Author Topic: Kenner nurses a neglected 04F back to health  (Read 223 times)

Offline The Buddha

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Re: Kenner nurses a neglected 04F back to health
« Reply #20 on: January 12, 2018, 10:35:13 PM »
Muriatic acid will eat aluminum and aluminum based alloys a lot faster than it will eat clean steel. It will eat rusted metal very very fast.
If your problem is that there is rust and heat that's gooped up in there and threads etc etc have shards of rusty metal preventing it from getting out, yea muriatic acid will get that eaten, but if you have cross thread type madness, you're gonna eat the aluminum fast.
On my first tank kreeming experience, I blew a hole in the petcock overnight trying to get rust out of the tank. Trust me, aluminum based alloy will go fast when you hit it with muriatic acid.
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Offline Kenner

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Re: Kenner nurses a neglected 04F back to health
« Reply #21 on: January 15, 2018, 12:39:59 AM »
To save my pride I think I'm going to quit keeping score since the Yellow Bird is running up the score.

So turns out my acid trial didn't work out. It was probably due to using used acid from a dead old battery and not fresh new acid. I resorted to continuing to drill the studs out. I drilled them a tad oversize for an m8X1.25 but that was to clear out more of the corroded-in bolt from the holes. I started with a 17/64 (0.263) but then went up one size to 9/32 (0.281) .... according to the machinery handbook the hole should be 6.8mm (0.268") for this tap.

I then recut the threads with an m8X1.25 HSS tap. The studs will screw in, but the threads feel a little weak. I am at a crossroads on what to do next. Since I am changing the configuration to be studs instead of screws I have a few options. First, I could slather the studs in JB weld and then thread them into the holes and let it cure. Since the studs won't be spinning to put the exhaust back on this should work fine as it just needs to mostly resist the tensile force the nut will apply to the flange. I am tempted to go this route because if it doesn't work I can always drill it larger and add the insert, once drilled larger there is really no going back (easy to remove material but very difficult to put it back).

The second option is to drill it out larger for a threaded insert. I have a set of E-Z lock threaded inserts coming from Amazon, but I am deciding whether I want to use them. They have an m12X1.75 outer thread. This requires drilling a 10.8mm (0.425") hole and the threads themselves have a major diameter of 0.475". I am concerned going this route because of how large the holes need to be drilled and whether it will weaken the head or encroach into the exhaust chamber. It appears there is enough aluminum meat but it'll be close. Has anyone gone this route?

The third option would be to oversize the bolts to the next thread size which is m9X1.25. I am very reluctant to do this because I hate having mis-matched hardware. It always feels like such a hack job if you do it that way.

I did take the opportunity to check the valve clearances and the compression on the Yellow Bird this weekend.

Left Exhaust 0.003"               Right Exhaust 0.004"
Left Intake   0.002"               Right Intake   0.002"
Left Compression 120 psi       Right Compression 120 psi

When I first measured the LI it was less than 0.0015 but unfortunately I didn't have a 0.001 feeler gauge (0.0015 was my smallest). The shim was stamped 245 and it measured 0.0966" with a micrometer. I pulled all the shims on my spare motor to see if one was small enough, but they were all too large at (0.105"X2 and 0.1104"X2). I resorted to sanding the shim down to 0.096" and reinstalled it. After that I could get my 0.002 feeler gauge under it which tells me it was just barely under my smallest feeler gauge so it was likely still within spec before the sanding. I will tell you that sanding 6 ten thousands of an inch off the shim took about 15-20 minutes. Those shims are made of hard material.

The compression is a little low according to the manual, but it also said to get the bike to operating temperature before performing the check. I did the check cold since the carbs are still off the bike waiting for rebuild kits.

Ken


Top pick -> Two inner threaded holes cleaned up after drilling out sheared screws.
Bottom pick -> Studs I will use to replace screws. These came from a 98-02 chevy cavalier exhaust manifold. I just happen to have a half dozen of them laying around from a repair I did on my natural gas cavalier.

Offline mr72

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Re: Kenner nurses a neglected 04F back to health
« Reply #22 on: January 15, 2018, 01:06:54 PM »
Good job getting the bolts out! And ditto that sanding the shim, although if it were me I think I would not trust that I could sand it and have it remain flat within 0.001", I'd be afraid it'd rotate on me.

Your compression is low enough that it may cause you problems down the line. Heck, you have it apart this far, how hard is it to pull the head and jug, hone the cylinders and put in some rings?

Anyway, about your options on the exhaust studs, I agree with you that using the existing holes/threads is the least risky way to do it but I wouldn't use JB Weld because of a lot of reasons, not the least of which is that if you manage to get threads cut in it without it just flaking off it still only has 500F temperature rating which is not half of what I'd want for an exhaust stud. OTOH I think your existing threads are probably sufficient if you use a high-temp threadlocker. Loctite makes one rated for 650F and these guys have one rated to 2100F if you can find it. I'd probably just Amazon-Prime the Loctite and put the stud in with that, then make dang sure I never over-torqued it.

IMHO. And that's a heck of a lot easier than trying to fill and re-tap the hole. BTDT, never seen it work right, always more trouble than it was worth... well except one time when I packed a broken threaded hole in a magnesium bicycle fork (disc brake stud) with plastic steel putty and then drilled and tapped it like it was brand new material, but that's not a temperature sensitive application and I had the PSP on hand (it's very expensive, like $80). And that was an M5. Whole different animal. If you have salvageable threads then threadlocker seems like the way to go here.

If you had the head off this might be a good time to try aluminum brazing ... in theory you could just coat the threads and reduce the holes a little then re-tap, or use this method, which sounds dodgy but maybe if you chased the threads after.... Maybe when you have to take it all down again in a couple of months for a top end rebuild to fix that 120psi compression ;)

Offline gregjet

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Re: Kenner nurses a neglected 04F back to health
« Reply #23 on: January 18, 2018, 11:42:50 PM »
had a look ate that material and it looks the go actually. Attached video of a use and the joint is stringer than the base. For this job could be a real alternative. BTW alu-brite should clean the hole very well then wash it with lots of water before use. CAREFUL of alubrite as it contains Hydroflouric acid which makes the other halogen acids look like pussies and is not at all good for you skin and body. It will absorb straight through the skin. GLOVES! For the bolt coat it with moly( very thin) or teflon spray ( temp stable) and the bolt should turn out very easily.
https://www.youtube.com/watch?v=RCrixbXz4rc
« Last Edit: January 18, 2018, 11:45:11 PM by gregjet »

Offline Kenner

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Re: Kenner nurses a neglected 04F back to health
« Reply #24 on: January 19, 2018, 06:55:12 PM »
I've been back at it in the garage. I decided instead of trying to hodge podge something together for the exhaust bolts that I would just repair them properly. I chose to go with a Time-Sert m8X1.25 kit for this repair. While Time-Sert is on the expensive end (the kit cost $73 US) in the end it was worth it. You get a fantastic repair that in this instance is stronger than the original because you are threading the studs in and out of a steel insert instead of aluminum threads (yes the insert is threaded into the aluminum threads, but once in it stays put and from my experience threads generally strip when tightening).

Another thing I like about the Time-Sert kit is that the inserts are very thin. They are only 0.372" diameter where an m8 bolt measures 0.307". The other inserts I was looking into were an m12X1.75 on the outer threads which has a diameter of 0.472Ē (these are much cheaper and can be installed with a normally available tap where the Time Sert tap size is non-standard). This means the holes would've been a tenth of an inch larger to fit the generic insert which would not have left much meat in the head. The reason the Time-Serts can be so thin is the inner and outer threads are synchronized so the peaks and valleys line up. (See picture below).

Next up is cleaning the carbs and installing the new bits from the K&L carb kits.

Top Pic: Time Sert cutout showing thread alignment.

2nd Pic: Time Sert Kit with drill, counterbore, tap, and installer (this is a thread rolling tap that forms the final threads on the bottom of the instert as it is installed)

3rd Pic: Holes prepped for install

4th Pic: Inserts installed

 
« Last Edit: January 19, 2018, 08:05:31 PM by Kenner »

Offline The Buddha

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Re: Kenner nurses a neglected 04F back to health
« Reply #25 on: January 19, 2018, 08:12:55 PM »
Why not helicoil ? There was no real need to do a timesert.
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Offline gregjet

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Re: Kenner nurses a neglected 04F back to health
« Reply #26 on: January 20, 2018, 08:01:32 PM »
That does a nice job I must say.

Offline Kenner

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Re: Kenner nurses a neglected 04F back to health
« Reply #27 on: January 20, 2018, 10:40:40 PM »
Y
Why not helicoil ? There was no real need to do a timesert.
Cool.
Buddha.

I donít realy like helicoils. Once inserted they can be a little tricky to start the threads and Iíve had experience with them bending at the first coil. I prefer a solid insert. I chose Time Sert because they are thinner than most inserts and require a smaller hole. Once you own the kit the inserts are only a couple dollars each and this thread size is popular on motorcycles.

That being said a helicoil probably would have worked fine since I am changing to studs but since I didnít have a helicoil kit already I chose to pay more and get what I believe are a better product.

Ken