The BSA A7-A10 Forum

Technical (Descriptive Topic Titles - Stay on Topic) => A7 & A10 Engine => Topic started by: muskrat on 15.07. 2009 15:00

Title: Big end nuts
Post by: muskrat on 15.07. 2009 15:00

G'day Blokes,
                 heres a curly one. Just fitted a lge journal crank in. Went to wind it round and got to 4o'clock and clunk. Wound it back to 8o'clock clunk. I counted all my spanners, none missing. Split cases, look for marks. The big end nuts hit the cases. I always use new nuts but had none so I put spring washers under the nuts. I removed the said washers and reassembled. Spins fine. A bit close don't you think ? Once I get up in revs and with a bit of crank flex will it take itself out to lunch ?
Cheers

Title: Re: Big end nuts
Post by: RichardL on 15.07. 2009 15:10

Others will fill in the missing details, but there is an issue of two or three different styles of nuts sitting on landings of various machined depths.

Richard L.

Title: Re: Big end nuts
Post by: chaterlea25 on 15.07. 2009 15:37

Hi Muskrat,
I wonder if the rods hitting the casings has anything to do with your offset gudgeon pin pistons?
the off set will alter the angle of the rod, maybe making the nuts stick out farther than before????
Just a thought!!
Regards
John O R

Title: Re: Big end nuts
Post by: bsa-bill on 15.07. 2009 17:22

long nuts need the botom corners ground off so far up

All the best - Bill

Title: Re: Big end nuts
Post by: muskrat on 15.07. 2009 22:16

Thanks fella's. Richard, would the correct nuts be listed in the parts cat for lge journal rods? John, would you agree that with the offset they would hit one way and not the other? Bill, Would Bastard Stopped Again ground the nuts for clearance at the factory ? Bill, are you "THE" BSA BILL from WA ?
Cheers

Title: Re: Big end nuts
Post by: beezalex on 15.07. 2009 22:40

I would feel safer clearancing the cases or barrels (whichever it's hitting) as opposed to altering the rods or bolts.  And yes, I'd give myself at least 1 mm of clearance to allow for flex.  Clay works well for showing clearances.  Good luck.

Title: Re: Big end nuts
Post by: chaterlea25 on 16.07. 2009 00:09

Hi Muskrat,
You are probably right, about them hitting one way and not the other!!
Another question, are you now fitting a large journal crank and rods to a small journal cases?
I have seen some cases with relief's ground into the casing, always thought it had happened when a bigend was failing?????
I am not in favour of taking any metal off the bigend nuts
Regards
John O R

Title: Re: Big end nuts
Post by: muskrat on 16.07. 2009 09:31

No john the cases are DA10 17*** and grinding the nuts would be the last resort. I will split cases againto check clearance. I would be happy with 1/16".
Cheers,
          Jim

Title: Re: Big end nuts
Post by: bsa-bill on 16.07. 2009 12:01

Bill, are you "THE" BSA BILL from WA ?

Sorry I'm in UK

All the best - Bill

Title: Re: Big end nuts
Post by: muskrat on 16.07. 2009 12:42

This is the BeezaBill I was thinking of. http://www.geocities.com/beezabill/ check out his workings. must be the long distances down here, gotta get there quicker, whatever you ride.
Cheers