02 May 2013

fork seals and cylinder heads

Still waiting for the gas tank to come back from powdercoat, but the decals for it did come in, and more importantly so did the fork seals.

Not stock, but apparently this is what Moto Macchi offers. New and Made in USA which is a plus. but I've never seen seals like these. For one, they're considerable smaller that stock seals and are intended to "float" along the stanchion tubes - secured by a 30mm washer that rests below the circlip on the sliders. I guess it'll work, and there's a lifetime guarantee (although I guess that's kinda useless if they don't work)... Now with the seals in, the sliders went back on and I can go ahead and mount the tires on my rims - I'll get to that on Monday.

While I was waiting for parts to arrive, I figured I'd address the oil leak on the bike. Appears to originate from the head and more specifically the upper pushrod seal.

Off with it's head


I like these heads better than BMW ones. Very easy teardown and rocker play is taken up by shims instead of pillow blocks. Those pushrods are weird though, I wasn't expecting the cam followers to be horizontal but the pushrods aligned vertically, they criss cross at a point and the exhaust is larger than the intake to accommodate the difference in distance to the rocker arm (because it's on the outside of the head and the intake is on the inside). I don't know why but for some reason I thought the cam was vertical, driven by a gear attached to the horizontal crankshaft, don't know where I got that idea, but that's what I was thinking.


oil leak confirmed, good thing I ordered new pushrod tube seals. That being said, the other seal is at the cylinder base, meaning that needs to come off too and I didn't order a cylinder base gasket (d'oh!). I could probably make one up with an xacto knife and gasket material, but there's supposed to be a dowel pin in the head that is missing and some other crap here and there so it looks like I'll be putting in another order with MotoMacchi in the near future.

high(er) compression piston... Aermacchi went up to 9.4:1 this model year


Didn't bother taking the piston and cylinder off yet, that can wait till I get the wheels back on and the remaining seals in. Overall, things are looking pretty good. Don't really see any valve recession (but I will be doing a proper leakdown test), no pitting or scoring on the piston or head, and nothing else immediately visible. Will definitely check con rod play when the cylinder is off, but if that checks out I don't think I'll dig any deeper. I want this back on the road, not under a microscope.

Kenny (referenced in a previous post) told me I'm the kind of guy that'll take apart a watch. I denied it, but he's probably right

1 comment:

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