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1970 Triumph Bonneville T120
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Discussion Starter · #1 ·
Hi again Vintage folks.

I'm experiencing exhaust leaks where the center pipe meets the header pipes. At first, it was just on the right side, so I loosened the clamps and nudged the center pipe to the right. Now, I've got a small leak on the left and the right is only slightly better.

Is there a trick to getting the cross pipe to seal?

741326
 

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you can use a high temperature sealant .

is the leak causing a problem?
 

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I used black Everbuild Heatmate silicon sealant on all of the joints when I replaced the exhaust system during the summer. The slots cut into aftermarket cross pipes are too long in my opinion (or the pipe’s too short) and it can be tricky making sure that no exhaust gasses escape. Get one side right and the other side leaks etc etc. Applying the sealant and making sure the clamps cover the end of the slots, as you’ve done, worked for me. I haven’t taken it apart since fitted but apparently the sealant is easy to remove, it remains flexible.

Chris
 

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Hi 2fdots, Permatex ultra copper silicone sealant is what I like. It seals good, takes this heat fine.

What I find is mark crossover with both felt pin & masking tape so you know where centering will be. Not marked it's hard to tell where crossover actually is left/right ways.

Remove complete exhaust system. Grease threads of all the clamp bolts so they tighten smoothly on assembly.

Clean pipes at all connections so sealant will stick. Smear sealant on head exhaust stubs, inside of main pipes, as well as outside of crossover & inside of crossover of main pipes. Assemble pipes on each side simultaneously with cross over. More or less fill the slots in pipes. Try to work quickly. Align the side pipes, mufflers, Wipe squish out quickly before it sets or is very hard to remove.

Putting masking tape on head area around stubs tends to keep sealant off fins. Also good plan to mask the chrome around the upper pipe area to save cleaning & reduce scratching chrome.

You may consider looking very closely as to how pipes are now. You can remove mufflers or not. Sometimes if exhaust is lined up well now, you can use muffler brackets to aid in alignment. You can use the front stays that are attached to motor case studs as alignment guides as well, so long as all fits good now.

This is one of my most hated jobs. Getting it all cleaned, sealed, lined up can be a real fight. The exact tolerance of the bend of pipes is a huge factor. Some just line up. Most do not. When side pipes are perfect it puts crossover in bind & not fitting tight. Greasing the clamp bolts really helps them to tighten properly. Grease will soon burn off of course, with lots of smoke.

Even though it seals well. You can remove pipes later without a big fight. Then tape up visible chrome & use small wire brush to burnish off the old silicone.

Once you finally get it all lined up & clamps tight, squish out cleaned up, let it cure 24 hrs. I've had very good results with the Ultra Copper on exhaust. Sold at auto parts stores in USA everywhere.

Permatex® Ultra Copper® Maximum Temperature RTV Silicone Gasket Maker – Permatex
Don
 

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I also use the high temperature silicone on all exhaust joints. No leaks and comes apart easily later. I use the black version often sold as sealant for central heating boilers with a 300C rating. The exhaust gets much hotter but the sealant still takes the heat. Just wipe it around both surfaces with a finger then slot together and clamp it.
Cost here is about £6 for a very large tube that requires a builders sealant gun
 

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alternatively, do nothing.
 

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1970 Triumph Bonneville T120
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Discussion Starter · #7 ·
Thanks everyone for your opinions and recommendations. The reason I'm trying to seal everything up is that I'm getting some popping when I decelerate. I figure the exhaust leak is one culprit. I think the carbs could also be contributing because they aren't fully sealing to the header. I've placed an order for the thicker gaskets - hopefully that solves it.

Anyway, back to the exhaust. I think I'm going to go with Don's recommendation of using the Permatex. I already feel that reassembling the exhaust is enough of a circus trick, why not add an additional element of difficulty by playing beat the clock with the sealer's curing time, LOL!

I'll post again after I attempt the feat and let you all know how it went. :)
 

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The reason I'm trying to seal everything up is that I'm getting some popping when I decelerate. I figure the exhaust leak is one culprit. I think the carbs could also be contributing because they aren't fully sealing to the header. I've placed an order for the thicker gaskets - hopefully that solves it.

I doubt the popping on deceleration is caused by the small leak at the cross pipe.

As far as the carbs starting with the 1970 (and thru to 1978 T140V) T120/T120R the factory used what is usually called a Fat O-Ring (part #70-9711) to mount the carb to the intake manifold. When properly tightened there will be an air gap of 2 - 2 1/2 business cards. Be aware if you overtighten this set up you will distort the carb bodies. They are then suitable to be used as paper weights.

Regarding the thicker gasket not something I would use but its your machine do as you wish. If this new gasket is much thicker than three business cards I suspect you will have a problem tightening the carb down. Do Not Overtighten.

Again I doubt this will cure the popping.

K 😷
 

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Discussion Starter · #9 ·
Thanks for the advice K! The process of assembling the exhaust before the Permatex sets is intimidating. If I can avoid that, I certainly will.

The thicker carb gaskets that I was referring to are the fat o-rings (part #70-9711) that you mentioned. The Amal carb rebuild kits that I bought came with the thin ones and they are not fully sealing.

Another symptom I'm seeing is a lot of blueing around the y-junction in the right pipe where it meets the cross pipe.

In addition to the carb rebuilds, I've installed new air filters, and new Champion N3C plugs gapped at .025. I have also worked through the steps in Bushman's Carb Tuning Secrets.

Where else should I be looking for the cause of the popping?
 

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The thicker carb gaskets that I was referring to are the fat o-rings (part #70-9711) that you mentioned. The Amal carb rebuild kits that I bought came with the thin ones and they are not fully sealing.

Another symptom I'm seeing is a lot of blueing around the y-junction in the right pipe where it meets the cross pipe.

In addition to the carb rebuilds, I've installed new air filters, and new Champion N3C plugs gapped at .025. I have also worked through the steps in Bushman's Carb Tuning Secrets.

Where else should I be looking for the cause of the popping?
I like the N3C plugs just what was originally spec'd.

AMAL kits will not come with the 70-9711 O-Rings as that is a Triumph item not AMAL

Bluing of the pipes is normal its the amount you have to watch for. The worst ones I can think of was the T140E when they were new. Not uncommon 40 years ago to see the pipes blued halfway down the front section.

As far as the popping that generally indicates a rich condition. Can you determine if its on both sides or just one?

Could be a choke not releasing, loose main jet, etc. I would be suspicious of the side that is bluing.

Looks like you got hold of a nice machine. Turn signals fitted tell me a bit about the PO. How did he connect the front ones. You should really turn the horns so the bell mouth is facing down. I assume you have grey face gauges and your VIN is either a PD or XD between about 32000 but no greater than 38000.

K 😷
 

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In addition to the carb rebuilds, I've installed new air filters,
Which air filters did you get? the paper emgo ones can be hard to tune for. The ones with gauze and more of a cloth type material are usually better.

For popping first place is the carb joints. ()if fuel level is good, and jets etc.etc.)
 

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I have used the permatex silicone but a very small tube and nothing like as good as the full mastic size canister available for sealing boilers. The black heat resisting type does not even show when cured. It has about 1 hour of working time. You can put quite a lot of it inside the pipe without worrying about running out of the little permatex tube. The black tube contains about 20 times the amount of sealant and applied with a gun instead of having to squeeze a little tube. I found that permatex was ideal for the primary cover Triumph round cover as it had good gap filling ability. It will also useful for fitting the primary if you have no gasket available.
My money is on the very cost effective boiler product at around £6 from a builders merchant or plumbing centre.
 

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Discussion Starter · #13 ·
I like the N3C plugs just what was originally spec'd.

AMAL kits will not come with the 70-9711 O-Rings as that is a Triumph item not AMAL

Bluing of the pipes is normal its the amount you have to watch for. The worst ones I can think of was the T140E when they were new. Not uncommon 40 years ago to see the pipes blued halfway down the front section.

As far as the popping that generally indicates a rich condition. Can you determine if its on both sides or just one?

Could be a choke not releasing, loose main jet, etc. I would be suspicious of the side that is bluing.

Looks like you got hold of a nice machine. Turn signals fitted tell me a bit about the PO. How did he connect the front ones. You should really turn the horns so the bell mouth is facing down. I assume you have grey face gauges and your VIN is either a PD or XD between about 32000 but no greater than 38000.

K 😷
Thank you for the additional guidance. Based on what you said, I'll wait until I get the thicker o-rings on the carbs before committing to the exhaust stuff.

I think both carbs are running rich. When diagnosing the seals, I sprayed starting fluid on the connections between each carb and the head and the engine bogged.

I plan to redo the carb tuning after installing the thicker o-rings. Hopefully, I'll be able to get the air/fuel mix correct when they're sealing properly.

I am the one who installed the turn signals. That, and installing a kill switch were the conditions my wife required in order to let me ride it regularly. :) The signals are not connected at the moment. When I hooked them up, I could only get the left front to flash. I found that current was getting to the others, but there was not enough voltage to get them to light up. I plan to redo the wiring this winter in order to get them working properly. I have a left hand switch from a '71 bike, which has a turn signal switch, along with hi/low beam and horn. I am hoping that I can remove the choke lever from the right bar and replace it with the former dip switch from the left bar and wire that up as a kill switch.

The horns are another issue. They work great, but the mounting bolt has sheared off the right one. I came back from a short ride and it was just hanging by the wires. To make matters worse, as it flopped around, it scratched up the original paint on the front fender. For now, it's being held up with zip ties. I need to figure out a more permanent solution. It doesn't look like the horn mounting bolt is listed in the parts book...

Anyways, this bike has already been a really fun adventure. I'm learning so much and having a blast - it's like working on a puzzle that you can ride! :)

Thanks again for the advice! I'll post updates as I progress. (y)
 

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I have a left hand switch from a '71 bike, which has a turn signal switch, along with hi/low beam and horn.
Hi 2fdots. If this switch is the alloy casing type with two black buttons and a black lever I don't think you'll have turn signals and hi/low beam on the same switch casing. These two functions were on opposite sides of the handlebars. Turn signals will be a three position lever and hi/lo beam two positions.

Chris
 

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Discussion Starter · #15 ·
Hi 2fdots. If this switch is the alloy casing type with two black buttons and a black lever I don't think you'll have turn signals and hi/low beam on the same switch casing. These two functions were on opposite sides of the handlebars. Turn signals will be a three position lever and hi/lo beam two positions.

Chris
Thanks Chris. My switch has a 3-position switch for turn signals, a 2-position switch for high/low beam, and a button for the horn, which can also be pushed upwards to flash high-beams.
 

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I am the one who installed the turn signals. That, and installing a kill switch were the conditions my wife required in order to let me ride it regularly. :) The signals are not connected at the moment. When I hooked them up, I could only get the left front to flash. I found that current was getting to the others, but there was not enough voltage to get them to light up. I plan to redo the wiring this winter in order to get them working properly. I have a left hand switch from a '71 bike, which has a turn signal switch, along with hi/low beam and horn. I am hoping that I can remove the choke lever from the right bar and replace it with the former dip switch from the left bar and wire that up as a kill switch.

The horns are another issue. They work great, but the mounting bolt has sheared off the right one. I came back from a short ride and it was just hanging by the wires. To make matters worse, as it flopped around, it scratched up the original paint on the front fender. For now, it's being held up with zip ties. I need to figure out a more permanent solution. It doesn't look like the horn mounting bolt is listed in the parts book...
Gonna approach this backwards on the horns. Horn mounting bits are shown on page 78/79 of the parts books . As I am unsure as to the bolt you are mentioning best I can say. Are you missing the bolt that attached the horn to the bracket or one of the bolts that attach the horn with horn bracket to bracket (83-1254). One bit of bad news for you I don't think you have Triumph Clear Hooter on the T/S (timing side). I believe it is a Clear Hooter 2733 used English automobiles. Anyway when you get to that point additional pictures would be nice. The wiring on your horns are very nicely done.

Horn mounting on the early 70, as yours, was attractive but many left the machine to be lost on the road or hang on and damage the fender. When one of mine let loose I was lucky like yours it stayed with the machine but no scratches.
Since then I have advocated safety wiring of the horns. Also be aware the front brake cable has been known to wear the paint on the fenders edge.

Next your original Horn/Dipper switch (I assume part #31563) is not suitable as a kill switch if you wish to wire same as the factory did. In 1970 Triumph wired the ignition thru the kill switch on the TR6C model. On that model when the button is depressed it broke the connection and the ignition shut down. The switch you propose to use works in a reverse manner. If you are going to leave chokes on the machine I would get a handlebar switch But then none of my Triumphs have chokes installed.

The turn signal switch you describe sounds like a LUCA$ 30447 which was used from 1976-1978.up to a point. Would like to see a picture of the switch. As far as the turn signals not lighting/flashing could be a weak battery or a bad ground. What I do with my bikes is get two eyelet crimp connectors and a short bit of wire. One eyelet goes under the bulb holder screw and the other goes under the stalk to head retaining nut. One last thing the bulbs Triumph used in the flashers have a different wattage form say an 1156. That also can cause a problem as the flasher unit that is used.

K 😷
 

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Hi again Vintage folks.

I'm experiencing exhaust leaks where the center pipe meets the header pipes. At first, it was just on the right side, so I loosened the clamps and nudged the center pipe to the right. Now, I've got a small leak on the left and the right is only slightly better.

Is there a trick to getting the cross pipe to seal?

View attachment 741326
I have push in pipes on my T140. I've used clear silicone to stop the exhaust from coming out. (Really annoying at stop lights). It works for a while.
 

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Discussion Starter · #18 ·
Hi everyone. The thick o-rings finally came. Installing them corrected the popping on deceleration, so I'm going to leave the exhaust pipes alone. Thanks again for all the great advice!

I was hoping that the wider space between the carbs and the manifold would also correct the high idle after the bike warms up, but no such luck.

The throttle slides move easily when the bike is cold. I have only tightened the mounting bolts for the carbs tight enough to make a seal, so I don't think I'm distorting the carb bodies.

What do you think could be causing the high idle when the bike is warm? Could the throttle springs be worn out? I haven't pulled the fuel petcocks off to inspect the filters. Could a dirty fuel filter reduce the flow enough to cause the bowls to fill too slowly? Other thoughts?
 

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I suspect your idle speed is set to high. Are you using the chokes when you start the machine?

On my machines I have deleted the chokes. Cold they will not idle and you have to "Blip" the throttle for the first few minutes. After the engine warms up it idles fine. You need to set the carbs and idle speed after the engine has warmed up

K 😷
 

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Discussion Starter · #20 ·
I suspect your idle speed is set to high. Are you using the chokes when you start the machine?

On my machines I have deleted the chokes. Cold they will not idle and you have to "Blip" the throttle for the first few minutes. After the engine warms up it idles fine. You need to set the carbs and idle speed after the engine has warmed up

K 😷
No choke on my machine either. The choke switch is still on the handlebar, but it's not hooked up to anything.

Maybe I haven't warmed it up enough before setting the idle speed. I'll go on a nice, long ride and try again. Always good to have an excuse to ride! :)
 
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