R75/6 carb rebuild question

[20715]

So the diaphragm is bad in my right carb. 1975 R75/6, 69,516 miles. I've owned it since nearly new, and other than a diaphragm on the right in the very early 1980's, the carbs have never been apart.

I've got a step by step video on how to disassemble my exact carb that was made years ago by a couple of guys in San Diego, plus the videos on Youtube. I took it to a friend today. One of those guys in his mid-60's who started working on bikes and cars and everything else mechanical while he was still in the womb. I have yet to see something he can't fix. I just wanted him to look at it, but he took quite a bit of it apart, bit by bit, cleaned and reassembled, basically just seeing how good a shape it's in. Which is pretty good - it's not varnished or sludged up at all.

At any rate, looking at what two diaphragms would cost, it looks like I might as well get a rebuild kit. I need to decide whether to disassemble and soak in cleaner, or just clean it as I go with a spray can of carb cleaner. My friend is going to help me, so I'm not worried about getting in over my head. I'm sure not going to spend hundreds of dollars sending it to Bing.

Any input appreciated. I have no local dealer. I've used Capitol Cycle off and on for years. I use the Max on line fiche, but don't recall ever ordering from them. At any rate, the OH kit is 13 1 1 258 051, $73.64 at Max. Capitol has the same part number with an A after it, for $35.95. I assume that's after market. I have no problem with that, if the quality is good. For example, I buy Mahle oil filters, once I figured out they made them for BMW.

1. Anybody have experience with that kit from Capitol? If not, I'll default to the safe option and pay more for the BMW. I'm especially concerned about the quality of the diaphragms.

2. I'll probably call Bing Agency tomorrow and price their stuff as well. But research here and AdvRider suggests they're higher than BMW.

3. There are the original floats. I would guess most people say replace them, after 40 years. But I was getting acceptable mileage, and they were keeping the fuel level at about 20 mm in each carb. They're very slightly "above" parallel, but I don't want to mess with bending the tab when the bike was running great until that diaphragm went last weekend.

4. I am worried about the o-ring on the throttle shaft, just based on what I read. Is it a problem? I guess that is why I thinking about not taking it entirely apart and soaking in cleaner.

Thank you for any thoughts.

 

[20774]

1. Capital Cycle? They used to be the thing back in the day, but most people don't even bring their name up in conversation. I've assumed they're selling off-brand, less than OEM type of parts/supplies. My thoughts are "you get what you pay for."

2. Bing has been mentioned as being higher in price. On most things carb-related, dealers can do a bit better...but worth a call to Bing anyway.

3. Floats? Probably should replace them just for the time factor. But it might be something you can put off for later...you don't need to tear the whole carb down to change them out.

4. O-rings? IMO, I would leave them alone...I would also not soak the entire carb as that will seep into where the O-rings are and possibly damage them. The shaft o-rings require some special work to get to them and you must deal with the small screws that hold the butterfly in place.

 

[mneblett]

Capital Cycle??? Don't EVEN get me started ...

Also check your dealer -- as high as Bing USA's prices are, the dealers are sometimes less.

 

[m_stock10506]

At 70k miles it is likely that your needles and needle jets are worn. I would replace floats, needles, needle jets and the diaphragms. Don't soak them, o-ring on the butterfly shaft might get eaten up. If you don't lay up the bike for months at a time you shouldn't get varnish in the fuel passages. Adjusting the float level on new floats is not that difficult. I wouldn't keep using 40 year old floats just to avoid making that adjustment.

 

[20715]

OK. Thanks for the counsel everybody. I ruled out Capitol. I called Bing. Nice guy, very helpful, but prices were significantly higher than the dealer. I just decided to call Gateway. They had everything in stock, except for one main piston needle. I didn't want to admit in my earlier post when I tried to pull the top off without first removing the throttle and choke cables, I put a very slight bend in it. My friend very gently straightened it using a plastic hammer and flat surface...it slides easy and true, and he pronounced it good, but I thought I would order one just in case. Gateway will have it in the morning, ship it all tomorrow, and I should get it Thursday or Friday. I am replacing the floats, and both float needles. They're 40 years old - they've served their duty.

I'm not going to soak the body, or the top. I'm not even sure I'll soak anything - might just use Chem Tool B12 spray, a brush and air. I'll decide later this week.

Thanks again.

 

[20715]

Success ! My first carb rebuild in the books. Then synched to perfection by a friend with his original mercury carb stix. Running like new!

 

[20774]

Many smiles now!!