Hello all,

As a point of introduction i am a 33 year old who has never riden a motorcycle (been on the back of f.i.l.'s springer and my deceased father raced a triumph in the early 70's on dirt tracks). My wife's father asked if i'd be interested in rebuilding an '81 Sportster that is literally a basket case. I said absolutely!

So, i've got parts all over the damn place and no doubt will become a frequent poster.

My opening question is this: i have the jugs off (bead blasted and painted, heads cleaned up at machine shop) and noticed both rods have some play. I assume this is really bad news but what's the best way to deal with it? Should i buy a new rod assembly (apparently the rods are not like vehicle engine rods with bolts?) and is splitting the case a big deal?

I was thinking of taking the case to the machine shop to have them clean it out but is that pricey? Can i (a mechanical infant) do it myself?

Thanks guys!

Erik

welcome to the forum.
pick up a service manual as it would be a lot of help.

I second the vote for a manual. You NEED it. The rods are not like a car with rod bolts, caps and plain bearings.

With the exception of machine shop work, the bottom end is about as difficult a job as you can tackle on your Sportster. It is not a job for a newbie. There are a lot of special tools required (lots of critical measurements) and special procedures.

Get a manual. Read it. Then read it again. Then decide if you are ready to tackle the job. Only you can determine that.

--Chris

Bottom end is the tough part on the HD engine.

If the rods need work / checked, the flywheels will need to be split, but then they'll need to be reassembled & realinged. You'll want an experienced pro to do this right- and while you're at it, you might as well get everything dynamically balanced- smooth out the shakes a bit. Once you get a pro to put the bottom together, you can do the jugs/pistons/top- its not that tough. I did an evo this winter.

thanks guys. i removed the pistons last night and found that the movement is actually side to side and there is no play when pulling up on the rods.

Hi there,

same is with my bike - It's a 85 Ironhead and the rod from the front cylinder is moving from left to right, at the end of the rod it's about 3 to 4 mm.

I myself decided to split the crankcase - for me it's also the first time I do such a job. Everything untill now went quite good. Like the others said, I read a manual about 10 times or even more.

Thanks to all the guys in this forum - I really appreciate the help you can get here.

J.Le

There are two types of side to side play. If you can move the small end of the rod side to side (left to right on bike) that is OK within reason. There's no spec for it, but it happens due to play in the bearing. The front rod will have more side to side play than the rear since it is supported by less bearing surface.

There is also clearance from side to side. You slide both rods from left to right, and see how much they move in between the flywheels. There IS a spec for that that varies between years, but it has to have some, and up to about .025" or .030" is OK. You can check between the side of the rear rod and the flywheel with a feeler gauge.

You need to yank up and down on the rods with the bottom end rotated into at least 4 places (rotate the flywheels to check the rods with the crankpin at 12:00, 3:00, 6:00 and 9:00.) You might feel up and down play in one position and not the other due to wear on one side of the crank pin. You should not be able to feel any up/down play - the spec is around .0015" (one and a half thousandths.) If you can feel it, it might be excessive.

--Chris

PLEASE get a manual....(in this case, preferably the Moco manual, but two is better!)

Sounds like you'll have your hands full

Keep us updated....Have fun!

thanks guys! I have the service manual and did some more reading last night and saw mention of .025 clearance on the rod/flywheel. this project had been tabled for about 2 years and i completely forgot how useful the manual was.:o haven't stuck a feeler gauge in there yet but i'm gonna guess it's significantly more than .025. Seems like this should be ok though as the cylinder would keep the rods aligned correctly.

jle what items are you farming out when you put the case/flywheel back together? i have none of the specialty tools and want to be as efficient (both time and money) in this as possible.

cantolina i have a 2 year old so nothing intimidates me any more.

chris thanks for the tip on the 4 positions! i will check this out when i get home today:doh