new carb parts - now missing some midrange punch

[rob650]

I apologize in advance, i know this is going to sound vague, hopefully other owners recognize this condition...

R65 with 75K miles.  I just installed:
new mufflers (MAC),
new main needles in the carbs
ran through carbs and replaced all old rubber o-rings
new throttle cables

i havent balanced the carbs yet.

The Good is the bike starts easier, idles and accelerates smoother and runs smoother over all.  The old mufflers had some cracks/leaks so im thinking the new mufflers, needles, and thorough carb cleaning all had a contribution to a smoother running engine.  Hasnt run this smooth in a long while.

The Bad -- it feels like i have lost a sizeable chunk of mid-range "punch" -- the kind you use to drop down a gear and get that short blast of speed to around a slower vehicle, or scoot up from 50 to 70 in a quick burst.  

My first thought is placement of the main needles.  Any thoughts?  Thank you.

[Barry]

Unless the balance is wildly out the likely scenario is you are now weak in the mid range due to either the mufflers or more likely the replacement of worn needles with new ones.  Is there also a possibility that the needles went back in one position lower ?   If so you could try raising them a notch.

I suppose one thing to do if it's feasible is to go back and make one change at a time to help diagnose the cause of the problem.

[montmil]

As Barry suggested, I'd try raising the needles one notch. That cleared up my '81 R65 after a carb rebuild.

[mrclubike]

Did you replace the needle jets  
 You need to replace both the needles and needle jets.
  
It takes very little wear in the jets and needles to change the mixture
it is only about  .001 of an inch difference between a 2.64 and a 2.66 needle jet
I put a 2.64 in instead of a 2.66 and the mid range was terrible

I just replaced mine
If I remember correctly the length of the needle sticking out of the piston is  39.5 mm when in the 3rd notch
41.3 mm in the 2nd
But check yours and go from there

[Barry]

These are the needle lengths I measured for each position but I guess there will be minor differences. Main thing to know is what the length is for the position you should be in as a check to be sure they are in the right slot.

1      42.37
2      40.57
3      38.79
4      37.10

Yes I was a little puzzled that the needle were changed and not the jets as it's the jets that wear the most. You can imagine that wear would very easily amount to a one size change in needle jet size and that produces a 10 % change in the jet flow area at initial needle lift.

[Einar]

Great question and input!

I was not aware of this adjustment, despite the fact that I rebuilt my carbs once already.

Is there a "standard position" for the carb needle? How do I know when I'm at the optimal mix?

[Barry]

The needle positions vary according to model year and market version usually being either 2 or 3, rarely 4 and never 1.  

I believe your needles should be in the 3rd position. Remove them completely and insert 3 clicks by rotating the needle in your fingers between each click.  If you have anything like a digital caliper take measurements at each needle position so in future you'll know where the 3rd needle positions is. At a pinch you could measure with a steel rule as the positions are almost 2mm apart.

[Einar]

Thank you for the clarification. Will investigate this when I take carbs off the next time, sounds like this could have an impact on both performance and fuel consumption.

[mrclubike]

Thank you for the clarification. Will investigate this when I take carbs off the next time, sounds like this could have an impact on both performance and fuel consumption.

Yes it has a huge impact on performance and fuel economy

The 82 r65 should be in the third notch
All the way inserted into the piston is the 4th notch all the way out is the 1st notch  

[montmil]

Thank you for the clarification. Will investigate this when I take carbs off the next time, sounds like this could have an impact on both performance and fuel consumption.

Yes it has a huge impact on performance and fuel economy

The 82 r65 should be in the third notch
All the way inserted into the piston is the 4th notch all the way out is the 1st notch  

Wondering if the needle sizes and positions are different in the Euro bikes as those here in the States.

[Tony Smith]

Thank you for the clarification. Will investigate this when I take carbs off the next time, sounds like this could have an impact on both performance and fuel consumption.

Yes it has a huge impact on performance and fuel economy

The 82 r65 should be in the third notch
All the way inserted into the piston is the 4th notch all the way out is the 1st notch  

Wondering if the needle sizes and positions are different in the Euro bikes as those here in the States.

Monte you took the words out of my mouth.

Beware Haynes manuals in particular, my (very old) Haynes manual (so old it does not cover the R65 at all) has entirely wrong needle and valve information for R50/R60/R75/R90 and R100s (Fer instance quoting Bing parts for the R90s and quoting the same parts/sizes for a "cooking" R100 and the 70hp R100RS).

The only way to be sure is to go back to BMW documentation, cross checked with what you took off you bike - if they differ phone a friend in the same continent and ask them to review their motorcycle.

[mrclubike]

I installed the 2.64 jets as the parts shows and it was way too lean with the needle in the third notch

[Barry]

Haynes is correct in that there were differences between Euro and US model jetting but I'm sure Haynes still contains errors. I'd be more inclined to trust the BING data. here:

http://www.bingpower.de/en/service/tuning-manuals/

BMW started playing around trying to meet emissions requirements around 80/81 so the jetting changed from one model year to the next and maybe wasn't optimum so who's to say the original jetting will work best now especially when you also consider they were set up for fuel available back in the day. Today's fuel containing ethanol will run weaker so some allowance has to be made for that.

My needles were originally in position 2 but I was quickly convinced that is not optimum as it produces a lean mid range similar to the Rob650's symptoms.  If you read period road tests for the R45 they describe a lean mid range condition so even back in the day position 2 wasn't quite right.  I experimented with position 3 and by shimming the needle jet even positions in between 2 and 3. The bike runs much better and gets better MPG.

Moral of the story is use the original settings as a base line but don't be surprised if you get better results today with different settings.

[georgesgiralt]

Hello !
I own a European factory manual for our bikes. I can supply the official European jetting for the 79 to 83 R45 and R65. As I got the manual around 84, I did not get the latest updates and my data is limited to the above given years.
I agree with Barry. If you have old parts in your carbs, freshen the rubber, change the brass fo new parts and ride. Then adjust to get a proper running engine.
In France, every automotive gas contains up to 5% ethanol, and 95-E10 has 10 % ethanol. There is also a E85 which has 85 % ethanol. The 95-E10 is said to replace all other mix in a near future.
There is a premium gas E98 which is supposed to have no ethanol (but can/may contain up to 5% per spec...) which is very good for our engines.
I tried to adapt the jetting for the 95-E10 and was unable to get a proper running engine (the gas has a very limited life due to the moisture it absorbs from the air so the jetting should change at every filling and maybe in between filling).
I ended having an engine less crunchy and with a very poor mileage. So I reverted to the 98 premium which is more expensive at the pump but less if you factor in the gas mileage !