Slow to up idle

[Blurredman]

Hello guys.


A quick question. My MZ ETZ250 of late has started to be a bit slow on the uptake after slowing down.


The idle is set to appoximately 1250 rpm. And that is fine. The bike runs but after slowing down to lights or junctions the rpm will decrease to 1k rpm, and it will slowly rise back up to the 1250. It doesn't go low enough to stall the bike but it is annoying, and esspecially with the electrial system being so thirsty on these bikes I gather if I rode with the lights off it might just stall.

Anyway. I've taken the carbruettor appart and apart from a few tiny bits of rust, the jets were cleared (clear anyway) and it was put back together and onto the bike. I've made sure that there are no obvious air leaks but this issue is still the case.

Any ideas where to go next?


Thanks in advance.

[Blurredman]

Okay. I've looked at some other things today.

The other day when I was riding home from work in the night (at 1am yay), I noticed a interesting powerloss when I initially turned on the lights, then turned on the high beam. It did seem noticably less 'free' with the lights on and indeed it did seem to turn at 200rpm less than it would otherwise. I don't often ride in the night and therfore need the lights but it's not a bike that has taken a great hit in engine power suction from having them on, considering it is an alternator(ish) type charging unit.

Anyway, tonight I had a look at taking the engine side cover and noticed little things like oil on the three black wires. I know these wires are particularly interesting as they can cause some funny issues if they're not connected properly (or at all) as i've found in the past. I sprayed the contacts nice and clean with WD40 on every blade/spade type item in the area and vaseline'd them up and put them back on after a little bit of tightening on the spade for a more solid grab.

From now on I was testing. It was a little better in power delivery but ultimately the idle issue was there (where it dips to 1k when just braked then rises slow) but interestingly sometimes the idle would just creep off down the tachometre until the bike just stalled. I took apart the carburettor. cleaned it, made sure there were no air leaks, checked jets, all fine. Put it back on the bike.

Bike has solved the issue where idle just seems to drop off but it has the original problem again. It is worth noting that I have changed the spark plug on my last few commutes to a normal copper one with little wear to see the effects of the fuel/air mixture. Which is fine, and it should be too i've not touched the adjustment for thousands of miles. I doubted this was the issue.

But, on this result I believe rather than an electric issue it might be a fuelling one, and thus when I get time (this weekend I suppose) I will take off the caburettor, carefully take it appart and do my usual boil in lemon juice trick that works just wonders. Hopefully this will solve all ills. But, while the time awaits, is there anything that past experience of users on this forum can point me at regarding the issue if it was an electrical problem instead of a fuelling one?


Thanks ,

Matt

[Blurredman]

Well, you know what they say. Don't get fixated on a probable solution when it might not even be it.

The carburettor was cleanest it could be, all up to spec and ready to go. No air leaks, no issues on fuel delivery from tank.

I decided it could not be the carburettor anymore. After all, this issue somewhat ocured minimally at first and then expanded into a constant annoyance. Cleaning the carburettor did absolutely nothing to resolve this the first time around, although it did give me a a negligable feel in power back.


I checked the points. Which I admit I knew they were a little worn, but it was timed correctly. How wrong I was to dissasociate the problem with the points as when I took them off to have a closer look it was obvious that they were well worn infact they may even be the originals which is quite possible considering the bike has done 25,000 miles now.

I changed the points for a new set I had spare, timed it correctly and gapped it correctly and oh my a much bigger spark and a heck of a lot smoother and I don't think it's a placebo effect. The bike used to be very smooth when deaccelorating which I knew was wrong, where is the well documented 'lurching' that occurs on a standard and up to spec machine? It was not there. Not it is back. And idles properly now too. I could never get a steady/constant idle recently. But now after braking for lights etc it sticks to 1,500 for a few seconds and then slowly decreases to around 1,300-1,200 like it should, and indeed used to.


I didn't listen to my own advice that I normally give, don't skip components just because they 'used to work fine'. The points were off centre by half of the contact and a big stepped plateau had been created. Not to mention the bottom contact no longer had any flint (i know it's not flint but i've forgotten what it really i). I don't know whether that was normal on the original component but it has the flint (i know it's not flint but i've forgotten what it really i) on both contacts on the new points set.


Regards,

[DAVID THOMPSON]

in the early 1970's i bought all the stock of a local BMW Shop

and in the goods were several sets of points sealed in bags

and i stored them

when i opened a set 10 years later they were useless they were in the bag with the springs coiled up and ready to install

AND THE SPRINGS HAD LOST THERE TENSION
bike would run fine to about 2500 rpm and loose power

when i installed a electric trigger unit it ran fine
bought a used bike that had been stored 15 years changed the points with new and road it home 300 miles
we could not get it started till i changed the points