Derbi flat reed just stopped

I have an 87 Derbi Variant Sport that I just got up and running after sitting for a few years. I cleaned everything, changed oil, new spark plug, ect. It had been running fine for a week or so, a couple of tanks of gas through it and then it just died at full throttle running down the street. I figured something clogged the carb or fuel line, so I took it apart, cleaned it, everything seemed good, still won't start. So I checked it for spark and there is good spark, so I put in a new plug. I have gotten it to start for a couple of strokes only, but it would not stay running, just a quick sputter, but enough to let me know there is life there. Any suggestions as to what to do next, I'm stumped?

Re: Derbi flat reed just stopped

did you lose compression?

Re: Derbi flat reed just stopped

Nope, compression seems fine. I didn't run a compression test on it, but it has the same resistance on the compression stroke when pedaling/pushing as always.

Re: Derbi flat reed just stopped

you should run a compression test, if you say it died at WOT you could've seized it and the ring(s) could be fucked up... it may have just enough compression to start ... but not run well. i've had that happen to me.

Re: Derbi flat reed just stopped

Thanks for the idea, but compression test is coming up consistently over 125, so I don't think that's an issue. I'll take any other ideas!!

Re: Derbi flat reed just stopped

you cleaned the carb?

cleaned the points if it has points? double checked the timing?

if it's got compression, spark and fuel flow it should start.

Re: Derbi flat reed just stopped

sounds like a fuel issue....

1. check you are getting fuel flow to your carb + make sure your float is not stuck

2. you mentioned you checked for spark and then changed your plug? does the new plug spark?

3. could be that vibrations made the points gap shift (adjust timing) or an electrical short.

Re: Derbi flat reed just stopped

Yup, as I said in original post I took the carb apart to make sure nothing little had clogged the jet. I cleaned the points, and the timing is correct. I understand that if it has fuel compression and spark it should run, that's the reason for the post :-).

Re: Derbi flat reed just stopped

Carb has been removed, taken apart, thoroughly cleaned and reinstalled. The new plug has spark and the timing is correct. I would expect no spark if there was a short, right? not sure where to turn next?

Re: Derbi flat reed just stopped

you took fuel line off carb and checked flow through petcock?

compression+ fuel+spark= run

??

Re: Derbi flat reed just stopped

Absolutely, that was the first thing I did.

Re: Derbi flat reed just stopped

Anyone have any other ideas?

Re: Derbi flat reed just stopped

How do I check the amount of "spark" the engine is getting?

Re: Derbi flat reed just stopped

Charles Nalbantan /

In the same boat with my ds50. Same thing happened to me a week ago. Was told it may be a fuel flow issue back between the petcock and tank filter (upstream from the inline filter). I'll check out/clean the tank and petcock over the weekend and let you know if I find anything.

Re: Derbi flat reed just stopped

Gee, multimeter

Re: Derbi flat reed just stopped

Does it continue to run if you spray short bursts of starting fluid into the carb?

Re: Derbi flat reed just stopped

Gee, that's an informative answer! What Exactly am I looking for with the multimeter? What is "enough" spark?

Re: Derbi flat reed just stopped

Nope, it only sputters, it's not continually runing, like I said, just enough to show there is life. Spraying starting fluid does not keep it going.

Re: Derbi flat reed just stopped

Thanks, I'll do the same. I'm getting good fuel flow from the petcock with the fuel line off and the petcock turned on, but I'll give it a shot anyway.

Re: Derbi flat reed just stopped

Charles Nalbantan /

Had all the same symptoms last week wiith my '89 Derbi of many years. Here's what I did.. Now she runs like new and starts right up! Removed and cleaned the fuel tank. Removed and replaced the petcock (filter on it sits inside the tank and was pretty gunked and there was corrosion inside...probably could have used the same one after taking it apart and cleaning it, however) removed, took apart and cleaned the carb (loaded with gunk). Replaced the in-line fuel filter (be sure it's set in the right direction...not all replacements are marked as such) I use the clear view type with the white trans screen i find best for 2cycles...and you can see) If the flow direction isn't marked, can't hurt trying it the other way).

Before all this it was running... Then just stopped..having all your exact symptoms. Like you, Starting fluid only allowed me to know there was a good spark... So I just worked back from there covering all bases with fuel flow. Like Richard S says..spark + fuel = combustion. Let me know if I can help with any questions. Best of luck.

Re: Derbi flat reed just stopped

Thanks Charles, I have done all of those things (I did not find the "gunk" on the filter in the tank/on the petcock that you did) and am still having incomplete success. I say incomplete because I have gotten it started and have run it down the block only for it to die again. It now starts intermittently and I believe it is a problem with the coil/plug wire, so I ordered a new one. I think this because it seems if I move the plug wire around after it dies and try to start it again it will start sometimes, but if I try to restart it without messing with the wire it does nothing. If the new coil and wire don't work I'll retrace the fuel line steps again. Thanks for the advice, I appreciate it.

Re: Derbi flat reed just stopped

Try running a dedicated grounding wire to the outside of your spark plug - I agree it could be a grounding issue.

Also, take your plug wire and snip the ends so there are fresh segments for the coil and boot to thread into.

Orrr... you can just wait for your parts to get there.

I've had several bikes now spark on the case and no sparky sparky in the cylinder - worth a shot.

What's your voltage going into the HT coil? (edited)

Re: Derbi flat reed just stopped

REEDS

Re: Derbi flat reed just stopped

I clipped the wire with no luck already, so i'll just wait for the parts to get here b4 I mess with it again. I have not tested the voltage coming to the coil, do you know what it should be?

Re: Derbi flat reed just stopped

What about the reeds, I have removed, inspected, and cleaned (not they needed it) the reeds. There was nothing wrong with them, what's your suggestion?

Re: Derbi flat reed just stopped

at least 3 volts on points and more than 6 if cdi.

I'd check all grounding points through the ignition. CDI or points?

Re: Derbi flat reed just stopped

points, I'll check it and the grounding points too. Thanks!

Re: Derbi flat reed just stopped

No Luck with anything. So far I have completely cleaned the carb. 3 times, removed and cleaned the petcock and internal filter, removed and reconnected all of the grounds, replaced the coil and spark plug and verified the timing and voltage output. I have removed and cleaned the intake and reeds and verified there is vacuum. Compression tests verified the rings are good and there is more than sufficient compression. It starts when it wants to and I have been able to go for short rides but then it quits again and sometimes will start right back up, sometimes it wont. It doesn't make any sense to me and it's pretty close to becoming a boat anchor!!

Re: Derbi flat reed just stopped

On and off stuff like that (in my experience) is usually ignition.

Does it run like it "always does" when it does run? or is it poor or mediocre? Sometimes you just have to step away and come back to it.

Re: Derbi flat reed just stopped

Thanks, I was thinking it almost had to be the ignition but I just don't have the "proof" so to speak. I went back into the garage after my last post and decided that I saw some oil buildup where the spark arrestor connects to the pipe, so I took the spark arrestor off, pedaled like I stole it, and got it started again. It was running great (although very loud) but it did not want to idle unless I brought it down to idle slowely. If I came to a stop it stalled (and started back up easily every time), but if I kept a little twist in the throttle when coming to a stop I could let go of the throttle after I was stopped for a second and it would idle. I don't really think the exhaust has anything to do with it, but didn't want to leave the detail out in case I'm wrong and it matters. So I guess I took the long route in answering your question, but it basically does run normally (other than the stalling at stop) when it runs.

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