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1970 Bonneville T120R

6K views 31 replies 7 participants last post by  GrandPaulZ 
#1 ·
Recently got a 1970 T120R Bonneville. It's been sitting for 40 years. Mostly there. Rusty and dirty. Owner thought engine was seized but it isn't. Clutch is stuck though.
Got it running briefly.
Plan to make it a rider, Rebuilding carbs. Replacing plugs, points and plug wires.

It needs a few things to make it right. Chain guard, rear frame and grab rail are needed if anyone has parts to sell.

I also got a numbers matching titled frame and engine. Engine turns over. Rear frame has had the battery box mounts removed though.

Should be enough to keep me busy for a while.
 

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#4 ·
That looks a lot like mine did three months ago, though yours has had some customization somewhere along the way. Definitely a bike that can be put back together right and it looks to be mostly complete. I am confused a little by the pictures because there are some pieces I do not recognize, and some items in a different place, and I am not sure what is under your carbs, or whether those carbs are the same as mine were.

New Amal carbs are not that expensive and I think worth it. Not only are the old ones likely worn out, the new ones are improved in a number of ways, most significantly, they deal with the fact we now have alcohol in gasoline. Make sure you get them jetted for your altitude if you buy them.

My best luck in consistently getting the correct and good quality parts has been Waldridge. Among many other items, I bought a new chain guard from them and I am deciding with my painter/powder coater whether to keep it or fix the old one, so I will let you know about that. A new unpainted chain guard is $187 Can (about $150 US). This stuff adds up.

BTW I have tried a half dozen other suppliers too, and some have better prices on specific items like specialty tools and next day delivery, but you do have to specify the exact part number and if they have a cheap part and a more expensive item available, trust me, you do not want the cheap one. It may be that my recommendation is best for someone who does not have a lot of experience, like me, and it appears you do.

Looks like a great project. I am looking forward to seeing your progress.
 
#6 ·
Carbs are cleaned and back on. I've attached pictures. Air cleaners are modified to take a 1 inch wide filter. The filter element foam was deteriorated so all that's left is the screen. Screen measures 1 inch wide by 3 1/2 inch diameter. Anybody have a recommendation as to a filter element that will fit or a replacement filter that will clear the oil tank and side cover?
 

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#8 ·
Thanks GrandpaulZ.
I'm going to leave the oil filter on. I tried looking at EMGO for a suitable air filter element but didn't find anything. I think I will have to cut one down.
I have a grab rail coming from Vintage Triumph Supply. They also had the other major parts I wanted used at reasonable prices.
 
#9 ·
Hi Mike,

needs a few things to make it right.
rear frame
'68 and '69 650 are the same as '70; T160, T150 and '68-'74 350/500 are basically the same but some brackets are different.

grab rail
Black-'n'-chrome were peculiar to '70, but not all of 'em, some were all-chrome. Any '73-'75 'dry frame' has the same 7/16" ID gusset holes as '70, '71/'72 'dry frame' is basically the same but has small-ID gusset holes (for reflectors).

Air cleaners
Screen measures 1 inch wide by 3 1/2 inch diameter.
recommendation as to a filter element that will fit or a replacement filter that will clear the oil tank and side cover?
Try K&N SEARCH BY DIMENSION. Not sure if they still do the element that fitted inside the Triumph chrome bands and end plates but the Amal-replacement Mikuni kits include a "Universal" filter and, as you'll see, there are also ones with offset and cranked outlets.

Hth.

Regards,
 
#13 ·
Wheels are off and bearings removed. New parts on order. Rear wheel cleaning up nicely.

Going to use UNI foam on mesh from air cleaners until I find a better solution.

Plan on cleaning, treating rust and painting as needed without completely stripping down to frame. I'm going to keep steel fenders as they are, dents and all.

Rear frame loop was bent down. I got it to go back to original angle pretty easily. Method suggested by a friend.

Took off sissy bar. Proper grab rail coming.

Check out the chain guard that came off. Appears to be brass. Heavy! Note where chain was rubbing. Proper guard on the way.
 

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#16 ·
Disassembled my forks today. Didn't need any special tools to get them apart. Fork tubes have rusty areas. Some where seal slides. There's one lower bearing with some damage on the OD. Restrictors have some light rust. One of the "bottom members" has some scoring on the lower ID.

My plan is to keep the bottom members and maybe hone the ID on them, without removing too much metal. I'm going to scrap the fork tubes and get new ones. I'm trying to decide whether to replace all the bearings or just the bad one.

The fork seals will be replaced. I'm seeing ones with a metal case being sold as replacements. Mine don't have that. Will the metal case ones fit? Any recommendations?

Any recommendations on using reproduction fork tubes?

I'm attaching some pictures.
 

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#19 ·
Thanks GrandPaulZ. I'll check the weight of the chainguard and see how much shipping would be.

Do you think my fork leg is shot? I'm not finding these for sale anywhere. I'm probably looking at replacing both fork assemblies. Got any suggestions?

Mike
 
#21 ·
Hi Mike,

Do you think my fork leg is shot?
No. Pretty-much every part (with the possible exception of the sliders?) is available brand-new. Problem is they're pattern parts, you'll be wise to do your own quality-control measurements from the workshop manual before you start assembling.

I'm not finding these for sale anywhere.
Depends how you're searching: you're unlikely to find "FORK ASSEMBLY" (complete with yokes), search with individual part numbers in the '73-on format - e.g. "triumph 97-3904" for stanchions.

Google says Baxter has the sliders (97-3921 and 97-3922) for $230 each ... dunno if they're new though ...

Certainly here in GB, those stanchions could be straightened, rechromed and ground back to size. 'Apparently' more-expensive than new stanchions but if whatever "new" kicking around the dealers is under- or over-size (regularly :bluduh) reclaiming originals might be less time-consuming - and would be less-expensive - than trying to make "new" work ... :cool:

Also be aware a new pattern stanchion might require a new top "Cap nut" - between '70 and '71, Triumph changed the thread from 26 tpi to 28 tpi; although '70 and '71 conical-hub stanchions aren't interchangeable, last pattern pre-'71 stanchions I had dealings with had 28 tpi threads ... :Not again

Hth.

Regards,
 
#22 ·
"Certainly here in GB, those stanchions could be straightened, rechromed and ground back to size."

I got a quote from EC Grinding in California of $224 per stanchion. I'm going to buy new. Thanks for the info, I know now what I need to be asking when ordering new stanchions and bearings.
 
#24 ·
I'll PM you when I scrape up some play money, thanx.

OK, I'll hang on to it for a while.

You should be okay to re-use the fork leg, you might want to tape some foam to a long drill bit, and wrap the foam with emory cloth; zip it up and down for just a few seconds in a drill, and only near the bottom 3 inches or so.
I have a 240 grit ball hone coming. I might try your method first though. Thanks.
 
#26 ·
I used a 240 grit ball hone just enough to break the glaze on the inside of the fork legs. Did it using 10W fork oil. Did not remove all the longitudinal lines. I like the way they came out. I doubt that I removed a measurable amount of metal. We'll see I guess.
 

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#29 ·
Got the front end back on. Haven't made a lot of progress but took off the rear frame and swingarm. Cleaned all the parts removed. Next is cleaning the back of the main frame and the engine. Then will be painting frame and associated parts. Slow going now. Other projects (67 TR6C) and bikes to ride.
 
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