The New And Improved Unofficial R65 Forum V2

Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: MR.E on August 31, 2011, 04:09:21 PM

Title: balancing carbs
Post by: MR.E on August 31, 2011, 04:09:21 PM

Hello

how do i 'balance' the carbs on he bike?
I've just given both carbs a full overhaul, with all new parts & o-rings but the left side of the engine seems to have alot more ooomphf behind it at the exhaust.
The bike ticks over ok seems to struggle occasionally for half a second or so but i don't think it's perfect.

SO, how do i balance the carbs?

thanks

Title: Re: balancing carbs
Post by: Bob_Roller on August 31, 2011, 05:14:21 PM

You need a manometer or vacuum gauges one attached to each carb .

Do a search for manometer on this site, there's instructions on how to construct one for a low cost .

Title: Re: balancing carbs
Post by: Barry on August 31, 2011, 05:26:56 PM

For carb balancing the objective is have both butterfly's open by equal amounts at idle and for both to open at exactly the same time when you twist the throttle. Comparing the vacuum side to side with a manometer is an easy way to ensure both things and they are cheap to build. It is possible to get close enough to run well by a careful mechanical set up which can then be checked with a manometer afterwards.

There is also the mixture screw to set. Start with 1/2 turn out from gently closed and adjust in small increments to achieve maximum idle speed.

Should be lots of threads if you do a search.

Title: Re: balancing carbs
Post by: RSMike on August 31, 2011, 05:58:09 PM

If you feel like spending a few quid on vacuum gauges, I would highly recommend carbtune ( twin column model), nice easy to read display, no power supply needed, reasonable price

(https://bmwr65.org/smf/proxy.php?request=http%3A%2F%2Fwww.carbtune.co.uk%2FImages%2FSSL11411s.jpg&hash=20e686f3a17636ce5c7e8d6ca3b42bbfb34181a0)

http://www.carbtune.com/

Title: Re: balancing carbs
Post by: montmil on August 31, 2011, 07:24:48 PM

It's all in here. Simple language. Effective techniques. The only carb synch'ing info you need.

http://www.airheads.org/content/view/183/98/

Monte

Title: Re: balancing carbs
Post by: nhmaf on August 31, 2011, 07:52:57 PM

RSMike - I like the carbtune myself - I have the 4-channel model so I can adjust the carbs on my Kawasaki GTR as well as the airheads.

Title: Re: balancing carbs
Post by: 79beem on September 01, 2011, 02:00:38 AM

I built one of these, very simple and cheap.
Carbs were way out of balance.
Tiny adjustments result in big changes on the manometer.
Have a big fan going like the clappers at the heads to keep her cool. That way you don't get all clammy and panicky  :o when the fluid is going up and down up and down..........
And don't put to much fluid in the manometer.

Title: Re: balancing carbs
Post by: Lucky_Lou on September 01, 2011, 02:08:58 AM

Quote

Hello

how do i 'balance' the carbs on he bike?
I've just given both carbs a full overhaul, with all new parts & o-rings but the left side of the engine seems to have alot more ooomphf behind it at the exhaust.
The bike ticks over ok seems to struggle occasionally for half a second or so but i don't think it's perfect.

SO, how do i balance the carbs?

thanks

Where abouts in Yorkshire are you ? i have the mark 3 "Texas" tuner i am near J39 M1 i would be happy show you how to do it, or do it for you.  
Lou

Title: Re: balancing carbs
Post by: Dizerens5 on September 01, 2011, 03:27:30 AM

Say it softly but if you hold a hand against each exhaust with engine idling it will give a surprisingly good idea of the balance in a quick check. Confirm later with a manometer (unfortunately that means crawling on the floor with a little screwdriver!)

Title: Re: balancing carbs
Post by: MR.E on September 01, 2011, 06:54:29 AM

Quote

Where abouts in Yorkshire are you ? i have the mark 3 "Texas" tuner i am near J39 M1 i would be happy show you how to do it, or do it for you.  
Lou

Cheers for all the replies, i'll look into the gadgets for them.
Lou, i'm in North Leeds - Shadwell -
Thanks for the offer, if you can PM me your phone number i'll have a chat with you about them.

Cheers lads

Title: Re: balancing carbs
Post by: Lucky_Lou on September 01, 2011, 01:43:20 PM

PM sent, Your just up the road should be no problem getting it sorted.
Lou

Title: Re: balancing carbs
Post by: MR.E on September 01, 2011, 03:09:13 PM

brilliant thanks

Had a friend lend me some gauges tonight, but i can't seem to get it right.

now whoever had the bike before has cut the 2 mid pipes that join each side of the exhaust (left to right), and welded each hole closed so the exhaust pipes no longer connect together.
Will this make a difference to the bike?
it seems to ride ok but i've no idea what it should be like!

Thanks  

Title: Re: balancing carbs
Post by: Lucky_Lou on September 01, 2011, 03:18:58 PM

The ballance pipes will improve performance pre 81 had 1 crossover post 81 has 2, at this stage i wouldnt worry too much about it, the carbs can be sorted without. Is the exhuast system stainless steel ? or chrome ?. Parts a freely availiable from Motorworks (Huddersfield) Motobins (post) or ebay
Lou

Title: Re: balancing carbs
Post by: MR.E on September 01, 2011, 03:22:14 PM

exhaust is stainless & i fit some of these - http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=120720633860 -

OH boy is it loud!!
looking for a baffle to fit inside that will hopefully give a bit of back pressure!

i've become quite a frequent visitor of motorworks over the last few weeks!!!
thanks