Novice Yamaha SR125 firing intermittently

[dopplerhire]

Hi all - complete bike novice looking to introduce myself and ask for advice.

I've just bought (perhaps rashly) a 1987 Yamaha SR125 for a couple of hundered quid on eBay. The bike looks good, has about 20k on the clock and has been stored in a dehumidified garage for 10 years. It is known to have intermittent firing issues, but how bad this is I'm unsure as I'm due to pick it up this evening.
I'm thinking to check along the lines of spark plugs, air intake. Any other ideas? Plus any basic bike checks I can do to assess overall condition much appreciated?

Thanks

[edd]

I'd suggest its most likely a spark issue. My friend's SR 125 had an interesting CDI problem very similar to yours. If he hit his CDI it would work again for a while. Im not suggesting that you do this or that this is the problem BTW. I'd try replacing the spark plug for starters, then work from there. If the plug is the problem then it will only have cost a couple of quid. Even if you replaced the coil, plug lead, and CDI it wouldnt cost a fortune on an SR. Just look out for parts on eBay. Try the plug and post what happens.
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[dopplerhire]

thanks, I hope to get a chance to check the ignition system over the weekend. A bit more info. for now is that the spark plug was changed a couple of weeks ago. On testing it yesterday, I wouldn't really class it as running, it seems like it's about to fire - het a few rumblings and just dies off without ever really kicking in. From the other forums I thik I've got to also check:

Fuel/filter/strainer/injectors for any blockages
Same for air - filter/carb
Coil/cap
Worst case - compression = opening the engine and replacing the piston/rings.

Is this a fair estimation of what needs checking? If so, an order of priority would be handy as the kids will only let me have so long to tinker! Plus in a worst case scenario and a compression problem is likely, are there any specific tests I can do,, plus how much would I be looking at for rings?

[mchaggis]

Make sure none of the ignition circuit connectors have corroded up or uncrimped themselves. That'd cause a misfire for sure.
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[davidimurray]

Hi

A couple of months ago my girlfriend got an SR125. Went to look at it, it was only a couple of years old and with 5K on the clock it should be fine. However, it had not been used for a year. As a result it wouldn't run unlees the choke was out and it struggled to idle.

Bought it and got it home - drained the fuel and cleaned the tank, cleaned the carb jets , new plug and oil change and it now runs like a dream.

Cheers

Dave

[dopplerhire]

Thanks for all your help!

I've managed to get the bike running by completing stripping the carb, removing all the jets/float and soaking/clearing with carb cleaner. The main jet especially was absolutely clogged/varnished up and throttle slide needed reseating.

I do notice that if I progressively throttle (still all done standing still), that she takes up fine, but to go from zero to full throttle immediately she stalls (is bogs down the correct term?). Not sure if this is normal or whether I should look at other parts too.

I'm in the process of cleaning out the tank/filter etc but it all looks reasonably good condition so don't think this will help much.

Most stupid of questions, but unfortunately forgot to check with the owner: Will this take 4-star or unleaded, my gut feeling on a 1987 is leaded, but need to check!

Finally a couple of questions:

Looks like the horn doesn't work and indicator relay might need replacing. Connections seems fine. Any idea where I can get replacements (eBay?)

Also, the chrome exhaust is lovely just needs polishing. Any ideas what polis/technique to use; wheel chrome looks a little rusty - can I clean this off anyway?

thanks again all!