Choke needed after jet replacement

[Bill Parker]

Recently purchased a 1984 R65 with 63,000 miles. I cleaned and overhauled the carbs (new O-rings, gaskets, diaphragms) with little change in performance. Last week I changed the needle and needle jet to the same parts that were in there originally (but with 63,000 fewer miles)

Previously, the bike would start without using choke, just opening the throttle a little (I'm in N Florida). Now I have to use the choke on the first click or it is very difficult to start and won't take throttle until warmed up. After warmup, it works fine. Which of these behaviors is normal?

Thanks

Mr. Bill

[Bob_Roller]

Sounds like the carbs were running on the rich side, until you replaced the older possibly worn or degraded parts with fresh parts .

[montmil]

Sounds like the carbs were running on the rich side, until you replaced the older possibly worn or degraded parts with fresh parts .

Florida, Tejas or Phoenix, the Airhead Bings will need the Enricher Circuit utilized for starts.

Here's the likely scenario, or close to it, when you overhauled the carbs:

     Steel needle that is, by design, wobbly when correctly installed in the slide,
     Brass needle jet enduring the constant wear from 63,000 miles of steel abuse,
     Needle jet worn beyond spec and allowing an overly rich fuel draw,
     Which caused the "No Enricher Circuit" issue.

You done good, Mister Bill. Welcome to The Herd. Now... Photos, please, or the inmates become agitated.

[Bill Parker]

Thanks to all. And photos as requested. Thus far have replaced tires, battery, rebuilt carbs and forks, and, most recently, replaced steering head bearings. New top-end seals and rings are next (compression is 90 psi hot, both sides). Using it to commute 40 miles/day and it is a much better in-town bike than the R1200st.

I've found this community very informative and helpful. Thanks to everyone.

Mr. bill

[mrclubike]

That is exactly What Mine did after I did a needle and needle jet replacement
I put the .264 jets  in as per the Max parts manual but it was way to lean
So i went to the .266 as it had in it and it is running  pretty good and my MPG went from  about 42 up to 49
But now with the weather cooling off  I am going to go to the ,268
I did min at about 60K miles


FYI  
A top end reseal and cleaning would not hurt at all
I was also having  a Pinging issue and I had to pull the heads  & cylinders and clean out the carbon  ( I did not replace the rings)
Just did that yesterday  (62K miles)

[Barry]

So i went to the .266 as it had in it and it is running  pretty good and my MPG went from  about 42 up to 49  

It's been my experience too that excessively weak mixtures produce worse MPG.  

Given the stock jetting was for a different fuel spec than we use today it's also been my experience that the stock needle position/needle jet is too weak and was even a little too weak back in the day according to period road tests. I've raised the needle a notch which is a big change and it runs vastly better with better MPG.

Needle jet increases are a more subtle change. A one size needle jet increase results in a jet flow area increase of 10% at initial lift reducing to 2% at maximum lift compared to raising the needle from P2 to P3 which results in a jet flow area increase of 44% at initial lift reducing to 5% at maximum lift.

[Bill Parker]

Are the needle notches counted from the bottom or the top? Mine was in 2nd lowest, an that's where I put the new needles. I only have one more notch of lift left.

[Barry]

They are counted from the top with 2nd and 3rd being the most common positions.  position 1 and 4 are much more rarely used.  Only the later carbs have needles with grooves like the pic below but it illustrates the order of positions for all needles.

It's always good practice to measure the length of needle that protrudes as a check that they are in the correct position and indeed both in the same position.