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[gemini641]

I just installed a K&N air filter and the shorty pipe (w/o baffle) on my 2005 Deluxe and started the rejetting process. I was surprised to find the carb already had a 120 main jet rather than the 115 main jet sold as "stock". The pilot jet, however, was the stock 25. I went ahead and put in a 27.5 pilot jet and left the 120 main jet in place. I did not move the needle valve clip yet. She sounds sweet but runs only OK . I can't seem to get the mixture to "lean" out using the air mixture screw.. The plug shows rich and even worse, when I crack the throttle sharply open while standing at idle, the engine just stops abruptly. I don't think that's good!!

I have removed the PAV system, sealing off the exhaust outlet and the manifold inlet. Is that a factor?

Anyway, any suggestions out there from someone who has successfully tuned their carb?? All help appreciated....

Tom

[Thumper]

It might help to determine at which throttle position you are having problems.
Carbs are designed to address 4 general positions: 0-1/8, 1/8-1/4, 1/4-3/4 and 3/4 to full open.
The carb's mechanical design has four circuits that correspond to each of these throttle positions - and each can be adjusted. Identify the throttle position that has the problem and you've likely identified the circuit that needs adjusting.

0-1/8 - idle circuit: affected by both the idle (aka pilot) jet and the idle mixture screw.

1/8-1/4 - The cut-away portion of the throttle valve (the cylinder that moves up and down inside the throat of the carb).

1/4-3/4 - The needle as it rises and falls inside the jet

3/4-Full Open - The size of the main jet

Amal provides a good sequence for tuning a carb.

With a thoroughly warmed engine, go out and first test the main jet.
Run your bike fast, getting the throttle to 3/4 - full open.
Determine if there are any rich or lean problems there.

Next, adjust the idle.

Third, verify that the throttle valve cutaway is correct by driving at 1/8 to 1/4 throttle.

Fourth, verify that the needle is sitting at the correct position by driving at 1/4-3/4 throttle.

Finally, go back and readjust the idle (2nd step) as needed.

Here are some links:

http://www.hitchcocksmotorcycles.com/amal/mk1_conc_ht_7.html

http://www.iwt.com.au/mikunicarb.htm

http://www.motorcycleblog.org/bulletblog/afterexhaust.html

http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html

https://www.johnsmotorcycleparts.com/Keihin_CV_tuning_tips.htm

Good luck!
Matt

[gemini641]

Thanks, Matt...

I'll try your method...and link to the references...

Ride safely,

Tom

[t120rbullet]

http://www.mikuni.com/pdf/vmmanual.pdf

CJ

[Thumper]

I just installed a K&N air filter and the shorty pipe (w/o baffle) on my 2005 Deluxe and started the rejetting process. I was surprised to find the carb already had a 120 main jet rather than the 115 main jet sold as "stock". The pilot jet, however, was the stock 25. I went ahead and put in a 27.5 pilot jet and left the 120 main jet in place. I did not move the needle valve clip yet. She sounds sweet but runs only OK . I can't seem to get the mixture to "lean" out using the air mixture screw.. The plug shows rich and even worse, when I crack the throttle sharply open while standing at idle, the engine just stops abruptly. I don't think that's good!!

I have removed the PAV system, sealing off the exhaust outlet and the manifold inlet. Is that a factor?

Anyway, any suggestions out there from someone who has successfully tuned their carb?? All help appreciated....

Tom

Tom,

BTW, I just put a Hitchcock's perofrmance kit on my Electra X. It uses an Amal. Surprisingly, the idle circuit mixture has a big effect on the overal mixture. If I have it too rich or too lean it has a noticable affect on throttle ranges up to 3/4 throttle.

I wonder if that's more the result of our thumper design than an Amal characteristic. If so, your larger pilot jet might be affecting more than you would normally expect.

matt

[bikeniterider]

I am a newbie to the board. I installed the Electra performance kit on a customers bike and the difference was terrific. I bought the kit from Royal Enfield USA which has the JRC flat slide carb.  I like these better than the AMAL carburetors for several reasons. The Amal's wear our quickly and can be quite fussy. The flat slide also has better response. I thought that the main jet it came with was a little too rich so I installed one of the smaller jets that they supply with the kit and it worked great. It can be seen here Royal Enfield USA

[dewjantim]

I replaced my stock air cleaner with a K&N and changed to a goldstar exhaust. Changed low speed jets to 30 and main jet to 130. Bike runs perfectly, starts on first or second kick usually without choke, and for some strange reason gets 20-25 more mpg than stock. Went from 75-80 mpg to about 100mpg. Now I get 300+ miles per tank!!!! Dew.

[deejay]

I replaced my stock air cleaner with a K&N and changed to a goldstar exhaust. Changed low speed jets to 30 and main jet to 130. Bike runs perfectly, starts on first or second kick usually without choke, and for some strange reason gets 20-25 more mpg than stock. Went from 75-80 mpg to about 100mpg. Now I get 300+ miles per tank!!!! Dew.

Do you ride a bullet or an electra?

[dewjantim]

I replaced my stock air cleaner with a K&N and changed to a goldstar exhaust. Changed low speed jets to 30 and main jet to 130. Bike runs perfectly, starts on first or second kick usually without choke, and for some strange reason gets 20-25 more mpg than stock. Went from 75-80 mpg to about 100mpg. Now I get 300+ miles per tank!!!! Dew.

Do you ride a bullet or an electra?

I ride a bullet. Dew.

[deejay]

I have the brit exhaust system and k&n filter. I was running the same setup on my bullet for about a week (30 pilot, 130 main). People over at the Yahoo board seemed to think this was way rich. I confirmed this theory when I noticed slightly dark exhaust smoke and a dark plug. Yesterday I switched down to a 127.5 main which sputtered a bit until I moved the main needle to the bottom notch (needle set at highest relative to carb slide). Now the bike pulls like an ox and seems to be running very nice at all rpms.

Thats my 2 cents.

[dewjantim]

I have the brit exhaust system and k&n filter. I was running the same setup on my bullet for about a week (30 pilot, 130 main). People over at the Yahoo board seemed to think this was way rich. I confirmed this theory when I noticed slightly dark exhaust smoke and a dark plug. Yesterday I switched down to a 127.5 main which sputtered a bit until I moved the main needle to the bottom notch (needle set at highest relative to carb slide). Now the bike pulls like an ox and seems to be running very nice at all rpms.

Thats my 2 cents.

My bike doesnt seem overly rich, although these bikes do run a little better on the rich side. The goldstar muffler is pretty much a straight through affair. There is a 11/2 hole running all the way through the pipe with baffles on the sides. It is very loud when on the gas, but is reasonable around town if the revs are kept down. This is probably the causes the difference in the jetting of our two bikes. Dew.

[deejay]

Brit style exhaust is straight through too... but, as I've found out all of these bikes seem to be different. Your needle could be set different too, i was surprised how much of a change that made to my bike.

[dewjantim]

There could also have been a few changes in the bikes from 2000 to 2006. Dew.

[Kevin Mahoney]

We answer jetting questions all day long. Of course there is a lot of science that goes into jetting, but there seems to a bit of art as well. We can give you a general range, but each bike and each situation is different. If you are racing you compensate for humidity, temperature, altitude etc.