Yamaha rd200 running problems

[yamaha_eric]

I have a 1980 Yamaha Rd200. 2 cylinder.
The bike starts well but then after about ten second dies (sounds as if it is stalling).
when the engine is running it has no power and wont rev up.
The spark is good and there is petrol getting to the carburettor and sometimes if i put my fingers almost completely covering the intake it starts even better but still dosnt carry on running.
The battery is fully charged.
I thenk the problem is the carburettor but i cant find a book on the bike.

Eric

[sono]

I too strongly suspect carburator to be gummed up (Be careful to select cleaner that is safe for rubber parts).

Another possibility is ignition problem from a weak battery or choke not operating (unlikely). :-/

Incidentally, you should also perform a COMPRESSION TEST, and make sure your valves are properly adjusted. It is VERY common on such an old motorcycle to see valves guides so dirty thay valves are remaining half shut. No compression, no power, hard to start.

I found FOUR service manual at Ebay.co.uk just by searching for "rd200 manual" on Ebay search Engine.

[Searchguru]

As with most things there are a number of possibilities. As you say, the most likely is carbs. I can't remember whether the RD200 has an off position on the fuel tap. If it has then try the following:
Run the bike on the stand for as long as it will go for. The second it stops, turn the fuel off. Remove the float chambers from the carbs and see if there is any fuel in them. It could be that the fuel is taking its time to get into the float chambers due to a blocked fuel tap filter or gummed up float needles. By doing this test you should quickly establish that fuel stavation is the cause.
Another possibility, though much less likely, is that the exhausts are so badly clogged with carbon etc that the pressure is building up and stopping the engine.
I would suggest you check out the following website as you are bound to find the answer to your problems there.
www.aircooled-rd.com

Just had a further thought:- Before you try the above, undo the petrol tank cap whilst the bike is running and see if it keeps going. If it stops, no harm done anyway but if it keeps running then your tank's air vent is blocked. Don't try restarting the thing with the cap undone because you'll end up splashing fuel everywhere. It could suddenly get very warm!

[sono]

Hi again,
In addition to our comments so far...
I might add to the basic checkup prior trying to start again:

Make sure you bleed your gas and try with some FRESH gasoline. Don't forget you probably have a RESERVE position to flush too.  Anything older than 3 months without gas stabilizer will make it much harder to start and maintain a regular RPM.

Before you go ahead cleaning and adjusting the carb, cut your gas line and insert a gas filter. Your gas tank is likely contaminated with some rust and else that could ruin your efforts.

Make sure your air filter is clean and in good condition

Make sure you have checked contact points adjustments (ignition). The service manual will provide the specs.

Use the Troubleshooting section of your service manual.

[yamaha_eric]

Hi all
I reckon it could be the exhausts are slightly blocked up as Searchguru said as i have cleaned out both the carburettors with the air compressor and cleaned out all the old gunk.
I will try cleaning the exhausts out at the weekend and inform you on how it goes

[pogotri500]

Hi there, Another thing you should consider are the crankshaft oilseals! Being a 2 stroke it relies on good crankcase compression. If the bike has done a fair milage or even stood for a period of time the seals can harden then be unable to maintain a seal on the crank. This will lead to poor performance and give the symptoms you describe. Just a thought! Cheers, Dave.

[yamaha_eric]

I have cleaned out the exhausts this weekend and it still won't run for long so i and going to buy some new condensors and try that.

Eric

[Searchguru]

Eric,
Condensors are definitely worth a try, though it still sounds more likely carbs or as Dave says, crankshaft oil seals (from the symptoms described).
Is the bike new to you or been off the road for a long time?
If the bike has been running perfectly then manifests a problem it may be easier to determine. If you acquired it with this problem then that's a bit more difficult.

As an afterthought - start it then switch the fuel off. See if it runs for any longer (floats are set too low and it's drowning, when there is fuel). If it dies even quicker (floats are set too high and it's starved of fuel). If there's no change I am at a loss without 'the laying on of hands'.
Second afterthought - are the slides in the carbs opening at exactly the same time and are the needles set the same?

If your anywhere near my part of the world I'd happily have a fiddle (if you'll pardon the expression!) 'cos I do like a challenge.
Tony.

[yamaha_eric]

Changed the condensers and set the points gap to 15thou  this weekend and it starts up easily every time but still stops running after a while like before.
Just wondering does anyone think that the spark timing could be wrong?

Eric

[Searchguru]

Have things improved at all since your first post. By now you will have tried everything and may have had an improvement but now don't know which bit made it better. You haven't mentioned spark plugs. I take it that you have changed these for new as one might be failing as it gets hot. If you've already changed them what do they look like after the bike has stalled? It could be that they are oiling up and that's what is causing the stalling. Are you using the standard oil system or premix?

[yamaha_eric]

The spark plugs are new and when it stops they are a little wet but the oil mixture is controlled by a mixer on the end of the crankshaft and two pipes to the carbs so i didnt think that the could be changed?

Eric

[Searchguru]

It could be that the oil system is working perfectly it's just that the engine isn't getting hot enough to burn off the two stroke oil. How long in seconds/minutes does it run for from cold? If you get it to start again after that how long does it run for then? I'm still thinking fuel/carbs here. If it is consistent times when cold and consistent on every restart it's not likely to be electrical as that would be far less predictable. If it is very unpredictable then I would trace backwards from the sparkplugs to the battery. I had a persistent failing on my XTZ660 (I know - four stroke) but it turned out to be two problems. Broken joint between HT lead and plug cap and the ignition cut out switch on the side stand which was occasionally shorting. Sometimes it coughed but kept going other times it coughed and died. You'll get there eventually by trial and error. Only do one thing at a time cos if you fix it you need to know what it was that made you a mechanical god!