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1988 sportster Bad Crankshaft ... what now? HELP!

I'm assuming the diagnosis is bad lower rod bearing. If so, how does a mechanic know this for sure? Are you confident in your mechanics diagnosis?
You mentioned an upgrade to 1200, did someone do this work and then just not put it together? Could it be a sloppy top end job and the ticking is the piston skirt?
In either case something needs to be done before failure.

Before I bought any parts I would do a compression & leakdown test to get an idea where the top end is. And maybe before taking motor out of bike disassemble top end and measure jugs & pistons. At that point you can spin, push n pull on the rods to try to get a feel on the lower rod bearing.

Well....I would take all apart and figure what's needed and cost. You can see if its worth it at that point.

Best advice so far. You really do need to know what needs repairing/replacing before you roll up your sleeves and dig in.:coffee This could be one of those projects that you start and wish you had not, so do the homework first.:s
 
I'm assuming the diagnosis is bad lower rod bearing. If so, how does a mechanic know this for sure? Are you confident in your mechanics diagnosis?

You mentioned an upgrade to 1200, did someone do this work and then just not put it together? Could it be a sloppy top end job and the ticking is the piston skirt?

In either case something needs to be done before failure.



Before I bought any parts I would do a compression & leakdown test to get an idea where the top end is. And maybe before taking motor out of bike disassemble top end and measure jugs & pistons. At that point you can spin, push n pull on the rods to try to get a feel on the lower rod bearing.



Well....I would take all apart and figure what's needed and cost. You can see if its worth it at that point.



Best advice so far. You really do need to know what needs repairing/replacing before you roll up your sleeves and dig in.:coffee This could be one of those projects that you start and wish you had not, so do the homework first.:s


Thank you gentlemen,

Ok, I'll try to answer.
Diagnosis is worn-out/ bad crank shaft.
I took the bike to the mechanic with the loud ticking noise (like a loud sewing machine type)
I bought the bike as a basket case where 60% of the bike were brand new parts.
The engine was all together with a 1200 upgrade done.
A 3" stack of receipts for all parts and engine work totaling $7K
The guy had gone gaga chroming or buying new chrome everything (nuts, bolts, front end etc etc he really had lots of money into it.
I put the bike together and just mounted the engine the way it was.
Since the first time that I started the sound was there.
I checked everything I could think of and everything I was told by the good ppl here in the forum.... But sound never disappeared.
That's how I got to the mechanic.

When I took it in he listened to it and rode it around the block a couple of time..
He said that it sounded like the 12 upgrade was done in old cases,cylinders etc and it sounded like an incredibly loud valve train.
We agreed that he would double check things...check valve adjustment and push rods adjustments to see if it would get any better.

He called two days later and told me that he had taken the front cylinder off and that after inspection his diagnosis was * a Bad crank shaft.

The shop has an incredible reputation for being honest and straight ppl... And I didn't feel like he was lying or anything like that.

I picked up the bike and reviewing what he told me what I can see is that if I move the piston rod up and down it seems pretty tight just the way it should be but when moved to the sides it has about 1/2" of movement and he explained that that was the big problem.

How does that sound so far?
Sorry about the long post
 
..........
He called two days later and told me that he had taken the front cylinder off and that after inspection his diagnosis was * a Bad crank shaft.

The shop has an incredible reputation for being honest and straight ppl... And I didn't feel like he was lying or anything like that.

I picked up the bike and reviewing what he told me what I can see is that if I move the piston rod up and down it seems pretty tight just the way it should be but when moved to the sides it has about 1/2" of movement and he explained that that was the big problem.

Sorry about the long post

That cuts it...you have bottom end issues! I'm set back that some one would do a top end and not inspect the bottom while it's apart :wall

I agree with all, study, then do the work yourself. You said it's a second bike and your not in a hurry. You also installed the motor/trans yourself....the second time is twice as fast :D

Don't worry about the long post.
Keep us posted on this project (pictures to please).
 
Time to get the books out and start to read an familiarise yourself with what is ahead when tackling something like this I read up in stages do the first bit of the strip then back to the books and read up on the next part

Brian
 
From what I have found side play is a normal movement at crank shaft to connecting rod after crankpins are properly tightened.
S&S recommended rod side play is .015" to .035"
 
From what I have found side play is a normal movement at crank shaft to connecting rod after crankpins are properly tightened.
S&S recommended rod side play is .015" to .035"

By watching the video it does look a wee bit more than .035" however a quick test may be to try a .035" feeler gauge in the gap and see if there is still some movement
I would think that any side play would be to allow for heat expansion and closer to .015" is what would be best

Brian

Update on this post as I got round to opening the relevant book but this is for post 1990 sportsters I do not have info for the 1988 but it may be similar
connecting rod side play at the crankshaft 0.005 to 0.025 service limit 0.030 so best check with a 0.025 feeler gauge between flywheel and connecting rod

Brian
 
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Brian

Update on this post as I got round to opening the relevant book but this is for post 1990 sportsters I do not have info for the 1988 but it may be similar
connecting rod side play at the crankshaft 0.005 to 0.025 service limit 0.030 so best check with a 0.025 feeler gauge between flywheel and connecting rod

I checked my book(Clymer) for rod specks on "Late 86 and on" and it states same as Brian stated.
I watched your video and noticed you still had the other cylinder on. I usually remove both cylinders. While holding the piston end of the rods I rotate the flywheels a small amount, stop an check for any up/down movement I will do this in several locations, sometimes 2-3 times. If I find any noticeable movement then the crank bearings a shot. I would be more concerned about up/down than side to side. Did they also check your piston to cylinder clearance? Keep us posted.
tourbox
 
Guys, that's not "side play" we are seeing. Side play would mean the rod moves side to side; the center line of the rod moves side to side but stay perpendicular to the centerline of the crank. That rod does move side to side but the centerline of the rod does not say perpendicular to the crank. The mechanic's diagnosis is correct; bad rod bearing.:bigsmiley21:

The question for the OP is how to proceed now. If he has the tools and the skills, pull the motor/trans, split the cases and send the wheel set (crank/rods) out to Silvermoon, Darkhorse, Rev Performance for repair.:coffee
 
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