Engine turns over but does not start

[njsharp]

Hi all,

A couple of months ago I bought an '83 R65ls. This is my first motorcycle and I am psyched about it, but I'm pretty much clueless to every aspect of the vehicle. I expected that I would need to get my hands greasy with this bike sooner or later so I bought some basic tools and a service manual.

Things went fairly smoothly for a while, fixed the horn, adjusted the clutch when the it began to drag, then last week I had just gotten it started when two blocks from home it died at a red light. I thought I just hadn't given it enough throttle, but when I tried to start it again, the engine wouldn't go. I was pretty low on gas, so I thought that might be the problem. I pushed it down to a nearby gas station and filled it up. However, when I tried to start it, the same thing happened. The engine would turn over but would not start. If I kept it at very low RPMs, it would run but clumsily and as soon as I gave it more gas it would die.

I've done a little research and it sounds like it could be a number of things. I decided to start at the fuel tap to check if anything was blocking it. I removed the fuel tap, but realised that I don't have a tool to remove the retaining ring from the lever. So I'm a little stuck with that one. Any suggestion on how to disassemble the fuel tap?

Other than that there seem to be a myriad of other things that could be at fault. Judging from what I've described, does anyone have a suggestion of a good place to start looking?

Thanks!
Nathan

[Rob Valdez 79 R65]

Do you have spark?  
Remove one of the spark plugs (or both), plug them back into the spark plug cap, and lay them on the cylinder so they are grounded.  This is CRITICAL so you don't damage your ignition control unit.
Turn the engine over and watch for a fat, blue spark.  A weak spark just won't get it.

Examine your ignition coil.  (try draining some of that gas, first, so your tank won't be so heavy!)
If it is the original coil, it probably needs to be replaced.  They crack very easily.  We have pictures around here, somewhere.  (just do a search for "crack-o-matic".  Remember to change your search parameter from "week" to "all posts".

You should remove the heat sink from the ICU and apply some fresh heat sink paste (I can't think of the proper name, right now).  It is sold at Radio Shack and auto stores.

For fuel, you should just disconnect the fuel line from the 'T', and with a glass container, observe the fuel flow when you turn on the petcock.
Before you dismantle your petcock, you had better drain the tank!!!
I think that plastic ring just pries off with a screwdriver.  I haven't done that yet, either.  Replacement rings are available if you break it.  http://www.bmwhucky.com/010016.html

[montmil]

Ditto Rob's thoughts.

If the petcock is flowing fuel, look elsewhere. Check for spark and be sure the battery is charged. Put-putting around town below 4K rpm will not generate enough charge to the battery to keep it up. A Battery Tender belongs in every Beemer's garage.

Could be junk in the carb/s. Could be a bad coil. Could be rotten diaphragms. Could be a lot of things but first you must confirm the primary needs for ignition: fuel, air, sparks and compression -all at the proper time.

Keep us posted as to your discoveries. BTW, Dyna Brown coils rock... along with new plug wires, caps and sparklers.

Monte

[Bob_Roller]

Welcome Nathan, you've got a bit of work ahead of you .

Has the bike sat around being unused by the previous owner for an extended time, or was it still in frequent use ?

Remove the fuel cap, is there a red liner on the inside of the tank, or do you see rust ?

Pull the fuel line off of the fuel tap, or remove the nut that has the fuel line attached to it, there are two different fuel taps that could be installed, turn the tap on and see if you get fuel like Rob has said .

Next would be removing the carb float bowls and see whats 'living' in there .

The ignition coil as mentioned by Rob and Monte is a prime suspect, the original coil is black and gray in color and should be one of your first replacement parts, with you living in a damp coastal area it will give you problems, if it isn't the problem already .

Do the spark plug leads have a metal cap at the spark plug end, if so, they need to be replaced, they are most likely 27-28 years old, again in a damp environment old leads will give you problems .

[Justin B.]

My '82 would not run when I bought it and the shop thought it might be the bean-can.  It turned out to be the coil but the hall sensor in the bean-can can also cause a no-spark situation.

[montmil]

Here's a quick check to confirm the under tank ICU is functional:

1. Unplug the connector between the trigger unit (bean can) and ICU/amplifier. That's the three-wire lead from the bean can to the nylon connector under the engine front cover. NOTE: Disconnect batt neg cable before removing front cover. Reattach cable after front cover is removed.

2. Stick a straight pin or a bit of paper clip pin into the ICU connector's center pin. That's the connector coming from the top of the engine case.

3. Remove a spark plug, reconnect the ignition wire and be sure the ground portion of the plug is in good contact with the head and that you can observe the spark gap.
 
4. Power up the ignition. Every time you ground the pin sticking out of the connector, you will get a spark at the plug if the ICU/amplifier is good. In that case the problem is probably your trigger unit/bean can. If you do not see that spark, then your problem is not likely your bean can but likely the ICU. Fix that problem first.

Monte

[njsharp]

Thanks everyone for the advice.

I added 'spark plug socket' to my tool list.

The bike was regularly used previously and has a Dyna ignition coil installed already.

Fuel seems to flow fine through the petcock even though I found a chipped piece of tank liner inside. From what I can tell the filter is beneath the petcock? Could it be the filter at fault?

The tank is lined and shows no sign of rust. Though a spot of liner has chipped off at the bottom.

I'll let you know what I find when I get the spark plugs off.

[Rob Valdez 79 R65]

Apparently you don't have the original tool kit?  There is a spark plug socket in that.

If it is a straight-type petcock, like this

then there are two screens.

One small

which is at the bottom, below the valve, and one large


that covers both tubes up inside the tank.

If it is a angled petcock

there is only the large screen.

Some folks here have added an aftermarket filter to their bike.  I've never found the need for one.

[njsharp]

Unfortunately I do not have the original tool kit.

My petcock does not look like this. There are no tubes protruding from the top like that (so i don't have any reserve...).

[njsharp]

Followed Rob's advice to check the spark plugs. They were giving a pathetic spark, so I bought some new ones. But they are no better...

Sounds like I should check out the Bean Can and ICU next. What do these look like?

Thanks!

[montmil]

Nathan,

Before you jump in too deeply, I'd suggest you purchase a shop manual for your bike. Both Clymer and Haynes publish decent manuals that will assist you in identifying "faults" and the various components of the BMW. They may also prevent unnecessary damage to the ignition system. These tools will aid you in getting the BMW back up and running.

Visit a local BMW dealer and check out their service manual offerings.

Monte

[Justin B.]

If it was the bean-can you would get no spark at all and I don't know if the module could fail in a mode that would produce a weak spark - normally solid-state devices work or don't work.  What color is the spark?

[Lowen]

My guess would be the coils, they were the first thing I had to replace on my 84'

[Bob_Roller]

I'm in agreement with Justin, that the normal failure mode for both the bean can and the ICU is it doesn't work, not a weak spark .

How does the battery look ?

Does it appear to be an old battery ?

Is it a serviceable type where you add water to the individual cells ?

Remove a cap on one of the cells, is there any liquid in there ?

If it appears to be alright, charge it over night then try starting it again .

With the spark plugs removed from the cylinder and placed on the cylinder fins, with the key in the 'ON" position, toggle the kill switch from on and off .

Does the spark appear to be any better doing this, than it does while using the starter ?

[Rob Valdez 79 R65]

Have you determined whether or not you have the original coil?  If so - get a new one now.
http://www.motoelekt.com/ignition.htm

Same for the spark plug caps & wires.  I replace mine every few years as a maintenance item.

I like to go to Mike's XS supply for my NGK caps and wires.  http://www.mikesxs.net/products-27.html#products
He has zero-ohm, 1K [ch937], and 5K [ch937] caps.

If you have your original wires, use a soldering gun to remove the tips that go into the coil.  Put these on the new wires.  They are superior to the clamp-on type.