How do I lift the curse from my R75/5?

[166926]

I know I cursed it the other day by bragging that it started right up after I put in a new battery. Haven't ridden this particular bike in 2-3 years. I went on about a 10 mile ride, no problem.

I then put new fuel lines on the bike, and jb welded on one of the name tags that goes on the starter cover that fell off shortly after I got the bike way back when. Final curse?

I didn't use the bike for two weeks, but I have it on a battery tender. Of course, now it won't start. It turns over, semi-catches, but nothing. It's even worse with the choke on.

Now, I have to figure that somehow putting on new fuel lines may have done something, I may have knocked something loose, who knows, so today, here's what I did:

Took bottoms off of the carbs - both had gas, but not overflowing. Equal, respectable amounts.
Turned on the petcocks, and saw gas flowing into carbs. It likewise stops when I press up on the floats.
I checked the sparks upon starting (the lay the plug on the head and start the bike trick) - no problem there (it has a dyna ignition)
I then did a 1/2 A$$ carb clean - I pulled the main jets and idle jets, cleaned them, and blew air through them as well as the passages on the carb (still on the bike)
Put it all back together, and its a little better, but that may be wishful thinking. Still won't start.

Before I go completely mental here, what am I missing? I'm really stumped, becuase this is the only change since I last used the bike - the fuel lines, and there's gas getting to the carbs...

 

[PGlaves]

Make sure that the throttle cables are properly seated in the adjusters where they attach to the carbs. If one is pulled up out of the adjuster it can cause your symptoms.

 

[166926]

Throttle cables are seated

Just checked, and the throttle cables are seated.

Thinking out loud though, since I think I have fuel and spark, what is missing would be air. If the choke makes it worse, as in it won't sputter at all (like it will with the choke off), I'm wondering if this isn't an air issue.

I wonder if I did something to the air filter, when I replaced the fuel lines? It's not like it can go in backwards or anything. I guess the test will be tomorrow - I'll take the air tubes off and see if I can get it started.

Thoughts?

 

[godfather]

Is it possible the diaphragm is bad and got worse after the initial ride?

 

[ccolwell]

Thinking out loud, or at least on screen, if it's worse with the choke on then something is making it to rich. So it's either getting too much fuel or not enough air. The first seems unlikely and you don't, or shouldn't, have a diaphragm on a /5. I think the air filter is the most likely culprit -- perhaps something has made a nest in there?

If not, it's because anything prior to a /6 responds badly to cheap adhesives. They want something from BMW that costs at 68.75 DM per ounce. You will have to sacrifice a virgin squirrel from the depths of the Schwarzwald to remove the hex.

 

[yankeeone]

Are the throttle cables adjusted to tight? how many turns out from the seat did you set the jet. Will it start on starting fluid ? this happened to me , it was to tight on the throttle cables.

 

[bikerfish1100]

how old was the gas in the tank?

 

[37796]

R75/5 curse

I would also check the points. If the rubbing block was dry and you rode the bike for the first time in two years the points may have closed up enough to prevent starting. They will wear down quickly without a little point grease on the cam.

 

[lmo1131]

The first seems unlikely and you don't, or shouldn't, have a diaphragm on a /5.

You absolutely have a diaphragm on a /5, unless someone replaced your Bings with something else. Actually, you have two, one in each carburetor.

Best place to start is at the beginning. Disconnect the battery... pull the front cover, check your points and the wire that connects them to the condenser. Check your ignition timing through the port in the crankcase, check your valve clearances, etc., etc., etc. And pull the tops off of the Bings and check the diaphragms.. .. . .

edit - check the clamps on the enricher shafts (choke) to make sure they haven't slipped.

 

[166926]

Update- now it started....

So I took the air tubes off, and hit the starter, and after a few coughs, a decent backfire pop out the right carb, and a little prayer, I hit the starter again, and it was almost like taking a running start. It started and ran fine. Got exhaust out both mufflers, so nothing's plugged, but I swear, after the backfire, and 3-4 seconds spinning with the starter, away it goes. I'm going to wait an hour and see if it starts.

Which makes me wonder, wtf?? Did the backfire clear something out?

Now, I wonder what will happen when I hook the air tubes back up?

I'm going to say that for every start, we must weep a drop of oil for all the bikes that don't.

 

[20774]

Plugged air filter? Unwanted guests living in the engine top area??

 

[yankeeone]

I wonder if something changed on the cables when you took the tubes off?

 

[166926]

No critters in the air box area - I was already in there. I don't know about under the starter cover, though. Although I did, on another /5 find a few mice in there once.

I'm wondering if the filter isn't plugged, but again, it wouldn't explain how it became plugged after the first ride, and just sitting in the garage.

To be honest, I don't think I've ever seen a plugged air filter on any vehicle. I've seen dirty, but the bikes or cars always ran. My 914 had a layer of oil, dust and debris that formed a 3-4mm thick cover over the oil cooler, resulting in the car always overheating. But that's another post for another website.

I just started the bike again - no problems.

Tomorrow I'm going to see if it starts with no tubes again, and the hook the tubes back up to see what, if any, difference I see.

If that's the difference, then I have to imagine that it's the air filter. I'll take pics.

 

[166926]

I wonder if something changed on the cables when you took the tubes off?

I'm going to say no, becuase I took the tubes off several times during this exercise, once to change the fuel lines, and once to clean out the carbs. However, I only tried starting it without the tubes connected today, which led to success...

 

[44006]

fuel (good fuel), spark(at the right time) and compression are necessary to run

You seem to have confirmed both fuel and spark are present

Suggest you check the valve adjustment and confirm that cold engine has at least a little gap or
click between rocker and valve stem when valve is fully closed - when you said backfire did you mean BACK fire as in back through the carb - this would mean probable tight intake valve which makes starting difficult or impossible - tight valves make bike sometimes start when totally cold and not restart when warmed up

Next confirm spark is going off at the right time - check static timing - get advice from someone else
on this - I don't mess with electronic ignition - I always remove it and go back to points

bad diaphragm should not have anything to do with starting since starting takes place with slide at
bottom of its motion - bad diaphragm will keep you from applying power to pull away but will not
affect starting

confirm air filter is not oil saturated acting like choke - that might explain why start with air tubes off but not while on

confirm choke cables are actually working the lever on back side of carb and when off the lever on the carb is pushed all the way down to hard stop against limit pin

 

[yankeeone]

fuel (good fuel), spark(at the right time) and compression are necessary to run

You seem to have confirmed both fuel and spark are present

Suggest you check the valve adjustment and confirm that cold engine has at least a little gap or
click between rocker and valve stem when valve is fully closed - when you said backfire did you mean BACK fire as in back through the carb - this would mean probable tight intake valve which makes starting difficult or impossible - tight valves make bike sometimes start when totally cold and not restart when warmed up

Next confirm spark is going off at the right time - check static timing - get advice from someone else
on this - I don't mess with electronic ignition - I always remove it and go back to points

bad diaphragm should not have anything to do with starting since starting takes place with slide at
bottom of its motion - bad diaphragm will keep you from applying power to pull away but will not
affect starting

confirm air filter is not oil saturated acting like choke - that might explain why start with air tubes off but not while on

confirm choke cables are actually working the lever on back side of carb and when off the lever on the carb is pushed all the way down to hard stop against limit pin

nice writeup

 

[PGlaves]

You have fairly clearly described a situation where the bike was not receiving sufficient air. This is indicated by the notion that using the enricheners (choke) made it worse. You essentially confirmed that there was an air delivery problem when you removed the air tubes (thus bypassing the air filter), and after a pop or two which probably cleared excess fuel from the spark plugs, the bike started and ran.

So in my opinion the problem lies with the air filter, or the air filter area at least. So removal of the filter housing, the filter, and the starter cover is what I would do next.

On the off chance that in installing new fuel lines you made a splice at a non-stock location, or somehow damaged a fuel line in the air filter area I'll mention it. If you have a fuel leak from a fuel line in the air filter housing you could (with the air tubes installed) be drawing extra fuel in with the air, making the mixture too rich for the engine to run. Very oddball but I've seen crazier things happen.

 

[166926]

I ended up starting the bike against yesterday, with the tubes off. It was a bit of a grind to get it to start, but it did start.

I then put the tubes back on the bike, and started and ran it a few times. No problems.

So, I think the next thing is checking the valves. I will say that the bike seems quieter than my /2, perhaps the valves are tight? I have it in my head that tight valves = loss of compression = you've got to crank the starter a lot to build up some compression before the bike starts. Is this correct?

But how would the removal of the air tubes play into this? Would removal of the tubes essentially let more of the air fuel mixture into the head, somewhat compensating for the tight valves?

 

[dennisdarrow]

I ended up starting the bike against yesterday, with the tubes off. It was a bit of a grind to get it to start, but it did start.

Are you saying that you had to "grind and grind" the starter to get the engine to run?

I then put the tubes back on the bike, and started and ran it a few times. No problems.

You let the engine idle in place for several minutes? Went for a ride? You started and stopped the engine over a period of time?

So, I think the next thing is checking the valves. I will say that the bike seems quieter than my /2, perhaps the valves are tight? I have it in my head that tight valves = loss of compression = you've got to crank the starter a lot to build up some compression before the bike starts. Is this correct?

I know that sometimes the older air cooled engines are compared to tractors; but are you saying that the engine turning over without starting builds up "pressure" inside of the combustion chamber like a compressor or boiler?


But how would the removal of the air tubes play into this? Would removal of the tubes essentially let more of the air fuel mixture into the head, somewhat compensating for the tight valves?

If your air filter chamber and or air filter are saturated with fuel then yes, removing the air tubes will bypass the filter and allow straight O2 with no fuel mixed with it into the carburetor before fuel is added to the mix. Compensating for tight valves by doing this??........Perhaps someone can truly give you a better answer that will solve this true dilemma and quandary you find yourself in........God bless.......Dennis

 

[44006]

"the bike seems quieter than my /2, perhaps the valves are tight?"

Quiet usually not good - please confirm valve adjust and report back here
All other monkeying around is a waste of time if valves not closing properly