Triumph T160 chopper to Bobber build.

[Tricky13]

Thanks for the offer, but i am not really a standard bike guy, think i have only ever owned two in my life, although thees days comfy suspension is getting far more appealing.

[farmall]

Miles Engineering cloned the Rob North road race frames and someone else in the UK makes them now. They are a very nice home for a triple.

[Tricky13]

Well the dam thing is still fighting me ...again, took it out again today and its trying to run on two, and one if it gets a chance, looks like the carbs are coming apart again, i suspect the float levels are making it over fuel and stopping it firing.
Wish it was still the 80s and i could just nip to a mates and pick up a nice set of Mikunies, but they seem to be hard to come by these days.

[Dougtheinternetannoyance123]

I myself hate those old Amals,, Ill put them on a restoration if need be,, But for a rider or anything custom its a Mikuni or a good affordable option is the JRC/PKW carbs. I am a dealer for JRC still and they are very nice. I just ordered a set for a buddy who managed to get his dream bike. A vincent Rapide with sidecar. The amals were giving him crap, so these carbs are going on.

Triples are famous for holing pistons due to fuel issues,, you are also supposed to slightly jet the center carb rich to avoid seizure as well because it runs hot.

See: https://www.tr3oc.com/forums/topic/k...rcbrill-carbs/

See: http://www.triumphrat.net/classic-vi...pwk-carbs.html

Also excellent review here by BSAOC Calif members: Pictures on their page

http://www.bsaocsc.org/images/June_13_Piled_Arms_1.pdf

Purpose:
The purpose is to find a replacement for the Amal carb that came stock on Brit bikes.
That is necessary for several reasons. Even though the new Amals are offered in several
models as replacement carbs, Amal
managed to reproduce all the faults of the original designs and add some too. Those
faults are:
1. Slides made of the same material as carb body promoting galling and fast wear leading
to both sticking slides and loose slides that allow air around them through excessive
clearances which makes the idle
uneven.
2. Flanges from the carb body to the motor's intake manifold that when over tightened
permanently distort the carb body, causing the slide to stick in its bore. Once the body is
distorted the precision of the carb is lost.
3. Some have come through the manufacturing process crudely made. Are they Chinese
or Indian copies or is Amal's quality control not that good?
4. Pilot jets that are pressed in bushes not meant to be removed or resized, stuck down in
a passage way that is prone to clogging if the bike is stored with gas in the carb. This
passage way is not easy to clean as there is access only to one end as the passage way is
a right angle turn off another main passage.
5. Idle and transition circuits, including small holes into the mouth of the carb, that are
prone to clogging and hard to thoroughly clean.
6. The latest one for me is the sinking float. My friend's relatively new Concentric's float
filled with gas while out on a ride, about 50 miles from the truck. We had to drill a hole,
drain the gas from the float, epoxy up the hole, and pray we would be able to get back to
the truck before the float filled again. We could find no hole for the fuel to leak into the
float in an in-field inspection of the float. The float again filled to about 20% full in less
than 20 miles of operation. Add to that the comment from a Piled Arms poster that he
had to buy and test about five floats to get one that didn't leak.
Common fixes for these maladies is to have the slide bore of the carb fitted with a
chrome or brass thin liner or have the slide hard chromed to start with. But if the body is
The JRC Carburetor, An Assessment…...By Lynn Bennett
13
already distorted these fixes might work off the bike but once the carb is bolted to the
manifold the sticking slide returns. Brute force bending the carb
flanges back into place or machining the flanges flat still leaves the body of the carb
distorted. The idle bush is drilled out and a separate idle jet is installed in the float area
of the carb (available because the first version Concentrics came with an idle jet in the
float bowl area, not underneath the air screw adjustment). Amal moved the idling function
years ago because idle quality suffered initially with the jet so far from its source of
suction, the idle air passage.
A New Carb:
In a casual request for information on the JRC (Bill Getty) carb that I only recently
heard about, Bill Getty offered to allow me an evaluation carb after hearing that I write
TECH articles for the Piled Arms web page. The carb arrived with a new throttle cable
(which was not required or used), a plastic tee for the fuel lines, several feet of fuel line
(again, I had my own which I used), a set of six hose clamps (Sorry Bill, but they were
sub standard and two broke while I tightened them…used the name brand micro clamps
from an auto parts store), and several main jets (130, 132, 135, 138) all leaner than the
main jet installed (140) in the carb.
The carb is from the Keihin PWK family and is marked as a PWK 30 but the bore actually
is oval and measures 30mm vertically and 28mm horizontally, perfect for my Triumph
Trophy Trail as it originally
came with a 928 28mm Concentric. It is a modification of the standard PWK 26 mm
carb but consideration is being made to get Keihin to make a new body for a full 30mm
body.
Continued on page 14
14
The carb was jetted as follows:
Main Jet…140. (may be a bit rich so will make adjustments on the first field test)
Slow Jet…38 (same as pilot or idle jet)
Needle jet was a pressed in jet (unknown size) but only one size appears in the Keihin
parts catalog.
Needle unmarked and in middle clip position.
Slide (not marked but measures about a 2 1/2 cutaway (?) and is chrome Plated, Yea!)
The air jet size is fixed.
For specs, the comparison
should be
made between the
Concentric, the JRC,
and the Mikuni. The
Concentric is a simple
carb with only a
few choices for needle
and needle jets
and a fixed air bleed
system for the main
and idle jetting. The
JRC is also a simple
carb with only one
needle jet but about 35 needles with various tapers and needle diameters allowing a reasonable
choice with only one variable for mid throttle tuning, the needle itself. The JRC
slide is a modern flat slide with chrome plating to avoid galling of the carb's slide bore,
unlike the Concentric. The Mikuni has virtually an infinite choice of needles and needle
jets, and changeable main system air bleeds (air jets). With a dyno and enough time and
knowledge a person could get the Mikuni jetted perfectly but I don't have the knowledge
or the dyno and with all those variables for tuning, the Mikuni can be a nightmare to jet.
Not so the JRC or the Concentric. The Mikuni's have a rubber
manifold while the JRC's flange mount is rubber isolated from the body (no body distortion
from flange over tightening as on the Concentric, Yea!). The Mikuni and the JRC
have starter systems that include a jet
and an air passage while the Concentric has a cable operated choke and a tickler button
to flood the carb for starting. The floats of the Concentric are mounted to the removable
float bowl while the Mikuni and the JRC carbs have them attached to the carb body. The
JRC carb requires that the main jet and needle jet holder be removed before the float
bowl can be removed and even then you have to snake the float bowl around the floats to
The JRC Carb. Continued
15
get it off. Finally the JRC is sized externally to fit in the space allotted for a Concentric,
with an intake bell that is the same size as the AMAL carb to allow the stock pancake
filter assembly to fit perfectly.
Specification wise the Concentric is simple to tune but very prone to wear and damage
from abusive maintenance. The Mikuni is complex to tune but pretty good for wear.
The JRC is a simple carb, simple to
tune, and very wear and maintenance abuse resistant by design.
Bill Getty (JRC) tells me he has successfully jetted a version of the JRC carb for the
following bikes: Triumph T140, TR7, TR6, T120, T160,T110, T100 and TR5T, an Ariel
4 (same jetting as TR7). He has not yet done any Norton, or BSA but has plans to do
so. The jetting for the BSA's or Norton's can not be too far off equivalent Triumph displacements.
He offers only the one slide but has yet to have anyone request a slide different
from the one provided. Bill is willing to share tuning information and will stock
jetting for the carb. He is upgrading the hose clamps

JRC Install:
All went well but I did have to shorten the bike's left side manifold mounting stud as it
bumped into the JRC carb body. The carb is fractionally longer than the Concentric so
Continued on page 16
16
fitting it to my Rickman may be more of a challenge than the fitting I did to the TR5T
Triumph Trophy Trail (no air box…just a filter sock). But the JRC Carb is much shorter
than a Mikuni of the same bore size. My original cable worked fine as did my air filter
sock that was on the original Concentric, formerly mounted to the bike. The bike started
right up after the install. I tweaked the idle speed screw and the air screw after the bike
warmed up a bit. It idled very smoothly, ran smoothly and had no flat spots anywhere in
the power band that I could determine running
up and down the street in front of my house. It certainly ran at least as good as the Concentric,
if not better. So far it looks like a better choice for a Brit carb replacement than
either a new Concentric or the Mikuni.

[Dougtheinternetannoyance123]

Post too long, these hipsters with their crackberrys gonna hate me.

Field Testing:
The test ride was a 60 mile loop from 3000 feet to over 6000 feet, on both paved and
dirt roads and some jeep roads. The bike starts more readily from cold or hot. The enrichment
system (pull the plunger up and its detent locks up for starting) is adequately
rich for starting but not overly rich, so you can let it idle for a few minutes with the enrichment
system on. The bike ran well at all altitudes with no flat spots or rich bogs.
The needle jet and needle seem perfect with the clip in the middle. The motor accelerates
smoothly which tells me the slide cutaway is correct as well as the slow jet (pilot
jet) is probably correct as well. The idle is smooth and can be made to be very slow
without the engine stalling. At altitude I tried many times to induce a rich bog by giving
full throttle at slow engine speed. No rich bog. The carburetion was near ideal, to the
best of my abilities to tune a carb.
I pronounce this carb a viable alternate to the Amals and a better choice than the hard to
tune Mikunis or the problem prone Amals. JRC has the jetting for my bike right on. As
for pricing, what a deal! At this time the price is $116 for the carb, only. All the extra
piece parts I got are to be extra. Except for the gas line, the tee, clamps, and the heavy
duty return spring there is really nothing else you need. It is indeed a bolt on mod.
Conclusion:
The JRC carb is indeed a viable, good alternative to either the stock Concentric or the
Mikuni. See www.jrceng.com for the dealer list (JRC is a distributor, only, and does not
sell retail). Many thanks to Bill
Getty of JRC for all the help.

[Tricky13]

Thanks for the info, unfortunately i have experienced quite few of the Amal foibles, i have got a one size larger main jet in the center carb, which is running fine, its the other two buggers that are giving me grief, i am in two minds whether to get some stay up floats and reset the float hight and see how that goes, or start looking for new carbs, but i have spent enough on this beast already.

Out of interest what does a set of JRC carbs run to, and would they lend themselves to being fited to the original T 160 carb gantry without too much butchery? and would i be able to get jets for them in the UK?

[Dougtheinternetannoyance123]

I posted a bunch of stuff on Amals and tuning on other posts here. I can make them work, just dont like to. With modern fuel the stay up (Viagra) floats are the way to go along with the modern viton tipped float needles. I also posted about some methods on the adjustment of float height. I hear positive stuff about the premier carbs,, but its still an amal concentric just improved, (Sort of turd polishing IMHO)

I will give you an exact price on Tuesday as I just ordered a set for a local guy. But they are more affordable than the Amals and 10x better quality. Site sponsor LowBrow customs is also a dealer for them, and we source those carbs from the same wholesaler. I am no longer an active dealer but I suggest people support a good vendor like lowbrow as they are friends. But I do still work with a few select customers and still have a dealer acct.

To answer your question on running them on triples, I try to avoid Triples myself, (I have 2 here that are headed to the UK in Aug) so I have not personally fitted them to a triple, but I have heard of a number of people who have and positive results. Theres some discussion of that on those links I posted and I am sure theres more out there. I am sorry I cant more directly advise on that. I DO have a Honda 4 cyl CB750 but other than that all my bikes are twins and singles.

As I said on this topic in other threads, I really like Mikunis, but these carbs are a good setup and I would recommend them to anyone.

[Tricky13]

Couple of new pics, i have added a different headlight, adjusted the seat mount to get the front lower, and also wrapped the pipes, have also fitted a new larger 1/2" Harley master cylinder as the braking was a bit iffy on the rear, will add more pics soon.

Made a few other additions like digital voltage meter, and re fitted the carb bell mouths with the addition of some cone filters, like a lot of bikes it will be an ongoing project of refinements.

[Tricky13]

Quick update and some pics that will actually show (THANKS PHOTOBUCKET!:apoke!Did a quick tank repaint, just a rattle can job so not perfect but will do for now, also just took the misses out for the first time...loved it...apart from the large bumps, doing well, hard tails at our age.

[Tricky13]

Been a long time since i added to this, recently uprated the rear brakes due to using a Harley master cylinder so the ratio was wrong so had a rather wooden feeling rear brake which quite frankly didn't stop me to well and as i had the wife riding pillion on the odd occasion i took it out i wanted to be safe so i got hold of another Lockheed caliper and made up another carrier so now have two calipers on the rear which has balanced the whole system and given me proper brakes, other than that i have had it in a classic bike show mainly for the easy parking wouldn't win anything because of the classic orientation of the show but it was good to see so many nice bikes.

Must admit that after doing a few miles on the roads around these parts i am now thinking of something more modern with suspension.

[farmall]

Must admit that after doing a few miles on the roads around these parts i am now thinking of something more modern with suspension.

Given the insane prices Triples go for in the UK you should be able to sell your nice example for a profit.

Alternate option, convert to a stock or aftermarket frame and run a suitable seat so you can both enjoy the ride. You could prepare the swingarm frame then bolt on most of your bits in a weekend.

https://robnorthtriples.com/

[TriNortchopz]

Good to hear you improved your brake. Should be easy to sell if that what you want.
Maybe a spring seat for your passenger too? Could always weld a sprung plunger section on the back and still keep your spring seat...

FYI, I shared a link to your build thread and a photo of your chop in this thread:
1975 Triumph t150 Chopper

here: http://www.choppersaustralia.com/for...php?f=5&t=8527

[Avon]

Great looking build.

Back in the 70's, there was a shop called "The House of Triumph" in New Orleans. I can still hear Geneo gripping about how Tridents' middle cylinders would overheat and throw the middle rod. I know that high flow oil pumps were available for twins. Not sure if any were made for the triples.

Just a thought, but, can anyone think of a way to tap into the oil flow for the middle cylinder to add an oil cooler, just, for it?

[Tricky13]

Probably a bit of a myth, all multi cylinder engine generate more heat at the inner cylinders, but its rarely by much unless the mixture is incorrect to start, the Trident is often jetted a bit richer IE richer needle position etc,
Most multi cylinder engines and especially turbocharged are fitted with oil squirters under the pistons to help cooling,
The std T150/160 oil pump is a gear type rather than a plunger, and inherently higher flowing and higher pressure anyway,
the problems arise from the way the oil passages flow as the pump feeds the crank plain bearings directly, and then through the crank to the rod bearings, so if the mains are worn the rod bearings don't get the required flow or pressure and quickly wear and fail, this usually results in a rod braking and going through the case...hence the reputation for throwing rods.

[farmall]

I'd just hang a Big Fucking Cooler on the engine and not worry about the middle cylinder (except to richen its mixture, that works). My T150 engine will get one when it makes its way into my Miles Engineering frame, but getting the last few bits is a bitch because the maker who took over can't be arsed to answer my emails or letters and my phone calls won't connect.

You couldn't overcool an old Britbike unless you ran it in a vat of liquid nitrogen. Given a choice between greater production costs and being blinded by a burning penis Triumph management would have been navigating with striped canes, but they still ran (surprisingly well made) coolers stock to make up for too little finning and insufficient oil volume.

Triples are great fun, sound wonderful and are fun to ride but obsolete as a Watt steam engine for modern use.