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After a 30 year ‘rest’ from motor biking I bought a 1991 Africa Twin XRV 750 RD 04. Had not problems with in until staying in the Alps last year the bike suddenly started running very rich, with loss of power and difficult tick over. I wear an altimeter watch for trekking and eventually figured out this always startedwhen passing a certain village at 670 metres (2300 feet above sea level) and got a lot worse at the top of the pass, 1300mts (4200 ft). When it happened again in Andorra I tried using 4 star petrol and this seemed to slightly improve things. A group of Germans expressed sympathy/amusement as the bike staggered to the top of a mountain pass. One told me he used to have an old Africa twin that did that and I needed to get a new BMW - like theirs!!
This year I plan a trip in East Africa that starts off and spends a lot of time between 1000 and 1500 metres above Sea level.

Anyone have a solution to this problem and is this normal for an RD 04 ????

I have read one fix is to reduce the main jets by 1 or 2 sizes per 1000 ft above sea level. So to prepare for the trip I have experimented by coming down by 2 sizes on both main jets. It is very fiddly and not exactly a roadside job. Where I live (close to sea level) it has resulted in the bike running slightly hotter with no other ill effects but fuel economy (which was already poor) now seems worse at about 33 mpg.
I am no expert on bike mechanics so would appreciate any advice or suggestions - or should I buy a BMW?

 

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OVALTEENY !!!
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Welcome to the forum

Aside from the basics - are the carbs balanced, clean air filter, no fuel filter problems, fuel pump OK

Ist off you should check out the choke plungers to ensure none have stuck causing the rich running problems you describe

Next would be check all the electrical bits (coils , HT leads) for intermittent problems

Altitude up to 2400 mtrs does not affect any of the Africa Twins with standard settings

I've ran mine many times above this level. The only time it struggled was above 4200 mtrs in the Atlas mountains and I could feel the lack of power. Even at 3000 mtrs in the Alps it was OK but we were not riding fast off road at that height
 

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Ran mine forover a month at 2k+ metres. No probs. As paul suggests, Maybe a choke stuck or if its been round the clock a worn jet?
 

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On the Stella Alpina a few years ago, I ran my RD04, along with friends on two RD07a's up to almost the top of 9000+feet and all three bikes ran flawlessly.

I would suggest there is more to your problem than the jets, and checking the entire choke assembly (lever, 3 cables, splitter, and two plungers with springs, is a good place to start.

33mpg sounds pretty poor, so something isn't right. I reckon any of my past RD03/4's could achieve 50mpg unless I was being chased by the police!!

Start with the basics, examine the carbs for cleanliness, check the diaphragms, make sure the air filter is clean, correct spark plugs and good spark, and good fuel pump and filter. Check the tank is breathing OK.

Good Luck

Bob :thumbup:
 

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Junior
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Have same problem , I have 90' rd4 and from day 1 was running rich 36 mpg , 5 years later I decide have look at problem .
1st I synchronize carbs , then adjusted air mixture screws , when I turn them back it was nearly 3 turns on each side so done by book 2 1/4 , that was last week, will check mileage this week .
Only one thing I notes when carb tune was connected I open choke and only one side was effected ...
 

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Discussion Starter #6
Thanks Paul, Foz and Bob,

I did look at the choke plungers and fuel pump because they seem to be common problem areas with this vintage of Africa twins. As you say the economy with this bike has never been good. The thing that got me was the fault suddenly became noticeable at just over 2000 feet - like making a switch. Then when whenever below that height it went away.
At the time I went to the Honda dealer in Bolzano (North Italy) who could find no problems after they had changed the plugs and tested it. Then exactly the same thing happened on the way back up into the mountains passing the same village.

If this is not a common problem with the RD 04 then as you say I need to go through all the basics.
Thanks again.
 

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Discussion Starter #7
Really interest in how this turns out vinas. I would say that I was also getting about 36 mpg originally. Thanks
 

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I live at 1400m and my RD04 runs fine here, and regularly from 500m up to 2000+m so as others have said it must be something else - certainly not a typical RD04 problem. Good luck solving it!
 

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They are old bikes & prob been through a few hands.
As mentioned, check the basics inc choke operation, fit new stock oe mains, check the needle & emulsion tube for wear - are the needles std or have they been shimmed up???

Phil
 
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