75 XLCH teardown
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Tourer
Joined: Mar 2007
Posts: 271
Likes: 13
From: OKC
I measured the bore at the casting lines, for guidance. Moved the calipers back and forth while holding outward pressure to see what the largest reading I could get. Then did it 90 degrees from the other position with essentially the same result. I got readings from 3.320 to 3.356 both times. Won't really know what the actual bore is until i get some correct measuring tools and do it again. Will let you know.
Oh, here's a side question. What do you guys use for media to clean your parts in a bead blasting cabinet? I used to use silicone glass bead on VW heads but I think I heard where seed hull has become the new non-abrasive/cleaning media of choice these days.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
Nope... you're as surprised as I was when I came up with the same number PG. Course, this was reading it with dial calipers so I was only getting about a half inch down into the bore. Take a look at the pic; the cylinder wall ball honed very clean. The rings on the piston show normal wear and all rotate freely with no broken pieces. There isn't any gaulding on the piston skirt; in fact other than the carbon on the combustion surface, the pison looks real good. It all looks very rebuildable with the exception of the bore maybe being WAY over tolerence.
I measured the bore at the casting lines, for guidance. Moved the calipers back and forth while holding outward pressure to see what the largest reading I could get. Then did it 90 degrees from the other position with essentially the same result. I got readings from 3.320 to 3.356 both times. Won't really know what the actual bore is until i get some correct measuring tools and do it again. Will let you know.
Oh, here's a side question. What do you guys use for media to clean your parts in a bead blasting cabinet? I used to use silicone glass bead on VW heads but I think I heard where seed hull has become the new non-abrasive/cleaning media of choice these days.
I measured the bore at the casting lines, for guidance. Moved the calipers back and forth while holding outward pressure to see what the largest reading I could get. Then did it 90 degrees from the other position with essentially the same result. I got readings from 3.320 to 3.356 both times. Won't really know what the actual bore is until i get some correct measuring tools and do it again. Will let you know.
Oh, here's a side question. What do you guys use for media to clean your parts in a bead blasting cabinet? I used to use silicone glass bead on VW heads but I think I heard where seed hull has become the new non-abrasive/cleaning media of choice these days.
Did you not say the piston tops are stamped '+.070'? I am wondering if someone got some aftermarket pistons (.080 or .090 over) and fitted those to the last rebore? If so that would be stamped on the piston tops.
As for the bead blaster material, I use glass beads myself. I do not think seed shells would be too effective for cleaning heads and carbon. It may work though. I never tried it myself.
pg
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Tourer
Joined: Mar 2007
Posts: 271
Likes: 13
From: OKC
Yup PG, the piston tops are both stamped 070.
Just got back from a week at work. Will see about getting the other cylinder off and getting them measured correctly.
May try to tear down the motor this week.
Another odd question. Did the XLCH (75') come with anything other than the peanut tank? Still can't get over the fact that the rear mounting hole seems to have been drilled in the frame when there is a stock one an inch further back.
Just got back from a week at work. Will see about getting the other cylinder off and getting them measured correctly.
May try to tear down the motor this week.
Another odd question. Did the XLCH (75') come with anything other than the peanut tank? Still can't get over the fact that the rear mounting hole seems to have been drilled in the frame when there is a stock one an inch further back.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
Yup PG, the piston tops are both stamped 070.
Just got back from a week at work. Will see about getting the other cylinder off and getting them measured correctly.
May try to tear down the motor this week.
Another odd question. Did the XLCH (75') come with anything other than the peanut tank? Still can't get over the fact that the rear mounting hole seems to have been drilled in the frame when there is a stock one an inch further back.
Just got back from a week at work. Will see about getting the other cylinder off and getting them measured correctly.
May try to tear down the motor this week.
Another odd question. Did the XLCH (75') come with anything other than the peanut tank? Still can't get over the fact that the rear mounting hole seems to have been drilled in the frame when there is a stock one an inch further back.
For 1974 and earlier the frame had 2 sets of tank holes. The 2.2 gal tank found on the XLCH bolted on at the front, just behind the steering tube. This bolt has a pair of collars on each side of the tube web so the outside surfase of the collars was exactly the inside of the tank mounts ears.
The 2.2 gal tank bolts on to the frame at the rear with a hole through the top tube.
The other tank found on an XLH was a 3 gal tank. This is larger. It uses the same front hole to mount the 3 gal tank as the 2.2 gal tank, uses the same collars.
But at the rear there is a lug sitting on the bottom of the top tube. This has a hole through it for the rear bolt on a 3 gal tank. The lug is as wide as the inside distance of the 3 gal tank lugs and uses one bolt through it. No collars are used here.
That may not answer your question, but up to 1974 only two tanks existed. The 2.2 on a CH and a 3 gal on an XLH.
pg
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Tourer
Joined: Mar 2007
Posts: 271
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From: OKC
Thanks PG.
I definitely don't have a 3 gallon tank. I'm not familiar with them, but have to guess they would be similar in size to the current 1200 custom tank.
I'm just bugged by the holes in the backbone... the tank doesn't seem to fit in what appears to be the stock hole. Take a look at the two attached pics.
In the one, I've drawn a yellow arrow to the front mount location, an orange arrow to the drilled hole in the backbone the current tank bolts into, and a red arrow from above to the hole in the frame with a welded in spacer that appears to be a factory design.
In the second pic, you can see the rear of the tank bolted on.
Maybe you guys see something I am not. I don't think the tank I have is non-standard, but I don't get why the hole in the frame had to be drilled? Is the front mount wrong, maybe? Dunno...
I definitely don't have a 3 gallon tank. I'm not familiar with them, but have to guess they would be similar in size to the current 1200 custom tank.
I'm just bugged by the holes in the backbone... the tank doesn't seem to fit in what appears to be the stock hole. Take a look at the two attached pics.
In the one, I've drawn a yellow arrow to the front mount location, an orange arrow to the drilled hole in the backbone the current tank bolts into, and a red arrow from above to the hole in the frame with a welded in spacer that appears to be a factory design.
In the second pic, you can see the rear of the tank bolted on.
Maybe you guys see something I am not. I don't think the tank I have is non-standard, but I don't get why the hole in the frame had to be drilled? Is the front mount wrong, maybe? Dunno...
Last edited by Yosemite; Dec 27, 2009 at 09:37 PM.
The difference between a 79 to 81 tank and those for up to 78 is the position of the rear mount tabs. On 78 and previous they are at the very back end of the tank; on 79 to 81 they are an inch or two further forward. I do not know what year is your frame or your tank, but take another look considering this information.
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Thread Starter
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Tourer
Joined: Mar 2007
Posts: 271
Likes: 13
From: OKC
Look now. PC locked up. Had to post message and then edit to add in pics.
Mick, look at the back of the tank in the one pic. What does it make you think? The serial number on the frame says it's a 75'... presuming it hasn't been faked. No reason for me to believe it isn't the original frame.
Mick, look at the back of the tank in the one pic. What does it make you think? The serial number on the frame says it's a 75'... presuming it hasn't been faked. No reason for me to believe it isn't the original frame.
Stellar HDF Member
Joined: Feb 2006
Posts: 3,035
Likes: 17
From: Houston Texas
I took the liberty of marking up one of your pics. The three holes I have called out what they are for. it looks like this to me.....
The hole in the lug beneath the frame tube is certainly for the large tank's rear mounts.
The next hole going forward (unused on yours) is the hole used to mount a 1971 through 1974 2.2 gal gas tank.
The third hole where you have the tank attached looks to be:
1) Looks too far forward to mount a 1971-1974 2.2 gal gas tank.
2) Looks to me like someone drilled this to use for the tank you have. The tank you have may be for a later model that has the rear lugs farther forward than in the 'older days'.
Your petcock is sitting right where it should be.....in front of the carb.
The above is my best guess anyway.
pg
The hole in the lug beneath the frame tube is certainly for the large tank's rear mounts.
The next hole going forward (unused on yours) is the hole used to mount a 1971 through 1974 2.2 gal gas tank.
The third hole where you have the tank attached looks to be:
1) Looks too far forward to mount a 1971-1974 2.2 gal gas tank.
2) Looks to me like someone drilled this to use for the tank you have. The tank you have may be for a later model that has the rear lugs farther forward than in the 'older days'.
Your petcock is sitting right where it should be.....in front of the carb.
The above is my best guess anyway.
pg