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#890552 09/11/22 8:58 pm
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RE: 1971 T-120R: I put two new AMAL 930's on this bike a few years ago. I have owned the bike since new. It had been sitting for many years and was not running well after I put it back in service. The new carbs made it run fine. It sat for about 15 months and on start up would not idle and missed badly. Would not rev past 3000 rpm without crapping out. An initial cleaning didn't help. I bought the idle jet cleaning tool (drill bit). Cleaned the jet, brake clean came shooting out all the orifices in the jet. Still didn't run right. Took off the carbs, left the idle jet in, spray brake clean in the the idle adjust orifice and it came shooting out of the two tiny orifices in the throat. When I reinstalled, it was only running on one cylinder. Cleaned them both again, fresh gas, new plugs, removed the petcock screens, add paper fuel filters to both carbs, inspected the tank. Put the bodies in an ultrasonic filled with white vinegar for 20 minutes. Seems to idle OK on the center stand, revs up. On the road, it misses constantly in normal operation, not so much with wide open throttle. Repeat the ultrasonic cleaning and it improved but it still misses. Boyer brandson ignition. All the tests check out. Get a good steady spark with a test plug on both cylinders. While observing the spark, I get an occasional star burst. Is that indicative of anything? It seems every time I clean the carbs it improves but it's not right. It's getting tedious. I think I can do the job blindfolded at this point. Can the e10 gas do this kind of trouble in such a short time? Is there a better solvent than white vinegar? Thanks
Sam

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scrap #890567 09/11/22 11:06 pm
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I think the carbs are clean by now. You've got other problems. Good battery???


1968 T120R
1972 T120RV
Any advice given is without a warranty expressed or implied.
scrap #890577 09/12/22 12:03 am
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Have you checked the ignition timing?

scrap #890578 09/12/22 12:11 am
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You did not mention what type ignition is on the bike. If it is a Boyer, they do not like to run with low voltage. I do not remember the exact voltage. if it is a standard Triumph system clean and reset the points and check for bad capacitor.


1951 ZB GS
1953 BB GS
1953 Super Flash
1954 Vincent BS
1963 RGS
1956 Triumph T110

scrap #890580 09/12/22 12:56 am
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On my 74 Honda I can run the bike with the points cover off and can see spurious sparks to ground coinciding with unhappy running symptoms. Aftermarket points assys for this particular bike are not so good. Symptoms exactly as you describe, just a thought. I've not had a reason to do this with the Triumph but maybe a possibility?

Last edited by slofut; 09/12/22 12:58 am.

'68 Bonnie, '70 TR6r
'74 CL360
trail 70's and minitrails
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I once had a similar fault where the bike ('69 T120R) ran fine til it hit about 3000 RPM. Then it would cut out, sputter. I spent hours on the carbs only to find out there was a loose spade connector on one of the coils. After finding the problem I went thru the whole wiring tightening all the connections.
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Don't fixate on carbies, maybe start checking coils, ignition switch and connections etc.
BTW there was a bad batch of NGK spark plugs - actually chinese knock offs that even fooled the experts. I had two sets for my Trident before I became aware of the issue. Once I found out I swapped to Bosch...to be sure to be sure.

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Originally Posted by desco
I think the carbs are clean by now. You've got other problems. Good battery???
Good battery, always above 12v

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Originally Posted by Emlupi
Have you checked the ignition timing?
Spot on with strobe

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Originally Posted by bsalloyd
You did not mention what type ignition is on the bike. If it is a Boyer, they do not like to run with low voltage. I do not remember the exact voltage. if it is a standard Triumph system clean and reset the points and check for bad capacitor.
Boyer, all the readings on an ohmeter check out. Magnets pass the test. Good ground.

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Originally Posted by bsalloyd
You did not mention what type ignition is on the bike. If it is a Boyer, they do not like to run with low voltage. I do not remember the exact voltage. if it is a standard Triumph system clean and reset the points and check for bad capacitor.
Boyer, all the readings on an ohmeter check out. Magnets pass the test. Good ground.
Originally Posted by tridentt150v
Don't fixate on carbies, maybe start checking coils, ignition switch and connections etc.
BTW there was a bad batch of NGK spark plugs - actually chinese knock offs that even fooled the experts. I had two sets for my Trident before I became aware of the issue. Once I found out I swapped to Bosch...to be sure to be sure.
I am running NGK'S. I'll change them asap.

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A while ago I posted an article about NGK not making plugs for Triumphs anymore. I tried to find it but don't want to go through 14,000 + hits. Try Denso, my favorites or Champion.
In the meantime a loose or corroded electrical connection has my vote.

https://www.denso.com/global/en/products-and-services/automotive-service-parts-and-accessories/plug/

Last edited by desco; 09/12/22 5:34 pm.

1968 T120R
1972 T120RV
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I don't have much to offer in advice beyond what the others have suggested. However, I would like to mention that brake cleaner may not be the most suitable solvent for cleaning carburetor passages. I had a similar situation with old gas residues in my T120 after an overly long winter storage. Removing the pilot jet screw and spraying carburetor cleaner through all the various orifices and passages did clean out the residues, so I was lucky on that. I also carefully wrapped all painted surfaces with old blankets and rags. The point is though, brake cleaner is a very different solvent than carb cleaner. Brake cleaner is mostly a hexane type solvent with fast evaporation and no residue. Carb cleaner is more like a toluene with very different properties. I'm not sure the vinegar wash would dissolve organic waxes and residues either. Anyway, as others are suggesting, it probably is electric, but if you do hit the carbs again, I think a more aggressive solvent formulated for carb cleaning would be more effective than the brake solvent.

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https://performancecycle.com/pj1-super-cleaner/

Best cleaner I've found. Does not harm paint and most plastics.
I am not affiliated with them.


1968 T120R
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Coleman camp stove fuel, or model airplane fuel, may be of help.

Both are what is called "white gas," with few or no additives.

Back when I built plastic model cars, I used model airplane fuel to strip old paint off of them.
It didn't affect plastic.

A warning about using vinegar: I use it to strip rust and old zinc plating from used bolts. Household vinegar is 3 to 5 percent acidic.
It MAY have a bad effect on die-cast metal, which most carburetors are made of.

scrap #890651 09/12/22 10:54 pm
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Giow plug model plane fuel is methanol with a bit of lubricating oil. The best stuff has a small percentage of nitromethane....


61 hot rod A10, 89 Honda 650NT .On a bike you can out run the demons
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Harbor Freight sells inexpensive jewelry ultra-sound cleaners. I have one to clean parts. I use hot water and the wife's liquid laundry soap. It works well and I have used it to clean carb bodies and all other kind of parts. The AMAL carb bodies I have cleaned with it turned out well. I generally clean the big chunks off a solvent and put them in hot soapy water in the ultra-sound cleaner, rinse, dry, and you are done. Especially dirty parts may require several cycles.

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+1 for the HF ultra sonic cleaner.
I use it with heated water and a squirt of dish washing liquid from the kitchen.
Cleans carbs extremely well.
Need to do the carb bodies twice---do it once (when some of the carb sticks out above the liquid surface) then turn it over and repeat.
Recommended.

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Hi scrap, White vinegar is excellent for cleaning carbs.

It sounds like you have Premiere carb with removable pilot jet?

It has the holes on sides & center hole. The fuel passage to bowl is quite large & cleans fairly easily.

Premier & normal late carbs have stay up floats & viton tip alloy needle. Even though visually very similar there are many differences from original carbs. An important one is float level setting. The liquid level is actually the same. However to achieve this level top of float must be just above & level with gasket surface of bowl, holding bowl upside down with finger holding pivot pin.

Also make sure the needle clip is secure in slide & not winding up in the spring.

As was mentioned battery volts under load is important.
Full charge of battery is at least 12.6v. Key & headlight on you still want to be about 12-12.3v ish.

Starting motor & running you stil want over 12v. Much higher revving.

I’ve had good results with Champion spark plugs. N3, became N3C. Now… renumbered to 801.
If you ask for N3C they can’t find them. Ask for 801. They often don’t stock but can get next day.
Make note in your parts book 801.

So far the ones I buy the box says 801, yet printed on plug is still N3C. Made in Mexico. I buy them in box of 4 from Oreilly’s auto parts. Very good price.

Once thing about them is tip can vibrate loose. It’s threaded on. I’ve found cure is put split type lock washer from ACE hardware under the tip. It feels so tight when you unscrew it, But I’ve seen many come unscrewed while riding. Bike runs on one cyl. You look down & plug wire fell off. Then you find tip stuck in wire cap. Have to remove spark plug & screw it in to remove tip from cap. I can usually change plugs every 6k miles. Regap ever 3k miles.

In a side note, some EI demands resistor plugs or connectors. (Never both). RN3C is now renumbered to 880. Again you must ask for the new #. Very few places still sell 880 & they are much more costly. N3 was common in Chrysler products in 50&60s. The resistor plugs were used only for short time from what I can tell, so little demand now.
Don


1973 Tiger 750
scrap #890738 09/14/22 12:46 pm
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Did you check for an air leak???

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Originally Posted by TR7RVMan
Once thing about them is tip can vibrate loose. It’s threaded on. I’ve found cure is put split type lock washer from ACE hardware under the tip. It feels so tight when you unscrew it, But I’ve seen many come unscrewed while riding. Bike runs on one cyl. You look down & plug wire fell off. Then you find tip stuck in wire cap. Have to remove spark plug & screw it in to remove tip from cap.
Or just use the NGK caps which go directly on the threads.


"Gosh, it's not a 1/4 20, must be metric."

72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"

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Originally Posted by Tridentman
+1 for the HF ultra sonic cleaner.
I use it with heated water and a squirt of dish washing liquid from the kitchen.
Cleans carbs extremely well.
Need to do the carb bodies twice---do it once (when some of the carb sticks out above the liquid surface) then turn it over and repeat.
Recommended.

I have an HF ultrasonic cleaner. I often wonder, when I buy anything from Harbor Freight, should I throw it in the trash as soon as I get home or should I waste my time and open the box. Seriously, I used this cleaner three times and I guess I got my moneys worth. Like they say, three times is a charm. It did not work on the fourth attempt. Needed a 6 volt battery charger, went to HF, did not work out of the box, 2nd unit did not work out of the box. Read a review, customer claimed the charger caught fire. Bought a Schumacher on line. As they say, Good Price, Good Quality, Good Features. Pick any two, you can never get all three. Waiting for new bowl gaskets and o rings. If it's still missing, I'll get new Bosch or Champions and will report back. Thanks for the advice.'

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Harbor Freight is great for an extra set of wrenches in the shop or some do dads, but Proto it ain't.

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Harbor Freight is great for tools which only see occasional use, or for that spare set of spanners or screwdrivers to hang in your shed so you don't have to walk back to the shop for a 1/2" wrench.
I love my HF electric impact driver. $40 for over five years of removing clutch and crank nuts? Yes please!


"Gosh, it's not a 1/4 20, must be metric."

72 T120V cafe project "Mr. Jim"
72 T150V "Wotan"

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Originally Posted by DavidP
Harbor Freight is great for ....... that spare set of spanners ......
Yes!

I have a set specifically for grinding on, welding on, or whatever else is needed to make special tools. That way I don't have to sacrifice my better wrenches.

And their giant 3/4" drive sockets are an absolute bargain compared to Snap-on.

Last edited by Stuart Kirk; 09/16/22 4:53 am. Reason: Thought of something else.
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