cold start problem

[manxr65]

i have just done putting carbs back together after putting new internals in and i cant get it started , one carb is is always backfiring , and i mean backfire and loud. i have basic settings , half turn on mixture and a full turn on idle stop screws .
one carb is over full of fuel and i need help
thanks

[montmil]

i have just done putting carbs back together after putting new internals in and i cant get it started , one carb is is always backfiring , and i mean backfire and loud. i have basic settings , half turn on mixture and a full turn on idle stop screws . one carb is over full of fuel and i need help thanks

Here's my take, in no particular order...

If one carb's float bowl is "over full", correct that issue by checking the float needle seat for fuel line junk which may be keeping the rubber-tipped float needle from closing all the way. Also, confirm the float is not hanging up on something and that it is adjusted to the proper level.
   You might try dropping the float bowl, turn on the fuel tap and s-l-o-w-l-y raise the float and check where the fuel stops flowing. Be sure and place a pan under the carb to catch the fuel. No smoking, either.

Check the enrichener (choke) bits. The rotary valves are handed, meaning there is a left carb disc and a right. Check choke cables to confirm chokes are fully 'off' when desired.

I might back off the the idle stop screws so they are not touching the butterfly arms. If you have a half turn or so on the idle mixture screws, the bike should idle just fine. Later, do use a manometer to balance the mixture screws for a smooth idle... after you correct the over-rich backfiring concern.

Make sure the new diaphragms are installed correctly. The little tab on the rubber rim goes into a matching notch on the carb body.

Confirm the tiny hole in the bottom of the enrichener fuel reservoir is open. That's the small chamber in the float bowl that contains the long, brass tube that feeds the enrichener circuit.

OK, you got some things to check out right now. Let us know what's happening afterwards and we'll all try to get you going proper.

Do be advised, Manx Man... us folks in the Colonies will be stuffing our pie holes on Thursday, Thanksgiving Day, so any responses from us may be with mouths full and slightly gobbled, uh, garbled.

Monte

[manxr65]

could a sluggish battery cause the same problem

[montmil]

As the battery in your BMW powers the ignition and electricals, it "could be" an issue with the odd running... maybe. Best way to determine if the battery is creating problems would be to charge it up and see how she runs.

Monte

[Bob_Roller]

Do be advised, Manx Man... us folks in the Colonies will be stuffing our pie holes on Thursday, Thanksgiving Day, so any responses from us may be with mouths full and slightly gobbled, uh, garbled.

Hey, some of us have to work on holidays and weekends, to keep this country running, while you the 'royalty', stuff your 'pie holes' .  [smiley=ROTFLMAO.gif]

[montmil]

Do be advised, Manx Man... us folks in the Colonies will be stuffing our pie holes on Thursday, Thanksgiving Day, so any responses from us may be with mouths full and slightly gobbled, uh, garbled.

Hey, some of us have to work on holidays and weekends, to keep this country running, while you the 'royalty', stuff your 'pie holes' .  [smiley=ROTFLMAO.gif]

Definitely beats working the "pat down" line at Sky Harbor. [smiley=whip.gif]

[Dizerens5]

Manx are you sure your valve clearances are ok? Easy to make a mistake and leave too little, -- maybe because the R65 adjusters seem to have a pretty coarse thread?

[Darwin_R65]

Also some BMW manuals quote original clearances, whilst BMW did release a technical bulletin where they changed the clearance.

http://www.bmwr65.org/htdocs/yabbfiles/Attachments/Valve_Clearance.pdf

[Semper Gumby]

Do be advised, Manx Man... us folks in the Colonies will be stuffing our pie holes on Thursday, Thanksgiving Day, so any responses from us may be with mouths full and slightly gobbled, uh, garbled.

Hey, some of us have to work on holidays and weekends, to keep this country running, while you the 'royalty', stuff your 'pie holes' .  [smiley=ROTFLMAO.gif]

Definitely beats working the "pat down" line at Sky Harbor. [smiley=whip.gif]

Hey!  NO GROPING!!!!  Thanks for reminding me about that service bulliten Darwin.  Crikey I've been using .006 and .008 since 1993 though.  What was I thinking!  (I'll give .004 .008 a try next time in though -- Hey that is going to open the intake valve sooner and close it later.  Hmmmmmm)

Apologies for thread degradation.... 8-)

[manxr65]

right got new battey at the cost of £120, i checked float bowl for height of petrol and its about half way up about right
also noticed that the float needle was still letting petrol in when float was all the way to the top , so i hope by adjusting these problems it will run now ,
let you soon
ps,  half way up float bowl is ok yes .
thanks

[Barry]

also noticed that the float needle was still letting petrol in when float was all the way to the top

Adjust (carefully bend) tab that pushes up float valve so that fuel flow shuts off when float is parallel with carb bottom.

ps,half way up float bowl is ok yes  

Depth of fuel in the bowl measured from the centre well should be 22 - 24mm.  I don't know how many mm half full would be but it's not something you should estimate just by looking at it. For best results the levels needs to be set quite accurately so that both sides are within 1mm of each other.

[manxr65]

 well new battery on and float bowl adjusted and still nothing, bike turn over but not trying to fire, mixture half turn out and throotle just over half a turn .if i touch the choke it just backfires when i turn the key off. i keep checking plugs and they seem wet ,would the spark plug stop firing when replaced . but the bike is just not trying to fire at all
i have checked valves and i have a spark on plugs when out , rechecked carbs and still nothing, what to try next
please help

[manxr65]

also i been thinking i have 85 carbs in a 79 engine , i have the needle set at number 3 maybe it should be number 2 , would this make a difference . ie make less fuel into the carb

[Barry]

i have the needle set at number 3 maybe it should be number 2 , would this make a difference . ie make less fuel into the carb  

Yes it would put less fuel into the engine but would not affect starting and idling so I doubt if this would make any difference.

Do you know anyone with a set of good carbs that you could subsitute to help isolate the problem or show that it lies elsewhere like ignition timing or valve timing.

[welshman]

I have just finished the same carb. refurb as you and unless you have altered something without knowing it has to be incorrect reassembly. If you have the time, get Mike Fishwick's service notes from the BMW club's South-western region secretary. They have all the parameters/settings for most combinations of carb/bike. The choke(starting carburetter) is one of the obvious places to start!(sorry) and you can find pics on this site. I always set the idle mixture screw one turn out which gives some leeway in initial adjustment. Make sure the cables are reasonably balanced by eye and feel in the ferrule at the cable adjustment end on the carb top. If the bike was running fine before you did the carb. strip I don't really see it being an electrical/ignition problem but it wouldn't hurt to do a static timing check and a running one if you can get it run at all. As other posts, check the float chamber jet in the corner,it is a very small orifice and quite fiddly but needs to be clear. +1 for floats also. Glyn.