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#142618 06/07/08 2:18 pm
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I'm running an AMAL 930 with 1 1/2" pipes and repro stock silencers--very quiet. I'm interested in taking off the silencers and running some old cheese grater style, fiberglass wrapped baffles for now. I feel the need to make some noise, but don't want to sacrifice power or reliability.

Q: What jets should I get? I understand it's trial and error to some extent, but I'm looking for a solid start. I don't just want to buy a pile and try them blindly. If anybody knows of a good needle, jet, adjustment setup, I'd appreciate the help. Any tips, welcomed. As you may have guessed, I've never done this before.

Pros and cons, sure, but no purist leave it alone advice please. I'm just trying to make a good bit of noise til I can get some proper vintage $ilencers with a good sound.

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hello. i have a 70 tr6. im running stock TT pipes. 930 carb with a 220 main jet. im in the 2nd notch on the neddle. when i do a plug chop, its perfect. very loud and properley tuned for my bike. you dont want to be to lean. i have run a a 200 main jet in the pas, however, i like to play it safe with a 220 main jet. find a optimal adjustment without being to lean. best wishes. Dan

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thanks for the tip! Just the kind of info I need.

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how can you tell the size of neddle or jet you have i am waiting on new 1 and 1/2 inch header pipes and i am going to put on some old cerry bomb kind of muffler sould i change my jet thank you bob

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i have run as big as 250 and as little as a 200. keep it rich with short pipes. you will notice a big differance with changing the jet sizes. Dan

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On a TR6 with straight pipes or straight pipes with open slip-ons, 220-240 on the Main Jet should do it.

I run 1 1/2" headers with open slip-ons. Originally, the bike had been a flat tracker with 1 3/4" 2 into 1 pipes and a 230 Main Jet. When I swapped pipes, no adjustment of the needle setting prevented an extremely rich condition. Upon inspection on the "230", even to the naked eye, the 230 was larger than a 240, probably more like a 250....it had either been drilled larger by the previous owner or had been misstamped from the factory. Switched to a true 220 and the plug reads are spot on.

bobmc, The jet #'s are stamped on the jet bodies. The larger the #, the fatter the jet....


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thank you, I am going to run 1 1/2" headers with 12" slip ons with baffels they look like little cherry bombs, should I change the jet, and do you have to change needle. thank you, bob

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If your's is a TR6, a 220 Main Jet would be a good place to start. I didn't have to change the needle on mine, just used the original that was already in the carb. :bigt:


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1971 tr6r 650 thank you i am waiting for my headers to arive so i can try it bob

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Quote
Originally posted by disturber:
I'm interested in taking off the silencers... I feel the need to make some noise, but don't want to sacrifice power or reliability.
And "noise" isn't all you'll be making, my friend. You'll also be making a lot of people mad. Including every cop you come within 2 miles of.

While I agree you could get it jetted after awhile and maybe increase the horsepower output by 1 or 2, you'll never actually realize anything from your labor. The reason is because you'll never be able to get into the upper RPM ranges or go very fast at all without John Law on your tale.

You'll end up "tippy toeing" around town at 2800 RPM trying not to get another ticket. Then once the cops get to "know" you, mufflers or not, they'll always be watching YOU. Even with zero tickets you'll still end up deaf.

No mufflers is simply a loosing game, my friend.

:bigt:


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Rf. like a drum waking the dead. short pipes wake the dead beat neighbors. and yes, eventuly i will deaf. until than, take care. Dan

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While advice has been given, is it usefull. In my opinion, No! Most of the riding will be done on the slide cutaway and needle jet and little on the main jet.

Giving advice without knowing the gas level in the bowl, condition of the carb body, size of the slide cutaway and condition of the needle jet (as little as a few tenths of a thousandths will change the jettng where the bike is run the most) is a waste of time.

I would be interested in the condition of the body - worn bodies lean the mixture at lower throttle openings.

Condition and size of the needle jet - worn needle jets make the bike run very rich at lower throttle openings.

Height of gas in float bowl

etc. Now thats the advice I would be looking for.

Now most of you have never checked or replaced your needle jet, but it is singly the most used (and abused) jet in a AMAL carburetor!!!!!!!!!!!!

While you want to have the proper main jet, unless you are running at throttle positions well above 1/2 throttle (3/4 -Full), the main jet has no appreciable effect at the throttle openings typically used for street riding. If you choose to run your bike with straight pipes shifting at 3/4 plus throttle all the time you would probably be arrested for the noise you would make.

As far as guessing the main jet size when changing exhausts, compression, etc look up the stock jet and get one two or three sizes larger. Go from their.

Dan, if you are seeing performance changes at lower throttle openings when you change your main jet something is radically wrong. You should be able to take the main jet right out of the carb and the bike should run right up to 1/2 throttle with few rich symptoms.

Often I find with straight pipes you end up with a smaller main jet, but let the bike tell you what it needs.
John Healy

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Thank you all. Mr Healy, I appreciate the well thought out response and will be sure to look into all the other elements you've pointed out. Thanks all.

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I'm running 1 1/2" non crossover pipes with EMGO Dunstall replicas on my 72 TR-6.

I'm at a 240 main with the needle raised all the way.

Very strong for a 650.

Oh yea also have Boyer and non restrictive air filters in the stock airboxes.

Still sorting all sorts of stuff out but getting closer and closer to killing all the gremlins after being rescued from a barn for 35 years.

Staying as stock, with modern upgrades, as possible.

TD

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Johns theory on the importance of the main jet in everyday riding is pure truth. A few years ago at bikeweek in daytona, one of my buddies rode his A-10 all week, all over daytona and deland and it never fouled a plug. After we got back to Indiana, while checking the bike over,he discovered he had borrowed the main jet for one of his race bikes and had forgotten about it. So there you go. Jack

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thank you john. Dan


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