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Hello forum! I've been absent for a while making great progress on my '69 Thunderbolt restore. The first attempt to assemble the cases I had the cam in a bind. Second time around I got it right and within tolerance. I fit the case in the frame. Fitting jugs and head was straight forward. It felt good to set the valves and put the cover on. Fitting the rest of the stuff has gone without any significant problems. Until the exhaust. All new for what that's worth.

I fit each pipe to the head separately and made sure the tab on the pipe lined with the tab on the frame.
Then I lined them both up with the crossover pipe and slowly wiggled them into place.
[Linked Image from i.postimg.cc]
[Linked Image from i.postimg.cc]

Both pipes fit the tabs on the frame:
[Linked Image from i.postimg.cc]
[Linked Image from i.postimg.cc]

The drive side silencer fits and the bracket is close to fitting, more on that in a moment.
[Linked Image from i.postimg.cc]

However the timing side won't fit no way no how.
[Linked Image from i.postimg.cc]
[Linked Image from i.postimg.cc]
[Linked Image from i.postimg.cc]

How do I bend the starboard pipe into position without screwing it up, ruining the chrome, or otherwise jacking it up? I think it needs to come down and out a bit.
Similar on the port side, even though the silencer mounts fitting the bracket to the lug would put the whole thing under a lot of tension, which can't be good, that pipe needs to be bent up just a tad.

I also noticed that in order to align the silencer bracket with frame lug, the silencer had to slide so far over the pipe that the pipe bottomed out against the internal baffle. Again, that doesn't seem right. I'm highly temped to shorten the pipe by about an inch or more to allow the exhaust to expand a bit before shoving it down the baffle tube.

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This is small consolation, I have a restorer friend, we were discussing ill fitting exhaust pipes one day, he was of the opinion that probably 90 % of pipes for twins fit poorly, rather than trying to bend pipes into position, he would fit as best he can then after a few heat cycles the pipes would "adapt " to the correct run. Not much help.
The 1970 balance pipe set up is a one year only, having tabs to frame rather than engine mount.

I would start by slackening the balance pipe and frame tab mounts, see if you can chivvy the silencers on and put heat resistant packing between possible contact areas, re tighten balance pipe, after a few heat cycles tighten mounting points until all are firm if the pipes have " given " to the correct run.
This is all too common with pattern stuff, I would like to recommend a supplier who has pipes that fit properly every time but I cant, .
I cant tell from the pic , if the tab fastener is a 5/16 diameter bolt, go for a 1/4 " bolt to give a little more wriggle room.Possibly consider an additional bridge piece between pipe / frame tabs to allow the pipes to sit outboard a little.
If only the pipe makers would tweak pipes for the correct fit after checking on an alignment jig before chroming, after chroming its too late to do much about it.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
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It doesn't help that your silencer brackets are the wrong way around, they should be "leaning forward" not "leaning back" as yours apear to. (put the one on the left silencer to the right silencer and vise versa)

However this will probably gain you an inch at most where the silencer is in relation to the frame.

Everything else as Gavin said, slacken everything off at the head end, I'd even take the bolt out of the frame tab and see where everything lines up before putting it back in, even if you need to use a 1/4" bolt for now.

As for silencer length I've found some "big name companies" to have the down pipes too long, I had to cut 3" off one side once and 5" off the other, this left the pipes entering the silencer by 2", I will however use this big name company again as their downpipes don't discolour as easy as the "eBay" brands. Their silencers are too restrictive for my likeing, I buy Brituro whilst I can still get my hands on whats left.


Change of note, you've probably not finished setting up your brake light switch position yet, but if you apply the brake in its current position you will break the switch, the lever on the switch wants to be behind the bracket, not before it.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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For what it's worth, the brackets on my silencers are reversed from yours (left one to right side and vice versa)

The bracket's front edge is vertical while the back one is diagonal and, where the bracket meets the silencer, the point that dips down below the mount is at the front as well.

However, that's not to say your exhaust pipe isn't sitting too far back or isn't too long. On the right (timing) side, the clamp holding the two together on mine is just slightly behind the footpeg mount.

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Bad fit is the curse of reproduction stuff.

It's been the complaint of both motorcycle and automobile restorers for decades.

The worst of it is: Their stuff ain't cheap in price, either.

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You will win some silencer space if the Timing side pipe tab is fitted below the frame tab rather than above it.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
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Well, I was hoping for a relatively stress free system. Above the frame tab is where it wanted to go and still be able to wiggle into the head and crossover. Still I have a bit more flexibility with the tabs. The brackets is an easy fix as well. They got all mixed up during cleaning and painting, I went off the parts diagram, obviously I got that wrong as well. That's why most of the frame parts are only finger tight. I mounted the fender, then tool box. Nope that won't work. There are loose fasteners all over the place till I'm satisfied everything is in the correct place. I'm just happy it's starting to look like a motorcycle.

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Well, I'm making progress, I think.

I put assembly lube in the head to fit the pipes without crossover. I plan to use anti-seize on final assembly.
[Linked Image from i.postimg.cc]

I think I have the brackets sorted out.
[Linked Image from i.postimg.cc]
[Linked Image from i.postimg.cc]
[Linked Image from i.postimg.cc]
[Linked Image from i.postimg.cc]

Pipes are level at the rear, and the crossover outlets appear parallel when I lay the crossover on them.
[Linked Image from i.postimg.cc]

Drive side exhaust tab to frame tab is relatively stress free.
This is the best I can come up with on Timing side.
[Linked Image from i.postimg.cc]

Do I need to make a little bracket?

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I just talked to a friend who is a welder about making a bracket for me. He suggested that when that header gets good an hot, it might pull into place and bolt down. Sounds worth trying. If that doesn't work I can always make a bracket.

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Ignore making the pipes level at the end, do what you can to get the brackets close. Pipes level at the end are a fantasy.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
Cagiva Raptor 650
MZ TS 250
The poster formerly known as Pod
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Try fitting the pipes and cans without the balance pipe, with it in place put a 12" ruler across the balance pipes stubs, level/? probably not, welcome to the world of pattern parts. I cut my balance stub on the bad side and had it rewelded to suit,the chrome gets wrecked, some are worse than others.


71 Devimead, John Hill, John Holmes A65 750
56 Norbsa 68 Longstroke A65
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The spacers you have packing the silencer bracket between the frame, believe it or not actually go on the other end, so you have that fugly long stud/rest holder and then the spacer, then the frame and then the silencer bracket. Some pattern ones are also longer so incorporate the extra distance the spacer provides.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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Originally Posted by Allan G
The spacers you have packing the silencer bracket between the frame, believe it or not actually go on the other end, so you have that fugly long stud/rest holder and then the spacer, then the frame and then the silencer bracket. Some pattern ones are also longer so incorporate the extra distance the spacer provides.
I was wondering about this myself. Started thinking "have I been putting it on the wrong side the entire time?"

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Hope Gary doesn’t kind me sharing this:

Originally Posted by Gary E
[Linked Image from i98.photobucket.com]


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)

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I've moved the spacer outboard. That bought me a bit more clearance between silencer and frame.

I'm curious about the header pipe to head connection. Initially I tried to fit it dry, I worked the pipes in but it was a struggle. This time around I lubricated the head with a dab of assembly lube. This allowed me to insert the header pipe more easily and verify that the pipe is bottoming out. A mechanic friend recommended using anti-seize for final assembly. He said copper, aluminum, doesn't really matter.

The collar appears to me nothing more than a heat sink, and possibly an indicator if the pipes creep out.

So other than the crossover pipe completing the triangle, what is keeping the header pipe in the head? Heat expansion? Is there a risk of blow by?

What about exhaust systems with no crossover, what keeps those headers in the head?

Thanks

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For about 67/68 the pipes had a tie bar fitted, this was technically a better way of keeping the pipes together in the head, prior to that there wasn’t anything. Had the pipes come out in parallel then even the tie bar wouldn’t do much.

The exhaust rose doesn’t do a great deal, and not all bikes had them fitted. When I had my silencer ceramic coated I removed them also.

As for exhaust goop, high temp sealer is fine for the job, ideally you want to swage the pipes with an expander so that they fit tightly into the head otherwise they rattle about and start hogging Out the port even more.


Now let’s all have a beer beerchug

68’ A65 Lightning “clubman”
71’ A65 823 Thunderbolt (undergoing restoration)
67’ D10 sportsman (undergoing restoration)
68’ D14 trials (undergoing transformation)


Moderated by  Allan G, Jon W. Whitley 

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