Engine rattle whilst cold

[flipper]

Here is a vid of my TTR600 before the rebuild kinda sounds the same i think .

Only difference is that its all the time.


http://www.youtube.com/watch?v=-OT4yEMfctg

TTB

Wow - that is a bit noisy!

[flipper]

Just seen your vid Flipper

Things expand when they get hot so I'd expect more noise as your engine warmed up if it were the piston hitting the head or valves.

Is there any more vibration when it's rattling?

Mates have had metallic sounding air leaks in their cars before, granted not that loud, but it would explain why it goes when you use the choke & perhaps the leak seals when the engine is warm

The USB camera is a great toy, I bought mine after reading Bernieboys experiences

Rick

I am unsure of the expansion rates of the different materials, so I won't yet write off the possibility of it being a piston touching the head when it's cold. I've been reading a few car forums after googling 'deck height' issues, and many people say that the problem can be heard only when the engine is cold.

Yes, there is a little more vibration when it is rattling.

I still have to check for exhaust leaks - will update when I do.

What brand of camera did you get? How many LEDs did it come with to light up the view?

[xtzrick]

What brand of camera did you get? How many LEDs did it come with to light up the view?

THIS is the camera I got


It's 10mm in diameter, has 2 meters of cable & 4 LEDs & can be had for under £10 if you look around. They can be bought with different length cables but can be tricky to line up & focus, it's a case of twisting the cable to line up & adjusting the brightness of the LEDs with a wheel on the camera button (the bulge in the cable with the chrome bit in the pic above)
Holding it steady can be a twat when you want to take clear static pics for a forum.

Couple of pics I've taken using mine as an example of pic quality I've got so far
Gear wear & weld inside a carboned up exhaust.



EDIT: Checked my nose & Bernieboys camera seems a lot better quality

Rick

[Eric66]

Any update Flipper?
REgards Eric

[flipper]

Nothing to report as yet.

I've had some issues with my 4X4 that have demanded my attention for the past week, and I'm still working on that.

So, the TT is just waiting patiently in the background for it's turn...

[flipper]

Well, I've finally had some time today to tear down the top-end and have a look at what's happening.

I think I've found the problem - too much piston clearance, or an ovaled bore.

At the top of the stroke the piston can be 'rocked' fore and aft enough (with the gudgeon as the pivot) that the piston crown tips. This means that the top of the piston can touch the head at those points where the head is flat at the front and rear of the combustion chamber.

My guess is that as the engine warms and everything expands, the clearance becomes enough that it no longer touches, or perhaps the piston expands enough to reduce the amount of clearance to the bore and stops the rocking from happening.

There are visible 'shiny' patches on the front and back of the piston crown, and also on the flat parts of the combustion chamber, showing where the piston has been touching.

I've also worked out the cylinder is from a later model XT600 (2KF embossed on the side of it). That is a bonus, as it means I can rebore it and put in an oversize piston to suit.

Now, what piston to get...forged or cast, standard compression or 11.5, 1mm oversize or 2mm....hmmmm, so many options.....


On another topic - has anyone used Time-serts in their cylinder to fix up stripped head bolt threads rather than helicoils? The threads in the cylinder were feeling a bit 'soft' last time I put it back together, so I'm thinking they could use a tidy-up whilst I've got it apart.

Many thanks for all the help and suggestions everyone has offered for trying to sort out this problem!

[nop]

I think you should just cut to the chase and install a 673CC kit!

[flipper]

A big-bore kit would be nice, but the wife has put a ban on me doing that.

She remembers the ongoing costs associated with my last TT600, which was fitted with a Powroll 640 kit and many other hot-up pieces.

It made tons of power, but unfortunately tended to blow gearboxes on a regular basis...

So for this one, I figure that I had better just keep it fairly mellow

[flipper]

Just a follow-up on this thread...

I've just finished putting it back together after getting it rebored to fit a 1mm oversize Wossner forged piston. Having the XT cylinder (steel liner) made life much easier, as the normal TT bore would have needed a nicasil coating done too.

It purrs like a kitten now - no more knocking rattle when cold.

I also fitted time-serts to the head bolt threads in the cylinder.
At some stage previously a couple of the threads had been helicoiled, but they weren't working all that well any more. The time-serts have given the threads a new lease on life, and allowed me to torque up the head bolts quite happily.

Thanks to everyone for all the help along the way!

[Mezo]

Good to hear & thanks for the follow up.

Mezo.