June 18, 2019, 08:03:41 PM
HDBitchin, a Harley Davidson Forum
Cookie Settings

Author Topic: Twin Cam88  (Read 371 times)

0 Members and 1 Guest are viewing this topic.

October 10, 2018, 11:52:28 AM
Read 371 times


I am wanting to build a Twin Cam motor. I have most of the internals ( acquired from a wrecked bike with busted cases ). I found a set of cases and purchased them. After running the numbers I learned the cases are from a B motor. All my parts are from an A motor. Can I combine the two? Is that opening a can of worms? Any help would be appreciated. Thank you.

October 10, 2018, 12:25:50 PM
Reply #1


Welcome to the forum!

Without looking a bit deeper at the mechanical differences I can't give an opinion on the "can of worms". I will look into it but as of right now I am not sure what you might have as issues.

Take a look at this thread. It gives a good look inside the B Motor's counterbalance operation. The video maker does a great job of showing the B Motor's guts and showing oil delivery passages that the Balancers would use.

Twin Cam B Motor Counter Balancers

October 10, 2018, 04:20:42 PM
Reply #2


Thanks I watched that video earlier. It was very informative on how it operates but it doesn’t compare the two types together. I’m thinking that running it as an A motor is theoretically possible but without another case to compare it to I’m concerned that I may have to shim or space the erea where the balancer shafts once were located. The exploded diagrams in the books aren’t very clear. At least to me. Oh well worst case scenario I can build a B motor when I get all new parts or trade my cases for a set of A cases. I got a good deal on all parts involved so I’m good either way. You can never have too many Harley parts. Right? Thanks again.

October 10, 2018, 05:02:20 PM
Reply #3



I am working from an iPad at the moment but what I was going to do was use this below link on a real computer later when I had the opportunity to do some detailed views of the two versions of the motors.


The above link has detailed parts manuals in microfiche format on Ronnie's Harley Davidson. This a great tool for seeing exploded part views for most years and models of Harley.

Obviously you can search a Touring model for the exploded view of an A motor and a Softail model for the B motor view exploded.

October 10, 2018, 05:29:54 PM
Reply #4


The parts finder link is awesome thanks. Unfortunately all I have is a smartphone, no computer, so I could only zoom in so far before it became so blurry I couldn’t see anything. I have a couple of factory parts catalogs on order, one for Softail models and the other for Dyna models. That should give a picture of each motor. Maybe I could lay em out side by side. I didn’t think I needed a computer anymore until I went to that link. That would be easier and cheaper than paper catalogs. Thanks for all your help.
Like Like x 1 View List

October 10, 2018, 06:38:25 PM
Reply #5


I use that parts finder link a bunch!! It is a good link to bookmark. 

October 10, 2018, 07:01:43 PM
Reply #6


Supporting Member
Also need to consider how each engine mounts to the frame.  The "A" motors are rubber mounted and the "B" bold directly to the frame.  You'd need to be sure whatever frame you have/will get is compatible with the engine.

Someone needs to chime in on the transmission mounting.  I know the cases vary between the model lines but don't know what mount differences there are or if they are interchangeable.  Also, the Dyna and Softail lines have one length primary and the tourers have a shorter one.  Might be an issue?

Good luck.
Never attribute to conspiracy that which is adequately explained by incompetence.

October 11, 2018, 11:15:17 PM
Reply #7


Global Moderator
@Tbone61  what year are you trying to build the motor for? that would be helpful on checking parts catalogs.
HD Motor parts catalog list the same Screamin Eagle Hydraulic cam chain tensioner and high flow oil pump up grade kit for 99-05 Dyna 00-06 softail, 99-06 touring.
so it looks like some parts are interchangeable.

I cant find a measurement for the mounts but my understanding is the reason Harley made the B motor for the softail was they did not want to change the frame line and look of the softail, and they would have had to change the frame to accommodate the extra room for the rubber motor mount and the area for motor shake on the mounts. And they thought the vibration was to harsh without some type of vibration cancellation. here is a article from cycle world that mentions this in the 200 88 B section, I have read it in a few articles. 

October 12, 2018, 03:12:05 AM
Reply #8


According to the VIN # the cases cam off of a 2004 Softail. I just picked them up a few weeks ago.  The Flywheels, rods, pistons, jugs, heads, and rockers I bought at a swap meet about 7 or 8 years ago and honestly I don’t remember what year or model the guy said they came off. Im sure it wasn’t a Softail though because I remember asking the guy if the parts would fit my bike.  I bought them thinking I might be able to use them as spare parts for my 2005 Softail Deuce. They’ve been laying around my shop ever since. I guess I could look for part numbers and cross reference them using the part lookup link to see which years they fit. I’m not sure if it would tell me weather or not they were for A or B motors.

November 01, 2018, 08:04:02 AM
Reply #9


Global Moderator
You will need to build as a B motor with the counter balance shaft. You will have oiling issues if not built as a B motor
Like Like x 2 View List


The Harley-Davidson names and logos are Trademarks owned by Harley-Davidson, Inc. This site is not affiliated with Harley-Davidson.
All trademarks are the property of their respective owners and may be registered marks in some countries. There is no affiliation or endorsement claim, express or implied, made by their use.
All artwork in the HDBitchin logos including "Popeye" our Harley riding and forum surfing mascot is artwork that is © of HDBitchin
© HDBitchin, a HD Forum 2013 - 2019 All rights reserved.