Can you pick out the noise?

[westburyst]

Hello,

Just wondering if you are able to make out the extra noise coming from the cylinder. It is more evident when the actual scooter is physically in front of you. I thought I'd record it and get your opinion. Even on the video I can make out the noise. Don't know if it is normal or not. This is the first time I've owned a Lammy. I've been searching hi lo in the net for videos of Lammys running/being started and some do not have this noise and a couple appears to have this noise (btw mine is a SIL GP200 92'). I am just unsure and it is driving me nuts. :baddevil:
I've just recently had the the cylinder re-bored and replaced the piston as it was scored quite considerably. Changed seals and bearings. To me it appears to be like a high pitch jack hammer - perhaps pinking or pinging. It appears more obvious when the camera is in front of the cylinder.

As always appreciative of any inputs/suggestions.

I am hoping that her sound is normal but I'll wait for your feedback :shocking:

http://vid910.photobucket.com/albums/ac ... 032010.flv[/photobuckvid]



Cheers

[netweasel]

If it is coming from the top end, it could be piston-slap. Which means the bore is too big for the piston (so the re-bore might not have been done within the tolerance of that specific piston).

[westburyst]

If it is coming from the top end, it could be piston-slap. Which means the bore is too big for the piston (so the re-bore might not have been done within the tolerance of that specific piston).

Thanks for the reply, I gave the spec tolerance from the 'Sticky' book to the re-boring company.
I believe this side of things should be ok.

Cheers

[netweasel]

If it is coming from the top end, it could be piston-slap. Which means the bore is too big for the piston (so the re-bore might not have been done within the tolerance of that specific piston).

Thanks for the reply, I gave the spec tolerance from the 'Sticky' book to the re-boring company.
I believe this side of things should be ok.

Cheers

Is there a chance that the rebore was done without a proper measurement of the piston, and just done to the spec that the piston was supposed to be? It has happened before and not too uncommon of a mistake. I bought a bike that had a brand new top-end, supposedly done to .0025" tolerance, and it was actually closer to .005". It made the same sound.

It could also be the big-end bearing in the crank.

[westburyst]

If it is coming from the top end, it could be piston-slap. Which means the bore is too big for the piston (so the re-bore might not have been done within the tolerance of that specific piston).

Thanks for the reply, I gave the spec tolerance from the 'Sticky' book to the re-boring company.
I believe this side of things should be ok.

Cheers

Is there a chance that the rebore was done without a proper measurement of the piston, and just done to the spec that the piston was supposed to be? It has happened before and not too uncommon of a mistake. I bought a bike that had a brand new top-end, supposedly done to .0025" tolerance, and it was actually closer to .005". It made the same sound.

It could also be the big-end bearing in the crank.

When I dropped off my cylinder I left them my new piston as well so they can do the proper measurements. I'm quite confident they did it correctly. When I took out the crank, the big-end bearing visually seemed ok and did not have much play and rotated smoothly.
So what did you do to fix your problem? Did you get another re-bore and a new piston?
I suppose the only way to find out if they did the re-bore incorrectly is if I take my cylinder back to them and get them to re-measure?

I did not mention before that there are a few air leaks happening. 1) between u bend and exhaust , I need to get a good fitting exhaust clamp , a bit of oil splutter is coming out from this. 2) carby clamp screw is rounded not tightening properly , I need to get a new one as I can feel a bit of air coming out beetween the inlet manifold and the carby.



Is it possible for the two lines (used to align with pickup) on the fly wheel to be off? Perhaps when it was made the person marking it stuffed up? Perhaps my timing is not correct because of this and is too advanced?

I have two fly wheels. One that originally came with the scoot when it was running on points and another is the one that came with my new electronic kit (BGM stator/Ducati cdi).

The arrow markings on both fly wheels are more or less on the same area but the two lines are not. Would this be always the case if one was for points and one was for an electronic setup?
I am using the flywheel that came with the electronic kit.

I did hear this pinking / pinging noise even before the re-bore but I think only heard it after I changed to electronic ignition.

cheers

[bristolmod]

My monies on piston slap as well- does it improve/ disappear when the engine is at the correct operating temp?

Were the ports chamferred slightly prior to reassembly by the boring company/ yourself? Could be the piston rings very slightly catching the edges

Small end bearing?

Flywheel area- something just touching?

Squish too narrow? Piston kissing the head?

Chris

[westburyst]

My monies on piston slap as well- does it improve/ disappear when the engine is at the correct operating temp?

Were the ports chamferred slightly prior to reassembly by the boring company/ yourself? Could be the piston rings very slightly catching the edges

Small end bearing?

Flywheel area- something just touching?

Squish too narrow? Piston kissing the head?

Chris

I'll check the squish clearance and the ports. Nope I did not chamferred the ports I am hoping the boring company did.
If the squish is too narrow and the piston is kissing the head would you visibly see damage on the piston head?

Cheers

[westburyst]

the firing marks can be miles off on the flywheel and stator, use a timing gun to make sure the timing is what you intended.



Cant tell from the video but your video has inspired me to make a new BBcode for everyone to use to embed photobucket video's


see this to find out how
http://scooterotica.org/forum/viewtopic ... 767#p67767

Yep, I'll double check with a timing gun. Some many variables to consider

[westburyst]

For all the good folks that has replied to my post can anyone actually here the noise I am talking about from the video that
I've posted?

Perhaps someone who owns a standard GP200 with electronic kit can be nice enough to post something similar to mine so I can compare the two.


Cheers

[desi]

Can hear the noise loud and clear, your description as "high pitch jack hammer" is spot on, unfortunately don't have any suggestion but would also love to know if this is what pinking sounds like
.