10,000 mile M8, Stage III +
#81
12-09-2017, 06:07 PM
Seasoned HDF Member
Well if you can take a simple pair of side cutters and cut the screw as I have I would not assume 85000 psi at all. The truth is I do not know what they are other than steel but the side cutter let me know it's nothing special so "average steel" would be my best guess. They are tri-lobe so they are not cutting the treads but regardless running them over the recommended torque levels is not a good thing to do. Every specification for an 8-32 going into AL material has those number well below what MoCo has tried so far! It seems like something is wrong if 6061 has higher numbers than 2024 has, yet 2024 shows a lower yield point here. Since it's going into cast AL the best way is to use the industry standard testing to determine maximum torque but I do not have several engines laying around to perform the necessary test . Since you refer to early manuals are you talking M8 or twin cam? Bottom line is they are coming loose and the MoCo's attempted fixs has been to raising the torque value on the screws. It did not solved the problem, so they raised them again and still has not solved the problem.
The shear is because the mass of the oiler is 90 deg to the mounting position of the screws and sticks out about 1 3/8". It they had not thinned the oiler mount out, only where the mounting screw holds there might be something more that could be done but as it stands now the limit is these 8-32 screws. Making a new oiler with proper thought to mounting would go a long ways to making a better seal, as would fixing the casting on the case side would too.
If one wanted to tap the hole do not use a cutting tap, use a roll form tap.
The shear is because the mass of the oiler is 90 deg to the mounting position of the screws and sticks out about 1 3/8". It they had not thinned the oiler mount out, only where the mounting screw holds there might be something more that could be done but as it stands now the limit is these 8-32 screws. Making a new oiler with proper thought to mounting would go a long ways to making a better seal, as would fixing the casting on the case side would too.
If one wanted to tap the hole do not use a cutting tap, use a roll form tap.
Well if you can whack the screw into 2 piece you got to have some pretty good hands and cutters.
As far as torque goes Trilobe needs more.. From Taptite..
From
https://www.taptite.com/taptite/taptite2.asp
While this spec is for 3/16 steel plate. It definitely says that the screw can hold up to 75 in lbs before failure and recommended tq is 45 In-lbs. I found 4 mm (close to #8) for aluminum and they say 38 inch-lbs if you convert from nm.
6061-t6 is not a strong as 2024-t4 ref Machinery's hand book 26 in both yield and tensile.. Should probably use the numbers for A356 casting aluminum tho.
The reference for torque was from a twin cam SM.
How much does the oiler weight? HD has been using the same type in the Sportsters for some time and have had not had any issues as far as I can tell.. The oilers in the Sporties likely see more vibes then an M8. After all the M8 has a counter balancer an the Sporty don't. I think it's more likely that when HD went to production they screwed up on the initial TQ setting. 38 in-lbs would be a good number for first tq. 30 for second. The screw won't have any problem stretching..
Thread forming tap would be the way to go if want to use the tap for sure.. H2 class fit is easily available..
#82
12-09-2017, 06:58 PM
If you read the notes in a lot of the tri lobe manufactures it states they use a low carbon steel and induction harden just the threads! I was unable to locate any more information than that for small screw applications. When I cut the screw it was no big deal, so I assumed that MoCo bought the cheapest ones they could.
If I had several engines to test with it would be easy to determine what the torque should be, but one must understand that you wreck the thread doing the industry standard testing. It's not hard to do as you just torque the screw into the joint until something begins to yield. Now understand that the cast AL is most likely going to be the first thing to yield and that is the engine case! Once it begins to yield you record the torque value. Test a dozen or more times on different holes and screws. then average your results. Take the average number and multiply by 60%. You now have the optimum tightening value for that joint. You are suppose to do the test at the normal temperature the joint is exposed to, so in this case I would guess that to be about 180 F. Once we know those numbers, then we can move on to what the gasket is going to do once torqued to whatever that number comes out to be which is another unknown thing in the mix.
In the older applications it was metal on metal with a much smaller oiler and a o-ring to fill the gap and seal the joint. That would allow for some movement over the temperature range that the gasket may-not be doing.
All in all it's just another thing that needs fixing and something that IMHO should have been done much better than it has been.
If I had several engines to test with it would be easy to determine what the torque should be, but one must understand that you wreck the thread doing the industry standard testing. It's not hard to do as you just torque the screw into the joint until something begins to yield. Now understand that the cast AL is most likely going to be the first thing to yield and that is the engine case! Once it begins to yield you record the torque value. Test a dozen or more times on different holes and screws. then average your results. Take the average number and multiply by 60%. You now have the optimum tightening value for that joint. You are suppose to do the test at the normal temperature the joint is exposed to, so in this case I would guess that to be about 180 F. Once we know those numbers, then we can move on to what the gasket is going to do once torqued to whatever that number comes out to be which is another unknown thing in the mix.
In the older applications it was metal on metal with a much smaller oiler and a o-ring to fill the gap and seal the joint. That would allow for some movement over the temperature range that the gasket may-not be doing.
All in all it's just another thing that needs fixing and something that IMHO should have been done much better than it has been.
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Thingfish (12-09-2017)
#83
12-09-2017, 08:40 PM
Advanced
#84
12-10-2017, 01:47 AM
Grand HDF Member
Steve,
I am debating between a stage III and stage IV for my 114. I hardly get above 5k rpm. Run around 3 to 4K for the most part. What would be the best cam for a rider that enjoys quick burst in and out of the twisties, but hardly ever gets over 90mph. Smooth Power would preferred.
I am debating between a stage III and stage IV for my 114. I hardly get above 5k rpm. Run around 3 to 4K for the most part. What would be the best cam for a rider that enjoys quick burst in and out of the twisties, but hardly ever gets over 90mph. Smooth Power would preferred.
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Wardognal 1958 (12-10-2017)
#85
12-10-2017, 08:01 AM
Outstanding HDF Member
Steve,
I am debating between a stage III and stage IV for my 114. I hardly get above 5k rpm. Run around 3 to 4K for the most part. What would be the best cam for a rider that enjoys quick burst in and out of the twisties, but hardly ever gets over 90mph. Smooth Power would preferred.
I am debating between a stage III and stage IV for my 114. I hardly get above 5k rpm. Run around 3 to 4K for the most part. What would be the best cam for a rider that enjoys quick burst in and out of the twisties, but hardly ever gets over 90mph. Smooth Power would preferred.
The following users liked this post:
Wardognal 1958 (12-11-2017)
#86
12-11-2017, 12:47 AM
Advanced
#87
12-15-2017, 07:55 PM
Steve,
I am debating between a stage III and stage IV for my 114. I hardly get above 5k rpm. Run around 3 to 4K for the most part. What would be the best cam for a rider that enjoys quick burst in and out of the twisties, but hardly ever gets over 90mph. Smooth Power would preferred.
I am debating between a stage III and stage IV for my 114. I hardly get above 5k rpm. Run around 3 to 4K for the most part. What would be the best cam for a rider that enjoys quick burst in and out of the twisties, but hardly ever gets over 90mph. Smooth Power would preferred.
Stage 1
Fullsac MX headpipe
Fullsac muffler cores
High Flow A/C
Mastertune II
Stage 2
Fullsac MX headpipe
Fullsac muffler cores
High Flow A/C
TTS-150 M8 Camshaft
Mastertune II
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