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Believe I have carb problems, help!

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Edward Jones
(@14979)
Posts: 56
Trusted Member
Topic starter
 

I was last riding my 1981 R100RT in Florida over the winter of 15/16. I made a few mistakes when I brought it back to Maine, first I must have used ethanol, E10, fuel, then I parked it and got busy with many other projects, until this spring without draining the carbs. Well needless to say I had a mess on my hands. So I got a couple rebuild kits from CapitalCycle and proceeded.

Once the green crud was cleaned away things looked good. I’ve rebuild carbs in the past so these CV seemed pretty simple, haha. But anyway, I cleaned the passages, checked and cleaned jets, etc. The floats appeared good, both weigh 13gr and float about 1/3 out of a bowl of gas. I set the float level to shut off just slightly below level with the carb body and when I open the bowl and measure, I loose a little fuel , I’m at about 19-20mm next to the overflow tube.

So my problem is, she will only start for a few seconds then die. I can rev to about 3500rpm then she dies.
I’ve checked the spark, cleaned the plugs. Also clean fuel lines and filters.

The idle mixture is set to 1/2 turn. When I crank I can see the carb pistons lifting on the pulses so there seems to be good vacuum. I did not replace the main needle or change it’s position they are I believe stainless steel and looked good, i.e. clean and smooth. I think I got the choke assembled correct just by looking at how the circuit works, 4 holes at bottom, teardrop at top.

Any ideas? Also on a 60deg day should this bike need full choke, at least for a few seconds?
Thanks

 
Posted : 05/20/2017 17:33
Edward Jones
(@14979)
Posts: 56
Trusted Member
Topic starter
 

Hi Scott,
Yes the pilot jets were both clogged, I ran a small wire through both and followed up with carb cleaner until I has a nice flow. Then carb cleaner up the passage to squirt out in the throttle neck(?). Same with the idle passage.
Well tomorrow instead of the great warmup ride for my Summer Solstice, Single State, Saddle Sore 1000, I'll be tearing those carbs down again, I must have missed an air passage or something, dang I wish I had one of those fancy ultasonic washers 🙂
Do you know of a diagram that shows all the internal passages? That would really help I think to be able to check off a passage as I get carb cleaner through it.
Thanks!!
Edward Jones

 
Posted : 05/20/2017 18:09
Edward Jones
(@14979)
Posts: 56
Trusted Member
Topic starter
 

Feeling kinda sad, best I can tell, and it is confusing, in Maine ALL gas is E10. Thank you Iowa Corn you have convinced the gullible and paid for politicians that Corn Ethanol is "Green". Now if it were sugar ethanol you might have a point, but corn ethanol is simply a wealth transfer from the many to the few.

 
Posted : 05/20/2017 20:40
Edward Jones
(@14979)
Posts: 56
Trusted Member
Topic starter
 

FIXED AND RUNNING FINE! I did pull both carbs back off and double check all air/fuel passages, choke, etc. I did not see anything obvious. I set the idle mixture to 1/2 turn per spec in my 1994 "Clymer BMW R-Series * 1970-1994"
Well initially she was still stubborn, but better. Next I turned both idle mix out to 1 turn, better.
Anyway the final setting is 1-1/4 turn. Which coincidentally is the initial setting fro the 1979 R100RT. Then it hit me like a baseball bat, I was reading the initial setting for the 1980 bike! 🙁 I scan up the page and there is the 1981-1984 R100RT is 1-1/4 turn, insert head banging here.
My humble apologies for all the nasty thoughts I had about Clymer between Fix and finding my error.
This certainly explains why she would run at about 3500-4000rpm but not lower.
Edward Jones

 
Posted : 05/21/2017 18:40
James Carr
(@11771)
Posts: 29
Eminent Member
 

This site has a great series of "how to" on the Bing 64 carbs. There are 3 parts to it so scroll down to see them all.
http://www.electricmotorglider.com/

 
Posted : 05/27/2017 00:14
Edward Jones
(@14979)
Posts: 56
Trusted Member
Topic starter
 

11771, Pretty cool, I didn't know the Bing 64 was still in modern use. I thought pretty much every engine bigger then a chainsaw motor had gone FI. I like messing about with old bikes, but can't deny that FI is more efficient and reliable. I had a good laugh when I saw that the Triumph Bonneville T100 has Fake carbs hiding the FI! 🙂
Edward

 
Posted : 05/28/2017 14:53

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