Mechanical Help! Mechanical Noise - TC88B

[banquo]

2003 TC88B, Stage 1, 40,000 miles, regular services.
New and worrying mechanical noise started today...
Start engine, and for about 1 second, I get a loud tapping noise. Imagine tapping on a 6" vice with a hammer. Just for a second or two, and then it goes.
Supposed to be heading 400 miles down to RTTW on Friday, so it's a worry. No abnormal noise after the engine's started, and it runs fine.
Out of 5 starts, I only heard it twice, but it was noisy, and I've definitely never heard it before.
I've had 3 ideas:
1. Compensator nut - pulled the primary tonight, and the nut is not slack. No sign of end play. M6 tensioner working fine. No broken spring.
2. Big End - surely not... Never seem to hear of any big end problems on the Twin-Cam, but that's what it sounds like (going away when the oil pressure builds..). Anyone had a big end problem on a TC88B?
3. Lifter problem? Although I've only heard it twice, it seemed (maybe) to come from the right hand side. Maybe a lifter not returning properly, and getting clattered by the (stock) cam? Is that possible, or likely, and what would cause it???

Next plan is to pull the cam box cover, because I'm due to check the tensioner shoes again anyway (next to no wear at 20,000)

Anyone got any ideas, or suffered a similar problem?
Any checks that can be carried out other than pulling the whole thing to bits...?

Suggestions welcome, otherwise it looks like we won't be making it on Saturday...

[the_monster]

sounds like a tappet not pumping up straight away at start up. mine sometimes goes clank on the first turn - it runs big lift cams and hi comp pistons - but it fires and everything is fine. try checking the tappets first before ripping it apart.

[Phil]

JAKE............RELAX!. Put the spanners down & back away.

Occasionaly the engine will stop (not often) with the top of the cam lobe directly under the tappet roller. Over a few hours the slightly worn tappet will bleed down with all the spring pressure on it.

Next start will take a few revs of the engine to pressure up the tappet again.

I talk to lots of panicked customers with this issue.

If it runs good after the tappet quiets go on your way & have fun.

Phil.

[kevin bolden]

Bloody good answer. I wish all problems could be solved so well

[banquo]

Thanks guys. Running against the clock here. I have to go to Belgium for a coupla days, take an old lady to the airport, and work the rest of the time, plus the underground cable that takes the power to my garage has gone down to earth, so haven't got any lights.
And the bathroom ceiling came down on Saturday morning......

Blood pressure could be better right now....

That's encouraging that you both think the 3rd and least worrying option is the most likely...

I'll have a go at sticking the primary back on by torchlight, and see if I can get a chance to check the tensioners before we leave, although as it's only 1000 miles round trip, it should be OK, unless they're already gone...

Fingers crossed, and thanks again for your support!

From what you say, I assume that the lifters normally sit there on a cylinder full of oil remaining from the previous running, so no rattles on start up, but when they get worn, that oil can drain off, leaving it unsupported, and large clearances until the oil pressure builds up again..? That about right?

[Stuarty]

Originally Posted by banquo

Thanks guys. Running against the clock here. I have to go to Belgium for a coupla days, take an old lady to the airport, and work the rest of the time, plus the underground cable that takes the power to my garage has gone down to earth, so haven't got any lights.
And the bathroom ceiling came down on Saturday morning......

Blood pressure could be better right now....

That's encouraging that you both think the 3rd and least worrying option is the most likely...

I'll have a go at sticking the primary back on by torchlight, and see if I can get a chance to check the tensioners before we leave, although as it's only 1000 miles round trip, it should be OK, unless they're already gone...

Fingers crossed, and thanks again for your support!

From what you say, I assume that the lifters normally sit there on a cylinder full of oil remaining from the previous running, so no rattles on start up, but when they get worn, that oil can drain off, leaving it unsupported, and large clearances until the oil pressure builds up again..? That about right?

Jake,

If it helps, I have a wee generator that you can use to get some light in yer garage. I can nip up with it tonight.

Sent a PM with mobi number.

Let me know

[banquo]

You're a wee gem Stuarty, but I'm working tonight, and off to Belgium tomorrow. I've made up a wee inspection light from an old tail lamp and can wire this up to the car battery for when I get home on Thursday. Will have a go with that on Thursday night. Feeling reassured by the advice above, I'll get down there if it doesn't break...

Really appreciate your offer: you are a true gentleman!

[Scotty]

Did you check the alternator rotor was tight as well as the comp sprocket?

[banquo]

No, 'fraid not...
How do you check it?

[banquo]

OK, so tensioners are still OK, but the knocking hasn't gone away.
When I posted the 1st time, I'd only done 5 starts since I first heard it, but now having been down to RTTW and back (there goes another 1000 miles..) I have a bit more to go on, as I can make it happen now.

If I start up the cold engine, and push the choke in so it's running at well under 1000 rpm (potato territory) then it does it constantly, and it doesn't go away. On a warm engine, the tickover is 1000 rpm or so, and I don't hear a thing, but if I engage 1st, and let the revs drop by slipping the clutch, then off it goes again - clunk, clunk, clunk. It sounds like something loose, because when the engine is running smoothly, I can't hear anything, but when at low rpm, and hunting a bit, you can hear the knocking, in time with the engine.

Does that eliminate the lifter as the problem? I'm guessing it does, because once it's pumped up, it should disappear?

Encouragingly, nothing propelled itself through a crankcase on the way down or back to RTTW, but clearly there's something not right.

I'm going to try and get it running slow, and take a screwdriver stethoscope, to see if I can get a better idea of where it's coming from. Might fit the stock pipes too, because it's hard to hear anything with the SEIIs...

Any more ideas out there, and Scotty, is there an easy way to check the rotor, or does it all have to come down...?