OzVMX Forum
Marque Remarks => Spaniards (Bultaco, Ossa, Montesa etc) => Topic started by: Nitram on May 28, 2012, 10:36:13 pm
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I'm in need of a cylinder head for my 250. The bottom end is 63M Cappra, but the head and barrel are from a Scorpion I think. Not sure actually. But there are 4 head bolts, and it's a short stroke 72.5mm bore barrel.
Anyone got a spare head they don't need ?
Cheers,
Martin
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to help id what u already have has the cyl u have has it got two long studs or four bolts cheers chris
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martin
here is 1 on ebay
http://www.ebay.com/itm/1973-MONTESA-250-RICKMAN-CYLINDER-HEAD-/330673953908?pt=Motorcycles_Parts_Accessories&hash=item4cfdb41c74&vxp=mtr
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I thought you were on holiday's Jim, get a life. ;)
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he must be on holidays also. jim at $200 dollars usa dollars i dont think he will jump at it :D and we still dont know what hes got till he tells us whether he has 2 long studs for carby mount or 4 bolts for a bolt on manifold.
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Yeah, as Spanish said, $200 is not something I'm about to jump at. Usually you get a whole Montesa for $200 !! Just kidding !
Anyway, here's a picture of the head I have now. I only want another one because the compression with this one is huge. I havn't measured the CCV but it's virtually impossible to start with the prick-of-a-Montesa kickstart hitting the footpeg after only 90 degrees of swing. The compression is miles high. So my plan is to get another head and do a little machining on the lathe to get it down to something more user-friendly. Hope that's not too sacrilegious..................
(http://i5.photobucket.com/albums/y176/Kommer/P1140917.jpg)
(http://i5.photobucket.com/albums/y176/Kommer/P1140918.jpg)
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nitram looking at your picture u have the right cyl but look for a king scorpion head at the right price ::) and u can mill away for a while . montys start great if the timing is set right like anything else just get your sacks closer to fuel cap to start cheers :o
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Serious, you can stand up and put your weight (well, my puny 72kg anyway) on the kick starter and it just doesn't budge.
If anyone has a spare head to fit something like this lying around, let me know.
Cheers,
Martin
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my spare engine has 2 spark plug holes
1 for the plug
the other for compression release.just like in the 1 from the usa.yes the head is expensive i bought a spare gp250 five motor for 250.00
jim
the internet still works in the uk steve 4.09pm uk time 1.10am sydney time
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How does milling the head make less compression??, why dont you use the one you have?? or just wack a decompression douver back in the spare plug hole? If its that hard to start I tend to think it has other issues
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My VB360 was bloody hard to kick over with the short arc of swing, so I looped a cable tie around the frame to hook up the footrest - gave me a full swing, made it a 1-2 kick starter. Still had to stand on a log to get high enouth though.
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here is one in the uk
http://www.ebay.co.uk/itm/Vintage-1970-s-Montesa-cylinder-head-fins-all-there-/221040229110?pt=UK_Motorcycle_Parts&hash=item3377063af6
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My VB360 was bloody hard to kick over with the short arc of swing, so I looped a cable tie around the frame to hook up the footrest - gave me a full swing, made it a 1-2 kick starter. Still had to stand on a log to get high enouth though.
Be very careful of doing the old lifting the foot peg trick as you can easily swing the kick starter past its normal swing and do some serious damage :(
I have found that all 'new' Monty engines after a rebore and new top end feel like they have far to much compression but once well run in this seems to reduce to a normal feel. My VR250 felt like it was locking up when it hit compression when first started.
The trick (when cold) is to ease the engine over several kick strokes with the fuel and choke on and no throttle to prime the engine then ease over compression and return the kick start to the top for a full stroke (90deg) and give it the old hev-ho. (this is the Ross Nimmo approved method and it works). First or second kick every time yes the log helps for the 360/414 due to the effing great big piston
My VR250 took several tanks of fuel to completely free up to what I consider to be normal compression feel when kicking
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Thanks for the replies, and special thanks to Rob (monte34) who had a spare head that was just right. It is very similar as far as finning goes-except for a few short fins of the LHS to clear a high pipe, and it has spot for an extra plug. I didn't measure the CCV, but the combustion chamber is clearly a little bigger and when fitted it brings the compression pressure back to something pretty normal. I guess it may knock a little bit of the edge off the performance, but it'll be worth it I'm sure.
And yes Montynut, when the piston was new the thing could only be pushstarted, and then in about third gear.
Anyway, all fixed now.
Cheers,
Martin