1970 Bonneville Amateur Rebuild - Triumph Forum: Triumph Rat Motorcycle Forums
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post #1 of 19 (permalink) Old 08-12-2019, 10:32 PM Thread Starter
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1970 Bonneville Amateur Rebuild

Let me say I should have started a rebuild post a while ago, because I have come a long way, thanks in large measure to other posters. I hesitated in part because my level of mechanical competence is far below most in this section. But I can't be alone in this, I have learned a couple things and I still have questions and a way to go, so here goes. I will spend a couple posts doing catch up, trying not to repeat earlier posts.

As background, I spent quite a lot of my youth working on old cars with my father who always had a project on the go. That largely ended 37 years ago with university, then a busy professional career, family obligations, the usual thing. My cars changed from things like a quirky 1968 VW or a restored Mercury Cougar to a reliable Toyota Tercel, and eventually newer cars that just went to the dealer for servicing once a year. I had a Kawasaki 400 back then, but gave up motorcycling too until the kids graduated about 7 years ago. All of which is to say, I am at best a poor mechanic and surprised when things go well.

This spring I convinced my brother in law to fly to Los Angeles, rent motorcycles, and take the coastal highway to Carmel where the Quail motorcycle show was happening. Fantastic ride and amazing show, worth googling. Everything from new electrics to maybe a dozen Brough Superiors. Definitely a bucket list ride. I caught a bug there.

About 2-3 months ago, I found it, the bike I wanted to restore. A 1970 T120R Bonneville, partly disassembled and not running for 20 plus years. I trusted the owner, took a risk, bought it and had it shipped. It was exactly as described, mostly complete and original. Picture below.

My goal is not to have a bike for show, but a fun bike to ride around the city that is mechanically reliable. I have a trouble free 2014 BMW R1200, which I love on the highway, but I find a little much to pull out of the garage for city trips.

First thing, I had to change the handlebars, then get it running. I followed the many excellent replies to my inquiry on this site. Changed oils, gators, plugs, gas lines, lubed cables, checked compression, cleaned carbs and gas tank, set points, new battery, cleaned everything, etc. And it ran, not well, but it ran.

So I doubled down and bought more things, like new Amal carbs, tires, some cables, some rubber pieces and so on. A few comments on this. If you are buying new carbs, make sure they jet them to your location. My city is 3800 feet above sea level, and I suspected it was running rich, though I also (it turns out correctly) thought I might have bigger problems. Tires are something you can do yourself, but it is a real bear to do, and I would not do it again with 25 year old tires.

I have so far used 5-6 parts suppliers, all North American. On this subject, you get what you pay for is lesson 1. It is in my very limited experience not worth buying something cheap if an original British or well made American component is available. Second, the parts on the bike are generally better made than replacements. Lesson 3 is that many people talk like they know what you are asking for, then send you the wrong thing. You do need to quote the part number and ask a few questions to avoid the tedious task of sending stuff back. By the way, I have finally found a great supplier.

I will end this post by saying that after all this, I insured the bike and took it out for a good 20-30 km ride. It shifted badly but all the gears worked. This turned out to be in part due to the casings on the second set of throttle cables I bought being too long - I had a bike shop shorten them. The bike pulled really well and I had it up to 60 mph. Lights all worked. Speedo and tach worked but the speedo needle bounced around. Brakes worked but were not acceptably easy. By the time I got back it leaked oil from just about every gasket or plug, except the bottom casings. Second picture below, where you can see I have new, but incorrect, gators and I am still working on getting that front fender to align correctly. Could the rear stay be too long?
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post #2 of 19 (permalink) Old 08-13-2019, 12:17 AM Thread Starter
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The cop out or the wise decision?

I want to get this introductory thread caught up, because I do have some questions. Now we are about three weeks ago, and I have an attractive but leaky mechanically unsound motorcycle. I have the Haynes manual, the 1970 Triumph shop manual, parts book, and have watched most of Low Brow Customs Triumph 650 rebuild on youtube, some sections a couple times. I have also searched the net for help and done a couple more posts on this site. Remember that I am someone that, beyond seasonally changing tires on vehicles and oil changes on a motorcycle, really has not done a lot of mechanical work for over 30 years.

First, I decide all the remaining cables have to be replaced, and all the rubber. So I comb through parts books and order those items. Also, I need the right washers for all drain plugs. Order those too. I buy a cheap motorcycle lift. Ordering motorcycle parts must be a kind of disorder, since I also order too many other parts to mention. Gasket sets, oil sending unit (wrong one comes first time), cable for choke (which I was going to do away with but in a fit of nostalgia decided to keep), etc.

Bike lift works great and allows me to see many things I was missing. One was that the washer on the sump drain plug could be spun, even if the plug was tight. Pic below. That turned out to be a problem with the plug, not the casing, so I order one of those, but not before panicking and posting on this site.

Definitely, the whole top end has to come apart because every gasket and o ring is leaking. I get ready to pull the rocker boxes off, and wonder whether I will ever be able to get the valves set correctly again if I loosen them. So I leave it for a couple days. Eventually I man up and take the top end apart. Pics below.

It all comes apart fairly easily. No stripped or stuck bolts or nuts. But it is obvious even to me that this engine needs work. I really do not know how to assess how much work, or whether the bottom end needs to be done. I took the pistons off, but unfortunately did not take a picture of the bushings, not knowing that would be important.

So I need some help. I look for a machinist or mechanic, call a couple and go visit a couple vintage shops. I basically get bad vibes. A couple places are filthy, one guy condescending, etc. I finally find the name of an obscure machinist in a vintage motorcycle organization website. No internet presence except a road number in a small town, a phone number and one review from someone with a combination of letters and numbers as a handle. In my world, kind of spooky.

I call him, the conversation is short, but he asks me to bring it down, and if I can bring the engine too as it might help him. At this point, I am still thinking I may do this myself, but at least I should meet him. I load it all up in my truck and get a little lost in the country. I ask a farmer and he tells me go back a mile up the road. I finally find a place which is a weathered garage with an 8 by 12 inch sign and a couple of old Harleys out front. Well, I am here anyway.

I knock on the door, kind of hoping nobody is there. The door opens and it is motorcycle heaven. A complete machine shop with dyno, impeccably clean, several fully restored bikes including an old Ducati. The work looks not just good, but perfect. He basically anticipates what I am looking to do, not in the sense of selling me, but more like seeing if we see things the same way. He tells me that he has been operating for 28 years by word of mouth and that gives him as much work as he wants.

Anyway, back to the bike. Rocker boxes look great and original. Two rocker arms are a little bent. Valves will need to be cleaned and checked. Cylinders are scored so need to be redone. He was very troubled by the piston bushings, which were partially discoloured and look a little like the side of the pistons, and were an indication to him that I probably also had main bearing issues. The long story short, I left it with him and he will tear it down to give me a quote. What a relief.

So assuming the quote is reasonable, this may be a disappointment to those of you that know engines. The mechanic/machinist did give me a fairly long list of things I should do to make it mechanically sound so that is probably what the remainder of this build is going to be about: brakes, wheel bearings, front fork rebuild, rear shocks, electrical, get the fenders right, maybe EI. All things I hope are within my sphere of expertise, with a little help from those here.

Picture of the bike below.
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post #3 of 19 (permalink) Old 08-13-2019, 09:31 AM
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Very nice project, and nicely "back-filled" as far as your early trials with it.

You didn't do the "wrong" thing by taking it to a pro (a REAL one). If he's okay with it, you should try to visit him once in a while, while he is actually working on the engine or inspecting the internals.

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post #4 of 19 (permalink) Old 08-13-2019, 11:48 PM Thread Starter
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Thanks, he actually suggested I go out at certain stages if I can. Let's see what it is going to cost. Not fully committed yet, but in spite of spending many hours on the internet and with books, there are still pretty significant gaps, not too mention the absence of any of the specialty tools I would need. And some of the advice conflicts, or at least involves some judgment.

When I took the gudgeon pins out of the pistons, I tapped them with with a long socket that fit and a small ball peen, like the guy on the Low Brow Customs video does it, with a caution to be careful. They came out fairly easily, but I did feel like I should not be hammering the rods sideways with a hammer. Turns out that is correct, and the mechanic had at hand the gadget to take them the rest of the way out of the pistons. Bottom line is I want this to be done right, and I have a lot of respect for the people that have spent years doing mechanics and know what they are doing.

Did a couple of small things today. Received new petcocks - the old ones were cheap replacements and one leaked - but I also need the outside washers as well as the rubber/metal inside ones, which I have. I will order those. Also cleaned 50 years of dirt off the underside. Installed new centre chrome strip as it was pretty cracked on one side and did not sit right. Replaced the gas cap gasket a while ago. Paint on tank appears to be original and looks pretty good, so when I get the washers I will wax the tank and that is done.

Of course, the new petcocks have a thread to attach the fuel lines, rather than just a pipe the lines were pushed over and clamped, so I will add new fuel lines to the next parts order.
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post #5 of 19 (permalink) Old 08-14-2019, 08:26 AM
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Wax is your friend.

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post #6 of 19 (permalink) Old 08-17-2019, 01:00 PM Thread Starter
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When does patina become disrepair?

I am going to check and renew basically everything mechanical on this bike. The engine will be professionally done, but I also intend to do all bearings, brakes, shocks, forks and I have already bought new carburetors, tires and most of the rubber bits. I intend to ride the bike regularly. I do not intend to show it and probably will not sell it for at least a decade.

I read on this forum and elsewhere that it is best to keep a bike as original as possible. "Patina"is desirable and even manufactured by some. I am undecided and on a slippery slope here. I will leave the tank as is, though I did have to replace the ($70!) centre chrome strip, the petcocks and rubber mounts. The incremental cost of going to near showroom condition at this point is not going to be that great.

I guess to me, moving parts and broken things are not patina. They need to be work right or be replaced. I am okay with a few nicks in chrome. It is the rest I am unsure about.

So here are the questions.

There is some rust on various parts of the frame. Powder coat the whole thing, spot paint or do something else to preserve the patina?

What about smaller items like the kickstand, zener, side panel tool box or battery holder, which have similar small issues? Paint? Professionally or just with a can of primer and gloss paint?

Nuts and Bolts: A number of the bolts are pretty rusty. Should I replace them? Use stainless? If not, is there a way to stop them from continuing to rust?

Wiring: I am assuming it is 50 years old and the cloth cover is oil soaked in places. But it works. Replace?

Spokes: They are fine, but obviously not showroom.

Rear Fender: Cracked, but otherwise ok.

I realize this is to some degree personal preference, but would appreciate comments.
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post #7 of 19 (permalink) Old 08-17-2019, 02:14 PM
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Had the same problem with my bikes in the past and decided to powder coat frame, front end and all brackets, battery box and stands to have a solid, not rusting base to attach all the rest.
Unfortunately later I decided I don't like shabby looking wheels, so rebuilt those.
Now only unrestored parts on my Trident are tank and side covers
I didn't have a problem with bolts and nuts, because most of last 40 years my bike spent in different garages not being used, so they were mostly passable.
Original loom was in great condition so after checking up of all wires and connections I decided to use it and later modified it for 3 phase alternator + reg/rec. and Trispark ignition.
The bike is a rider so it's only close to original with different front master, clutch perch and handlebar switches. This way is easier to operate with more effective front brake, better lights and no electrical gremlins for relatively modest money output comparing to full resto or heavily modified bikes.

Being in your shoes I'd do the same, painting or powder coating frame and front end + brackets and stands and rebuilding wheels ( which is not an easy job ).
I'd also exchange / repair the worst looking bolts and nuts, check an electric loom, installed an oil filter for the engine ( very important ) and upgrade charging system to 3 phase alternator giving you peace of mind in the lights department.
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post #8 of 19 (permalink) Old 08-18-2019, 09:54 AM
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Don't look too long or too closely at my old 1970 Bonnie (since replaced with a very nice restored one).

If you just look at it casually, it's pretty acceptable. If you look at it critically, as though you were trying to decide on whether to refurbish or restore, you'd have MANY decisions to make.

Try not to overthink it, do what YOU want to do for the final product, and ENJOY IT!
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For what it's worth, this was a first-kick bike, idled great, highway speeds without a fuss, felt totally solid and reliable. When I had TR6C scrambler pipes on it, I took it off-road on cow trails and jumped the odd small hill, climbed the dam at the lake spinning the almost-bald rear tire all the way up. It was a fun bike.
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post #9 of 19 (permalink) Old 08-24-2019, 12:39 AM Thread Starter
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Very good advice GandPaulz, and I think I now know what I want. I am going to do a complete restoration, using as many original or OEM parts as possible. Have it down to the frame now. Will get the fasteners CAD plated next week. That made more sense to me than going part stainless. I am going to powder coat the frame, and renew the paint on everything except the gas tank, which will be my "patina". Something like Adam M.

Ordered bearings today and a few other things including Pazon EI and a Podtronics regulator, and new coils. Also decided to order the wiring harness, because while the one I have works, it is 50 years old and there a couple places where I think I could have problems. Cannot find a rear fender, so I am looking for a stainless steel welder. The crack is under the license plate so great if he can make it look good, but the main issue is stopping the crack from growing.

My biggest worry right now is sorting all those fasteners when they get back. But I am taking lots of pictures. Appreciate the comments.

Anyone have a recommendation for shocks? I would like them to fit with the bike, but probably better than the OEM ones.
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post #10 of 19 (permalink) Old 08-24-2019, 03:05 AM
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Look for a professional auto restoration shop that are experienced with metal finishing. They should be able to weld and finish your rear fender so that it is barely visible. On the other hand someone more used to welding steel girders could quickly destroy the fender and leave it unusable.

Paint is the same as everything else, it serves a purpose. Once it no longer serves that purpose it requires replacing. A well preserved factory paint job is well worth saving but knackered paint is not patina, it's knackered.

There was a thread recently in the general forum about rear shocks, worth searching out and reading.

Rod
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