RXS engine running conditions

[Woodman]

Hi all

Brought myself a new bike (second hand actually, 1988), the RXS100. Faantastic little runner and some poke!

A few small teething problems however -:

It was running perfectly, but now its not!..
It will not start, as it did first time, and requires a substantial bump start to get it going.

Taking a look at the spark plug, it reveals oily/carbon deposits, and after buying a new plug (thinking this was the problem), the same has happened and I find the ceramic insulator has an electrical leakage now, and no longer sparks across the gap. Argh!

Is the engine running too hot, and has it burnt/broken the spark plug? Im using the recommended BR8HS heating rating plug as per manual. Anyone had this problem before?
It just does not want to fire!

Believe it could be the timing, but this bike has no mcechanical points contact, so it cant be that.
Is it worth buying a hotter rated plug?

Im using un-leaded in this two stroke motor, is that ok?

Have not taken apart the carb to clean it, as im a little apprehensive. Instead, have attempted to twiddle pilot screw, but with no luck with mixture. Would the carb be something that can easily become blocked?

Many thanks really appreciate help

Sy

[Robby]

Put the pilot screw back to how it should be.

First things first. Does it have two stroke oil in the bottle? Won't run too well otherwise.

Unleaded is fine.

Try also cleaning/changing the air filter.

[stinkwheel]

You could still have a duff plug. NGK plug quality has plummeted over the last few years.

I bought six B8HS plugs a while back and four of them were dodgy, electrodes broke down within a few miles leaving a weak and erratic spark.

Try another or see if you can get a nippon denso equivalent.

Another thing to check is that the oil pump setting is correct. Also have a look at the exhaust baffles. If they are excessively coked up this could cause rich running.

If the bike has only done multiple short runs for a while, there could be a lot of oil floating about in the bottom of the crankcases (indicated by clouds of dense blue smoke out of the exhaust when you rev it up). Taking it for a good flat-out blast should clear this.
____________________
“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles.

[Woodman]

This morning I set to work on the bike, and looked into the oil settings. On removing the oil pump cover on the crankcase, I immediatly noticed the lug on the oil piston was not lined on with the spot on the plastic disk that rotates with the throttle movment (therfore pumping oil into the cylinder).
Sorted that out.

I also cleaned the air filter really well, and put that back.
The carburettor was filthy inside, mainly with brown rusty looking deposits. They lay in the bottom of the float chamber.

I tried the bike out, and hey presto.. A good sound came from the engine that indicated a good mixture. The cookies smelt good!!


However on acceleration, she flooded and too much petrol was being fed into the engine..

We discovered that a pipe that came out of the carburettor had accidentley (!) been pushed onto an overflow nipple that it should'nt have been! So what was happening was excess fuel was accidentley beeing fed back into the carburettor.
Once removed, as it should have been before, it was fine! The engine is now running as good as I think it can be.

Spark plugs - I put the NGK plug back into the bike. It ran absolutley fine. Maybe a bit sluggish on tick over though, which suggests the spark is a bit weak. (On the previous plug it was ok).


Last think to do now is try and work with the low voltage power supply and get the indicators working and through the MOT!
I wonder why Yamaha used such a weak power setup? Or maybe its because that battery is about 17 years old! It must be if it has'nt been changed since. Possibly get a new one?

Cheers guys safe riding thanks for your help so far

Sy