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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Posted: 20:31 - 15 Dec 2021 Post subject: Press fitting alloy into steel dimensions? |
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I've bent a third pushrod on my Enfield bullet. I have concluded a large part of the issue is the pushrods are made of cheese.*
The pushrods are made of some sort of aluminium alloy tube with a hardened steel cup and an adjuster pressed over either end.
https://lh3.googleusercontent.com/pw/AM-JKLXuLowSjuAhQ3WQHoQMg7S28qvCgS3jmxDUasPHAyIzpvZqrMMx1JULIC0Y5wGFe6-MjVgAtrNpuFT_ExBC8pRqOBc-NY8NFGYiBFk5kMTVbZvZ4fo3_9S5D_Jpyl_1SLTbL6YF6cyeUB97It4kW82l=w1576-h886-no
My plan is to replace the aluminium with some good quality, named aviation grade stock (7075 T6)**. I'm just getting lost in the various charts, tables and types of fit. I can find good data for an interference fit for steel in steel and plenty of steel in aluminium but I'm struggling to find charts for aluminium in steel.
The aluminium rod is 10mm OD. The "sleeve" that pushes over it is roughly 9.4mm ID (they vary). I plan to measure the individual sleeves then adjust the diameter of the aluminium rod to suit each sleeve (I don't have a lathe so it'll be old-school going slowly with wet and dry). Then rod in the freezer, sleeve heated up and drive them on.
They are only working in compression and they do get hot so they should get tighter as they warm up.
The question. How much bigger in diameter than the steel sleeve does the aluminium rod need to be?
I'm also considering drilling into the ends of the rod a couple of mm, leaving a 2mm wall so it deforms slightly when it bottoms out in the sleeve. Good idea or stuipd idea?
* I've gone through most of the other failure-modes I can think of including valve springs coil binding, fouling the tappet at full compression, valve impinging on piston, hydraulic locking inside the tappet, valve guide seizure and valve float at high revs making the rod jump the tappet. I think the conclusion is it's either backfiring on startup (hopefully now fixed, I've removed the electronic random spark generator and put points back on) or simply that the rods were made in India for a 17bhp bike and I've got them in a 40bhp bike with hot cams and heavy valve springs and they are exceeding their design tolerances.
**I tried to source some 10mm chromoly tubing but it's like rocking horse poop. ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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WD Forte |
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WD Forte World Chat Champion
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Pete. |
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Pete. Super Spammer
Joined: 22 Aug 2006 Karma :
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Posted: 20:58 - 15 Dec 2021 Post subject: |
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Interference fits are normally approx. 2 thou per inch so at 10mm you're looking at 1 thou of interference or a bit less.
I'd be tempted to turn it to a slip fit, knurl it up and press it in with bearing retainer. It ain't ever coming out then. Or if you want to order the material and send all the bits to me I'll do the machining for you. ____________________ a.k.a 'Geri'
132.9mph off and walked away. Gear is good, gear is good, gear is very very good |
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WD Forte |
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WD Forte World Chat Champion
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Pete. |
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Pete. Super Spammer
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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Pete. |
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Pete. Super Spammer
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Posted: 23:56 - 15 Dec 2021 Post subject: |
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When you thin the ends don't leave a sharp inside corner, even a tiny radius is preferable. ____________________ a.k.a 'Geri'
132.9mph off and walked away. Gear is good, gear is good, gear is very very good |
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stinkwheel |
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stinkwheel Bovine Proctologist
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Pete. |
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Pete. Super Spammer
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Posted: 00:47 - 16 Dec 2021 Post subject: |
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I would not do that the end socket needs to stop against a shoulder. If you make a shallow taper the end piece will get hammered up the taper over time causing the clearances to change. You could rely on the end bottoming out in the socket but how are you going to know that it's bottomed out unless there's a drilling to let the air out?
The proper way is to set the dead length by locating it with a shoulder to seat against. ____________________ a.k.a 'Geri'
132.9mph off and walked away. Gear is good, gear is good, gear is very very good |
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virus |
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virus World Chat Champion
Joined: 17 Aug 2006 Karma :
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Posted: 19:19 - 16 Dec 2021 Post subject: |
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I think petes covered everything pretty well there as usual.
At work we do a few different fits including dovetailing and knurled interference fits etc. I think for what you need it to do I wouldnt worry about dissimilar temperature expansion, it will be negligible at that size.
Id be doing a 4 thou interference fit with a shoulder, making sure that its resting on the shoulder not the actual end of the bar like Pete has said that way you can inspect the fit periodically with no issues.
What ID, OD and length of pocket is there in the steel part out of interest? ____________________ own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance. |
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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Posted: 00:47 - 17 Dec 2021 Post subject: |
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virus wrote: |
What ID, OD and length of pocket is there in the steel part out of interest? |
Haven't measured it up properly yet but the ID is in the ballpark of 9.4-9.5mm. Pocket is approximately 10mm deep. One is tapered out from roughly 10.5mm OD to approximately 13mm OD, the other end is a 13mm hex.
I heated the ends of one rod and removed them (by literally pulling them off with a pair of pliers, I could have used my fingers if it hadn't been hot). It honestly looks like it's been turned down to slightly oversize, had a slight chamfer ground onto the end of the rod then been hammered/pressed in until it bottomed out against the shoulder. The adjuster end (with the hex) has the residues of some sort of brown fitting compound on it, the tapered end looks like someone took four or five longitudinal gouges out of the surface of the alloy with the tip of a file or a scribe then pressed it in.
I had an idea, assuming the socket is actually 9.4mm, that I could run an M11 x 1.5 die down the end of the rod, dress the shoulder end with a fine burr/file so the final turn lands up square then sand off the threaded section with fairly course abrasive until the thread is barely visible, then fit with heat and green bearing fit.
It's not seeing any real tension or rotational forces, just compression (and apparently, slight bendfing!), I just need the ends to stay on.
I've got a bit of extra bar and three bend pushrods so I can have a practice fit first. ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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virus |
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virus World Chat Champion
Joined: 17 Aug 2006 Karma :
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Posted: 18:32 - 17 Dec 2021 Post subject: |
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I cant see why that wouldnt work, I think Id try and hand file a left hand thread simmilar to suit if I were going that way though, think of the Die thread being half of a knurl and you putting the rest in with a needle file. That should give the retaining compound a bit more to pocket into. As you say, at least youve got a few get out of jail free cards, and 10mm of press fit thats in constant compression doesn't sound likely to fail to me.
P.S, I was going to ask why you have an M11x 1.5 die but then I remembered that the Enfield's are made of all sorts of bullshit thread forms ____________________ own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance. |
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Islander |
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Islander World Chat Champion
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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Posted: 19:37 - 17 Dec 2021 Post subject: |
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I actually bought a die. I went cheap on the basis it only has to survive four small cuts into alloy. Cheaper than a knurling tool! I looked down the thread charts to see what had a minor diameter closest to what i wanted
I might use it another time to put a random oddball thread on a bike just to fuck with the next owner. I've done it before, the main engine mounting bolt on the last enfield I sold is a UNF.
Enfield do it too. I'm sure it's just to fuck with people. There are three M7 nuts on bullets, holding the alternator stator on. They made studs with cycle thread on one end and M7 on the other. They also used an M11 fine on some of their petrol tank fuel tap couplings.
Hitchcocks make an adaptor to fit larger amal concentrics to 500 bullets, their studs are M8 into the head and a cycle thread nut. I know why they did it, because there is limited clearance and the cycle thread nut they used has a smaller hex but they could have just used JIS M8 nuts which have a 12mm hex (which is what I did to fit the manifold for my big mikuni). ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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virus |
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virus World Chat Champion
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Nobby the Bastard |
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Nobby the Bastard Harley Gaydar
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stinkwheel |
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stinkwheel Bovine Proctologist
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virus |
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virus World Chat Champion
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Posted: 22:17 - 17 Dec 2021 Post subject: |
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stinkwheel wrote: |
You should suggest they start using Whitworths, then at least they will be sound from an engineering point of view and most people wouldn't have the first idea what they were looking at anyway. Or start the great BA threadform revival? |
Oh this customer has been around since the 40s or so, they wanted to switch to some metric bullshit none existant thread because their customers started to finally find suppliers of Imperial fasteners ____________________ own: 81 xs1100g...
owned: 85 rat CG (sold), 91 GS500e (stolen), 84 gsx400f (scrapped), 81 z250 (siezed, siezed, scrapped), 83 cb250rs (sold), 84 gpz750r ratfighter (killed) 84gpz400 (sold), '80 cb650 ratfighter (wrote off) 95gsx6/12f ratfighter (killed) 91 xj900 (sold)
stinkwheel Well I just had my hands up a pigs fanny. Which makes your concerns pale into insignificance. |
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stinkwheel |
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stinkwheel Bovine Proctologist
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Posted: 23:52 - 04 Jan 2022 Post subject: |
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Tried a few things on "scrap" alloy (ie not the 7075). The thread cutting was trickier than I thought, couldn't get it started straight enough and finished on a neat enough line, even with the piece in the drill press and the die in a drill vice.
Here's what I came up with. I slotted some 10mm ID steel tube and de-burred the inside edges to give me two tools. The longer split piece is effectively a collet so I can grip the piece in a drill chuck without marking it. The shorter, partially split piece is a distance stop to clamp on at the line where I want the step. Some masking tape on there for extra grip and safety.
https://lh3.googleusercontent.com/pw/AM-JKLVoy6rV-MRRNhW0_1Awrf52wkWmYc2mefEG12bZ0IqUpnvoQMxrbHAHRbwGNK_KoGo0ydkbWLJnEu-PJJ6ymeC9EiGdYIJLX60MIZMLssVzGAljr12Ljk-0s4DtwrXFXaxtwvKe7LOBIS9ARQ1-J0nH=w1576-h886-no
https://lh3.googleusercontent.com/pw/AM-JKLWGUfOeDYAMTSMn_bjBLG8BgK_OdYd2qsmTNjn0WUqVCyvWj_rmcfVWsgB-4EgG6seQdIZ2jDRvnEEfIXtRFFR2WrrdriFEAQNLfSbTsefUMKm00Q7XxTyUQuSyeaT2guX6hT8U0evx7OCBD2ia96d_=w1576-h886-no
Then I chucked it up in the drill press and with it at a low speed, made horizontal strokes with a second cut file along the bottom using the edge of the distance stop to set the depth. I considered grinding a "safe" edge on the file to butt against the stop but it wasn't removing a significant amount of material from the steel.
I did have to support the piece with a gloved hand to get enough force without bending it too much.
https://lh3.googleusercontent.com/pw/AM-JKLUS8siabaWBxCVo1kTUENePYzgr_hAq67nhp70geIYgDUZlKHxsd3fmaR_3P2Cj65UwxVBhE75UMSYFqFcQLhGuHIDsthdtZTFUDw8DQPQw3Az43oj9c-mMCtUjRGnOcUtS9_Uep22SMJugGe6Ew6Ak=w499-h886-no
I did ten file strokes then measure, then as I got closer, dropped it to 5 then using lighter strokes. Considered dropping to a third cut file but figured the texturing was probably going to be helpful for getting a good bond. I'm quite pleased with how even the file cuts are.
Here's the result.
https://lh3.googleusercontent.com/pw/AM-JKLWjGEP-hcUBk8khJTksqTqBfLOVKpJ_LvOsul5cPB20gLk2mEj5yTN7GqvbKfjzNkNnE54nyfxS6IAYygys-T-Svh1Xj7B0tyrwC4T2tUJ9EZWf_43QcW5uDqExnOy7Ox8XGu2ov6_wGuEVokaLaYdI=w1576-h886-no
Then pressed the ends on using a sash-clamp and green bearing fit.
https://lh3.googleusercontent.com/pw/AM-JKLWzT8tuAh2TSvQYOg_EYFtNrdjTccmHa_M_qlEjw78SCLCclsI_sfDuTygWjV84Eo4u6QREpSWtqVJgaFtq-eC0Q9UHtnfvp5OIkPo7ju33knBAtWQPjX7ICGLRmxJFS4yJ92qrn749fbxs7pFOVYHq=w499-h886-no
I did have an isse with the non-adjuster end. Butting it against the step was probably the wrong choice here. I think it needs to butt against the end and come down to flush with the step because the steel end tapers to a point. I split two of them on fitting.
https://lh3.googleusercontent.com/pw/AM-JKLUjPDlZVrH_y9aT1XbKjiU81fM-MogGCcCcAQfw85mkv_lE5kd1znbmBVAr9xHstISZR0TCTmlU5EK7wtOQ0dhOqMG-MZgXzIVAzdVE0Q6eXxmAubQENTyC47CD0p1Mn5HbQLfZzM6CrWpD7X757mk1=w1576-h886-no
I've now found a different type of end which doesn't come to a point like that so i'll wait for them to arrive before going any further.
Original on the left, mine on the right. There is a 20g difference in weight but the one on the right is solid 7075 bar, the one on the left is hollow tube of unknown grade. I made it 2mm longer becaue i've fitted an extra 2mm compression plate.
https://lh3.googleusercontent.com/pw/AM-JKLVQ0M0cnOulvg3cvQIlPSgNoUVt4V-EN2YNDH1VKvhqzpb8Ui6BxOJmKQ3eGzxZl2Thq0fhEnOe-5LQyentjXzJKJ8Q_Q0YioLoNjtPw_fttFWq7Fd6BmH1rIMkQQVJ1CRH9qMGCXiwbesct808PQxg=w499-h886-no
I did also have to drill into the adjuster end of the bar because the threaded adjuster that screws in goes up inside the rod about 10mm. I achieved this by making a drill guide from a block of alloy with a 3mm pilot hole then a 10mm hole part with into it. Slotted the bar into the 10mm hole then drilled my pilot dead centre using ther drill guide. I then opened the guide out to 5mm for the M6 adjuster thread. Next I fitted the end on the rod and ran a tap down it so the thread continues into the alloy from the adjuster. That way, when it's screwed in, it will be engaging with both the adjuster and the rod. I forgot to take pictures of this. ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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jeffyjeff |
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jeffyjeff World Chat Champion
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A100man |
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A100man World Chat Champion
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Posted: 13:05 - 07 Jan 2022 Post subject: |
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All I can say is that (classic) RE owners are a dedicated bunch..
..foolhardy, but dedicated. ____________________ Now: A100, GT250A, XJ598, FZ750
Then: Fizz, RS200, KL250, XJ550, Laverda Alpina, XJ600, FZS600 |
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stinkwheel |
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stinkwheel Bovine Proctologist
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jeffyjeff |
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jeffyjeff World Chat Champion
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Hong Kong Phooey |
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Hong Kong Phooey World Chat Champion
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stinkwheel |
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stinkwheel Bovine Proctologist
Joined: 12 Jul 2004 Karma :
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Posted: 16:21 - 07 Jan 2022 Post subject: |
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Hong Kong Phooey wrote: | I know nothing about the RE engine architecture, but presumably it's ancient and cam operates pushrod which is direct to rocker arm then valve. Cam likely gear driven than chain, so timing is probably not the cause.
In that case a cheesy rod would be an issue on any engine using the same spring rate wouldn't it, regardless of cc?
Unless the higher output engine revs higher, and requires a dual valve spring or uprated set to mitigate against valve float.
If that's the case I'd expect more owners to have complained.
If the rods were intentionally designed to be sacrificial, what's the next weak link in the chain, rocker arm? |
Cams are gear driven off the crank. A follower runs on the cam which pushes the pushrod which bears against the rocker then valve.
The higher output engine revs significantly higher (about 1,000rpm higher and peak power is up in that extra rev range), the cams have significantly higher lift to the point the engine casing had to be machined out to accommodate them and it's fitted with significantly stronger valve springs with wider spacing to avoid bounce and becoming coilbound. So it's fair to say, the rods are under a great deal more stress than in a standard engine. The pushrod adjuster screws have been known to let-go on the standard motors, these have been upgraded but I have bent a couple over the years.
Yes rocker arm would probably be the next thing to let go, but I have upgraded those too. Thinking about it, the 1/4" cycle thread studs that hold the rocker block onto the head would probably also be in the firing line for stripping out of the head leading to the rocker blocks moving up and down, although that would be a relatively "safe" failure mode. ____________________ “Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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Old Thread Alert!
The last post was made 2 years, 80 days ago. Instead of replying here, would creating a new thread be more useful? |
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