OzVMX Forum
Marque Remarks => Maico => Topic started by: KTMaico on January 21, 2013, 12:07:58 pm
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Has anyone here tried the RKtek modified head on their maico 490? I would like to know what differences in performance and starting are.
Kevin
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http://www.2strokeheads.com/VintageMX.htm
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I'm soon to send them my 360 oval and 350 squarie heads to RK TEK. I'm just waiting for my welder mate to get a new bottle of Argon so he can weld them up for me before I send 'em to America. flyingdg and Brad Van B both have experience with the head mod and DG especially raves about it on his blog http://1974maicogp450.blogspot.com/ (http://1974maicogp450.blogspot.com/). Not sure of the 490 but if it works on the earlier stuff it must surely be of benefit to a 490...(not that they need much help ::)) If my Maicos show serious improvement I may experiment with one of my Yamahas.
http://www.2strokeheads.com/ (http://www.2strokeheads.com/)
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I bought a head in the US and had it sent to RKTek to make the modification and to fix a broken fin. I have got the unit back now and after fixing the fin repair with my dremel (I can't beleive I had to do this), I bead blasted the head so it looks like new. I will be Ceramic coating the combustion chamber and doing some mods on my cylinder before re-assembling and testing. I was hoping to get some first hand impressions on the mod, I know Doug has had this done and raves about it. I just thought there may have been a local guy thats done this already. First hand experience.
If anyone is interested I can post photos of the before and after and eventually post some impressions after I have tested the bike. I am also adding the new 18mm De-comp Valve to the cylinder.
Kevin
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id be interest to see the rework done in pics
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Don't coat the combustion chamber whatever you do. That stops heat going into the cylinder head likey to bring on detonation sooner.
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Don't coat the combustion chamber whatever you do. That stops heat going into the cylinder head likey to bring on detonation sooner.
Lozza, that's the reason behind the Ceramic coating of the combustion chamber as I understand it. To keep the heat in that area for better ignition. I plan on ceramic coating the top of the piston and the exhaust port of the cylinder. I beleive this has been recommended and done on other two stroke race engines to increase the fuel combustion and thus increase in power. If this is wrong I would love to know. I already have my pipe ceramic coated inside and out.
Kevin
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Well it isn't done on GP winning engines and the people who design and tune them will tell you it's a great way to start the engine detonating. It stores heat transfers it to in the intake charge instead of the underlying metal. If it helps your ignition, then you need a better ignition.
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Why would you want/need more power from a Maico 490 engine?....they are reknown for being the horsepower king of the day and even now you would smack most modern 450's in a straight line....the head mod would make an improvement because it is a shit design std....but maybe thats one of those quirky things that worked but defy's logic?...fark Kev, why dont you just ride it instead of spending another 20 grand on it and then getting your pants stolen again?
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http://www.cicceramic.com.au/coatings/cylinder-head-coatings
http://www.performancecoating.com.au/cylinder-head-piston-coating
http://swaintech.com/why-coat-a-two-stroke-piston/
And a technical paper on ceramic coating combustion areas of two strokes
http://www.osti.gov/bridge/servlets/purl/10194664-iM12hl/webviewable/10194664.pdf
Thanks John for the input, have you found my RH tank mount bracket as yet?
Kevin
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You all know that I like the RK Tek head mod, but I have heard from other Maico and CZ riders that have had there head recut. There is a rider down in TX or is that up from OZ? that has won every class he has raced this last year on his 440 maico. I ask him if he had heard of the head mod? He told me he had the mod done and that it was the single best mod he has done to his maico and he had the newer maico head design. I know Fritz up in the NW had his 440 done and after he rode it he sent them his 490 head to RK to have the mod done. I have had them recut about five maico heads a RM465 a RM500 and three 84 RM250 heads. The maico heads are night and day better than stock. The RM465 and 500 the same thing, the 84 RM250 was better but not as good as the Maicos and the RM big bores. The CZ400 has had a lot of good feed back also. I have never rode a 490 with the head mod so I can't say if it is good or not but if it is like all the heads for maicos I have rode it will work good.
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Doug,
I thought you did the CR480 head also. Any feedback on that one?
;D
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http://www.2strokeheads.com/VintageMX.htm
Paul,
Looking at the photo at the link it looks like the mod has cut into the stud holes. How can you get a seal will those cuts?
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i had a 440 magnum engine resleeved to 490
to cut a long story short you have to machine the 440 head to fit over the larger sleeve and it cuts in to the stud holes a bit(same as the pics)it seem to still seal ok and i saw the bike getting around at cd 9 ok
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I forgot about that head. I have never started the bike (bad me) But as you know there is guys on the cr480 site that have did the mod and love it. Tim lives down the rode from me and he did his 480 liked it so much he had his RM500 done after that.
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That is the way the 440 and bigger maico heads are made ( cut into the stud )
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Old head and new head
(http://i1113.photobucket.com/albums/k501/KTMaico/P1060459.jpg)
Modified head chamber
(http://i1113.photobucket.com/albums/k501/KTMaico/P1060460.jpg)
Closer look at the head chamber
(http://i1113.photobucket.com/albums/k501/KTMaico/P1060463.jpg)
Repaired Fin, hard to pick after I had to use a Dremel and bead blasted the head.
(http://i1113.photobucket.com/albums/k501/KTMaico/P1060465.jpg)
I still have to do the ceramic coating of the head, piston and the exhaust port after a little port work. Hopefully it will all be done and finished in a couple of weeks (time permitting), and the fun part of run-in and testing can begin. I hope it is worth it all in the end.
Kevin
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Any feedback on whether this head mod is worth doing ? I have a couple of projects on the go, that I wouldn't mind having this mod done to, if it makes a noticeable difference. I am sometimes a bit wary of our USA brothers though, as they can be the masters of hype. Harley Ferguson are the classic example of this, where they can convince people to pay a year 2050 price tag for something that is basically a 1950 product ;).
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I'm having my square barrel 350 head done so I'll let you know when it arrives home Mark. The word in Maico circles is very positive. Brad Van B has it on his Maicos.
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Thanks, Firko. I would expect the modification to have a more noticeable effect on a Maico than almost anything else, because the standard Maico combustion chamber design looks very agricultural and primitive (although it seems to work ok). Some of the heads that I want to have done, already have fairly straight forward looking hemispherical combustion chambers, so it may not get the same result to be worth the expense. I don't think that I would get any of my combustion chambers ceramic coated , like KTMaico, because I would logically think that an air cooled cylinder head would be required to radiate the heat out (not hold the heat in). I'm not a rocket scientist, but I think that ceramic coating the top of the piston might be worth trying .
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I agree my 490 needs more power I'm having trouble getting to the 1st corner 1st. I'm usually 3rd or 4th behind the other 490 Maicos. Really they don't need to be changed and they aren't necessarily the most powerful, but they do put the power down better than any other 500.
If I get a good jump I'm 1st, the other bike/riders usually get a better jump than me, I can run everyone down except the other Maicos.
The head modification may have more to do with unleaded fuel as I do know it was common to modify 2 stroke heads when unleaded fuel became compulsory. Please note Classic MX & DT bikes can use leaded fuel. Getting it is the problem.
The real Kevin TM
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For your consideration Gentleman,
Personally, I dont know why you would want to alter an 81/82 490 Maico, a properly maintained and correctly jetted 490 will hold its own against any Modern 450, ie; with a good rider of course. If you were going down this track, I would definately ring Paul Stacker in Melbourne 039459 9535 and tell him your intentions, Stackers would be the most knowledgable people going around, it might save you time, money and a lot of grief.
Good Luck
Ken Baker #54
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Thanks Ken are you bringing your Maico and your son up to Echo Valley for the Post Classic Champs in April.
Check out the facebook page [url]https://www.facebook.com/events/1382144772030061/?ref=5[/url
Also Harker is # 54
Kevin
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I have two with the mod. I promised to do a comparison between standard and modified heads. I'm embarrassed that I haven't yet done it. It shall be done sooner rather than later.
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Aprils a big month with HBBB and the Aussie Titles back to back, should be right to get there, looking forward to it. 54 is my ex race no from back in the day in Victoria ;D looking forward to meeting you all.
Ken Baker #54
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Any feedback on whether this head mod is worth doing ? I have a couple of projects on the go, that I wouldn't mind having this mod done to, if it makes a noticeable difference. I am sometimes a bit wary of our USA brothers though, as they can be the masters of hype. Harley Ferguson are the classic example of this, where they can convince people to pay a year 2050 price tag for something that is basically a 1950 product ;).
HD is not convincing anybody that their bikes are advance alien technology. People in the Motion Picture Industry, Cable Networks and Print Media have convinced people that the bikes are "cool".
Just like a 1974.5 Maico G.P. is cool, but by today's standards they are junk. ;D
(I never had any interest in Yamaha DT/RT-1's until Firko and others posted some of their bikes here and I watched "Little Fauss and Big Halsy" for the first time.)
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HD is not convincing anybody that their bikes are advance alien technology. People in the Motion Picture Industry, Cable Networks and Print Media have convinced people that the bikes are "cool".
I'm a bit with Jay on this, I don't think Harley Davidson has brainwashed a generation of motorcyclists. I'm sure they're producing bikes for a market that just plain isn't into "crotch rocket" style road race influenced bikes. The fact that they've hardly changed in half a century is the selling point, not unlike modern Triumphs building a visually similar modern Bonneville or Morgan sports cars having changed very little since mid last centuries. These companies have seen a market and concentrated their shtick towards them.
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There would be lots of guys in Aust. that can machine squish bands.
The one I know would want the barrel & bottom end including the head and base gaskets so he can calculate the clearance properly
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Rather ironic that with the Aprilia GP program had 100 staff headed up by the worlds greatest two stroke tuner (Jan Thiel) with 2 dynos testing 5 cylinder and head designs for 5 days a week for 13 years settled with a head design like the one on the left above. Jan even thought that head was 10 years ahead of it's time and the design probably came from legend German tuner Jorg Muller.
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I have two with the mod. I promised to do a comparison between standard and modified heads. I'm embarrassed that I haven't yet done it. It shall be done sooner rather than later.
I like your attitude 090, "can do attitude" is always uplifting, i'd like to know your opinion on the comparison too. I'd also like to know the chamber volume of both heads as a comparison too, i've ridden a bike with this mod, nice power, long and smooth...BUT it had the compression changed, bore size changed, different carb too..yep the head mod made the difference all right, it was done a fair while ago too, didnt have the "flutes" of the U.s. one but had it welded up an re-machined by a Sydney machinist who is now living the hippy life on the mid-north coast of New South, lucky bastard! He reminded me of this mod late last night over a bourbon, he at one end of the phone and me on the other whilst explaining how his RM250z is running! (no the mod was not on this bike)
n.b. i cant help wondering if, all things being equal other than the combustion chamber shape, if this is not just a detonation fix for a big bore engine?
Kt
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Rather ironic that with the Aprilia GP program had 100 staff headed up by the worlds greatest two stroke tuner (Jan Thiel) with 2 dynos testing 5 cylinder and head designs for 5 days a week for 13 years settled with a head design like the one on the left above. Jan even thought that head was 10 years ahead of it's time and the design probably came from legend German tuner Jorg Muller.
Maico has used that head design since 1978 and it was a noticeable improvement over the previous more traditional design. I think the 'key' to the RK Tek design is the 'sunburst grooves' machined into the combustion chamber. I'm not doubting the brilliance of Jan Thiel or Jorg Muller but I'm prepared to try somebody else's new idea. If it works, my bike benefits and I've learned something. If it's a failure, I put it down to experience and go back to what I used before. The word on the street is that the RK Tek system is beneficial so why not give them a go? http://www.2strokeheads.com/ (http://www.2strokeheads.com/)
I had Peter Reynolds do a similar head (without the flues) for my DT1 from Hell many years ago and it, and a piston crown mod made a 2 bike length difference in acceleration and noticeably improved the bikes tractability. I still have a welded up head here that was going to be the Mk2 version. If the Maico conversion is successful I may well send the Yamaha head to RK Tek.
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http://www.dootalk.com/foru Ams/topic/221983-rk-tek-back-to-back-head-test-vs-stock/
Here is a link to a snowmobile forum that is talking about the RK tek head. All I can say is I've had them recut some of my heads and they work good. The maico head, RM465 and RM500 worked the best of them all that I've had done. I had a 84 RM250 head recut and it worked better just not night and day like the Maico and big RM's. I'm rebuilding a hodaka 125 wombat to ride from Utah to Athena Or. for hodaka days and have a Carabella 125 welded up that RK Tek is going to recut to run on the wombat. I'm 100% sold on the RK Tek head mod. DG
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I can't get the link to work Doug.
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I don't know why it doesn't work. I did a google search for (snowmobile challenge RK Tek) and that is how I found the forum talking about some testing that was done on there heads. DG
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http://www.dootalk.com/forums/topic/221983-rk-tek-back-to-back-head-test-vs-stock/
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Rather ironic that with the Aprilia GP program had 100 staff headed up by the worlds greatest two stroke tuner (Jan Thiel) with 2 dynos testing 5 cylinder and head designs for 5 days a week for 13 years settled with a head design like the one on the left above. Jan even thought that head was 10 years ahead of it's time and the design probably came from legend German tuner Jorg Muller.
Maico has used that head design since 1978 and it was a noticeable improvement over the previous more traditional design. I think the 'key' to the RK Tek design is the 'sunburst grooves' machined into the combustion chamber. I'm not doubting the brilliance of Jan Thiel or Jorg Muller but I'm prepared to try somebody else's new idea. If it works, my bike benefits and I've learned something. If it's a failure, I put it down to experience and go back to what I used before. The word on the street is that the RK Tek system is beneficial so why not give them a go? http://www.2strokeheads.com/ (http://www.2strokeheads.com/)
I had Peter Reynolds do a similar head (without the flues) for my DT1 from Hell many years ago and it, and a piston crown mod made a 2 bike length difference in acceleration and noticeably improved the bikes tractability. I still have a welded up head here that was going to be the Mk2 version. If the Maico conversion is successful I may well send the Yamaha head to RK Tek.
Jan Thiel has 25 or 26 world titles to his credit. There has not been an objective test only owners say so. The function of a squish band is to create turbulence the radial lines won't make any more of that. The narrower squish will let the engine rev easier.
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I had RK do the head on my 81 490 after riding with their mod on my 74, 440 radial. The bike seems to pull cleaner and longer from bottom through the midrange with more than plenty eye watering rev on the top end. If you look at all the modern 2 stroke mx bikes they all seem to agree that this type of dome and squish band arrangement is the most efficient way to compress, ignite and burn a 2 stroke mixture. I'm not sure what the physics of the flutes are but Kelsey at RK Teach told me of all the 2 stroke head designs they tested while working with a university on clean burn 2 stroke development this was the best head design they had. I think it's a combination of the most efficient head design, including the proper squish band width and clearance as well as the compression ratio set up for the fuel you run. The top hat Maico head design is certainly better than the double plug radial design (I ran a 1980 440 head on my 440 radial before going to the RK head) and this is the next step up from that.
I feel it was money well spent, it makes the 81 490 just that much better than it already is.
Fritz