New project Introduction and questions

"Mic check, test, test, check..."

(you had to be there. I was roadie for our high school band)

I found the main bearings came out of the cases with no interfierence fit, but the new Andover bearings were a little bit bigger and interfierence fit is restored. The old bearings od are 3 or4 thousands smaller.

Ok. Redo. Learned quite a bit in the process. First, I calibrated my mic. It was a little off. Second, I was holding it too tight against the journal. Watched a ton of videos.

I have one journal at 1.749(44.433mm) and the other at 1.748(44.420mm).

Given that info, can I use standard bearings or do I need undersize bearings? If undersized then must the journals be reground?

My crank journals are similar to yours so I polished them up and will fit the connecting rods and see how they move when doing a drop test. Thats when you let them fall under here own weight and see if they are smooth and not to loose or tight. I bought standard. I am also no expert.

Plastigauge. It looks a bit goofy but it really works to measure bearing clearance. Mic'ing takes a lot of experience to develop the right touch to be accurate.

htown16 said:

Plastigauge. It looks a bit goofy but it really works to measure bearing clearance. Mic'ing takes a lot of experience to develop the right touch to be accurate.

Genuine Plastigauge - How It Works

Plastigauge how it works for measuring the clearance of a wide variety of bearings and cylinder heads.

www.plastigaugeusa.com

Click to expand...

ok thanks.

That was going to be my next question: Plastigauge.

The used bearings I pulled out are standard and they are worn, I'm sure. How can I accurately verify using Plastigauge without new bearings on hand? Its not like I can purchase them, verify, and then return if they're not right.

You are correct you would have to buy the bearings to check with plastigage. With the second set of numbers you are now just slightly out of low side spec of 1.7500 by 1 and 2 thou. You might be able to get by with this with standard shells as long as the crank is not scored. Also are you checking in multiple position to determine if the wear is oval. You must regrind the crank to use oversize shells. Recommended clearance on the bearing to journal is 1 thou. Do you have a workshop manual? Commando cranks must be ground with a radius (see manual). Most automotive machine shops are reluctant to do this because it is not common practice now and they have to specially dress the stones to do. My recommendation would be to take it to an automotive machine shop and have them measure it and inspect it. You can show them the grinding proceedure but you may have to send it to a Brit bike shop to have the actual work done.

Yes, I checked it from multiple positions as well as the middle and ends for any taper. I was just curious how people use the plastigauge without new bearings on hand. It wouldn’t make sense to do it with used bearings.

After reading some more it makes more sense to me now. That’s what the regrind specs are for. Thanks!

There’s an engine shop near my work. I’m going to stop by and see if they can verify my measurements for me. I don’t think it’ll need any work, but i do have the workshop manual handy for the radius specs

Ok. Dropped by an engine shop. He measured 1.7499 on one journal and 1.7487 on the other. I took my used bearings with me. He used plastigauge and torqued to 25 ft-lbs and they showed .001 and .0015 on the strip. Crank was good. No scoring, no oval, and good polish. Advice was given to run a new set of standard bearings, new con rod bolts and nuts, and it will be fine.

Now that I understand how this works, and re-reading everyones comments, my question of undersized bearings answered itself.

On to the cylinder heads now.

rv1890 said:

Now that I understand how this works, and re-reading everyones comments, my question of undersized bearings answered itself.

Click to expand...

"Live, and Learn"

I was cleaning out my oil pump since the case had some sludge and I wanted to make sure none had gotten trapped inside. While doing so I noticed these two shims, but didn't see where they came from. I don't think they were inside, but I could be wrong. Maybe behind the seal? I looked up some videos and checked the workshop manual, but cant find anything. Any thoughts?

Shims

Yes they should go behind the seal if required which I assume they are in order to give the correct seal compression.