Dunstall Replicas - 1971 OIF T120R

[Bloodknot]

BTW, there's more general stuff on the other thread dedicated to restoring and modifying this bike (same forum). But to answer your question, the way I bent up the side covers didn't contemplate containing the air cleaners--though it could have. They're just external and kind of boring as seen below. I was looking for a lighter, simpler departure from the OEM cast airbox--though, as I type these words, I realize that I could make a nifty CNC-machined, 6061 clamshell one-piece unit that would take a K&N panel or oval filter. Hmmm...

Since this is an OIF model, and the covers arc more or less straight back from bosses welded to the backbone/oil tank--and because I kept their height modest for aesthetic considerations--there isn't a ton of room in there. I'm running a Boyer Bransden ignition (came on the bike), but a 3-phase alternator managed by a vintage Honda rectifier that hangs aft of the battery from an aluminum L bracket bolted to the underside of the OEM twin coil mount.

The ignition switch position and heavier gauge leads, a la stock (2nd pic), takes up the scant room under the tool tray--which I'll probably duplicate in aluminum left over from the covers (not yet polished and striped here).

Many thanks for this information. My thoughts are to do it in 2mm stainless steel and the right hand side will be a replacement oil tank and canister oil filter arrangement with the left hand side being toolbox/battery compartment.

 

[grandpaul]

Well, where could one get a copy? Though it's way off topic, my first novel, "Lion at the Door," is on Scamazon. It's about a former POW and FBI profiler who's put in charge of the first Homeland Security office in NYC in the wake of 9/11.

Old Bikes is $15 + postage (under $5 in the U.S.) for paperback copy, $10 digital (.PDF)

paypal to grandpaulz athot mai ldotc com

 

[NM Bonny]

Many thanks for this information. My thoughts are to do it in 2mm stainless steel and the right hand side will be a replacement oil tank and canister oil filter arrangement with the left hand side being toolbox/battery compartment.

Wow... I would really like to see this when the work is underway. Very cool. I should've been more creative with mine--could've used a two-in-one coil like I run on the '51 FL, and that would've had created more room. But for some reason I defaulted to the OEM dual coil mount. Still, it'll look cool when polished and painted and the side covers are light as heck.

 

[NM Bonny]

Old Bikes is $15 + postage (under $5 in the U.S.) for paperback copy, $10 digital (.PDF)

paypal to grandpaulz athot mai ldotc com

I'll email you mañana - thank you.

 

[NM Bonny]

BTW - those weighing in on this project may be interested in a thread I started about a vintage tour. It would be really neat to continue tracing the route per my suggested method of connecting the participants, so as to include those among you who'd like to go.

Very sorry that we can't include you guys across the pond. Though, that said, if someone took the trouble to fly all this way just to take part, I suppose I might be convinced to let him (or her) ride The Paint Shaker, my modified 1951 Harley FL Pan-Shovel, shown here during yesterday's test ride (it reached 45 Fahrenheit, my low-end threshold for riding an un-faired motorcycle).

Not a classic Triumph but still a kick in the #@@ to ride--and really soothing vibra-massage via the fingers and toes...

 

[NM Bonny]

Old Bikes is $15 + postage (under $5 in the U.S.) for paperback copy, $10 digital (.PDF)

paypal to grandpaulz athot mai ldotc com

Sorry, spaced this out due to holidays. Looking forward to the book!

 

[grandpaul]

Sorry, spaced this out due to holidays. Looking forward to the book!

Is that your Paypal I just received? it had no name, just the mailing address.

We're frozen in for a couple of days, I'll get it out soon.

Thanx!

 

[NM Bonny]

Is that your Paypal I just received? it had no name, just the mailing address.

We're frozen in for a couple of days, I'll get it out soon.

Thanx!

PM sent - yeah, it's me.

 

[NM Bonny]

Question: since whenever this original engine wears out, this bike will end up getting a 750cc kit, would the OEM mufflers be too restrictive to handle the added displacement? If so, that would eliminate any uncertainty about whether to move up to the Dunstall replicas.

 

[speedrattle]

try em and see. i have an old morgo, and i run 2 into 1 alphabet headers, open stock pipes, and stock pipes with open reverse cone megaphones. all will do over 110, but the megaphones are good for 117

 

[NM Bonny]

try em and see. i have an old morgo, and i run 2 into 1 alphabet headers, open stock pipes, and stock pipes with open reverse cone megaphones. all will do over 110, but the megaphones are good for 117

You mean, try the OEM mufflers or the Dunstall replicas? I'm (still) leaning toward the latter...

 

[speedrattle]

try whatever you have first. put the OEM pipes on and see how the engine performs. then take em off and run the open pipes. the length will be wrong but the performance will be better or worse, and may tell you something. then buy the dunstalls and see if you like em more. there's no way around spending the money because you have to experiemnt.

with things like pipes, there is simply no substitute for test-it-and-see. theoretically open pipes have the best potential, but the sharper these machines are tuned, the more sensitive they are to minor changes in pipe length because of sonic effects. cant get around it.

i have various sets of pipes of different lengths and diameters and configurations hanging around my shop everywhere. some have only been used once. you have to test.

these guys are immensely useful and not expensive:

https://coneeng.com/

 

[NM Bonny]

try whatever you have first. put the OEM pipes on and see how the engine performs. then take em off and run the open pipes. the length will be wrong but the performance will be better or worse, and may tell you something. then buy the dunstalls and see if you like em more. there's no way around spending the money because you have to experiemnt.

with things like pipes, there is simply no substitute for test-it-and-see. theoretically open pipes have the best potential, but the sharper these machines are tuned, the more sensitive they are to minor changes in pipe length because of sonic effects. cant get around it.

i have various sets of pipes of different lengths and diameters and configurations hanging around my shop everywhere. some have only been used once. you have to test.

these guys are immensely useful and not expensive:

https://coneeng.com/

Okay, understood--thank you. You're right that I'll have to spend a little dough, but what else is it for?

 

[speedrattle]

you cant take it with you.

 

[sikatri]

you cant take it with you.

That’s the truth!

 

[Bloodknot]

As Steve Parrish, Barry Seene’s team mate and renowned practical joker says on the back cover of his autobiography “Don’t die wondering”.

 

[NM Bonny]

I'm back at it after a hiatus, and ran across this video. (BTW - I watch Youtube on Firefox with ad blocker, and it's wonderful.) What the guy did when fitting pea shooters, which he said are essentially straight-through mufflers with a perforated core pipe wrapped with media, is block off his crossover pipe--thus yielding two independent exhausts.

While the purpose of the crossover seems to be chiefly to reduce noise by directing each cylinder's exhaust pulse through both mufflers, it also had the effect of relieving too much of the back pressure with a less-restrictive muffler design.

I'm most likely to be running the bike with the stock mufflers in place initially, which have internal baffles. So, I will try it 'as is' initially just out of convenience. But I'm 99% sure I want a modified exhaust with a straight-through design--or perhaps a partial baffle as discussed earlier. At any rate, in that case I probably won't want the crossover pipe further decreasing the back-pressure.

The guy also noted that tuning was a bit more straightforward with independent exhausts.

Any thoughts or applied experience in this regard?

 

[NM Bonny]

All rightee then...

I've done a lot of agonizing about this decision and have settled on a set of Emgo 80-84050 mufflers. I think they'll look smashing on this bike and I've now listened to them on a bunch of videos.

I'll research the best upgraded packing and rewrap the cores before fitting the mufflers to the bike--which will have to happen after rebuilding the swing arm and going over the clutch and primary if memory serves...

It's looking like KM Jones has the best price on UK-made exhaust header pipes. I think I'll just get his balanced set because it's cheaper but also because if I don't like the way it runs balanced, I'll just block off the connecting pipe per the previous thread.

 

[NM Bonny]

Okay, the mufflers are on the way.

I've settled on non-crossover UK made LF Harris pipes (mine are rusted firmly onto stock mufflers & scored here and there), on the way shortly after brief Q&A with KM Jones. I'm retaining the vacuum balance tube @ intake manifolds for now.

When the mufflers get here, I'll pull the cores and examine them and post pics, re: the above discussion about the disc midway down the core, and what by all accounts is crummy wrap. Acousta-fil is best UK wrap but I haven't yet found best US alternative.

Also curious to see how many of the end plate holes are drilled. This, like the plate inside the core, means opportunities for tuning.

 

[NM Bonny]

The Dunstall replicas got here, and I was a little disappointed to discover that they're significantly heavier than the OEM cans: 15.5 oz or just shy of a pound additional weight on each side (OEM muffler is 4 lbs, 2.7 oz). Ah, well, the 4 lbs I saved on the DIY front disc brake conversion leaves me still 2 lbs ahead...

That said, they are more slender toward the front--good for kicker clearance with my rear set controls conversion underway--and have fewer welds than the OEM mufflers, so they're sleeker and cleaner aesthetically.

It is too damned hot in the garage to fiddle with them today but I did note two things:

First, all of the holes in the removable end plate are drilled out (I'll have to do some math and compare total area to the outlet of the OEM cans--though flow characteristics are different with multiple holes vs one larger hole).

Second, the plate tack-welded midway along the perforated core is not solid but drilled with lots of teensy holes (see photo). I can't recall whether people have said their older Emgo Dunstalls had a solid baffle but for some reason I had thought so...

At any rate, I will pull the cores to see how skimpy the wrapping is, and if anything like others have experienced will upgrade with better material and more of it.

Since (per the other thread on restoration & mods) I'll be running unbalanced pipes and K&N filters instead of the OEM airbox, I'll be tuning the new Amals that came with the bike from scratch. I figure futzing with the baffles should be the last step after dialing in the carbs...