Carb overhaul mileage

[R0vers]

Did any of you mega milers (Yen ) ever have to/bother re-building the carburettors on your AT?

What sort of mileage do they start to deteriorate?

mine were fine @100,000mls.only the dredded choke cable needed replacing

[scarfacehugo]

After finding one damaged o'ring in my carbs,replacing it,it no longer backfires as I adjusted the pilot screws to 3 1/2 turns.This is the only way i can get a lean but not backfiring fuel mixture in the carbs. They should be set to 2 turns, 2 1/2 tops.

less turns leaner

more turns richer

(right? some carbs work the opposite way)

This means that there is still something wrong with them. I'm getting 2 new inlet rubbers, despite mine not showing any cracks, just a bit stiff. If this doesnt solve it, i'm getting the rebuild kits for the carbs.

Some people have said to me: " get bigger jets"
Well, i believe that an engine doesnt get lean just because its bored of being rich. I could get bigger jets and fix the problem, but not in a definitive way. My mind is set to find the cause for this strange problem.

How can i know if i'm using "cheap" petrol in this country?

[1gear1brake]

After finding one damaged o'ring in my carbs,replacing it,it no longer backfires as I adjusted the pilot screws to 3 1/2 turns.This is the only way i can get a lean but not backfiring fuel mixture in the carbs. They should be set to 2 turns, 2 1/2 tops.

less turns leaner

more turns richer

(right? some carbs work the opposite way)

This means that there is still something wrong with them. I'm getting 2 new inlet rubbers, despite mine not showing any cracks, just a bit stiff. If this doesnt solve it, i'm getting the rebuild kits for the carbs.

Some people have said to me: " get bigger jets"
Well, i believe that an engine doesnt get lean just because its bored of being rich. I could get bigger jets and fix the problem, but not in a definitive way. My mind is set to find the cause for this strange problem.

How can i know if i'm using "cheap" petrol in this country?

When I was having problems with my cut-off valves, I was horrified to find out just how much they cost. Anyway, I noticed a new set of RD07 Carbs for sale cheap on David Silvers website so I bought them instead. They differ from the RD07A carbs in that they don't have a throttle position sensor but seem identical in every other way.
So I still have this set of carbs (minus the 2 cut-off valves) sitting in my garage. If you'd like, I could send you this set and you can try each and every piece of these in your carbs until you find the culprit. Then you can replace what you've used and send them back. How does that sound?

As far as the fuel pump is concerned, I think that I would just swap it for a Facet electronic pump and never give it another thought. That's what I did as soon as I got my black @ after having had a pump fail without notice on my red one.

Dylan

[scarfacehugo]

When I was having problems with my cut-off valves, I was horrified to find out just how much they cost. Anyway, I noticed a new set of RD07 Carbs for sale cheap on David Silvers website so I bought them instead. They differ from the RD07A carbs in that they don't have a throttle position sensor but seem identical in every other way.
So I still have this set of carbs (minus the 2 cut-off valves) sitting in my garage. If you'd like, I could send you this set and you can try each and every piece of these in your carbs until you find the culprit. Then you can replace what you've used and send them back. How does that sound?

As far as the fuel pump is concerned, I think that I would just swap it for a Facet electronic pump and never give it another thought. That's what I did as soon as I got my black @ after having had a pump fail without notice on my red one.

Dylan

You are a very kind man, and I really do apreciate your offer, but seems like I've discovered my problem. The fuel pump wasnt feedind enough fuel, but still worked. Who'd say...?

Thank you once again, this gesture leaves me very happy to know that there is nice People in this overcrowed country.

If I come to need them, I'll get in touch with you.

[1gear1brake]

You're welcome scarface, glad you found the problem.

[longuito]

Hi Dylan,

I have been having trouble with my carbs for a while now, and since it seems you know your stuff, I thought maybe you could please help me. To make this as productive as possible, bear with me please as I explain the all of the background to the issue:

1. I live in Quito, Ecuador, which is almost 3000 meters above sea level, with much less oxygen than sea level

2. In late 2004 I ordered a Dynojet Kit and fitted the 120 jets and needles on the carbs. The kit also came with 124 jets, but were recommended only for performance exhaust. Nonetheless, the 120's seemed to work rather well in the altitude.

3. In early 2005 I was transferred to southeast Mexico (sea level) and shortly afterwards I made holes in the air box, fitted an arrow exhaust and upped the jets to 124, as instructed by Dynojets. The bike started running like a dream, although I did notice the idle was a little off and sometimes even stalled at stoplights. However, the bike continued to ride acceptably well while in Mexico, albeit with the idle issue.

4. Late last year I was transferred back to my native Quito, and so I decided to ride the bike down. While in Medellin, Colombia and a friendly mechanic offered to do some routine service on the bike (for free), and after that the idle and low revs were worse than ever (sounded like a Harley Davidson!). So I took it back ans asked him about t, and he told me that the jets were too big and I should switch back to the original 115.

5. Shortly after my arrival, I took it to my trusty mechanic here in Quito, and he showed me that he cannot synch the carbs because apparently the linkage shafts are worn and one throttle opens up slighly before the other, causing the malfunction. I cannot understand how this can happen on 46,000 km bike!!

6. After several trials and errors we have tried every possible jetting combination (125, 120 and now with the original 115). With the original 115 jets the bike is not as shaky but still not 100%. We have also changed spark plugs, checked valve clearances, etc...

I am at the end of my rope here and need some help. I just ordered some used carbs from Austrian Ebay and I am wondering if I should order anything else. What do you suggest? I realize this is a very long post, but short of selling the bike, I don't know what else to do. Thanks in advance for any help you can offer. Best regards

G. Luigi Rota
ATIC# 1977

[scarfacehugo]

Hi Dylan,

I have been having trouble with my carbs for a while now, and since it seems you know your stuff, I thought maybe you could please help me. To make this as productive as possible, bear with me please as I explain the all of the background to the issue:

1. I live in Quito, Ecuador, which is almost 3000 meters above sea level, with much less oxygen than sea level

2. In late 2004 I ordered a Dynojet Kit and fitted the 120 jets and needles on the carbs. The kit also came with 124 jets, but were recommended only for performance exhaust. Nonetheless, the 120's seemed to work rather well in the altitude.

3. In early 2005 I was transferred to southeast Mexico (sea level) and shortly afterwards I made holes in the air box, fitted an arrow exhaust and upped the jets to 124, as instructed by Dynojets. The bike started running like a dream, although I did notice the idle was a little off and sometimes even stalled at stoplights. However, the bike continued to ride acceptably well while in Mexico, albeit with the idle issue.

4. Late last year I was transferred back to my native Quito, and so I decided to ride the bike down. While in Medellin, Colombia and a friendly mechanic offered to do some routine service on the bike (for free), and after that the idle and low revs were worse than ever (sounded like a Harley Davidson!). So I took it back ans asked him about t, and he told me that the jets were too big and I should switch back to the original 115.

5. Shortly after my arrival, I took it to my trusty mechanic here in Quito, and he showed me that he cannot synch the carbs because apparently the linkage shafts are worn and one throttle opens up slighly before the other, causing the malfunction. I cannot understand how this can happen on 46,000 km bike!!

6. After several trials and errors we have tried every possible jetting combination (125, 120 and now with the original 115). With the original 115 jets the bike is not as shaky but still not 100%. We have also changed spark plugs, checked valve clearances, etc...

I am at the end of my rope here and need some help. I just ordered some used carbs from Austrian Ebay and I am wondering if I should order anything else. What do you suggest? I realize this is a very long post, but short of selling the bike, I don't know what else to do. Thanks in advance for any help you can offer. Best regards

G. Luigi Rota
ATIC# 1977

My good friend, like yourself I do not believe that a bike with those kms might have worn carbs. Impossible.

First of all you need to check your inlet rubbers. With all the putting carbs in and taking them out, if they are dry and stiff they will let air in even if they dont show cracks. if they let air in, the mixture will be too lean.

Number two is to lubricate the choke cables that tend to get stuck where the cable divides in 2.

Number three is to check the tank tap filter and change the fuel filter.

Number four is the fuel pump. Happened to me that the fuel pump was working but not with the suficient flow to keep the carbs full, making the plugs very white and backfiring whilst decelerating.

If you come all this way and find nothing, you'll need to buy 2 carburettor rebuild kits for the AT. These consist in 2 sets of o'rings and rubber seals to overhaul the 2 carbs.

In your post i didnt understand if your plugs are always lean or rich (light brown or dark).

Remember that the main jet controls cruise speeds and acceleration from half to full throttle.

The pilot jet (smaller 40 jet) and pilot screw (2 or 2,5 turns max) controls low rpm engine usage.

I've been dealing with carb problems in my bike for almost 2 months and if you could describe in detail what the engine does (backfiring, choking) maybe I can be more helpful.

This is all I can remember right now, let me know if you find anything.

[scarfacehugo]

...and sorry for answering a question that was directed to you, Dylan.

[1gear1brake]

...and sorry for answering a question that was directed to you, Dylan.

No problem scarface! You sound like much more of an expert than I am anyway

[longuito]

...and sorry for answering a question that was directed to you, Dylan.

Hello Guys,

Thanks for the very thorough reply, ScarfaceHugo. I just thought I would direct it at Dylan since he was the one who went into detail about the air cutoff valves, etc…

In any case, let me address your questions:

1. Inlet Rubbers: They seem OK, in the sense that they are not cracked and they seem to make a good seal, both from Engine to carb as well as from carb to airbox, but I will definitely order a pair to have just in case.
2. Choke cables were lubricated less than a month ago, although they do look like they could be replaced. Just for kicks I will order a new one.
3. Fuel Filter: I never thought of that, and third world fuel does tend to muck things up… I will give it a go
4. Fuel Pump: I purchased a Facet pump, but have put off installing it for some stupid reason. I will try that too.

In regards to the overhaul kits, I will definitely buy them, because I will need them sooner or later, and I could use them to overhaul the other set of carbs coming from Austria.

The plugs were replaced very recently (less than 1000 km ago, and although I didn’t see them myself, the mechanic told me they were shot and had to be replaced. He mentioned something about them looking shorted?!

The problem with the bike is definitely choking, (never backfiring), as the exhaust smells rich and when you try to accelerate from standstill it sputters somewhat like it would if one was riding with the choke pulled back.

Finally, the mechanical problem (one throttle opening up slightly before the other), is a legitimate problem, which I saw myself. It’s as if at one point one moves independently from the other, and according to my mechanic, that’s when the sputtering happens, and because of this, they will never be in synch.

I wish I could do these things myself and not have to rely on the mechanic, but unfortunately although I have a somewhat sound knowledge of basic mechanics, I don’t have the time to do it myself, and the bike is my everyday vehicle.

I hope this info helps so that you (or anyone else) can give me further input. I just hope it’s not an electrical issue (CDI, etc…).

Thanks in advance for all of the help, and ride safe!

G. Luigi Rota
ATIC# 1977

PS – So far I have been buying my parts at www.bike-parts.fr, good guys albeit somewhat expensive for my taste. Any suggestions on where to buy parts for the Africa Twin? Remember, they must accept “foreign” credit cards or paypal, and be able to ship internationally… Thanks again!