Maico 490 Head Modifications

[KTMaico]

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

[paul]

http://www.2strokeheads.com/VintageMX.htm

[firko]

 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/. 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/ 

[KTMaico]

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

[paul]

id be interest to see the rework done in pics

[Lozza]

Don't coat the combustion chamber whatever you do. That stops heat going into the cylinder head likey to bring on detonation sooner.

[KTMaico]

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

[Lozza]

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.

[Davey Crocket]

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?

[KTMaico]

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

[flyingdg]

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. 

[Tahitian_Red]

Doug,

I thought you did the CR480 head also.  Any feedback on that one?

 

[Tahitian_Red]

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?

[paul]

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

[flyingdg]

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.