Tight main bearings

nottsSteve · Post by **nottsSteve** » Sun Feb 12, 2012 1:26 pm

Was hoping for some advice about the main bearings on a 55 single.
I have had to have the drive axle replaced as it was badly worn. Both main bearings were badly worn too so have replaced them with 2 RHP ones.
Am a little concerned at how freely they spin now they are fitted. Lost a bit of their speed after they went into the crank halves (after cooling)and lost a little more speed after the new axle was inserted. Again, i needed to heat bearings and crank halves to allow the new axle to pass through bearings.
There are no tight spots and the flywheels rotate smoothly but the tightness of the bearing wasnt something i was expecting.
Any advice would be much appreciated.
Steve

itma · Post by **itma** » Sun Feb 12, 2012 1:41 pm

you need to read the recent thread on drive side bearings for comp models,a similar situation, turned out to be poor metric to imperial machining in Japan.

This is a recurring problem it would seem.

nottsSteve · Post by **nottsSteve** » Sun Feb 12, 2012 9:57 pm

Thank you Ken, interesting reading.
I note that i cant reverse the procedure for dismantling that i used to assemble ie as its all locked together now I cant freeze bits and heat others in the oven.
Is the best course of action now to apply some local heat around cases and knock out the axle and bearings together (not sure how much force is acceptable here).
And then use a puller to get the bearings off the axle.

itma · Post by **itma** » Mon Feb 13, 2012 10:17 am

yes warm the case, and it'll all fall out.
Do not bump the flywheels or they will go out of line,
The problem is the new bearings I'm afraid.

yet again itma the site misery will go on and on and on about how a good old part is worth 2 new ones.
I''l bet you replaced your bearings just because you could rather than they were worn out?

Merlin · Post by **Merlin** » Mon Feb 13, 2012 10:43 am

Comes under the banner :if it ain't brocken don't fix it:

SPRIDDLER · Post by **SPRIDDLER** » Mon Feb 13, 2012 11:27 am

quote:
Comes under the banner :if it ain't brocken don't fix it:

"Both main bearings were badly worn too so have replaced them..."

Do try and keep up, Merlin, there's a good chap

nottsSteve · Post by **nottsSteve** » Mon Feb 13, 2012 6:13 pm

The big one was badly worn, the smaller one was a maybe. Ill let my section have a look at it, see what they think.
http://i1097.photobucket.com/albums/g35 ... .jpgEdited by - nottsSteve on 13 Feb 2012 6:19:53 PM

nottsSteve · Post by **nottsSteve** » Mon Feb 13, 2012 6:15 pm

The axle maybe had a few more miles in it
Thanks Guys

http://i1097.photobucket.com/albums/g35 ... .jpgEdited by - nottsSteve on 13 Feb 2012 6:20:58 PM

itma · Post by **itma** » Mon Feb 13, 2012 6:48 pm

Thats not worn steve

its totally utterly

F*****D

dave.everitt · Post by **dave.everitt** » Sun Feb 19, 2012 11:22 am

Hi Steve'
I posted the discussion on ,main bearings for a G80cs. I recommend you read that thread, some of the commnets were really helpful.
The problem I found was that the bearings went very tight after assembly into the crankcase. In the cold crankcase I could only just rotate the bearings using fingers. I determined that this was due to binding against the spacing washer between the bearings. My solution was to replce the spacer with a new, smooth one, and to assemble the bearings one at a time. They now rotate more freely and I can rotate the crank by holding the axle. I removed the bearings several times, and tried several new sets, and even modified one set. My thread refers to a problem identified by Matchless and mentioned in one of their service bulletins. I also measured the size of the bearings and the crankcase, and had 0.0035 interference. Not an easy measurement, but if you have the tools it it good to do (I had help). I think that the RHP bearings are very good.
If you want any more from my recent experience please feel to contact me.
Dave