The New And Improved Unofficial R65 Forum V2
Technical Discussion => BMW Technical Q&A, Primarily R65 => Topic started by: Billmc on April 24, 2017, 08:36:22 AM
-
It's starting to warm up here on the 3rd coast and that's making it easier to start the old girl.
On the other hand, after a "spirited" 30 mile ride yesterday, coming to a stop light the idle settled in at 2,000 rpms and would not drop any lower. Blipped the throttle a couple of times but no change.
I have modified nothing over the winter and the ride last week did not change the normal idle she has had since the rebuild last summer of 900-1,000 rpm's.
Any ideas on what is going on and what I need to do to fix it??
-
Anyone have any thoughts to share?
-
It's starting to warm up here on the 3rd coast and that's making it easier to start the old girl.
On the other hand, after a "spirited" 30 mile ride yesterday, coming to a stop light the idle settled in at 2,000 rpms and would not drop any lower. Blipped the throttle a couple of times but no change.
I have modified nothing over the winter and the ride last week did not change the normal idle she has had since the rebuild last summer of 900-1,000 rpm's.
Any ideas on what is going on and what I need to do to fix it??
Could be a few things -
I'd start by looking to see if the advance/retard mechanism in the beancan is free of not - its a good excuse to clean and lubricate this often neglected and very important part even if it is free.
Next I'd be looking at the intake rubber "trumpets" that connect the carbs to the heads - if they are cracked and "old" looking replace them (by all means buy a length of the right sized rubber tube and cut to length, but make sure that the tube you buy is heat rated and is roughly as "stiff" as the originals, it is very, very embarrassing to have to do an emergency refit of your carbs by the side of the road (involving half a roll of electrical tape) when the couple of dollars saved in buying a length of tube and cutting comes back to haunt you in the form of a backfire and your carb making a strike for freedom, retained only by the throttle and choke cables :-(
Next did you remember to put the vacuum port screws back in after you most recent tune? Fun fact, you will never buy those 2.5 (or is it 3) millimetre screws if away from home. But a short length of 6mm internal diameter fuel hose or vacuum hose will slip over the outside of the vacuum port and you can then put a 6mm bolt or even a suitable self tapping screw into the hose to get you back on the road.
There are many other possible causes - like the enrichening assembly screws coming loose, air getting past a worn throttle butterfly spindle, but I would look at the first three before dooming myself to spending a lot of money.
-
Thanks Tony I will check those 1st and report back.
-
Next did you remember to put the vacuum port screws back in after you most recent tune? Fun fact, you will never buy those 2.5 (or is it 3) millimetre screws if away from home.
Keep going Tony it was 3.5 x 0.6
In the UK there are 50+ screws of that size in every house. It's the same thread used to secure light switches and power outlets. They are not flat head screws but they'll do as a temporary substitute in a pinch as I discovered when my originals got lost for a while in the garage ether.
-
Just a thought here because I am no gear head but learning. When I put in new points I discovered the old ones were set way low. When adjusted properly my idle (after warm up) was in your 2000 range. I simple re-adjusted my idle speed and happy since.
-
Ok so I had time yesterday to try to figure this out.
Checked the valves and found they were TIGHT so I broke them loose and re-adjusted to spec. Started her up and went for a ride. What a difference! 3,500 miles since last adjustment so that gives me a base line for when to adjust . The idle was still high but I couldn't detect any leaks or such. I spun the idle adjustment out a little on each carb and went back out. After 15 miles I came back in and she had settled into a nice 1,000 rpm idle.
Still had very good response, no backfire, and sounded great!
Let her cool off for a few hours and restarted her and no problems. Went for another ride and She is good to go!!!!
Thanks for the help and ideas!
-
Good that you are making progress. If you still have an intermittent hight idle it well may be the advance weights as Tony suggested. Our '80 R65RS had this issue and it was sticking weights. I would gett off the freeway, pull up to a stop sign and the idle would be 1500 - 2000 RPM - IIRC, it was a long time ago. One "test" to verify this was to put on the brake, slightly slip the clutch to bring RPMs down, and all of a sudden the idle would drop back to normal. Of course, shutting off the engine and restarting resulted in correct idle speed. Slipping the clutch and bringing down engine speed a bit seems to allow the weights to "un-stick" and return to their correct idle position.
When I pulled the beancan apart it was really nasty. After cleaning out all the grunge, and rust, normal operation resumed.
-
Since this is an '87 with electronic ignition I don't think that would be the issue but its not a bad suggestion to take a look in there...Thanks!
-
The "electronic" beancan still has advance weights in the bottom. The only difference is the reluctor and Hall-sensor instead of points. Unless you have an aftermarket ignition that replaces the beancan.