Mech

I can't quite be sure I'm reading the colour, or role labels, on the combination switch contact diagram, but it looks to me like the wire coming from the ignition unit is earthed to kill the spark, and open circuit to run. That wire also goes into that multi relay called "combination relay". I'd suspect that relay can kill the spark if all the safety features aren't satisfied. I'd unplug that and spin the engine somehow and it should have spark.

Doh. I got confused.. Well can a different part #11 be got. The one listed is 25 T.. Is your's 25T ? Perhaps searching for that part, with the number of teeth your bike has, might lead somewhere.. I looked and there are American models, UK models and Australian models. I'll bet the problem is that the bike was meant for some other market. If you send me the frame and/or engine numbers I will try seeing if I can find anything. I have seen references to buying a gear set which apparently, while having different teeth count, does the job.. Old posts though and no part numbers. It may be what's happened to this bike.

https://www.google.com/search?q=1986+handa+trx250+starter+gear+43%2F18&sca_esv=4a9fe3e51a0d056a&ei=WnsJZ4fyKu6m2roP5pjsgQM&ved=0ahUKEwiHh_PzhoeJAxVuk1YBHWYMOzAQ4dUDCA4&uact=5&oq=1986+handa+trx250+starter+gear+43%2F18&gs_lp=Egxnd3Mtd2l6LXNlcnAiJDE5ODYgaGFuZGEgdHJ4MjUwIHN0YXJ0ZXIgZ2VhciA0My8xODIGECEYFRgKSIgUUMEIWJIPcAF4AJABAJgBiASgAbMHqgEFNC0xLjG4AQPIAQD4AQGYAgOgAssHwgILEAAYgAQYsAMYogTCAgsQABiwAxiiBBiJBcICCBAAGIAEGKIEmAMA4gMFEgExIECIBgGQBgSSBwUxLjQtMqAHkQc&sclient=gws-wiz-serp Damn. I thought that was going to change into a tidy little url. So that's the part you need ? Better check all the other parts that might be different too/

I think this is your wiring diagram.. It looks like you need to check the key, kill and the other switch which I think might be a tether kill switch, there so a parent can pull on a tether and kill the bike. output.pdf

You need to tell us more.. That's what I think. Like, is it warm or cold, idling or with the throttle open, has it had any work done to it, has it had a tune ever.. I could be guessing forever why an engine might "randomly" shut off. My guess is, that, because there is very little in this universe that is completely random, that there will be clues which you are not telling us, that will explain the random and reveal it to be in fact some degree of chaos, not random.. haha.. Well you did ask for thoughts.. Any thoughts.

This is what the owners manual says about the stater... START BUTTON IS NOT EFFECTIVE Symptom, possible causes and remedy • Run down battery. • Defective switch contacts. • Brushes not seating properly on starter motor commutator. • Defective starter relay. • Defective main fuse. No mention of cdi. Since neither the spark nor the starter work, I'd be suspecting the key switch. Or wiring...

Is the spark-plug getting wet with fuel ? Does the spark-plug have a spark if you rest it against the head and crank the engine over ?

Oh too cute. The little mower that could.

I remembered in the night reading about someone who had a similar problem, except a bit worse in that the bike would barely move, and it was because there was a safety feature whereby the bike's revs were limited if the park-brake was on. He disconnected the brake switch(which was defective) and it went again. I can't remember if it was a yamaha or a kawasaki now though.. haha. Worth a look, or read in the owners manual.

It's a honda. It should be good.. Beautiful in fact.. haha

It would be a good idea to check the stator readings as well, and check the connector looks original.. If the stator or cdi has been changed with the wrong part or incorrectly it could run like this.

Check the charging system is charging, and regulating.. Just slap a volt gauge across the battery terminals and see it's 12.6 at rest, about 13.6 after it's started, and gets up near but no higher than about 14.7 with a few revs. Then turn the headlights on and it should be able to maintain about 13.7 volts. If you have a timing light put that on and check the spark isn't disappearing when the trouble starts.

Oh yeah Gw, get a wiring diagram. Drive-ons have safety features galore. You have to be sitting in the seat, with the blade disengaged, and with the cutters raised, in neutral, and it might start.. Oh, and full with oil.. And the hand-brake.. There might be more..

Some of the old suzuki were 12 volt and some were stator run cdi. You might need to ascertain what year and model and market you have to get the right wiring diagram. It's pretty much what Gw said though, and if you can match colours up you might get it to spark.

Just take the top cover off, in place, and check and/or change the needle position. That's easy. If changing the needle makes a difference, then move it some more till it's in the best position for running between 1/4 and 7/8 throttle. If that doesn't/can't make it run right, then take the carb off and strip, clean, inspect and adjust it.

#9 #11

I see someone posting a service manual for the 2008 Qlink Rodeo 700FI, but it turns out to be a yamaha service manual, for a YXR 700FX Rhino. Might be worth a look.

The three wires the same colour can be put in any order into the plug.

It's not strictly putting it in gear that's making it miss.. It's putting a load on the engine that's making the miss I'd think.

It's easy to muddle the spacers and/or washers around the clip on the needle slide on some carbs. Some have spacers above and below the clip. Some of the plastic spacers are quite thick and make a big difference to the running.

Haha..

Sounds good Gw. My son's got a walk behind self drive honda and he's in love with it. I've worked on the self drives and they are a very nice machine. Easy start, super reliable, cut and drive real nice.. Just like honda quads. Hopefully you will never need to take that engine out again after a cam belt and a service.

Yeah I checked it. Thought you might be able to extrapolate somehow.. haha. There are other sites like it. It did at least confirm it's for the Bayou. It's really only the last six numbers that are the engine number. If you looked in parts books it might just, if you are lucky, find they refer to parts changes by referencing the number. That's how you discover if it was some tricky situation where the part changed half way through a model year/run.

The bad running and the smoke are almost certainly two separate problems. If the smoke is a valve seal etc leaking it will most likely be the exhaust one if it's the evaporation scenario. If it's the inlet, the oil will get burnt and it smells like burnt oil, Evaporated oil smells different, more like oil. For the bad running, the carb would be the number one suspect, and easy to check. I'd clean it and check the slide needle's position. The running from about 1/4 throttle up is controlled by the slide needle and the emulsifier tube. You need to take the emulsifier tube out and clean it carefully, especially the tiny holes up it's side.

White smoke, if it's from engine oil is oil that's being evaporated but not burnt. It's common if a turbo fails for it to chuck oil into the exhaust manifold where it gets evaporated and makes distinctly white rather than blue smoke, and lots of it. In your case NH it might be a worn out valve guide, or just a valve guide needing replacing, or, a valve guide that's loose in the head. Another thing that I've seen make amazing amounts of white smoke(from a lawnmomer) was when someone had accidentally put chain-bar oil in the sump by mistake. That thing filled my yard with smoke you could hardly even see through.. And no, I didn't put the oil in it. I figured it was the wrong oil though because it smelt wrong, and when I asked the owner.. They'd just had it serviced at the chainsaw shop.. Haha.. too funny.