores but is there a consensus, or not, on the legality of home brewed set ups?
If there are precedents for yes, are they stand alone, and/or do they involve welded cylinders?
Thanks, Marcus
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If you can fit Reeds without external changes its in , if you weld (external changes ) its out , as the book states . But that could change under pressure as it is now , history gets rewritten to get more bums on seats .
or less bums on seats.
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Just make a copy of the GEM housing.
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I had a CR250M with a GEM reed valve set up on it. The cylinder still requires machine work to fit it. The inlet tract gets removed altogether and then the flange face needs welding and machining in order to mount the GEM reed block. It did pass scrutiny at Connondale in 09 but as has been said before, you can't rely on precedents as proof of eligibility. It is well known however that the GEM reeds were available prior to 30/12/1974.
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Bit strange to read that major work was required to fit a GEM to Hondas, they made units specific to each model & I assumed they were all straight bolt-ons with the only work required being to the piston like the 1 I have for my CZ
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Tony 27 i thought so as well on 250M.
Great track at Aria.
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There is no machine work required to fit a GEM reed to a CR250M, I had 2 bikes set up with them and they are bolt on. The only machining required is to the intake side of the piston
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There is no machine work required to fit a GEM reed to a CR250M, I had 2 bikes set up with them and they are bolt on. The only machining required is to the intake side of the piston
I have a spare 125 barrel with a square ported flange face that I reckon was from a reed conversion.
It looks like any bolt up reed is going to have a small area and obviously be a long way back...
How helpful is a reed on the CR250?
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The reed on the 250 was really good, I have a GEM one here for a 125 but never used it because it looks too restrictive..
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There is no machine work required to fit a GEM reed to a CR250M, I had 2 bikes set up with them and they are bolt on. The only machining required is to the intake side of the piston
No offense intended.....but you are dreaming. The inlet tract MUST be machined for the GEM reeds to work effectively. Otherwise, you are increasing the length of the inlet tract thereby negating any possible advantage of having the reeds. Secondly, the physical size of the reed block WILL NOT FIT ONTO THE STANDARD INLET MOUNTS. Yes, the intake side of the piston requires work as well, as does the transfer ports.
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An old thread talking about the same thing, welding on dt Yamaha reed housings was a period thing
http://forum.ozvmx.com/index.php?topic=13174.0
No offense intended.....but you are dreaming. The inlet tract MUST be machined for the GEM reeds to work effectively. Otherwise, you are increasing the length of the inlet tract thereby negating any possible advantage of having the reeds. Secondly, the physical size of the reed block WILL NOT FIT ONTO THE STANDARD INLET MOUNTS. Yes, the intake side of the piston requires work as well, as does the transfer ports.
If the GEM reed is the correct 1 for the motor it has the correct bolt spacing & is the same overall length as the standard manifold. I can show you a GEM reed block & piston port manifold together to show that.
There are holes needed in the piston & ideally the reed block & barrel should be blended as should the standard manifold
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There is no machine work required to fit a GEM reed to a CR250M, I had 2 bikes set up with them and they are bolt on. The only machining required is to the intake side of the piston
No offense intended.....but you are dreaming. The inlet tract MUST be machined for the GEM reeds to work effectively. Otherwise, you are increasing the length of the inlet tract thereby negating any possible advantage of having the reeds. Secondly, the physical size of the reed block WILL NOT FIT ONTO THE STANDARD INLET MOUNTS. Yes, the intake side of the piston requires work as well, as does the transfer ports.
Another forkn vmx know all..
My CR250M was fast with good power.
I won 2 Australian vmx titles and several Qld vintage dirt track titles so I'm pretty sure it worked. And like I said it bolted straight on!
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GEM addition to the CR250M was an absolutely pearler - made a big difference as JO says.
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An old thread talking about the same thing, welding on dt Yamaha reed housings was a period thing
http://forum.ozvmx.com/index.php?topic=13174.0
Thanks for that Tony; couldn't find that thread earlier.
With regard to weld fitting Yamaha reeds old sage Firko reckons:
« Reply #14 on: May 18, 2010, 04:24:42 PM »
You can run a reed cage as 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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There is no machine work required to fit a GEM reed to a CR250M, I had 2 bikes set up with them and they are bolt on. The only machining required is to the intake side of the piston
No offense intended.....but you are dreaming. The inlet tract MUST be machined for the GEM reeds to work effectively. Otherwise, you are increasing the length of the inlet tract thereby negating any possible advantage of having the reeds. Secondly, the physical size of the reed block WILL NOT FIT ONTO THE STANDARD INLET MOUNTS. Yes, the intake side of the piston requires work as well, as does the transfer ports.
Another forkn vmx know all..
My CR250M was fast with good power.
I won 2 Australian vmx titles and several Qld vintage dirt track titles so I'm pretty sure it worked. And like I said it bolted straight on!
I am far from a know it all. Unlike some that have won many titles and so there word is gospel.... I am not here to argue or lead others astray. Nor do I intend on making anything personal. I am simply going by my own experience. Perhaps my wording was a bit strong ::)
The GEM reed valves on MY CR250M did necessitate machining to the inlet port so they could be fitted. I had the reed valves with 3 petals either side so in effect, a 6 petal reed block. What was yours? There was absolutely no way the GEM was going to bolt up to the standard inlet port. The inlet port needed to be opened up both vertically and horizontally. I forget the height measurement but width was 75mm just so the reed cage could fit into the port. The mounts were 6 bolt. Not 4 like the stock set up so the inlet tract need to be machined to the base metal of the barrel and the original holes welded. Then machined again for a flat mounting surface. Only then could the 6 mounting holes for the GEM be drilled and tapped. Was your GEM reed set a vertically split set?
Anyway, long story short....The effort was well worth it. The Elsinore became a bike that was rideable everywhere. Not just in a straight line! It had bottom end response, a useable mid range and a top end that went on forever. It took a lot of time to get the jetting right, but with some valuable input from Gary Jones, the father of the Elsinore, It became a whole world better than the stock "light switch" Elsinore.
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My GEM reed had 4 bolt holes like std and as I've said it bolted straight on and was very close to the length of the std manifold so the carby fitted properly also. No machining was required although I did match it to the inlet port.
My reed block was vertically split but it was shaped like a W not a V and had 12 reed petals. I did away with that setup because the cage was bulky and too restrictive. I fitted a 6 petal horizontally split yamaha reed cage inside the GEM housing and it worked brilliantly.
I would say your GEM reed was not for a Honda because it was nothing like mine and I had 2 the same for CR250M's.
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I have the GEM catalogue. There were several fitments
CR250 74 and earlier #5342 (V12 reeds) - only requires piston mod
CR250 & MR250 75 and later #5372 (V12 reeds) - only requires piston mod
MT250 & Odyessy #5348 (V12 reeds) - some machining/mods to exterior of inlet port is necessary. Installation of boost ports is recommended
CR125 75 and earler using stock carby #5340 - no mods required
CR125 75 and earlier using 30-34mm mikuni #5346 - no mods required
CR125 76 and later using stock carb or 30-34 mikuni #5338 - requires some re-shaping and slight modification to inlet port
Boost ports recommended on earlier models but GP 75 and 76 cylinders only require minor mods in this area
MR175 stock carby #5352 (V4 reeds) - no mods required
MR175 with 30-34 mikuni #5353 (V4 reeds)- no mods required
Boost ports recommended for max performance
MT125 with stock carb #5354 - no mods required but some slight grinding of the cases needed. Boost ports recommended.
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Standard CR250 barrel & what i believe is the Gem setup that was avalible at the time, Did they work unmodified ??
(http://i1260.photobucket.com/albums/ii576/KAB171/IMG_0763_zpsgo4srjrj.jpg) (http://s1260.photobucket.com/user/KAB171/media/IMG_0763_zpsgo4srjrj.jpg.html)(http://i1260.photobucket.com/albums/ii576/KAB171/3754885f-b419-4caf-868f-4a079f71a05a_zpstgtshkx0.jpg) (http://s1260.photobucket.com/user/KAB171/media/3754885f-b419-4caf-868f-4a079f71a05a_zpstgtshkx0.jpg.html)(http://i1260.photobucket.com/albums/ii576/KAB171/45b73fb9-4669-403d-9245-d95a726bbffa_zps8tn1dqyy.jpg) (http://s1260.photobucket.com/user/KAB171/media/45b73fb9-4669-403d-9245-d95a726bbffa_zps8tn1dqyy.jpg.html)(http://i1260.photobucket.com/albums/ii576/KAB171/0c665264-98c3-42ce-97ba-ac14efec0ab8_zpst8lm9iak.jpg) (http://s1260.photobucket.com/user/KAB171/media/0c665264-98c3-42ce-97ba-ac14efec0ab8_zpst8lm9iak.jpg.html)
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That's the one KB, thanks for the pics.
They work ok std but I cut the centre out of my housing and used a Yamaha reed cage.
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Yep, that's similar to what was on my Elsinore KB. I should of mentioned that my GEM had the twin reed block with 3 petals on each side of the V. In total 12 petals. Maybe the GEM reeds I had were not meant for the CR??? I id buy the setup 2nd hand so maybe it was modified before I got it.....
Fitting the 6 petal reeds from a later model bike would be the go for sure. As Johnny said, I would think the 12 petal set up is restrictive in comparison to a horizontal set up.
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The Mossberger is a 4 bolt to the cylinder and 4 bolt to the cage takes 'another' Honda cage and stuffer that is the best set up. Hmm have a drawing of the Mossberger housing who does casting...............
The GEM reed cage is far from restrictive has lots of tip area which is exactly what V force did.
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i finally know what bike/models the after market reed setup fits that i got from the wreckers now so anyone want to buy as it wont fit what i brought it for without alot of work in adapting it to fit my rms125,thanks KB171 for posting the pics of it
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Lozza you got a drawing to reed up the H2 ? > Thats a thought I am playing with .
There is a place in the states who does reed valve conversions for H2s, will see if I can find the details after work tonight
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Lozza you got a drawing to reed up the H2 ? > Thats a thought I am playing with .
Would be very easy if you have access to a CNC machines ..... ;) John Aylor or JaMoo is what he goes by on many forums who makes the reed conversions. Need to do the cylinder as well to get the most from it.
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Lozza you got a drawing to reed up the H2 ? > Thats a thought I am playing with .
Here you go Walter
http://www.3cyl.com/mraxl/aylor/
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Pre 75 Hodaka 125 Super Combat MX, Great smooth power from it's stock read valve set up, standard ( OK close ratio) shitfull gearbox..... ::)