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#888956 08/21/22 4:38 pm
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Hello all -

I am not much of a social media fellow, but at the encouragement of GrandPaul I am starting this thread. If he can share his wisdom (thanks), I can share this project story. I've owned dozens of bikes over the years, and have been downsizing a 40 year (mostly German) collection. However, when a friend tipped me off to this bike, well, here I go again...

1976 T140V, not on the road in 20 years. Just came home with me on Thursday. 9,800 miles on it and matching numbers.

Put a new battery in it yesterday. Lights/horn all work. Good compression (did not yet put a gauge on it - the gauge is up in the garage next to my 4 wheeled Triumph TR6, also a '76). No spark either side. Boyer Mk III ignition. Carbs are missing, although Mikuni slides and tops are attached. Intake adapters well polished into the head. Will call M.A.P. in the morning. $$ I'm sure.

Someone more clever than me might be able to post pictures, but it is above my pay grade. I'm handy with a spanner, but less so with the interweb. smile

Updates as warranted.

Cheers,
Joel

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Hello again -

So, I subscribed and have attempted to post a couple of pictures. Here's hoping I did things correctly.

Bonneville 1.jpg Bonneville 2.jpg Bonneville 3.jpg
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Great pictures.

You've done it just right! Keep 'em coming ....

Lannis


Patriotism is supporting your country all of the time and your government when it deserves it.
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After an email exchange with Marino at M.A.P. (very helpful) I have two new 32mm Mikuni carbs on the way. Now to chase down that pesky spark issue...

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And I've no recollection of setting up the Steve McQueen avatar! The King of Cool and a great movie - I guess I'll leave it for now.

As an aside, I was a member here years ago when I had a G80 in a Sonicweld flattrack frame. Oh, the bikes I wish I'd kept!

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No joy from the old Boyer unit, so new Tri-Spark and coil, ordering today. This old girl needs to bark again, and soon!

Ironically, and something that often happens, today I came across a very clean old pair of Mikunis amongst my BMW stock. I knew I had a pair years ago but wasn't sure where. ID measured about 37.5mm, so too big anyhow. Will likely post them on buy/sell board soon.

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[Linked Image][Linked Image]

Looks like Christmas in September! Looking forward to a bit of time in the shop this weekend.

parts 1.jpg parts 2.jpg
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Really interested about your experience with these carbs. I'd rather use Amals.

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Left to my own devices, I would have put amals back on the bike. As it came with no carbs and the splayed head had been ported and polished, Marino at M.A.P recommended the Mikuni‘s. I tend to be a stock configuration devotee. Worst case is I buy a replacement head and carburetors. I will post my progress.

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DOPE
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your picture up there of the intake manifold adapter on the head-- i cant re-post a forum-hosted image- what you have is unusual.

are the new stud centers 60mm?

what is the diameter of the hole in the adapter? in the port where the adapter meets it? judging by the cuts in the allens, it looks like the adapter was mounted and then substantially enlarged togther with the port.

also, on the MAP Mikuni kit, what is the width of the exposed fabric element between the rubber mount and the chromium cap?

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Originally Posted by kevin
your picture up there of the intake manifold adapter on the head-- i cant re-post a forum-hosted image- what you have is unusual.

are the new stud centers 60mm?

what is the diameter of the hole in the adapter? in the port where the adapter meets it? judging by the cuts in the allens, it looks like the adapter was mounted and then substantially enlarged togther with the port.

also, on the MAP mikuni kit, what is the width of the exposed fabric element between the rubber mount and the chromium cap?
[Linked Image]

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thank you quinten

im curious because rubber Mikuni spigots are common with 60mm or larger bolt centers. they also make a rubber spigot with 50mm centers, but its super uncommon out in the real world, for some reason. sudco sells them i think, and it looks like the MAP mikunikit intbe picture above uses them.

this adapter apoears to have been made to mount a 60mm spigot onto the AMAL 2-inch (+/- 50mm) bolt centers. somewhat more work rather than just making up 2-inch spigots, but there they are. you can see that the passage through the adapter uses up almost all the room be9tween the allen screws. thats an issue with mikunis larger than about 34mm, because there isnt much room for the bigger hole. im wonderi g what size those Mikuni carbs were that are missing-- the ports may have been significantly enlarged.

im wondering what jets marino puts in his carb kits too

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Well spotted Kevin. I work in health care where the mantra is "you don't want to be an interesting case". Lucky me, the Triumph is an interesting case. Distance between new studs 60mm, opening 38.5mm. The slides that were on the bike measure approx. 35.3mm.

I discussed via email with Marino and he thought larger than 32mm would not be well utilized so I bought 32s. The rubber adapters did not come with the kit but Marino offered to switch out for a minor upcharge. I chose to buy separately so I would have more options at hand on the bench.

The filters are narrow - I have not measured but can and will.

Carbs bolted right up with rubber adapters.

Once I sorted out the nasty wiring job on the Boyer III from the previous owner, the Tri-Spark install was straightforward. Given the wiring mess, it is amazing that there is not a single rounded over nut or bolt head anywhere to be seen.

Of note, the Boyer rotor was no fun to remove. Running in the stud to pop the rotor did not pop. Soundly tapping the stud did not pop. Spot welding a copper body work pin and using a slide hammer did not pop. One trip to HF later ( I prefer better tools, but HF my only weekend option) and 20 minutes of grinding resulted in a fork with two fingers that fit behind the head of the stud and attached to slide hammer. Two pulls and rotor popped.

All back together, the bike coughed on the second kick and started on the third. Smoked quite a bit on the left, but cleared up considerably with more run time. Rode it up and back getting only to 3rd gear - no brakes yet. Pulls strong and smooth. Time to fix the brakes, fit new tires and go for a ride.[Linked Image]

measurments 2.jpg slides 1.jpg
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that slide diameter indicates that youre in good shape with a 32mm carb. the middle group 2 of the Mikuni body castings used a nominal 35.5mm slide to fit into 30, 32, and 34mm carb bodies. so the biggest carb that could have been on there was a 34. if your slides had been larger than that, it would have meant they came from group 3, which are 35 and 36mm venturis, and that might mean that your ports had been hogged out excessively.

that 38mm adapter diameter is pretty large, still.

i have found that 32mm mikunis work very well on unmodified triumph ports. theyre efficient, and so they can carburate even an oversize venturi. certainly the 34s i have on my morgo 750 T120 work just fine at any speed.

look for any low rpm issues, like a need to set the idle very high to keep from stalling, or gasping when starting out from a stop. once youre up to midrange, it should work just fine. did you write down what needles and jets marino put in those 32s? its been 45 years since i put 32s on my machine, and i cant remember what i started at.

by the way, im sure youve noticed that mikunis with pancake filters wont accommodate stock side covers. if you dont like the homemade ones you have, you can fit repro covers that bolt to the airbox mounts that look just like the old dry frame side covers. else there are covers from japanese motorcycles that fit well if you make up mounts.

why was this good-looking machine parked for so long?

Last edited by kevin; 09/07/22 8:10 pm.
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No idea why it was parked. I bought the bike less than a month ago from a fellow who got the bike through an estate.

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Fast forward to yesterday. I bolted on my shiny new Vermont plate, donned a helmet and gloves, started up and it died after 5-10 seconds. Now no spark. Ran first step on Tri-Spark diagnostics, no spark, no red test light. The recommissioning saga continues...

Last edited by Mountain that speaks; 09/22/22 12:54 pm. Reason: Duplicate messaging
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Probably a wire loosened up. Should be a quick fix. And, will give you a spot to watch in the future.


"Love 'em all.... Let GOD sort 'em out!"
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It is alive! Had a bad $120 brand new sealed battery. Ugg. Thanks again for the consult Marino at M.A.P.! Now to rebuild the master cylinders, calipers and likely replace rotors and pads as well. I'll flop on a new pair of Avon Roadriders, clean and repack the bearings while the wheels are off. More to come.

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So, I exchanged the old (new) battery for another new sealed one. Manufactured April 2022. Put it in the bike, put on trickle charge (battery tender) for one week. Charger cycled on and off through the week. Started the bike for the first time on Sunday - motor raced higher than before and died when I immediately turned off choke. That happened one more time. Then, no spark. Again. Ignition diagnostics = no spark, no red light. So I charged ~2 hours on 6 amp charger setting, no change. Just put on 2 amp charger setting this morning, will leave on for several hours.

Wondering if something is draining the battery at rest?? Any thoughts?

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Are you measuring the battery voltage?


"Love 'em all.... Let GOD sort 'em out!"
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Yes. 12.55 vdc yesterday at time of no spark, charged yesterday and this morning reading 13.01 vdc.

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Coil breaking down?

At least you know it RUNS, with no ugly noises.

In a case like this, work with only one new item at a time, till you cure it.

Last edited by GrandPaul; 10/04/22 5:28 pm.

GrandPaul (does not use emoticons)
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Too many bikes to list, mostly Triumph & Norton, a BSA, & some Japanese
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I agree on the one piece at a time approach. I bought and installed two new 6v coils from MAP at Marino's suggestion. Wired in series. I don't mind replacing some of these vintage electrics as I am looking for reasonable reliability. And yes, VERY happy it runs well when it runs! Thanks.

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Now running more reliably. Faulty kill switch. Bypassed in the headlight bucket and "Bob's your uncle". smile Great support from Steve at Trispark and Marino at M.A.P. - thanks.

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Good to hear. Hillbilly Biker and I are on the east side- Walworth and Marion. I just rebuilt my '76 Triumph. Waiting for a a Wasp frame.

750 rebuilt .jpg
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