OzVMX Forum
Marque Remarks => Maico => Topic started by: ola_martin on March 11, 2013, 08:33:09 pm
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I bought this cylinder for my 490, from a known German Maico specialist, it has a NOS liner fitted. But it all looks a bit unfinished... >:(
I looks like it's fitted a little turned to one side, so I guess I have to heat it up and turn it a little..? Any idea of temperature needed, I use a normal kitchen stove..
Also it looks like I need to clean up the ports, can I just grind the liner so it fits the channels in the cylinder nicely??
What do I do at the bottom end of it?
Grateful for any help or similar photos of good cylinders....
(http://i1222.photobucket.com/albums/dd485/ola_martin/InletInside_zps8c61338f.jpg)
(http://i1222.photobucket.com/albums/dd485/ola_martin/Inlet_zps950fc115.jpg)
(http://i1222.photobucket.com/albums/dd485/ola_martin/BottomCloseup_zpsae099213.jpg)
(http://i1222.photobucket.com/albums/dd485/ola_martin/Bottom_zpsa2626222.jpg)
(http://i1222.photobucket.com/albums/dd485/ola_martin/Exhaustport_zps43ee1389.jpg)
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Looks miss aligned to start with.
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I see no real problems there , the port windows in sleeves are always undersize, they would be to weak if they were correctly dimensioned. The missalignment comes from when the sleeve gets pressed in as the sleeve has a habit of twisting as it goes in (for reasons unexplained). After the rebore just match the cylinder to the sleeve and sand the exhaust bridge a little.
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Ola Hola,
The liner you have is for the Reed Valve and your cylinder is standard piston port. After re-alingning the cylinder clean up the ports and champfer the ports to stop any ring sticking. Most importantly I would fit your piston in the cylinder on the connecting rod and mark your piston with a permanent marker through the exhaust port. Doing this it will show where the bridge is in relation to your piston. With this information you can drill 3-4 holes in line going from just under rings down to above the piston squirt. This will help lubricate the exhaust bridge and stop a seizure. I have done this on my Maico 490 and I would also suggest if you are using a non dry film coated piston (Wossner coated Wiseco un-coated) to get the piston dry film coated. Added insurance.
Kevin
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All the piston port liners seem to have the reed valve windows in them, mine is the same.
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Thank you very much! ;)
But do you meen realigning by heating up and try to twist, or just matching the ports. Some places the twisted liner exposes a small bit of the cylinder wall next to the port...
I already have the Wossner piston...
Should I do anything to the liner at the bottom where the gasses comes up from the cases?
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Ola,
As John said his barrel is the same, mine is the same liner too, I would take it to a specialist and get it re-aligned. I am not sure if this is a job to be done at home. Are you running a standard head?
Kevin
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Yes I have a NOS head.
I have a oven that I use for heating cases to change bearings, once I heated a Huskycylinder to make the fins a bit softer before I straightend them, and when I took it out the liner almost fell out, wasn't very hot, under 200*C.... So I figured I could just do the same to the Maico and try to twist the liner, mabe it isn't so easy??
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Will depend on the interference fit between cylinder and liner, how easy it will come out and how much it will twist going back in.
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Ok, Lozza, so you think I shouldn't bother, and just match the ports like it is now? I would have to take some alu. of the cylinder in some places to get it smooth though...
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That is an absolute shit job Ola. Shame. I am really really busy, but I can not sit back and watch you be talked into adding even more mutilation. It already has the makings of an abomination, don't feed it. It is so easy to fix Ola.
Do it, like you have done all of the rest of the fine work that you have presented on here, Proudly and properly.
Firstly, do you have a hydraulic press reasonably close to your oven? and do you have access to a metal working center lathe with a spindle bore of all least 12mm?
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Yes I do, all of those things ;D
And if you're thinking what I'have been thinking, I'm sure that liner can be guided and locked in place while it cools off... ;)
But I'll be very grateful for your advice!
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Good on you Ola, sounds like you have it sussed ;)
Couple of things that come to mind. If you are going to make a guide bars, trust me, you should make and use five of them. Make sure the M8 x 1.25 pitch you cut into the end of the 12mm guide bars are done in the lathe with a spirex tap mounted in the tail stock of course(keeps everything true). Obviously make sure that before you cut the threads to relief counter-bore them to a depth of the length of the head stud shoulder +1.0mm. This will not only alloy them to screw all the way on, but also save you needlessly cutting extra thread into the end of them. Face the end, so that they nip up squarely and perpendicular to machined alloy face of the cylinder top. No need to over tighten them. Doesn't hurt to machine a slight tapper on the opposite end of the guide bars either, as a lead-in off course. Just makes it quicker and easier when dropping the liner into place on the way from the oven to the press.
You can machine up a stepped pushing plate if you please? I prefer to use dual plates with a very snug fitting center-bolt to amalgamate. Very important to leave the job in the press under pressure as it cools to ambient. Make sure to support as much of the liner hat as possible. The OD of the the pressing re-entery push (tool)plate should be as great as possible to extend just about all the way out to the guide bars. That way the liner hat is supported when pushed firmly home, onto the area against the top of the cylinder.
For optimum heat transfer between the two, you want a minimum shrink fit of 0.006", but no more than a max of 0.014".
To prevent heavy galling, break all sharp cylinder and liner port edges with a bit of 600 grit, just a mick hair. I have the measured liner ready with a film of loctite brand "nickel based anti sieze". Some will tell you to use special heat sink grease to aid heat transfer to the "Alloy atmospheric heat exchanger"(cylinder), but in the case of Maico's high aluminum content casting, they use the heaviest permissible shrink-fit interference allowable between these two dissimilar metals to actually engineer the max transmission of heat between the two materials.
Remember to do a test run, to have all your tooling and gloves set up ready. Do a dry run from the oven to the press. I do it in the house too, up to 250 degree, no problems.
And most of all remember that prior preparation will prevent a piss poor performance.
If you would like to share any more thoughts before you get to the port trimming stage? just say.
PS; If your lathe is big enough? It is a really good idea to true the base surface of the cylinder by fly cutting it at the finish of the job.
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Mick De,
You know your $#!^ by the sounds of it, it is so good to know there is expertise out there that are willing to share and offer up good advice. Good Onya Sir Mick De.
Kevin
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Thank you VERY much! ;D
My offer to pick up and drop of you tank was peanuts compared to this info....
I'll get on with it the next days then...
I have the oven in my shed, 4m from the press...
And I'd love some porting help when that time comes, these 490's are new to me, and it's going to be my first VMX racer. The other bikes I've built have just been put on their stand to look at, so I'd like performance to be good on this one.
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Ok, the liner's straigth. :)
12mm guides didn't work, the machined grooves was off center of the the headboltholes when the ports lined up, but it tapped easy in place and I put it in the press.
I was thinking to put the cyl on each crankcase while they're apart, and match the outside of the case/cyl ports...but I'm unsure on what to do on the liner-side of them.
On the rest of the ports I guess I put the piston in "bottom dead center" and mark of the bottom on all transfer and the exhaust on the liner?
Rest I'm unsure of, other than to just match the liner to the cylinderchannels? Angle on liner etc?
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Looked a bit at the bottom ports last night.
They don't match up very well at all... What can be gained by doing an effort here?
And the two grooves, whatever they're for ends up square against the lines, so I guess if they should work for something they need to be followed through the liner?
(http://i1222.photobucket.com/albums/dd485/ola_martin/IMG_0703_zps85bfae2a.jpg)
Here I have marked with black marker how much the cases would need to be taken out for the ports to match.... Makes a very narrow base for the gasket... Also everything looks so square and edgy, can't give much flow?
(http://i1222.photobucket.com/albums/dd485/ola_martin/IMG_0704_zps10246464.jpg)
Please bear with me, I've only been performanceworking with 4strokes before...
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Doesn't hurt matching it all up but doesn't make any difference to output either, it's a "feel good" modification.
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Disagree, matching the cases can give the bottom end a big lift.
smooth out all the dags in the transfer ports to barrel interface, match to the gasket edge and smooth radius any curves in the transfers. unless you have good porting specs from genuine hot up notes from the period, I dont touch the std timing. The main aim is to smooth any radius's or bends to a nice constant curve if you can and then just smooth the liner to barrel interface and smooth off the outer port edges with emery to prevent a sharp edge catching a ring. its at best a blueprinting process. In some cases of poor casting control, it can give a solid kick.
cant get a pic on ... :-[
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Ok, I'm a bit further, the engine came totally disassembled in a big box, with some missing shims, so it's a bit of a pussle for me as I've never seen one before.
So I've got the gearbox together and it shifts fine, the kickstartspring needs to be wound up one more turn, but I have an issue with the clutch.
First I put on a thrustwasher, about 1mm thick, then the basket, then the hub. I put on the long nut with the conical edge down as it looked to fit the hub that way. But now that I've tightened the nut all the way down on the threads I have an axial clearance on the basket and hub of 2-3mm, seems too much, but I can't figure out what's missing...?
Also can someone please tell me what ()()((( etc. setup to use on the clutchsprings?
Thanks for any help! :)
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;D
http://ozvmx.com/community/index.php?topic=24303.0
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Thanks, but I already have those. And I built it up according to that, except it doesn't say the thickness of the shims.
And they don't say if the clutchhub should have axial clearance, or if it should be tightened down tight with the nut.
And they don't say wich way to put in the clutchspringwashers...
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Disagree, matching the cases can give the bottom end a big lift.
smooth out all the dags in the transfer ports to barrel interface, match to the gasket edge and smooth radius any curves in the transfers. unless you have good porting specs from genuine hot up notes from the period, I dont touch the std timing. The main aim is to smooth any radius's or bends to a nice constant curve if you can and then just smooth the liner to barrel interface and smooth off the outer port edges with emery to prevent a sharp edge catching a ring. its at best a blueprinting process. In some cases of poor casting control, it can give a solid kick.
cant get a pic on ... :-[
Unfortunately dyno's and stopwatches tells a different story to the 'bum dyno'. Our dyno will measure down to 0.1HP and yet to see any difference in a engine that has had countless hours smoothing and flowing etc etc.
It doesn't hurt but makes no measureable improvement in output.
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(()) (()) (()) . 20 all up. Conical edge out. There should be a lock tab under the nut. The basket runs a needle bearing.
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Thanks you very much 090!
But on mine it seems that the locking plate has went over/around the nut (it has a 17mm 6-edge hole) and is held on by the springs...
Mabe I put the nut upside down, should the rounded edge on the nut face the hub or the clutchcover?
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Sorry, missed the conical edge out part... ::) ::)
Thanks again! ;D
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Thanks you very much 090!
But on mine it seems that the locking plate has went over/around the nut (it has a 17mm 6-edge hole) and is held on by the springs...
Mabe I put the nut upside down, should the rounded edge on the nut face the hub or the clutchcover?
Mine is the same Ola, the inside of the lock plate has been rounded out by the nut. It doesn't matter, just use some blue loctite.
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Cheers :)
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Ola,
Have you considered changing the clutch washers over to springs? I know mine has the spings and it seems to be OK. I have also started doing the ports on mine while I had the cylinder off getting the 18mm decompressor adapted to my cylinder. I am only doing a port clean and polish and not overly increasing the sizes and definately not playing with the port timing. I will post some photo's for you after I get it done and before assembly.
Regards,
Kevin
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Disagree, matching the cases can give the bottom end a big lift.
smooth out all the dags in the transfer ports to barrel interface, match to the gasket edge and smooth radius any curves in the transfers. unless you have good porting specs from genuine hot up notes from the period, I dont touch the std timing. The main aim is to smooth any radius's or bends to a nice constant curve if you can and then just smooth the liner to barrel interface and smooth off the outer port edges with emery to prevent a sharp edge catching a ring. its at best a blueprinting process. In some cases of poor casting control, it can give a solid kick.
cant get a pic on ... :-[
Unfortunately dyno's and stopwatches tells a different story to the 'bum dyno'. Our dyno will measure down to 0.1HP and yet to see any difference in a engine that has had countless hours smoothing and flowing etc etc.
It doesn't hurt but makes no measureable improvement in output.
Find that interesting but your right, the figures dont lie... The Psychology helps though ;D :D ;)
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KTMaico, I considered the Wheelsmith style spring, but my dealer didn't supply it, so I just went for a set of new washers for now.
I would be very grateful for photos and info of your porting, the bottom end is done now, so fixing up the cylinder is next.
I have matched the cases to the cylinder already, so I'm expecting a massive power increase, either physical or psycological ;)
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Disagree, matching the cases can give the bottom end a big lift.
smooth out all the dags in the transfer ports to barrel interface, match to the gasket edge and smooth radius any curves in the transfers. unless you have good porting specs from genuine hot up notes from the period, I dont touch the std timing. The main aim is to smooth any radius's or bends to a nice constant curve if you can and then just smooth the liner to barrel interface and smooth off the outer port edges with emery to prevent a sharp edge catching a ring. its at best a blueprinting process. In some cases of poor casting control, it can give a solid kick.
cant get a pic on ... :-[
Unfortunately dyno's and stopwatches tells a different story to the 'bum dyno'. Our dyno will measure down to 0.1HP and yet to see any difference in a engine that has had countless hours smoothing and flowing etc etc.
It doesn't hurt but makes no measureable improvement in output.
I can't agree with that either.
From my experience matching the ports gives an increase that can be felt in throttle response and acceleration out of corners.
A dyno doesn't measure throttle response nor does it measure engine performance at 1/4 to 3/4 throttle where a motocross bike spends most of it's time.
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Re matching ports etc.... if a reasonable amount of material is removed in tidying up and matching the ports, there will be an increase in power. Just polishing and knife edging the dividers wont do much at all. i did this to my 010 300 and no noticeable increase >:(.
i had a 2000 250 years ago and we ripped into it as it had plenty of fat around the transfers and gasket edges on the barrel. probably removed 2 - 3mm in parts and reshaped the transfers into the barrel into a smooth curve as they had a step like inner radius. the inlet port was cleaned up as it had serious casting dags all over so it was taken out 1- 1.5 mm in parts and the bridge seriously thinned.
it generated a lot more torque and shot onto the power much easier. I was out climbing 450's on steep open grassy hills in 3rd and 4th gear and in a straight line drag against a newish 07 250 it would pull 3 - 4 bike lengths on it. A mate still has it and everyone that rides it is amazed at the grunt it has for an old dunger.
The newer katos have a much tidier casting process and those potential gains aint there! :-[(dammit)