R25/2 Ride Gone Bad

[schrader7032]

I was out to get gas for the bike on 1/1/22. Thought I might have an issue getting it started but the bike started easily after the fill up. I was riding my usual route and was near making my turn for home, I noticed that the throttle seemed to be stopped and wouldn't go any further. It thought things were OK as I had enough throttle, plus it was uphill and into the wind. As I rolled off throttle to make my flip turn for home, the engine wouldn't slow down. It was clear that the throttle was stuck somehow. I briefly pulled in the clutch but the engine began to race. Letting the clutch back out, I reached up and pulled the key. The engine stopped and fortunately I was near a fire station. I rolled into their parking ramp. Somewhere in the all the confusion, I must have dropped my key...that's when I heard a car run over something...my key! I picked it up and saw that it was bent. I will try and bend it back or maybe just buy another one...my R69S key will work for now.

Wasn't sure if I wanted to try and figure out what was wrong. The firemen came over and we talked. After a bit, I saw
that the throttle cable sheath separated at the housing...I could see the cable inside. See the picture...this is with the throttle completely closed...lots of slack. I thought more about it and figure that the slide is frozen in the bore. That
would account for the engine revving and the slack.

I didn't feel like resolving the issue there, so called a friend who brought his truck, tie downs, and a wide board. With the help of the nice firemen, we got the bike into the truck bed and tied down. Eventually got it home...had to unload by backing the truck into a very sloped driveway, lessening the angle that the board makes to the ground...was easy to roll out.

It's been cold out, so haven't even taken a look. I plan on first removing the rock strainer/filter and using a mirror to look inside the carb throat. I suspect I'll see nothing but the jet needle indicating the slide is stuck. I may try tapping on the side of the carb with a screwdriver to see if it releases. I'll eventually take the top of the carb off and see what's going on.

So, I either have a cable issue...maybe even a sharp transition right there at the top of the carb ...or the slide is stuck in the bore. Once I figure that out, I can go from there.

[jwonder]

Kurt, sorry to see that, but the old girl does look nice. As you know it’s one of 3 issues: slide at the throttle end, cable, or slide at the carb end.

I would love to know which one it is once you have figured it out.

I was going to make a snarky comment about a 25/2 and horsepower and being able to ride it home at full throttle with no problem but thought twice about that.

[schrader7032]

This is one thing that I want to investigate...certainly not good. I don't know why the cable has such a sharp transition into the carb.

[wa1nca]

Did the cable break at this curve above the inlet to the carb
Tommy

[schrader7032]

Don't know but will certainly be looking into that.

[San Arthur]

Kurt I would take the carb down, check the slide, the slide spring, maybe the needle is preventing the slide from closing?
After years of use the slides deform the carb sleeve.

Good luck and keep us posted.
Saludos and happy new year!

Arturo

[Bob Allan]

Hi Kurt.
Sorry to hear of your problem.
You spoke to me recently about my R26 steering head bearings on the Einzylinder forum.
Best wishes & I'm sure all will soon be well.

[Micha]

This is one thing that I want to investigate...certainly not good. I don't know why the cable has such a sharp transition into the carb.

Sorry to hear about this experience.
In case this is not the standard in your carb and I understand that it is not, should not you consider installing an angle arm that will help route the cable?

https://www.bmwclassicmotorcycles.com/p ... rt-one-33/

Nr. 3 on Salis pic.

[schrader7032]

Micha -

I thought about something like that but the parts list doesn't show for an R25/2. Probably the diameter of the twin cylinder top won't be the same as the single.

Once I get some warmer weather, I plan on doing all the things mentioned. First I want to do some triage so I can actually see where things sit before I start tearing it apart.

[schrader7032]

I finally braved the 60 degrees and sunshine! Time to take a look. I pulled the air inlet filter and can see that the full needle is showing...the slide is up in the top part. I then removed the threaded cap with carb still on the bike and you can see that the slide is sitting right there. It took quite a bit of finger force to push it down. Once I did that, I had throttle control back. But when I pulled it full again, the slide stuck. So, I likely could have fixed that on the side of the road, but if I were to get into a near full throttle situation, it would have stuck again.

I used some heat around the top of the carb body, but when I sprayed carb cleaner in there, the slide loosened up considerably. I pulled the carb from the bike but left the slide attached to the end of the cable. I measured the diameter of the bore and was getting over 27mm and the slide was measuring under 27mm, so I don't think there's an issue with the dimensions. I think I just have residue getting up on the top part of the bore and becoming a gum. Enough of that and it captures the slide.

Tomorrow, I'll give things a better clean and put it back together. Try some full throttle pulls. I'm thinking that should cure things. And I don't think the cable angle at the carb is an immediate problem, but I will try and position the throttle cable so that I have a more gentle curve there.