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Allan G, gavin eisler, kommando, lemans, NickL
Total Likes: 13
Original Post (Thread Starter)
by JJC
Does anyone out there have experience of A65 crankshaft end float on an engine with the timing side roller/ball conversion? The NKIB roller/ball bearing is supposed to hold the crankshaft in place such that end float is limited to the ball race clearance and so shimming is not neccessay. I have such an engine that has done around 30k miles since the modification and whilst changing the triplex primary drive chain recently, I noticed very exessive end float. I also saw the excessive movement when checking the iginition timing with a strobe pointed at the rotor. The still image produced by the strobe can be seen moving in and out as the engine rpm is changed. Having had a look behind the timing side covers, the balls of the NKIB bearing look like they are brand new. Nothing obviously wrong and I took the opportunity to re-torque the worm drive nut and lock nut. Any ideas what is going on?
Liked Replies
by Mark Parker
Mark Parker
Is the outer moving? Why I use a plain heavy series needle roller with no side load and a bearing in a plate bolted outside the alternator. Watch the T/side and move the crank. The outer should be held by the balls to the inner. Something has to be moving. It may move more when hot, but try pushing it, then levering it back.

There is only so much crush you can fit the bearing with. Checkout what is going on and what moves.
2 members like this
by JER.Hill

I'd suggest that it is actually the outer race which is moving in the casing. If the Brg is assemble correctly, then the oil pump screw holds it all together on the crankshaft, therefore the outer race has to move in the casing to allow any end float. If this has been happening it should show up on the oil pump and drive gear scroll not meshing correctly.
As Nick said adding a spacer will prevent this. I have used these types of Brg's in a number of engines and never had them walk about.

My tuppence worth

2 members like this
by DMadigan
I erred, you would have to open the cases and change the drive side bearing to use the thrust collar type bearing.
The thrust collar goes on the drive side bearing. You have the NF type which has the rollers contained in the inner race and the outer race has a single lip to keep the rollers off the case bore.
The NUP as a separate inner race lip that captures the rollers on both sides, taking care of the crank float.
Another arrangement is the NH type which has a separate thrust collar. This would require the distance piece between the bearing and sprocket be narrowed to accommodate it.
[Linked Image from]
Needle bearings do not like angular misalignment. The flexing of the crank makes the shaft rotate in roughly a cone shape so the rollers next to the crank web are loaded and the rollers 180 degrees around are loaded near the pump end. This causes the outer race to walk. Without something to retain the race in the case to will likely move. The triple's drive and timing side rollers are retained by retaining rings in the cases. They do not have nearly the angular misalignment of the twin with only two bearings holding the crank.
2 members like this
by NickL
When using the nk1b type bearing it's still not a bad idea to put a spacer
on the crank at the drive side to prevent the outer of the t/s bearing moving
in the case. Having used NK1A, NK1B, RNA, and NK1X types over the years
i still like to set the crank up so it's unable to move more than a few thou from
side-side. Relying on a needle race fit is not ideal IMHO.

1 member likes this
by JER.Hill

While you have not posted a photo of the set-up, I assume you have a lip on the casing which prevents the Brg moving out board? Just asking as I have seen one engine where there was no retaining lip on the casing.
I would heat up the casing and remove the outer race, add some loctite as you say and replace the outer race. Rebuild the crank into the cases and use the Brg as intended with the ball bro's. Then as Nick said in an earlier post, space the crank out using a spacer/shims as necessary. This should then allow you to use the engine.
It's a pity this site doesn't allow a simpler method of posting a photo, to help members explain what their problem is.

Hope this of help to you.

1 member likes this
by lemans
see this thread

I did two needle rollerconversions,
one, in 1984 and this bottom end lasted to 2012
one, a couple of years ago

in both conversions I used the standard axial crankshaft setup, just like ducati and a lot of other enginebuilders do.
the standard solution with a pressure plate and shims is adequate for normal use. and will stand a lot of abuse

regards Anne
1 member likes this
by DMadigan
You could modify a BSA 68-729 stator mount to go inside a Triumph (! that would be a real mongrel) to stiffen the stator support. There is about 28mm from the stator holes in the Triumph case to the cover joint and 22mm from the joint to the 68-729 stator seat. With the stator in the primary cover there is about 15mm from the back of the stator to the cover joint so the stator mount has to be shortened.
I would make a custom mount, since the outrigger bearing mount should locate on the rim of the stator laminations rather than the through bolts which have clearance.
Aren't we all lunatics for riding these old crates?
1 member likes this
by NickL
Mark, the chain is/was the same pitch etc, just duplex 82 links rather than triplex.
I did have an outrigger on my outfit at one stage but when i machined the case
for the 33 tooth sprocket. i couldn't fit it back on. This is an early set of cases so
there are just 3 stud holes into which we've made up an outrigger setup for the
32t sprocket. We could run a triplex chain on here if we replaced the sprocket
but getting one may be awkward.

I like your technical analysis of the crank but you must remember that stiffening
things up too much makes them break like carrots. Shafts must flex around the
bearing areas if they are just made from EN16 etc. Maybe EN40B nitriding steel
can be totally rigid but that's not the case with this old gear.
1 member likes this
by Mark Parker
Mark Parker
I was reading about Nigel Rollason's A65 outfit. He said they were getting over 90hp. Running a 3 bearing crank and a 3 bearing G/box main shaft. They put a bearing where the alternator would go which also controlled end float, As with my set up except mine is outside the alternator. I'm rebuilding one at the moment, a 90degree 744 that the bottom end has not been apart since about 1998 when it was built. It was running fine with good oil pressure but the alloy rods though looking in good condition are getting old and without a remote filter we were wondering about sludge in the crank.

Before I had a plain spacer between bearing and threads on the crank and the threads under it were a bit worn. So I made this spacer to use a Norton spigot nut under the bearing. So it slides into the bearing so the hex section acts as a washer between it and the alternator rotor. Because a loose washer in there is very hard to assemble. Then the spigot nut threads under it.

[Linked Image from]

Nigel said with these extra bearings primary chains gave no problem at all. As they would stay aligned. As late as 1986 the Hogg brothers on an A65 were taking wins in modern racing, causing headaches for Yamaha TZ700-750 outfits and 900 Z1s.

The outfits really tested drive lines and they showed just how potent A65s could be.

[Linked Image from]
1 member likes this
by DMadigan
Hi Mark,I took a slightly different approach. I made the spacer with a step pocket. The pocket is deep enough so the end of the nut does not bottom on it and the spacer locates on the stud. The bearing is clamped between the hut flange and spacer.
[Linked Image from]
1 member likes this
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