Thoughts on this noisy engine?

Hey team, I hope all are doing well.

For the first time ever, I recently did some top end surgery on my 650 that I've slowly been building up over the past year. I took off the head and cylinders, had them bored out (due to cylinders being out of spec), fited oversized pistons, lapped in all the valves etc and got it back together.

Sadly, it seems my lack of experience has thwarted me, as now when I give the engine some revs, it makes a fairly loud clickity clacking noise. I'm keen for your thoughts on what I might have overlooked that might cause this kinda noise:



My first thought is that I've not put the cam chain guides in quite right. Seems like the revs might be causing the chain to splay out and contact some part of the casing. I've ordered a new cam chain in the mean time.

I've also checked compression and we're getting 120 psi on all four - good enough for rings that aren't bedded in yet.

Any thoughts? I'm ok with the idea of pulling the engine again and going hunting, but before i get carried away I'm keen to know if there is anything small I might have missed or overlooked. Cheers!

 

Sounds like tha cam chain isn't tensioned properly to me.
Did you set the crankshaft to the C on the reluctor when you installed the camchain tensioner?

Is the camchain tensioner on your machine manual, or automatic? Yamaha used both types on the 650.

 

Great questions, k-moe. I followed the directions for setting the cam chain tensioner from the haynes manual I have, including rotating counter-clockwise to the C mark.

Fortunately I have a manual and automation tensioner. I've tried using both, following the normal steps, with no change. That's another reason I suspect the guides, since the tensioners made no difference.

It's reassuring to hear you reckon it sounds like the cam chain. Definitely feel more justified in taking things apart again to check my work.

 

The front guide can be tricky to get to drop into place. The rear is pretty easy since you can feel it through the locking bolt while it goes into place.
For me anyway

 

Have you synced the carbs yet?
Are you sure the exhaust collars are tight?

 

It's difficult to tell, but is the exhaust system actually fitted.

 

It dosen't look or sound like it to me, which I took into account when listening.

 

It doesn't sound too unreasonable until the engine speed is raised when the exhaust noise is more noticeable.

Fitting the exhaust system and trying again might be a good idea before tearing down the engine again.

 

Where can the cam chain hit inside the engine apart from running against the guides, the top cover.

 

If the chain is loose it could hit anywhere

 

I just thought it would make less noise on the guides rather than the top cover for example.

 

If the guide is loose the chain will rapp it against the case.

 

Hey team, sorry for the slow reply. Busy organising my wedding this weekend and trying not to be distracted by the XJ

Thanks hogfiddles, really good thoughts. Carb sync hasn't happened yet. This was one of the first times I'd cranked the bike up after the work I did, noticed the sound and haven't moved forward with syncing as a result. Definitely don't want to cause further problems by running the engine in it's current state.

You guys have good ears! Yes, the exhaust is fitted, but it's certainly not the stock exhaust. Unfortunately neither the bike I was given, nor the parts bike, have the stock exhaust. Both have this four into one straight through exhaust, so it's rather loud, even with the pipes on. I reckon once I have it running reliably, I'll go hunting for a way to quiet it down a bit. I don't want to be that guy on our street.

Good call on this. I'll double check the exhaust fitment. I'm fairly sure I got it all set up properly when done, but I'll tick this off before moving forward with internal stuff.

Yes! My thoughts exactly. Thinking about the path the cam chain takes through the engine, the only place I'd imagine it could contact anything that isn't a guide is across the top of the engine between the two cam sprockets. It certainly sounds like when the engine spins up and more centrifugal force is applied to the chain, the slack isn't being taken up by the guides, or tensioner and it's making contact with the top of the cover. Well.. that's my theory anyway.

Thanks again, guys. I'll check the exhaust mounting and go from there. My rough plan at this point is to get a new chain installed (with a link so I don't have to break the case) check the front guide is in correctly and have another shot at running the engine. If that doesn't help, then It'll be further dismantling to check that the rear guide is in place correctly (hoping to avoid this as it's a full head + cylinder block off kinda operation).

 

Exhaust side cam guide pocket in crankcase. This is the 900f engine.



The tensioner side guide tighten bolt B until it seats against the bottom of the tensioner blade back bolt off 1/4 of a turn and tighten locknut A.



Is your manual the same? You tried both cam chain tensioners I see but are they fully extended indicating the chain needs replaced? If the tensioner side bolt B and locking nut A setup is the same and the 900 f (but needing adjusted) could that be causing the guide to rattle against the case when you rev the engine?

 

Were new seals/gaskets used between the cylinder head and the exhaust header pipes. I had an exhaust flange come loose, the result was a ticking noise caused by the leaking exhaust gases.

 

Both guides can be removed and reinstalled without dismantling the top end. You have to do a little creative positioning to clear the frame is all.

 

Hey team,

I thought I'd come back and close the loop on this now that I've figured it out, despite the fault being embarrassing and entirely my fault. Hopefully it helps someone one day.

Short story

I tightened the cam chain tunnel fixings way too tight. Because the cam cover is on a rubber gasket, it crushed down to ruin the tolerance. This meant the cam chain was contacting the underside of the cam cover. Like I said, entirely my fault.

The fixings, particularly the ones around the cam chain tunnel should be tightened to 2 kgf m, or 14.5 lbf ft. (According to Haynes)

Long story

I've definitely read posts from @k-moe talking about making sure you have, and are using, a workshop manual. It's these sorts of experiences that teach you the lessons the hard way. Though, it's funny how it sinks in better when you've lived the problem.

I figured it out after putting in a new cam chain, which is a bit of a pain, but also nice to have sorted. Obviously I wasn't keen at all to do full surgery on the engine. I haven't broken or worked with chains before, so this was new in that regard too.

So I bought a riveting/breaking tool and the chain. I broke the old chain, broke the new chain, connected them up then carefully wound the engine over and fed the new chain in. From there, I took them apart again and used a rivet link to complete the new chain. It was a mission, but it worked. I also noticed that when doing the timing, the marks lined up much more precisely with their locations than previously, which is fantastic.

Following the whole ordeal of sorting the cam chain, I was putting the engine back together and tried turning it over with the cam cover off, just checking for oil ingress into the head. No noise. From there it was fairly obvious what I'd done. I checked the manual and they were miles too tight. I've now got it back together and it's sounding better than it ever has. I'm pumped.

Moral of the story, don't make assumptions about these things. I'm not experienced enough to be guessing at torque values.

 

Good work. You learned.
The other reason to not guess at the torque values for the valve cover is that the bolts are shouldered down-low. Overtightening them can crack the head.