Forum

[Isettaman]

Just putting my 1951 350 bullet crankcase back together. I pulled the crankshaft onto the two sets of roller bearings on the drive side and it looked fine. Mated the two crankcase halves together with the crankshaft rotating freely until the final tightening-up of the studs when the crankshaft became stiff to rotate. From my measurements, the conrod appearsto be in the centre of the crankcase so my problem is to identify what is wrong. It could be that I haven't pulled the crankshaft into the drive side fully but I cannot see a way to check unless I carry on until it locks up the bearings. The thrust washers could be too fat but they are as they came out.
One thing I'm not happy about is the O/D of the timing side thrust washer. Should it be the same as the ball race cage at 1.5" or 1 5/8" to match the bearing outer ring. Currently it is the larger diameter.
What are your thoughts?
What thickness should the thrust washers be?
Thanks
Dave

[Norm]

Who put the crank together? Is it true? What thrust washers have been replaced?

[Isettaman]

The crank went in as it came out. The reason for the re-build was ineffective oil flow/scavange so I split the crankcase to ensure that all oil ways were free running and clear. The original thrust washers have been put back in as they came out.

[mauri]

guessing you are talking about nr 18 and not nr14?







has distance piece nr 5 been put back in his place?

[Isettaman]

Mauri
Yes, it is no. 18. The inner spacer between the two ball races on the drive side is not listed for the '51 bullet, just the spacer for the outer edges. The circlips are not used either (just in case someone leaps in, there is no channel for the circlips to fit in).
Norm
Just had a check of crank - which I should have done before as a basic check - and it does appear that the two havles of the crank are out of line. I will have to take it to my mate's workshop with his accurate measuring gear etc and sort it.
I would still like to know the required thickness of the thrust washers as I now have absolutely no confidence in the original re-build quality of this engine.
Dave

[Norm]

Dave, if the crank is not true it will bind as you start to tighten the cases up

[Isettaman]

Thanks Norm

I did think the studs were not very tight when I took it apart.
I have spoken to my friend Colin and we'll centre it up on his lathe and measure how true it is
and then hopefully correct it.
I'll reprt back after my trip there on Tuesday.
Dave
PS I have ordered a new set of thrust washers as well.

[Tim NZ]

And if the main bearings are not correctly seated to full depth?


No mention of the bronze bush on the timing side? Was it checked? Has it been replaced?


Are you certain that the felt 'oil seal' on the drive side is not pinched?

[Isettaman]

It is always possible that the drive side bearings may not be fully home but I did use a press so am pretty confident.
The bush has not changed. The cork oil seal sits in it's own chamfered section and so cannot get "pinched up".
My main target is to get the crankshaft correctly aligned and replace the thrust washers with new ones, obviously checking the bearing seatings before re-assembly.

[Charlie]

Hi I'm rebuilding a 51 engine and I agree the washer thickness is critical to minimise end float. I've measured mine as follows, 0.105 od 1.733 & 0.0802 od 1.809. My crank is currently being repaired because the big end pin holes have worn in both flywheels. Once the crank is back I plan to compare it's overall width with the gap between drive side and timing side bearings so I can establish what washer thickness is required. Unfortunately the crank will not be ready for another three weeks so I'll keep you posted.