Engine case codes. What do they refer to exactly....

[LVBUSA]

Please help me understand the logic behind the case code and how that affects bearing selection and general rebuilding.

I have an 05' that took a dive at freeway speeds. Cracked off stator cover and side of engine.  Need to replace case halves. I've built a lot of motors in 35 years, but can't seem to come to terms with my Suzuki shop manual in this area. 

If case is ex. AAAAA, or BBBBB. What exactly does this represent in regard to the OD of the crank main bearings ?.

I'm missing the big picture and just want a good knowledge of what the factory was doing and how this affects the rebuild.

Also, the codes on the crank counterweight only apply to the journals on the crank, i.e. Rod and mains ?. Yes ?.

Apologies for the basic inquiry, just been racking my brain trying to make sense of this. 

Thanks for the read, any help appreciated.

A.


Ran search but couldn't come up with specific answer. Please direct me if this has already been explained.

[sportbikeryder]

The letter on the cases corresponds to a main bore diameter, each letter matching the location of the bore (left most is the first letter). The crank is the same way. There is a chart in the service manual showing case bore codes on one axis and journal codes on another. Cross the case bore with the journal diameter to get the bearing size. Bearing thickness is represented by colors (a paint mark on the side of the bearing shell)  Rods are the same way, just that the bore is marked on each rod.

[05calibusa]

Providing that your crank is within the specifications listed in section 3-78 of the service manual, you will use the crank and case codes to make your initial bearing selection.  In the example that you gave, the case code is AAAAA and the crank is BBBBB, you go to the table in the manual and you find that case A and crank B is a "black" bearing set.  Your example is easy because they are all black bearings (A-B).  In my case, the case code was AABBA and the crank was BAAAB, so starting from left to right you have AB=BLK, AA=GRN, BA=BLK, BA=BLK, AB=BLK.  Once you have installed the bearings in the proper locations, make sure you check the clearance with plastigauge.  To answer your other question, the codes only apply to the mains.  There is another table in section 3-80 for your thrust bearing selection.

That should get you there.  I know that there are some other threads that talk about where to run the clearance on the mains for better oiling, so if you find that your clearance is on the high or low side (or outside) of the spec, you can select the correct bearing to give the proper clearance.

[LVBUSA]

Really excellent responses.  That helps a lot.  Why did the factory settle on cutting each bearing cradle differently ?.  I've been trying to figure that part of it out the most.  Was it just a fact of machining that some were slightly larger, or smaller than the others ?.

A.

[05calibusa]

Really excellent responses.  That helps a lot.  Why did the factory settle on cutting each bearing cradle differently ?.  I've been trying to figure that part of it out the most.  Was it just a fact of machining that some were slightly larger, or smaller than the others ?.

A.

That part would be a mystery to me too.  One would think that you could get them all to match, but I guess nothing is perfect.

[sportbikeryder]

The tolerances are much tighter than conventional automotive engines. Most auto engines don;t have a variety of bearings to choose from with extremely tight thickness variation like the suzuki motorcycles. The difference in teh bearings is literally a few ten thousandths of an inch.

On a stock application, I doubt you would really notice any difference in life of the bearings if the middle of the range was just thrown in everything. 

I measure mine with bore gauges and micrometers. The stamped identifiers aren't necessarily very accurate. Many people will say the "only" way to assemble an engine is to measure everything. I am not necessarily a believer that that is required for everything.

[LVBUSA]

Gents,

               Just wanted to take a moment, Sportbikeryder and Calibusa, and thank you for your insights....I'm still left wondering about the tolerance difference, but I imagine in time it'll be just the way I view things with this build and all future one's with this design of bottom end. 

Your experience, and knowledge is greatly appreciated.  I've always been a "why" guy and when I bumped into this in the manual it just didn't make sense, i.e. different cuts, different locations.  As far as the bearing, and notation of the case half I will just follow the charts and make the best of the plastigauge and get things where the manual says they need to be.  This is my daily commuter, and yet when I look at the stock configuration on a build like this, it tells me a lot about what the original engineers were thinking.... 

Much, much thanks for your time and help !....

A.

[knecum]

Really excellent responses.  That helps a lot.  Why did the factory settle on cutting each bearing cradle differently ?.  I've been trying to figure that part of it out the most.  Was it just a fact of machining that some were slightly larger, or smaller than the others ?.

A.
[/quoate]      they didn't,  tooling bits wear out. So when they tool the machine up on Monday the first 25 case halves fall into the AAAAA  group. Then the next group may be Bs. Then the crank has its tolerances too.

[LVBUSA]

Wear and tear on the cutting tools. There ya go. Rather than make costly bit replacements constantly, they factor how many cuts they can make before the bits fall outside of usable spec.  Do production runs in phases, make bearing accommodations, then stamp the case and compensate with a bearing range. Now, I kind of figured there was a machining aspect I was missing in the bigger picture. Was driving me a bit nuts to say the least.  Just couldn't figure the process they were using to cut the halves is all. Excellent insight. Thank you for taking time to help me with understanding.

Do I have the right basic idea here ? Thanks again for the help. A.