Engine Sounds Like A Machine Gun

I got some time today so I took the cams out, they are marked but I can't find any undue wear on them. I received the new pair and have been all over both with digital calipers and can't find a problem severe enough to give the sort of noise I am hearing. I can't see any damage to the tappet assemblies, I still think it's a bent valve sticking when returning to it's closed position. Looks like I'm going to have to bite the bullet and get the head off :-( My other option is to go the engine swap route, or to just strip it and sell the parts. I will have a further think first. There is evidence that somebody that didn't know engines has had it apart before - there is silicon gasket everywhere and the cam retaining caps were all in the wrong positions. Nightmare.

 

Hi Ken, I bought it last week, we couldn't get it started when I went to see it so I got it at a bargain price. The guy that owned it didn't tell me much about it other than the clutch was knackered - he wasn't lying I got it started once I got it home - the fuel tap vacuum diaphragm had failed and so it wasn't getting any fuel. The engine was warm when I got there so it had obviously run for a bit. It is definitely a very loud and obvious mechanical knock, there is no blow from the exhaust. I will give it a quick whirl with the replacement cams but I'm convinced a valve is sticking, I just can't think of anything else that would cause this. I think Oldyam is right, I will put my Sprint motor in there, I may then repair this one, sell it and convert my Sprint in to a cafe racer.

 

Having put the finishing touches to my Trident I have now turned my attention back to my Trophy with the machine gun engine. I spent a most delightful afternoon getting the head off and was a bit surprised by what I found. It looks to me like there is significant evidence of water ingress - clean pistons, clean top of combustion chamber. Oh yes and a load of water in there too The head itself looks ok apart from on pot number 3 there appears to be a dark mark that would suggest combustion gasses escaping. The Tappets etc all actually look ok, I suspect my hunch of a sticking valve was incorrect, they all seem to move freely, I will confirm that by taking each one out and checking it. Here are some photos, anybody got any comments? would it be wise to get the head skimmed to be on the safe side?

 

Yes, I drained the coolant although I was surprised how much was left round the liners, I need to get that all out before removing them. It has me really baffled at the moment as I can't see anything that jumps out and explains the horrendous noise I was getting. Cam chain and tensioners are fine, it's got me stumped at the moment.

 

Yes, I drained the coolant although I was surprised how much was left round the liners, I need to get that all out before removing them. It has me really baffled at the moment as I can't see anything that jumps out and explains the horrendous noise I was getting. Cam chain and tensioners are fine, it's got me stumped at the moment.

 

I'll have a go tomorrow and see what happens. I'm not sure my spring compressor will fit, think it's too big, might have to get another.