Suzuki 2 Strokes

Hi folks!
I don't post many requests though I enjoy reading and occasionally contributing.
This time I'd most value others thoughts and experiences on a noise I had before my recent rebuild.
History:
UK GT550B, bought April 2012. Now in pieces though coming together fast after a full rebuild of the motor and cosmetics everywhere else. Before dismantling, when revved freely and allowed to idle back down, there was a distinct whine noise from under the clutch cover. I thought 'it'll be a gearbox input shaft bearing, or one of the clutch bearings, and I'll see it or hear about it when its rebuilt'.
But, the firm that did the motor and completely rebuilt the motor itself told me there were no issues with the gearbox or bearings, and in there only seals were renewed. Strike one for the noise finding journey!
Now I have looked closely at all the clutch components, I can see nothing that might account for such a noise (definitely not what I heard with a GT550A I sold recently, nor either of my other two GTs, a 380 or 750). The two large caged needle roller bearings are unmarked, the centre piece they roll on likewise almost new looking, the Borg warner starter clutch whirs smoothly in one direction and locks up as it should in the other. All thrust washers look to be there and in the right order.
So....while I still have the clutch cover off, does anyone have any suggestions / experiences to direct me?
My (reasonable, I think) fear is when I restart it, the noise will still be there, why would it not be?
Am I looking in the wrong place?
Might the crankshaft pinion / clutch basket gear meshing make a noise if awry? or can good-looking clutch bearings still make off noises? it was definitely not changing pitch with engine speed, but I judge with clutch speed / primary gearbox shaft speed. Can a working but invisibly defective one-way clutch device also 'sing'? its far easier to change all these while apart, but its a chunk of change I currently have no reason to spend. Also, the noise was too far to the rear to have come from the points cam bearings (which I have changed anyway for timing surety).
Thank you for any inputs,
Mike (UK)

I'd speculate that the noise may be from the drive gears on the crank and clutch drum. While it is still apart, inspect the gear teeth. You are looking for is depth of tooth engagement. If the shafts are machined too far apart (in the case) or too closely together that could be an issue. Likewise if one or other of the gears is marginally over or undersize, that could be an issue.

Tolerances back in the day tended to be a little looser than we expect today and it's possible there's a stack up of tolerances or maybe just the gears are at the limit of spec. Without access to highly accurate measuring equipment there's no way to measure gear shaft position and less options for moving the shafts if that's an issue.

I'd build it and see (hear) what the whine is like. If it's still bad, and there's no reason to suggest it would change, then try a different gear set - primary gear and clutch drum and see if that makes a difference.

Thank you TZ, what you say makes perfect sense and could be 'it'. If so, we agree it will be there when restarted. And if true, there's a way forward that isn't too invasive.

I deduce you don't favour the clutch bearings or the one-way clutch as culprits because they sound / look fine, from my description?

Just now, as I put the clutch plates and pressure plate on, I noticed something I'd missed before. I noticed some bright scrape marks inside the edge of the hole in the pressure plate. These should not be there. Measured inside diameter and showed it could sit outside the incomplete circular projecting casting inside clutch cover. And there were bright marks in places on the outside of that casting projection. This should not happen. I wonder if that cover been damaged? Can't see signs of it externally. The NOS cover I'm fitting is dull there; the old cover was badly corroded where it had been wet on its top for a long time. I don't like this as an explanation, as we'd expect it to wear itself to clearance quite quickly, with both pieces being alloy. However, I didn't run it for long, and I know from bodges found inside that it had been apart in the hands of its PO, and it had been off the road for many years, so who knows. That control will be run because of the new cover, but I don't expect victory there!

Cheers,
Mike

I reckon those markings are from a previous owner that hasn't tightened the clutch centre nut properly, and has not secured the nut with the tab washer properly. Most people don't have a socket THAT big in their toolbox.

This has allowed the nut to loosen over time, in turn allowing the clutch basket to wobble around a little.

I'm guessing this because about 3 years after getting my triple, the clutch started to slip momentarily when I went over bumps in the road. When I stripped the clutch, the centre nut wasn't even hand-tight - the tab washer hadn't been bent over properly by the PO and was barely touching the nut. The shock through the driveline of going over the bump would cause the basket to shift slightly, in turn making the clutch slip.

I'd agree with TZ about the noise being the primary gear set - I'm pretty sure these are machined as matched pairs. A previous owner may have replaced the clutch basket and not the crank gear. I don't think it causes a problem, other than just being noisy.

Craig, thank you for that. Perhaps of note, my clutch nut was so loose I did not even need to stuff rag between clutch and crank gear to get it off! So that's probably the bright marks story.
I'll post how I get on in due course - slow going but fun!
Mike

Strange coincidence, Mike. I noticed a noise every time I went in the garage and started working on my 550 (s) - like a whine/cry/sob. I eventually traced it to my wallet.

Must be 550itis. Or maybe advanced tripleosis.

Alan,
Funny you should say that - I felt something similar just now when I noticed a small drop of fork oil from one lower leg. Those blessed allens are very tricky to get properly tight - sigh.

TZ,
Here is the best picture I can take of the crank pinion mating with the gear on the clutch basket. I have no reference / experience to gauge it, but would appreciate any comments.

Clutch nut is now on and torqued to spec with the right tools and the tab dinged over well. I knew that massive tool kit with a couple of torque wrenches would eventually come in handy ) The crank pinion nut was not properly tight either. Funny washer that one, it has no tab, its a dished beast with the cup peaking externally so that it gets squashed as the nut tightens. Its mentioned in a Suzuki bulletin from J's which would loosen their loose crank pinions, so this was the EC.

Cheers,
Mike

It's been a while since I reworked my 550, but I think the protrusion in the center of the cover (first pic) should be a complete circle. There is also a seal in that hole the the tip of the clutch push piece rides in. Is that seal absent?

Thank you Coyote - you know, I'd missed that seal completely. It was not present when I dismantled the bike, so I didn't check if there was one. There is, so I've just ordered it.
I'm growing hopeful that the combination of insufficiently torqued clutch nut and probably the crank pinion nut (since the spanner size is the same) might account for the noise and the scraping. If its all flapping around even a micro-tad, it wouldn't be a heap of surprise if I hear some noise, and it really wasn't much - just of a nature that should not be there.
Cheers folks!
Mike

Coyote wrote:It's been a while since I reworked my 550, but I think the protrusion in the center of the cover (first pic) should be a complete circle. There is also a seal in that hole the the tip of the clutch push piece rides in. Is that seal absent?

That looks like one of the oil gathers that then directs it down the middle of the shaft . If that seal in the side cover was missing it does mean that directed oil was not going down the center of the shaft to feed oil to something on that shaft .

Dave,
Good advice. Looking at it, the clutch push-piece in the hole in the pressure plate is hollow as is the gearshaft the clutch runs on. On this machine, the objects rotating on that shaft are a carrier tube and around that, two large caged needle roller bearings which support the clutch basket itself. The hollow shaft and carrier tube have multiple holes in it, so what you said involves clutch roller bearing lube. Interesting!
Thanks,
Mike

Folks,

I've sorted this problem and thought the list might be interested to know what the source of the noise was. Big prize to Richard / TZ. Spot on that man. Honestly, I simply didn't know what to look for when I pulled it apart for the rebuild and as a result missed what is now obvious to me with a strong light and a good pair of specs

Cheers,
Mike

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