Head case

[Jez]

Hi, I hope this image below works. I know the link does. Further to a previous thread I have had to replace my engine. The new engine a aquired came from a low mileage 620 that was front ended and the forks smashed the front rocker cover...ouch!
Turns out the cylinder head has a hairline crack all the way through where you can see it is scuffed. In fact looking at the picture I took the seal between the head and the rockers cover doesnt even look that good.
Any suggestions to repair the head in situ? I really dont want to take the head off. It runs superbly.
Cheers in advance
Jez

[ img ]http://photos-734.ll.facebook.com/photos-ll-sf2p/v252/61/54/784623734/n784623734_973780_3794.jpg[ img ]

http://photos-734.ll.facebook.com/photos-ll-sf2p/v252/61/54/784623734/n784623734_973780_3794.jpg

[gremlin]

give it a good clean and try some chemical metal, or milliput or titanium putty. it will show, but will stop the leaking
Mr G

[dlloyduk]

Best way would be to remove the head and have it welded and machined.
Although its a pretty un-stressed part of the head the whole assembly will have to cope with a lot of pressure and stresses every time you use the bike.
Listen to it cooling down pinging and crackling that's the heads etc going back to normal size when cold. The crack will most probably spread, if you do insist in bodging with Chemical metal type products get hold of a crack detector kit and find the end of the crack. Then drill a hole right through it, this should help stop it spreading then, fill away file the excess of paint over it and cross your fingers.
Bye the way do you not have the heads of your old engine? Can you not find a second hand head on ebay? They are usually quite cheap when they come up for sale.

[jerry]

weld and machine is the proper fix.longterm.

[manwithredbike]

i'd partly agree with dloyduc. i'd look for an undamaged head. my experience of cracked heads including welded ones is that if they're not fixed spot on they only deteriorate, esp if you're doing a lot of miles particularly short runs where there's a lot of heating up and cooling down

[jerry]

looking at the photo I reckon it might be repaired in situ

[gremlin]

I love threads like this. oh you shouldnt do this, you shouldnt do that.
in realistic terms, anything other than replacing the head could be seen as a bodge.
looking at the picture, it looks as though it is a dig/ scrape wound rather than a crack. welding would be tricky as with all cast ali, then theres the risk of grinding disk dust entering the engine if its done in situ. if you want a simple solution give the putty a try, will cost you less than a fiver. for those doubters out there, we were using it back in my 2 stroke racing days to repair crank cases where the crank bearings had seized and spun in the casings with great success. and more recently when a friends R1 track bike spun a crank shaft shell in the case, build it up with t putty, re-machine and roberts your mothers brother (4 years later and an awefull lot of track days later still going strong) if it could take the extremes of heat and pressure under these situations ,then im sure that it can more than cope with holding back a bit of oil . but make sure you clean the area thoroughly with carbon tet or similar . if it doesnt work youve still got to get a replacement head, but its got to be worth trying for a quick fix.

Mr G

[jerry]

I do remember certain 1970s works Honda racers engines held together with Araldite and stuff.

[Nickj]

I rebuilt the waterpump on a KTM with Devcon. ran two full national class enduro seasons on it too. It's just a case of using what works where

[Jez]

Well thank you all for the advice. I opted to have it carefully TIG welded for now. It does show but is got me back on the road for the time being and I'll see how it goes :-)