Strange Rattle

[neo]

It

Edited March 21, 2009 by Neo

[copemech]

It

Edited March 21, 2009 by copemech

[neo]

What about up and down movement of the flywheel?

Hi Cope,

There is no up and down moment that I can detect.

So what your saying is there should be NO side-way moment at all ?

Will this only get worse?....Ridden every day how long have I got?

If I open the case I may as well do all bearings "crank and upwards" and all seals (and gaskets)...but what's that going to cost me?

Are there any other checks you think I could do before drawing a conclusion?

Best of balance.

Neo

[peterb]

Hi Neo,

If the motor was making a rumbling noise then it would be just the main bearings, usually a knocking noise from the bottom end, in time with the revs is the big end worn, maybe from the sand!

For main bearings, there should be no end float and no discernable up and down play.

I think you need to strip the motor down and take a look, you can leave the head on the barrel and remove as one unit.

Press the con-rod to one side and try for up and down play, there should be none at all, try it at TDC.

If main bearings, try the later sealed type, all seems very odd to me for mains to be completely sealed but by accounts on the forum, they appear to work, as Cope said, go for C3 clearence if you are not getting bearings from your Sherco supplier. Always replace the crank oil seals when pulling the motor down, use Sherco ones, usually high temp viton rather than std material.

If you find play in the rod, you'll need a new rod/pin/bearing kit and some one with a press to split the crankshaft.

Bye, PeterB.

[bark]

A deep groove ball bearing typically has more axial clearance than radial clearance. (I'm assuming that the crankshaft bearings are deep groove ball bearings.) So, if they start out at C3 clearance, won't they have a measureable amount of end play? Or, are they preloaded in some way to take up the clearance?

I work with rolling element bearings allot but am not an expert with how they are applied. And, the last 2t motor I had apart was an 87 RZ350, so no clue how these Shercos are put together.

Thanks,

Bark

[stork955]

Gday Neo, any discernable movement in the crank in any direction, and any "up and down" in the rod is no good. Also check rod side clearance - no more than around 25 thou between the rod and crank wheel means a rod kit is in order. Pretty easy to do, just use heat instead of large hammers! And for a rod, get your local bike shop to do the job, it takes the worry out of it.

Cheers,

Stork

[copemech]

In thinking about this, I would be more concerned with the verticle clearance, and if little to none, would discount the in and out movement. I am not sure if the crank will not possibly slide in the bearings just a bit, and since the bearings act to keep things centered up, there may be some tolerance there. And as long as these turn smoothly, well could last a long time.

If there was dirt in the carb inlet, the intake skirt of the piston couuld have some wear. I think it would be worth checking, as the skirt to wall clearance should be tight, like .001 in. or so.

[neo]

Hi Gents (Cope and all),

Yes I could not see/feel any up/down play when the flywheel was off. But I tried again with the flywheel on and I can move it (up/down) maybe 0.1mm (0.2 max). And the whole thing turns so smoothly without sound it's hard to see that this a the cause of the Strange Rattle.

I'm going to take the clutch cover and basket off and see what it all like from that side too.

But recalling that it does not make a sound while it's cold does this give an extra clue?

I can see the areas above the intake ports through the exhaust port and they look smooth. But would it be OK if I lift the barrel up (with the head still on) just below the piston rings and rotate the barrel 180 degrees so I can inspect the intake side of the piston through the exhaust port?...or would this be a crazy thing to do?

Best of balance.

Neo

[stork955]

Pop the whole lot off, you need to replace the base gasket anyway if its disturbed. Have a look and get it measured properly (piston and barrel) This will remove any doubts. It does sound like the bottom end is OK. My Techno has a dull knock when hot under load, the piston is at its limit clearance wise and the ring grooves are about knackered, which I'll replace once I'm finished tinkering with my TY's. Probably a similar thing by the sounds of it.

Cheers,

Stork

[the batt]

Hi all

Just had a 125 with a strange noise (rattle for a better word) Replaced

main bearings & gear box bearings. But turned out to be clutch gear & primary gear,

Hope this helps you.

[neo]

Hi all

Just had a 125 with a strange noise (rattle for a better word) Replaced

main bearings & gear box bearings. But turned out to be clutch gear & primary gear,

Hope this helps you.

Sure does....I'll check it out...many thanks.

Best of balance.

Neo

[copemech]

I think the item you made about it being only after warm makes a difference in things as they reach normal operating temps.

That, too me still makes the piston suspect. I think you would need to remove things to proprely guage them. These things are set up soo tight from new, there should be nil movenent between skirt and bore.

I will admit to having done some stress testing on my 2.9, probably running it well over 12,000 rpm on the road. I don't think the piston appreciated it much, has a bit of rattle hot, not bad though. Normal bikes will probably never see this.

Running the light clutch(springs out) and the lighter fluid to compensate, there is more noticable primary side gear rattle, although nothing like a gasser.

[neo]

Ok the cylinder is off.....and as suspected it's as clean a as a whistle. No scores anywhere piston or cylinder. The rings are smooth and move freely. It was also nice to see that it is still the "A" piston as the thin carbon deposit (on the top) sanded off with ease.

There is no detectable movement in the big or small end bearings. And I can't feel any movement on right side main bearing too. Although there is less of a grip and/or leverage on this side.

But my first concern is the amount of oil that appears to be in the crank case and coating the crankshaft flywheel. It feels like gearbox oil to me and if I wipe the crankshaft flywheel clean (at the top) then rotate it once, it's covered in oil again...Hmmm...am I seeing something bad or not?

Next step was removing the side cover and clutch plates.

Again it looks nice in there. There's a tiny amount of slack between the PRIMARY DRIVE CRANK PINON and the PRIMARY DRIVE CLUTCH PINON. But no noticeable wear on any of the gear teeth. So this looks fine to me.

My concern is there's movement (2mm left/right slack) [correction (1mm left/right slack)] between the PRIMARY DRIVE CLUTCH PINON (the big gear) and CLUTCH BASKET. Is this bad or is it something to do with the SILENT BLOCKs (M358) shown in the spare parts book. I can't remove the clutch basket HEX NUT CLUTCH at this time as I don't have a Basket holding tool and I don't want to risk damaging the Aluminium CLUTCH HUB. Any ideas how I can safely get a the HEX NUT CLUTCH off without a basket holding tool?

Also, when I go to refit the Cylinder is it best to fit new rings and do the rings need to be in a certain position before sliding the cylinder back over them?...I have not removed the piston or Pison Pin or Piston circlips so far.

It's all come to a stop now but it would be good to know what parts I need to order by Monday....So advice at this state would be greatly appreciated.

Best of balance.

Neo

Edited March 28, 2009 by Neo

[stork955]

Gday Neo, some clutches have a shock absorber built in, I dunno about the Sherco (A lot of dirt bikes don't bother) but that may be what you are seeing there with your free play. The rings each have a locating pin to stop them rotating into the ports. Be careful with these, make sure the gaps are lined up with the pin. Some need to be fitted the right way up also (the pin is mounted at the top or the bottom of the groove) One of the knowledgeable Sherco guys will let you know if its an issue for your bike I'm sure.

Cheers,

Stork

PS -did you get your piston and barrel measured? They don't need to be scored to be worn past limits.

Edited March 28, 2009 by Stork955

[jse]

can't remove the clutch basket HEX NUT CLUTCH at this time as I don't have a Basket holding tool and I don't want to risk damaging the Aluminium CLUTCH HUB. Any ideas how I can safely get a the HEX NUT CLUTCH off without a basket holding tool?

Also, when I go to refit the Cylinder is it best to fit new rings and do the rings need to be in a certain position before sliding the cylinder back over them

Neo

To hold the crank after the cylinder is off, take two short pieces of, say 1/2"X1" wood and place them front-to-rear under the piston, on either side, and then push the piston down so the skirt rests on the wood, which will lock the crank so you can remove the clutch hub nut.

In addition to Stork's advice, look carefully on the rings and if they go on a certain way, they usually will have a mark (like an "N" or a "T") on one side and that will be the "top" or the side of the ring that faces up. Before installing the rings on the piston, you also will want to check the "end gap" of each new ring by pushing it into the cylinder bore to about 2-3mm from the top (a little above the point where the top ring stops at TDC, so it is in the non-worn, or smallest diameter part of the cylinder) and then square it to the bore using the top of the piston, lightly pushing down on it. Measure the end gap with a feeler gauge to make sure it's within spec.'s. Check your manual, but generally the standard is .1mm per inch of cylinder bore.

If there is not enough clearance, you can dress the ends of the ring to provide a little wider end gap.

Jon

Edited March 28, 2009 by JSE