BMW R80 RT Motorcycle - poor cold starting

[Andy - G8MNM]

Hi

It is very unlikely that anyone here will have experience of the above bike but I thought I'd put up a post anyway. :D
Since I got the bike last year it has always been difficult to get it started when cold.
When it is warm it starts fine.
It has new plugs and is generally in good condition and runs well.

Well, it will be interesting to see if I get a reply.

Regards

Andy

[Jamie-Skinner]

The Choke seems at war here.. I think bikes have chokes.. :S

[OldTickTock]

Yup, the R80 does have a choke, as Jamie states have you looked at the obvious first? I'm sure you have, choke,plugs leads etc. A quick google brought quite a few hits for the R80 and poor cold starts. Perhaps asking on here http://www.bmbikes.org.uk/Forum/ would get a more informed and quick solution.

Chris

[Andy - G8MNM]

Thanks Jamie,
The choke does not like being used!

Chris,

Thanks for the forum info. I have now joined and submitted a post about the problem.

Thanks

Andy

[Retired]

Hi Andy,

Nice bike you have. I owned two R75/5's in 1972/3 the first second hand the second brand new.

Given the amount of bad weather have you tried spraying the electrics with WD40?

Have a look at the points as these can close up; my new bike started to play up and became quite lethal; it would only run on one cylinder until it hit around 3,000 revs then it would clear its throat almost pulling my arms off; on one occasion riding through Dewsbury on a busy market day I was cranked into a bend when it fired on both cylinders lifting the front wheel changing direction almost hitting a pedestrian.

I booked it in under warranty and it was checked over in the workshops by the top mechanic; on the way home the problem appeared again so in desperation I returned once again to the dealer to be told it must be the diaphragms in the Bing carbs so new diaphragm units were ordered. I went over once these arrived and the mechanic was on holiday but as I have rebuilt many bikes I was allowed to bring the new parts home and fit them myself. After fitting the parts the bike fired flames out of the exhaust so obviously the original fault remained. The bike was still under warranty and at that time cost as much as a terrace house to buy so I was rather timid of playing with it but decided to have a go.

I removed the front engine cover to gain access to the ignition points and found I could not insert a two thou feeler gauge whilst turning the engine to where the points should be fully open. I adjusted the points and the bike ran perfectly for the rest of the time I owned it.

What age is your bike Andy and what mileage has it covered. You might think the fault to be something complicated when in fact it might be something very simple being something out of adjustment.

What is the performance like when it does run; I know you won't take it over 70mph but what is it like at the end of the throttle cable; is the performance there if it is then this rules out a lot of the major problems like worn bores; pistons; valves or even broken rings.

Have you done all the basic checks like engine timing; tappets and points etc? is the air filter clean?

I used to work on the very first Honda bikes imported into the country and a friend bought a 175cc which ran perfectly like your bike whilst warm but then it would not start once it cooled overnight without new spark plugs being fitted; again this was another bike under warranty so it kept going back and each time it was fitted with new plugs it ran perfectly.

The problem became so bad that the dealer would send his daughter out with a pair of plugs but the fault could not be found. I ended up pulling the engine out and stripped it right down to its crankcase; I checked everything but all was in order and I could not find the slightest fault so I re-assembled the bike and wrote to Honda explaining the problem and what I had done so far; the bike had been bought from a different dealer to which I worked for.

I received a lovely letter from Honda with an apology asking me to change the air filter; the bike ran perfectly with a new air filter fitted starting easily from either hot or cold.

I used to balance the carbs on my BMW's using a vacuum gauge but then I was keen.

Two bikes I owned that were huge disappointments were an Ariel 1,000cc Square Four that broke one rear con rod and shattered two pistons whilst plodding up the M6 at a steady 70mph; I scrapped the bike after that. The second was a Norton 750cc Atlas that would break its piston skirts every time it was taken up to 110mph; the best thing that happened to that bike was to be hit head on by a lunatic driving with all his windows iced up in the middle of winter fracturing both my legs.

We are a knowledgeable bunch on this forum. By the way my rear tyre only used to last 4,000 miles on my BMW's, I was running TT 100's.

I hope my ramblings are of use but got to knock off as it's tea time.

Good luck Andy and kind regards, Col

[Jamie-Skinner]

Once the choke, always the choke! It was causing problems on one of our american cars, so we removed it.. wallah!

[Andy - G8MNM]

Thanks Jamie. The choke is currently redundant, it is looking for a new job!

Col,

Thanks for the very extensive reply to my post.
The bike has only done 20K miles from new and has had only one owner from new.
It is a 1986 model.
I haven't checked much apart from the plugs which are as new.
I must admit that I am much more familiar with my 1975 850 Norton Commando!
I have just ordered a workshop manual off Amazon today.
I plan to check carbs, ignition system etc.
I think it has electronic ignition?
I changed the ignition system on my Norton to electronic which got rid of the points and automatic advance/retard unit which made a big difference.

Regards

Andy

[Yorkie]

I owned an R80RT for 16 years until 2008, and they're not good starters from cold, even though mine was garaged. I found that the best way was to open the choke wide, open the throttle a little but don't 'blip' it, press the starter, and when the engine fires, hold the choke at the halfway position till the engine keeps ticking over as you ease the choke back off. I fitted a police style voltage regulator as I found that on short runs at lower speeds, especially with the lights on, the regulator struggled to keep the battery fully charged. I also used one of those automatic trickle chargers, which I kept plugged into the accessory point so the battery was always fully charged.

I don't know if you are familiar with Moto Bins at Spalding - BMW bike specialists for spares, repairs and advice. They're very knowledgable and helpful. For example, I had to fit new front fork seals, and the Climer BMW service manual (far more comprehensive than the Haynes one) stated the the front forks should be completely stripped down - a major job. Motobins mechanics said nonsense - put the bike stand on a bock of wood to raise the front wheel about nine inches by tipping the back of the bike down 'see-saw fashion' with the front wheel off the ground. Remove the front wheel, brake pad callipers, and lower forks, which will now have sufficient clearance from the ground to be completely withdrawn and their seals renewed and the lower forks refitted without disturbing the forks at the top end. It made a complicated job very straightforward. Motobins have an excellent forum which anyone can join, where you can post requests for advice, or search the archives - for example on 'R80RT poor starting from cold'.

Another thing to bear in mind which has a bearing on starting and smooth performance of the bike is that the carbs on R80RTs go out of balance after a few thousand miles. Really, you need vacuum gauges to balance them. I had mercury gauges but they're outlawed now, and the current ones have little rods which float up and down in the clear plastic tubes of the gauge. It's a simple and quick job to balance the carbs with gauges - there's a nozzle on each carb to which to fit the vacuum tubes.

A note of caution: R80RTs are noted for shedding the red paint on the inside of the petrol tank, which then lies in the carb bowls until you gun the throttle to overtake a lorry on the motorway, at which point, the debris is sucked into the carb jets, causing the bike to decelerate alarmingly. It's an obscure fault not easily traced, but it only take a jiffy to take the bowls off to check (though not of course when you're slowing from 70 to 30 in the outside lane of the M1!!). If the bowls are clean and all's well, then fine, but if there's any sign of red debris, don't just clean the bowls - drain the tank, take the tank off the bike (two minute job), remove the fuel taps complete with their tubular wire mesh filters, swill the tank out with paraffin (safer than petrol) to remove all the debris, refit the tank, and fit a proper fuel filter in each fuel line.

I fitted a taller screen to my bike as I found that the rake and height of the standard screen was such that I got buffeted at speed. The taller screen made a world of difference.

Hope that helps a bit.

Safe riding Andy - stay on the black stuff!

David

[Jamie-Skinner]

Years of my dad rattling on about the choke payed of ey'?

[beam me up schottky]

My attention was drawn to the low miles. Bikes, or any vehicles that have stood more than being used can suffer from particular issues as a result. My vote would go to fuel fouled carbs. Modern fuels are very nasty when they are left standing for even a few weeks. The deposits that can be left in carbs due to stale fuel can cause all sorts of problems. Unless there are other associated symptoms that could attribute the fault to another cause, I would dismantle the carbs for cleaning. The best method by far for this is ultrasonic bath cleaning.