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post #1 of 15 Old Oct 20th, 2006, 5:41 am Thread Starter
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Question Head Job-Tech Question

This winter I will be performing a major overhaul on the LT motor cam sprockets, chain ,sprag clutch etc.
The Question is has anybody rebuilt there head. I have 95K on the odometer and was wondering if relaping the valves to the seats is suggested in conjunction to new seals. Should I also change the valve springs. Suggestions ??

Pete Murray
IBA # 359 and
2014 RT
1973 R75/5
2002 LT 171 K Gone
2008 FJR 36 K Gone
Stroudsburg, PA
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post #2 of 15 Old Oct 20th, 2006, 7:35 am
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Why are you doing this so soon?
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post #3 of 15 Old Oct 20th, 2006, 10:17 am
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One suggestion BEFORE you start tearing it all apart: Compression test. If it's low, I'd follow it with a leakdown test. If the compression test comes up good, then there's no reason to worry about it.
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post #4 of 15 Old Oct 20th, 2006, 10:33 am
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Quote:
Originally Posted by murray
This winter I will be performing a major overhaul on the LT motor cam sprockets, chain ,sprag clutch etc.
The Question is has anybody rebuilt there head. I have 95K on the odometer and was wondering if relaping the valves to the seats is suggested in conjunction to new seals. Should I also change the valve springs. Suggestions ??
I replaced my valve seals (on the bike) at about 90,000 miles trying to overcome oil usage, but that was not the problem. At 100,000 miles I tore down the engine and found detonation damaged piston ring lands. I replaced the pistons, and looked at the valves, but they looked just great, so did not do anything to the head. If you don't have a valve problem, I would not mess with them.

By the way, "lapping" valve seats is an old, old idea, and is rarely if ever done any longer. If you do need to service the valves, have the seats and valves ground properly. Many years ago valve lapping was determined to cause earlier valve/seat failure. The reasoning is that when ground, the seats and valve faces have straight surfaces and as the valve head heats and becomes larger the seating surface just moves down a little on the surface of the valve. If they had been lapped, there will be a slight under cut surface in the valve head where the lapping occured, and when the head heats up and expands, the seating will occur on a small ring of un-lapped valve head surface, and damage starts.

Some valve grinding people will still put very fine lapping compound on the valve and hit it just enough to get an indication of seating surface to be sure the valve surfaces are properly aligned, but not enough to remove metal to any extent.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #5 of 15 Old Oct 20th, 2006, 10:38 am
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Quote:
Originally Posted by TimVipond
Why are you doing this so soon?
I was wondering also. My engine came apart at 100,000, but only because of the detonation damaged pistons. I measured everything and found that there was no reason to replace anything else. The engine went back together with the original crank and rod bearings, as there was no measurable wear. The cylinders had no measurable wear, and most surprising of all, the original ring gaps were just barely at the top of the INSTALL tolerances, not even encroaching on the allowable wear range yet.

Unless something unusual goes wrong, as did on mine, I would imagine the area around 200,000 miles would be very normal for this engine. Don was well over 300,000, and would likely have gone much longer if the bike had not been totaled.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #6 of 15 Old Oct 20th, 2006, 1:20 pm Thread Starter
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Quote:
Originally Posted by TimVipond
Why are you doing this so soon?
Thanks Tim, Dave. The truth be told I have to remove the head to properly drill out a exhaust stud and install a time cert. I thought while in there I would address these issues if necessary. Will be riding in the big one next august and want to reduce the potential with a mechanical DNF.
Will change cam,crank sprockets,cam chain, teflon rails, water pump parts,dreaded sprag clutch,rear main seal , oring, slave cyl, voltage regulator,starter brushes, Transmission bearings,seals, rebuild final drive.
Or If I find a low mileage engine and trans ( < 30 K ) this will save alot of effort and the cost will be about the same.

Pete Murray
IBA # 359 and
2014 RT
1973 R75/5
2002 LT 171 K Gone
2008 FJR 36 K Gone
Stroudsburg, PA
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post #7 of 15 Old Oct 20th, 2006, 2:48 pm
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Quote:
Originally Posted by murray
Thanks Tim, Dave. The truth be told I have to remove the head to properly drill out a exhaust stud and install a time cert. I thought while in there I would address these issues if necessary. Will be riding in the big one next august and want to reduce the potential with a mechanical DNF.
Will change cam,crank sprockets,cam chain, teflon rails, water pump parts,dreaded sprag clutch,rear main seal , oring, slave cyl, voltage regulator,starter brushes, Transmission bearings,seals, rebuild final drive.
Or If I find a low mileage engine and trans ( < 30 K ) this will save alot of effort and the cost will be about the same.
Be warned: I think the sprag clutch is the first part put on the assembly line, they they build everything else up around it.

That was by far the most involved job I ever did on the LT. Putting pistons in was a breeze in comparison, as the engine never came out of the bike. For the sprag clutch, you have to remove the engine/tranny, remove the tranny, clutch assembly, alternator, and then remove the intermediate housing. The sprag clutch is between the crankcase and intermediate housing, right in front of the alternator.

Tip: Be absolutely positive you notice exactly how the sprag cage is positioned so that you get the new one in the right way. Reverse it and you will be pulling everything out again. I got mine in right, but triple checked everything to make sure it was correct before putting everything back together. I sure did not want to do that job again!

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #8 of 15 Old Oct 20th, 2006, 2:49 pm
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Quote:
Originally Posted by murray
Thanks Tim, Dave. The truth be told I have to remove the head to properly drill out a exhaust stud and install a time cert. I thought while in there I would address these issues if necessary. Will be riding in the big one next august and want to reduce the potential with a mechanical DNF.
Will change cam,crank sprockets,cam chain, teflon rails, water pump parts,dreaded sprag clutch,rear main seal , oring, slave cyl, voltage regulator,starter brushes, Transmission bearings,seals, rebuild final drive.
Or If I find a low mileage engine and trans ( < 30 K ) this will save alot of effort and the cost will be about the same.

dang I got one, 130k

oh that was a < not a 1
<grin>

yes your in there rework your seats and valves why not, it
can only help can not hurt, I'd never take a head off with any amount of miles and not do a full valve job, I would reface the valves grind and the seats re lap them and take a good look to make sure they are seated correctly and in the correct position, clean the combustion chabmers ect ect ect, one thing i would do regarless is a leak down before I took anything apart on it







Tom

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post #9 of 15 Old Oct 20th, 2006, 6:02 pm
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Quote:
Originally Posted by tmgs
dang I got one, 130k

oh that was a < not a 1
<grin>

yes your in there rework your seats and valves why not, it
can only help can not hurt, I'd never take a head off with any amount of miles and not do a full valve job, I would reface the valves grind and the seats re lap them and take a good look to make sure they are seated correctly and in the correct position, clean the combustion chabmers ect ect ect, one thing i would do regarless is a leak down before I took anything apart on it

Tom
As I said earlier, "lapping" should only be done with very fine compound, and only just barely enough to see the seating pattern (2-3 oscillations), never to "fit" the valves. If the pattern does not look even all the way around, then the original grinding was at fault and should be rectified.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #10 of 15 Old Oct 20th, 2006, 8:08 pm Thread Starter
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Thanks for the help guys teardown should dictate the extent of repairs

Pete Murray
IBA # 359 and
2014 RT
1973 R75/5
2002 LT 171 K Gone
2008 FJR 36 K Gone
Stroudsburg, PA
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post #11 of 15 Old Oct 21st, 2006, 6:58 am
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Quote:
Originally Posted by dshealey
As I said earlier, "lapping" should only be done with very fine compound, and only just barely enough to see the seating pattern (2-3 oscillations), never to "fit" the valves. If the pattern does not look even all the way around, then the original grinding was at fault and should be rectified.
In case ya don't know, I have been a mechanic all my life, have built some pretty high performance engines as well as a tech for lincon Mercury toyota and worked indy HD shops,

That is all lapping is for to give the final step for a good seat, you do not want to cut the valve in, which if you have done a good 3 angle valve job shold not be aproblem, but some could lap them to death and cause a wider seating surface, which all that does is create more heat which is NOT a good thing

a good fit valve, the tech would have used blueing to start off IMHO, to check depth/width before and during the seat grinding, it leaves no room for error, well ok one can stil screw up it only takes a moment,
Not that I have ever Screwed up in the thousands or more jobs I have done ! ya know - ( ever, really, ok maybe once) , as long as you catch it your ok as long as you don;t do somethign stupid and damage a seat then have to replace a seat. I never ever had a come back, not on any engine.


Tom

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post #12 of 15 Old Oct 21st, 2006, 7:01 am
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Quote:
Originally Posted by murray
Thanks for the help guys teardown should dictate the extent of repairs

yuppers

have fun, if io keep mine i'll have to do it one day (in about another 200-300 k miles hopefully <grin>)

oh darn well if it is before 8/2009 i do have an extended

hehehehe

Tom

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post #13 of 15 Old Oct 21st, 2006, 2:49 pm
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Quote:
Originally Posted by tmgs
In case ya don't know, I have been a mechanic all my life, have built some pretty high performance engines as well as a tech for lincon Mercury toyota and worked indy HD shops, -------------------------

Tom
I really was not addressing my response to any one person Tom, just throwing it out for general consumption, as there are very many people who still think you can "lap" valves in as a seating process. Just trying to do my part to continue dispelling that myth that has persisted over the last few decades.

I realize that there are quite a few of us here that know better, but most likely don't.

I don't want to achieve immortality through my work...I want to achieve it through not dying.

David Shealey
Dandridge, TN
EX: '01 Black LT, BAT BYKE (Totaled at 110,000 miles)
IBA SS, BB, BBG, 10/10ths.
No bike now, but maybe in the future.
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post #14 of 15 Old Oct 21st, 2006, 7:17 pm Thread Starter
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Quote:
Originally Posted by tmgs
yuppers

have fun, if io keep mine i'll have to do it one day (in about another 200-300 k miles hopefully <grin>)

oh darn well if it is before 8/2009 i do have an extended

hehehehe
Dont matter Tom used new motors are inexpensive, perhaps easier to buy a low mileage motor when the sprag clutch needs to be changed.

Pete Murray
IBA # 359 and
2014 RT
1973 R75/5
2002 LT 171 K Gone
2008 FJR 36 K Gone
Stroudsburg, PA
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post #15 of 15 Old Oct 23rd, 2006, 8:23 am
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Oh, that kind of head job

Thanks,

Richard

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