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Connecting Rod Side to Side Play

1472 Views 6 Replies 4 Participants Last post by  althorne
Hi all,

Got the top end off for a rebuild - cylinders glazed and a couple of valve seats need recutting. 60,000km on the engine, so not sure why it needed doing so soon, but it is what it is. Those bits are at the machine shop.

I've noticed a little sidey sidey play on the front cylinder's conrod (dropbox video linked). I know a little bit is fine, but I'm not sure if this is too much. There is no up/down play at all.

The (big end) spec is 0.170-0.320mm with a service limit of 0.5mm. But I can't measure that from the top, and I'm loathe to drop the engine and split the crankcase unless I really have to - it's beyond my skill level, so I'd have to get a pro to do it at great expense.

But, that being said, there's no point doing a top end job if the bottom end is cooked. So, yeah, does this look like the bottom end needs doing, or do you think I can get away with it?

Video: video-1658200191.mp4

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My seat of the pants estimate is that you will be all right.

I think there is a way to measure it. Shoot a good light down at the big end. Make a tiny ruler on the end of a stick (at 90*). Just a few mm marks. Then wiggle the top end just as you are doing while doing video on the bottom end with plenty of light and that wee short ruler in the pic next to the gap. Then you watch the video and can make a pretty good guestimate.
Both DL's the crank moves side to side at idle. On the 1000 it's really obvious and called idle hammer. It also happens on the 650. So some side play is expected and typical.
These bikes simply don't have destructive bottom end problems. I'll concede there's always an exception but the odds are with you.

Don't obsess about it, put it back together and ride it.
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Thanks both. That's very reassuring! Will try to rig a ruler up to be sure, but if it's not giving immediate worrying vibes then that's good.

Never heard of the idle hammer - used to get a ticking noise on acceleration, but I put that down to the shot valves. Could be related?
It's under the same conditions just much quieter on the 650. Happens more with lighter oils. It's just with the V-Twin engine configuration there's a very small side thrust on the crank as the pistons go up and down. At idle that'll move the crank side to side and you MAY get a hammering sound at idle, clutch out. It's loud on some 1000's, and barely noticeable on a 650 at all.
The rear cylinder has a little bit of side to side play, but considerably less than the front. Also no up/down play.

Engine still has oil in it, but hasn't been turned on in a few weeks. Entirely possible it's drained from the bearing.

History of the issue is that over the last few thousand kms, the engine has been burning oil like it's nobody's business. Historically, it would drop about 100ml per 1000km, which I hear is about normal. But it started burning 500ml per fuel up (about 400km). The only reason I noticed at first was the engine started knocking; I'd topped it up before a big weekend trip, and it went through over a litre on the trip. Knock went away when I topped up the oil, but damage done I guess.

Jumped up to a thicker grade of oil as a bandage (Penrite 20w60) and consumption halved. Would have fixed it earlier, but time and money were in short supply.

Do you think that could have contributed to any lower end wear, or just the worn out top end I'm already getting sorted?
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