Bottom end rebuild. What's involved?

[Adam76]

1995 softail. Has 90,000kms (65,000 miles?)

Do I need to address the bottom end while I'm doing the top end rebuild with 10-1 pistons?
Nothing wrong with the motor,  just looking for advice with doing a performance build.

Thanks.

[xlfan]

At 65k miles, the engine must have been driven at idle for the necessity of doing the bottom end. I only used to tighten up the top end with .005" pistons with that short mileage.

[xlfan]

No need to bore the cases unless you want go big bore cylinders.

[Adam76]

At 65k miles, the engine must have been driven at idle for the necessity of doing the bottom end. I only used to tighten up the top end with .005" pistons with that short mileage.

OK thanks. So no need to touch the bottom end assuming it has been ridden properly and well maintained.

[turboprop]

At 65k miles, the engine must have been driven at idle for the necessity of doing the bottom end. I only used to tighten up the top end with .005" pistons with that short mileage.

OK thanks. So no need to touch the bottom end assuming it has been ridden properly and well maintained.

Maybe, maybe not.

Couple of variables:

What is the runout of the crank shaft? Just like TC cranks, the evo bolt together cranks can and do shift. The runout needs to be measured.

Engine balance? This is a bit more complex as some evo engines from the factory had almost perfect balance while others shook very badly. The old slot vs hole, production tolerance stack. The second part of this is the weight delta between the old and new piston assemblies.

If the engine in question was one that ran smooth and the delta is negligible and the runout is within specs then yea, nothing required. But all of this and the crankshaft endplay should be checked.

[Adam76]

At 65k miles, the engine must have been driven at idle for the necessity of doing the bottom end. I only used to tighten up the top end with .005" pistons with that short mileage.

OK thanks. So no need to touch the bottom end assuming it has been ridden properly and well maintained.

Maybe, maybe not.

Couple of variables:

What is the runout of the crank shaft? Just like TC cranks, the evo bolt together cranks can and do shift. The runout needs to be measured.

Engine balance? This is a bit more complex as some evo engines from the factory had almost perfect balance while others shook very badly. The old slot vs hole, production tolerance stack. The second part of this is the weight delta between the old and new piston assemblies.

If the engine in question was one that ran smooth and the delta is negligible and the runout is within specs then yea, nothing required. But all of this and the crankshaft endplay should be checked.

Thanks turboprop, yes crankshaft runout is the first thing I'll be checking.
It runs pretty smoothly, but what do you suggest I do when it comes to pistons? I was going to go with a set of Wiseco tracker 10-1 pistons, but won't be sure of any weight differences?
Thanks

[turboprop]

If the engine seems to have minimal vibration, then it would be safe to assume the balance is within an acceptable range and exchanging piston assemblies of the same weight would be an acceptable course of action. I would clean the old pistons as thoroughly as possible, like in an ultrasonic tank and then weigh them. Hopefully the assembly weights are very close if not the same. If the delta is more than say five grams or so, they could be lightened from the underside. This might all be for nothing.

[jsachs1]

Another thing to test/check. Position each connecting rod, near the top of the stroke, and see if they stick/stay in that position. Obviously remove the pistons first.
John

[Adam76]

Another thing to test/check. Position each connecting rod, near the top of the stroke, and see if they stick/stay in that position. Obviously remove the pistons first.
John

Thanks I'll definitely check that.
Cheers

[Adam76]

If the engine seems to have minimal vibration, then it would be safe to assume the balance is within an acceptable range and exchanging piston assemblies of the same weight would be an acceptable course of action. I would clean the old pistons as thoroughly as possible, like in an ultrasonic tank and then weigh them. Hopefully the assembly weights are very close if not the same. If the delta is more than say five grams or so, they could be lightened from the underside. This might all be for nothing.

Hey turbo, beside the crank what else should I be looking at checking or replacing on a high mileage evo?
Thanks

[turboprop]

The answer depends on what you plan to do. Is it your intention to leave the case in the chassis and simply redo the top end, or do you plan to pull the engine out of the chassis?

If the plan is to pull the case from the chassis, why not split the cases and check everything as if it were a new build? This is the type of stuff that keeps people up at night, 'Did I miss something, should I have done X?'.

If the case is staying in the chassis, I would check runout on both ends of the crank shaft, pinion end play, clearance between the pinion shaft and the bushing in the cover, same with the cam and the corresponding bushing in the cover. High mileage Evo engines have had plenty of time for hacks  to make 'Improvements'. I would be suspect of every threaded hole, not only for thread integrity/strength but also for para pits around them. I have never experienced a casting specific to FXRs that did not have at least two holes that required inserts and did not require lapping to get a flat gasket flange. Those aluminum lifter blocks wear out, try to find a set of oem cast iron blocks. Velva Touch figured it out and charged a fortune. I prefer the iron blocks, honed for the specific oversize lifter that is is going in each hole. Check the lip for the primary case o-ring seal. If there is any doubt, there is not doubt. Have that lip machined out and a steel ring pressed in. Might be a bridge too far, but you have a shop with the tooling to line lap the cases and cam cover do it. This is another one of those things that is hard to check, but I have never seen a used Evo case and cam cover that was perfectly aligned. A skim cut on the case deck might would help guarantee cylinder to case seal. The mounting areas on the underside of the cases is also worth taking a look at. Again, an aluminum case that is prone to vibration, a steel frame, would not be un reasonable to expect a certain amount of fretting down there.

Best of luck with your project.

[Adam76]

The answer depends on what you plan to do. Is it your intention to leave the case in the chassis and simply redo the top end, or do you plan to pull the engine out of the chassis?

If the plan is to pull the case from the chassis, why not split the cases and check everything as if it were a new build? This is the type of stuff that keeps people up at night, 'Did I miss something, should I have done X?'.

If the case is staying in the chassis, I would check runout on both ends of the crank shaft, pinion end play, clearance between the pinion shaft and the bushing in the cover, same with the cam and the corresponding bushing in the cover. High mileage Evo engines have had plenty of time for hacks  to make 'Improvements'. I would be suspect of every threaded hole, not only for thread integrity/strength but also for para pits around them. I have never experienced a casting specific to FXRs that did not have at least two holes that required inserts and did not require lapping to get a flat gasket flange. Those aluminum lifter blocks wear out, try to find a set of oem cast iron blocks. Velva Touch figured it out and charged a fortune. I prefer the iron blocks, honed for the specific oversize lifter that is is going in each hole. Check the lip for the primary case o-ring seal. If there is any doubt, there is not doubt. Have that lip machined out and a steel ring pressed in. Might be a bridge too far, but you have a shop with the tooling to line lap the cases and cam cover do it. This is another one of those things that is hard to check, but I have never seen a used Evo case and cam cover that was perfectly aligned. A skim cut on the case deck might would help guarantee cylinder to case seal. The mounting areas on the underside of the cases is also worth taking a look at. Again, an aluminum case that is prone to vibration, a steel frame, would not be un reasonable to expect a certain amount of fretting down there.

Best of luck with your project.

Thanks, that's a lot of great info. I don't have a machine shop in my city that does that kind of work, so hopefully when I check everything I don't find anything too out of shape.

I'm still debating whether to pull the motor out of the frame and split the cases or to leave it in the frame and just do the top end....
Cheers

[Adam76]

Best of luck with your project.

Thanks prop, I've got 2 projects going on at the same time. Something to keep me busy...

I have a question about head gaskets and bore size. When you use a piston that is say +.030 oversize - how do you get a head gasket with the same size? All I can find is STD bore size Cometic MLS gaskets.

Is it OK to use a std gasket that is smaller than the bore size? Doesn't seem right to me?

Thanks for any advice.

[turboprop]

Best of luck with your project.

Thanks prop, I've got 2 projects going on at the same time. Something to keep me busy...

I have a question about head gaskets and bore size. When you use a piston that is say +.030 oversize - how do you get a head gasket with the same size? All I can find is STD bore size Cometic MLS gaskets.

Is it OK to use a std gasket that is smaller than the bore size? Doesn't seem right to me?

Thanks for any advice.

You don't and it is not an issue.

Fun experiment. Measure the ID of every head gasket you can find. Then ask yourself if the cylinder were bored 30, even 60 thou over, would this gadget protrude into the cylinder?

Bottom line. 10k things to think about, but this isn't one of them.

[Adam76]

Best of luck with your project.

Thanks prop, I've got 2 projects going on at the same time. Something to keep me busy...

I have a question about head gaskets and bore size. When you use a piston that is say +.030 oversize - how do you get a head gasket with the same size? All I can find is STD bore size Cometic MLS gaskets.

Is it OK to use a std gasket that is smaller than the bore size? Doesn't seem right to me?

Thanks for any advice.

You don't and it is not an issue.

Fun experiment. Measure the ID of every head gasket you can find. Then ask yourself if the cylinder were bored 30, even 60 thou over, would this gadget protrude into the cylinder?

Bottom line. 10k things to think about, but this isn't one of them.

Thanks for clearing that up for me.    Like you said, at least that's one less thing to have to worry about.   

[bobrk1]

I had 135k on my evo I sold the motor running great I got a big inch motor, the shop I go to told me he had a guy come in with a dresser had 100k on it said to rebuild it cause he liked the bike. Took it apart and miked up the crank pin and the roller bearings , he said they were great put it together and tried it up, all the bike needed was a valve job and to be honed and new piston rings, granted you usually don't beat a dresser but I rode my bike hard at times and never had any complaints. Evo bottom ends were the best the factory ever made, the new 8 valves not so much.