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Discussion Starter #1 (Edited)
Last year I bought a very low mileage Sprint 955i - sub 6,000 miles. I had owned this bike previously but had sold it due to a bad walking accident that left me with a very weak right knee. Fast forward two years and following an oil change, the new owner was faced with a horrible screech coming from the engine. A local mechanic removed all ancillaries such as clutch and alternator for testing purposes and the noise persisted.

By this time my knee was much stronger, so I bought the bike back and fitted another engine. UK Winters being what they are, the original engine has been dragged into the house and almost fully stripped - almost because a) I left the head on and b) I haven't touched the conrod bolts yet. The mains look perfect, the crank turns smoothly, and there is no play apparent in the big ends. Have you seen the price of a set of conrod nuts/bolts?

When I fitted the replacement engine I found that the airbox wasn't seated properly and the stepper motor hoses were totally gone. It's amazing that the bike was running as well as it did. Doing a little straw grasping, could the noises have been due to the above? I never actually heard the bike run myself before I changed the engine.

Straw grasping aside, I suppose I'm eventually going to have to undo those conrod bolts. So, how many of you would reuse the conrod bolts? Though I may yet just keep most of the engine as useful spares.
 

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New bolts, every time

Sent from my SM-G955U using Tapatalk
 

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Sounds like a lot of hassle and expense. Are you sure the noise is coming from the bottom end? I think it's very unlikely that an engine with such low mileage would have a mechanical issue

Your thoughts around the air box could be the best option but the only true test would be to fit the engine and test
 

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It would help to know what year Sprint 955i so we know which series we're talking about.

ALWAYS use new conrod bolts. And pay particular attention to the torquing procedure especially the final angular measurement.
 

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Discussion Starter #6
Hi Macduff, I never heard the engine run but in the opinion of an experienced mechanic the engine was knackered. The noise was reported as being metallic screeching or squealing in nature. It was running fine directly after an oil change, PO went for fuel which was when it started. I'm sitting on the fence at the moment; the crank turns freely and smoothly, no play present, hence I'm reluctant to pull the big ends apart. On the other hand if the engine was rebuilt, fitted and still made a noise it would be 'annoying'. I'll have to get someone with more experience than me to have a look.

Hi Terry, the bike was built in 2004, probably one of the last of the 955i RS series, with the SSSA. As an aside it doesn't look much like an RS as PO converted it into an upright naked, which suits me perfectly (old bones).
 

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Discussion Starter #7
In the end I decided to unbolt the big ends and once again found nothing.

However I have found, lodged in the corner of the oil pump pickup screen where it was hard to see, pieces of what look like quite a large, but very thin shim. I have spent some time trying to find out where this metal came from, without success. One side looks rough finished, the other almost like chrome. I will try to post pictures below.

Is this a red herring? Where is the rest of it? Any and all ideas welcome.

P1020616.JPG P1020618.JPG
 

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o_O that's pretty scary. Can't think where that could have come from

I remember dropping a valve shim on my VFR. Thought I was going to have to tear down the engine until I found it stuck in the chain lube inside the front sprocket cover!
 

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Interesting and scary link.

Years ago I worked for EDS supporting Opel (GM) warehouses IT. I was shocked to see complete engines sitting in the warehouse with turbos not sealed off from all the dust and crap in the environment.

Who knows what other stuff finds its way into their engines as I imagine (expect) their standards are lower than Porsche's
 

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In the end I decided to unbolt the big ends and once again found nothing.

However I have found, lodged in the corner of the oil pump pickup screen where it was hard to see, pieces of what look like quite a large, but very thin shim. I have spent some time trying to find out where this metal came from, without success. One side looks rough finished, the other almost like chrome. I will try to post pictures below.

Is this a red herring? Where is the rest of it? Any and all ideas welcome.

View attachment 717683 View attachment 717681
Sorry to be the bearer of bad news but those are shards of a spun bearing shell. Mains or big end. Most likely big end (con rod shell) as they display the characteristic spiral 'pencil sharpener waste' shape.

Look again at the shells you've exposed in the big ends you've unbolted.
 

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Discussion Starter #12 (Edited)
I looked at the big end and mains shells very carefully, even using a magnifying glass. A local retired engineer looked at the bearing halves in the big end caps when he was passing and declared them to be 'perfect'. They are barely 'run in'. The main bearing shells are similarly unworn. Which is a pity, as that would explain everything.

The shards were more of a complete piece when it/they came out.
I wonder if this engine has had problems and been apart before?
 
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