1985 R80RT Very Hard to Start Cold

[MonoRT]

I am somewhat hesitant to write this because I know that many of you live in places where it actually gets cold. My 1985 R80RT is really difficult to start at or below 50 degrees Fahrenheit. These days, 50 degrees is about as cold as it gets a couple of miles from the ocean in SoCal. At 65 degrees and above, the bike starts with ease - even without the "choke". Once started, the bike runs just fine.
This behavior became noticeable last week. The starter seems to crank the motor over just fine (how thick could the oil be at 50 degrees?). I have a Datel digital meter wired directly to the battery (a 28 Ah WestCo) and I see the voltage go as low as 10.8 volts during prolonged cranking, but it pops back to somewhere between 12.8 and 13.1 volts when I take my finger off the starter button.

The motor spins and fires occasionally, but it is difficult to get enough consistent firing to start the engine running on its own. So far, I've been able to start the bike each morning, but it takes a lot of starter time to get the bike running and I know that can't be good for the starter.

Valve clearances look good; spark plugs look good and have about 2K miles on them. A couple of months ago, the bike was dying at idle and I purchased new plug wires, but I soon found out that the primary windings in my coil were failing (eventually, they went open and stranded me), so I left the wires alone and replaced the coil with a .7 ohm Dyna unit. This weekend, I put on the new wires, but that seemed to make no difference (old wires still seemed OK and measured 5K ohms each - new wires also measured 5K ohms each).

The starter is a Bosch and it has never been removed - original bushes and brushes for about 250K miles. I have Rick Jones' book on Boxer charging systems and he mentions that a badly worn starter could drive system voltage down to a point where it becomes difficult for the ignition system to fire the plugs.

How about the carbs? I've got the stock 32mm Bings and I believe that I have enough parts to rebuild them on-hand. A couple of months back when the bike was dying at idle due to the bum coil, I went through the carbs looking at the diaphragms, floats, jet stack etc? I did not pull the covers off the starting carburetors or enrichers or whatever you call them. I would not expect to have starting problems with two carbs at once - I'd think that the bike would fire and run (badly) on one cylinder, but I'm just guessing.

My bike lives in a nice, dry attached garage. I'm tempted to toss a 100w work light under it before I go to bed, just to see if the extra warmth makes it possible to start the bike without drama the next morning.

At all events, something is not operating correctly - 50 degrees should not make it hard to start the bike with full choke. Where do you-all think I ought to look?

 

[MonoRT]

More Info?

OK, I just read the "Boyer electric ignition" post where a similar hard to start issue seems to come down to a weak battery, bad connections or a worn starter.

I also called Rick Jones and asked him what he thought. Rick was also concerned about a failing battery or worn out starter.

Here's what I'll do: tonight I'll put a 60W light under the battery and I'll be ready to jump the bike with my Yuasa motorcycle jumper wires. If the bike starts OK with a warm battery, or if it starts OK with a jump, I'll really know to focus on the battery and/or starter.

I recently changed out the battery to starter cable and the battery to ground cable and I looked them over this weekend - those connections appear to be clean and tight.

 

[James.A]

There is a jet in the float bowl that feeds a brass tube in the body of the carburetor, which in turn feeds the enricher on the inboard side of the carb , right side/ left side accordingly. (choke function) If that circuit has any dirt in it, it will defeat the "choke function". This circuit is like an alternative carburetor that is designed to deliver an overly rich air/fuel mixture to a cold motor. The enricher is a variable jet. If the motor is difficult to start when cold, (ambient temperature) this part of the carburetor is most likely obstructed. The bike runs well after warmed up,...yes?

 

[grahamm]

Cool, interesting and useful bit of info.... Thanks

 

[MonoRT]

Yes, the bike runs well as soon as it gets started - even cold.

The enricher circuits appear to be "working" to some degree. In the morning, once I have the cold bike running, flipping off the choke lever right away will kill the engine. Until I've ridden a quarter mile or so, the engine won't idle without 1/2 choke. If the enrichers were not getting any gas, then I'd expect the choke lever to have no effect. On the other hand, if we're getting some gas, but not enough into the enrichers, that could be a problem.

This just the sort of carb info I was fishing for, so I'll try to check that out too. How big is that enricher jet? Can you run the end of a fine guitar string through it to make sure it is clear?

 

[donbmw]

It only takes one carb with a the choke system not working to make it hard to start when cold weather comes. When I bought my 1975 R90 it was in May come cooler weather it became hard to start. But after it was warm it ran great and no problem starting warm. Found one carb had a blocked jet for the choke. Went through the carbs and have never had a cold weather hard starting problem again.

Don

 

[1074]

Starting

I'd go along with Rick on this one if only based on the mileage of the bike. A worn starter will draw more current as you've indicated. I've had starters that, when hot, would actually lock up!

 

[lkchris]

Be sure there's actually fuel there to ignite.

Enricheners are one thing, but the engine needs extra air to start ... so crank with the throttle open just a little.

The enrichening is defeated if there are vacuum leaks. Carb rubber manifolds, vacuum takeoffs.

Carbs on cars used to have fast idle cams and fuel injected cars have idle control valves and Oilheads have a fast idle control (labeled choke) and all were the means to get the engine the little extra air.

 

[MonoRT]

Started fine with a warm battery

Last night I hung a 75w shop light alongside the gap under the battery box and left it on all night to keep the battery warm. Sadly, the temp was a balmy 55 degrees at 6:30 this AM, and that may have fouled up my experiment. At any rate, the bike started on the first push of the starter button (with full choke).

I am looking into starter service or replacement - as mentioned, whatever else may turn up, my starter is probably needing some attention. I am also wondering about further battery testing. And, I hope to mess with the carbs a bit this weekend.

 

[wecm31]

I'd suggest the carbs...

If the starter is spinning the motor, it can't be too bad. The 10.8 voltage while cranking seems about right.

Having said that, Rick's take is valid. Maybe ground a plug to the engine and watch the spark as you
crank the starter. And if the starter is as old as you say, its due for a look at some point.
Rick's Nippendenso starters are the best you will find...

But your current trouble sounds like carbs to me. A full rebuild would not only help with cold starts,
but with a fresh needle and main jet, you might find your gas mileage gets 5% better.

FWIW...I start my bike near freezing quite often. One hand holding the choke at full travel, the other
tensioning the throttle to just take up the slack in the cables. And she starts rough!! Takes a minute
or two before it will idle unassisted. I believe that to be par for the course

 

[happy wanderer]

I always start with the easy stuff. Have you load tested the battery?

 

[guenner]

Sounds like my problem, too

MonoRT,

you can check both exhaust headers for some temperature increase when she doesn't startup. This way you may find that one side is cold - means only one cylinder fires.

Also, when you open the throttle with enricher on you more-or-less disable the enricher's function because the enriched mix comes out at an opening AFTER the throttle plate.

So, when I start mine in colder temperatures I crank the motor for ca. 5 seconds with throttle closed and enricher on. Idea is to fill the cylinders with the enriched mix. While still on the starter I slowly open the throttle in expectation that with more air it may finally reach a combustible mix.

Works mostly in my case but it is a shortcut because I haven't found the real cause, yet.

/Guenther

 

[James.A]

Yes, the bike runs well as soon as it gets started - even cold.

The enricher circuits appear to be "working" to some degree. In the morning, once I have the cold bike running, flipping off the choke lever right away will kill the engine. Until I've ridden a quarter mile or so, the engine won't idle without 1/2 choke. If the enrichers were not getting any gas, then I'd expect the choke lever to have no effect. On the other hand, if we're getting some gas, but not enough into the enrichers, that could be a problem.

This just the sort of carb info I was fishing for, so I'll try to check that out too. How big is that enricher jet? Can you run the end of a fine guitar string through it to make sure it is clear?

I dislodged a blockage in an enricher jet at a camp-out a few years ago with the wire from a bread tie and a dribble of Makers Mark in the column for the jet that is part of the float bowl. I filled the column with the brown solvent and then started poking the opening for the jet in the bottom of the float bowl. After about a minute of gentle probing, a crum of some material dribbled out, along with the brown solvent, into the float bowl. A few more flushes with solvent and the float bowl re-fitted made the bike start easily. It was pretty easy to tell which carburetor to look at because one side would heat up much faster than the other.

There a some people who would tell you not to use anything to that is harder than the brass jet, to un-block a brass jet. I'd say that a blocked jet is no good at all. If you wanted to use the cut off end of a guitar string, try to use the smallest wire you have access to. .09 maybe? I do not know what the size of the jet inside the enricher feed is.

 

[MonoRT]

Today, it was even warmer at 6:30AM (62 degrees - darn climate change!). I had left the shop light next to the battery overnight and the engine fired right up.

I have a number of things to look into now. I want to load test my battery. Years ago I ordered a hand-held load tester from an American company, but they stuck a "made in China" sticker over the old "made in USA" printing. Treasonous dogs! Predictably, that load tester bit the dust after a couple of dozen tests. Now, I don't know who to buy a load tester from since I only buy "made in China" stuff at the very last resort. Will AutoZone or Sears load test a motorcycle battery?

This weekend I'd like to pull the carbs and go through them and check the enricher jets. I also have new floats, float needles, needle jets etc...

Then, there's the starter. While I'm trying to figure out what to do, I could pull the Bosch and try to lube the shaft bushings. Since I use my bike as a car and do a lot of start/stop riding, I've always wanted a low draw planetary gear starter. A Chinese copy of a Valeo is NOT an option for me. The Valeos seem to have been more or less sorted out, but I still hear stories that make it seem like the planetary gears were designed with the same cheap mindset that lead to the magnet failures. But, you can get all of the Valeo parts online at reasonable prices. The Denso starters are stunningly expensive, but I've owned Toyotas for decades and routinely see the Denso starters go 200K miles while being shamefully ignored. Of course, rebuilding the Bosch would be cheap and straightforward except that I can't afford the down time needed to send it out for a rebuild and then I'd still have a high-draw starter (reliable as an anvil though).

Gunther mentioned a method for starting in the cold. I am not sure why, but that method of spinning the engine over with the choke on and throttle closed and then slowly opening the throttle is what I have been doing for years - don't recall if I learned that from someone or just settled on it because it seems to work.

 

[James.A]

I can't think of a reason why Auto Zone or Advanced Auto or NAPA or any of the other parts stores would NOT load test your battery. I own a load tester myself, but if you can get your hands on a BMW Factory Workshop Manual there might be a page that would show you how to load test the starting system using an analog Volt-Ohm-Amp meter. I know that my /5 manual has that page in it. However, isolating the battery from the rest of the system and conducting a load test would be best.

Making sure that your battery can deliver sufficient current would be the tell-all test for your electric start concerns.

 

[jammess]

Very carefully check the float levels in the carbs. If the floats are even a slight bit off hard starting will be the result. "With the carburetor(s) off the engine, turn it upside down, resting on its own weight, the float arm must be perfectly parallel with the carburetor base. If the carburetor is mounted on the engine, the same parallelism must be maintained, but this must be ascertained WHILE NOT DEPRESSING THE FLOAT NEEDLE'S SPRING-LOADED PLUNGER INTO THE NEEDLE BODY" This quote from page 7 of Bing Carburetors from Bing Agency International L.L.C. carb maintenance publication. Adjustment can be made by bending the float-arm pointer with a small screw driver and or needle nose pliers.

You might also squirt some carb cleaner up the main jet while you are carefully checking the float levels. Careful float adjustment completely solved the cold start problem on my '81 R100RT. Also, if anybody has taken the carbs apart verify they didn't get the choke valves backwards on re-assembly.

 

[Jameslf1]

cold start

A few hints to your challenge from the 50+ years of repairs on all types of cars(old & newer) ,small engines & bikes. Repaired many pre 80's bmw & Hondas , but few 80s up so I can only draw from newer cars and small engines for your bike. We tend to look for complex things and overlook the simple as all unknowns are complex, while the knowns are simple. You have already found your problem w the light bulb.
I'll explain. Lean/cold engines need a richer mix and/or higher kv spark to start, more so than a warm engine. With the time/milage on your bike remember nothing last forever. All the threads/replies are good, normal and viewable. Electronics can/will cause problems cold,hot or any point in between. It's unlikely the heat made much difference to the battery since the starter spins good and battery volts stayed up ok. The heat rises up so most didn't warmth the battery but did warm the coils & ignition control unit providing it's somewhere near and above the lite.
Two small eng spark testers w 3/8s to1/4 gap = the spark needs on compression & cost $7-10 each will show if you have good spark cold. Be sure to never open circuit the hi tension wires as coil voltage will rise to max. from 3o to 50* kvs to destroy the ign.module. Be sure to NOT get the HEI ones which have a much wider gap & damage the module.
New coils and module can run into a bit so symthoms and tests will help find problems. Few people enjoy pushing their vehicle more tha a few miles. Hope this helps.

 

[MonoRT]

I should have provided an update. And, the spark testers are an interesting idea - ignition troubleshooting drives me nuts and anything the helps point to the problem is good to know about.

So, the So. Cal weather has been very mild, depriving me of chances to see how well the bike will start on a sub 50 degree morning.

I went right through the carbs replacing floats, float needles, needles, needle jets, gaskets, springs, cables and rubber bits. The only things that were really messed up were the o-rings on the idle jets and and on the idle mixture screws - and, one throttle cable was beginning to fray by the adjuster barrel. I also put in an order for a new planetary gear starter.

I got the carbs done before the new starter arrived and the carb overhaul alone did improve the cool start situation, but I did not get a chance to test a sub 50 degree start with just the carb overhaul. I replaced the previously untouched 250K mile made-in-Spain Bosch starter. A bit of a pain if you don't remove the lower half of the airbox. I have one of those WFMC mini-ratchets and that was very helpful getting at the starter bolts. I'll probably get the Bosch rebuilt and keep it as a spare.

I have a Datel voltage meter on the bike and I see that the voltage rarely drops below 11 volts while cranking with the new planetary gear starter, so that's also an improvement. One of the first things I did when I bought the bike new was to kill the stock small battery with errand running. I switched to the "big" battery kit and have used the larger 28-30 AH batteries ever since. Now, with an EnDuraLast alternator and planetary drive starter, I could probably get away with the smaller battery, but I really don't like pushing my bike and will probably continue to run the big batteries as insurance.

 

[Woodgrain]

Dried out carb bowl gaskets will cause difficult starting. You need a sealed system. Just sayin'.

woodgrain