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Jianshe js400 wont start

216 Views 15 Replies 2 Participants Last post by  Mech
I bought it from a mechanic who said it needed a stator, I replaced that and now it has spark but still wont start. So I took it to a shop where they said the crankshaft was bent and that it wasnt getting spark but it is... any suggestions? They spoke bad english so probably said wrong thing.
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Well you try to start it for a few seconds then you take the spark plug out and check if it's wet or dry, then you go from there.. If it's wet, you change the sparkplug in case it's failing under compression, and you check the compression. If the plug is dry, you start checking the fuel supply, first by undoing the carb drain screw and checking that fuel keeps running even after the bowl has emptied..
The sparkplug was mostly dry only had a couple tiny drops of gas or something on it. The carb drain screw stripped so cant do that, but the carb is fairly new and dont think thats the problem, When I hit the throttle gas squirts out of the carb towards the engine.
Oh and there is 2 tubes coming out of the air intake boot thing that suck & blow air, I think they hook up to 2 small boxes but cant figure them out.
Yeah.. never buy a vehicle off a mechanic !

If the fuel supply was working right, but there was no spark at the plug, the spark plug would be drenched with fuel after a few cranks with the choke on. If it was firing it would have burnt the fuel up.
So.. it's not firing since you have some fuel on the plug, and that could be either no spark at the plug or it could be insufficient fuel to fire.. Sparks have a lot more trouble jumping through compressed air than they do through atmospheric pressure, so spark plugs can fail to spark when there is compression in the cylinder even though they seem to spark every time when they are resting on the head getting checked. I'd try a new plug to eliminate that as the trouble, then, if it kept getting a little bit of fuel on the plug, but not drenched, I'd assume it wasn't getting enough and so start looking at the fuel supply.
You should check the fuel is running out of the fuel hose at the carb. If it is, then I think I'd take the carb off and strip it right down completely and clean every jet and passage..A squirt with carb cleaner out of a can is not enough.
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Mk so what would happen if I just dumped a little bit of gas into the sparkplug hole? Would it give it a boost or something? And the carb isnt getting enough suction to pull all the gas in, a good portion drips back out when I crank it and it the throttle, found that out today.
Sparkplug is new and works fine. And when I said there was gas on the plug I meant very little.
Yeah try a small spoonful down the plug hole.. good plan.
When the things get worn in engines they loose their compression and their vacuum. How's the compression ? Have you checked the valve clearances ? A tight inlet valve will cause spitting out the carb.

Is it a four stroke ? Is it a racy sort of thing or more a work horse ?
No have not checked valves. Its a 4stroke its more of a work horse, it was used for deer unting before it broke. Has of accessories, horn, speedometer, headlights stuff like that.
It's pretty common for carbies to spit a little fuel out the back like that when they aren't starting right. If it's puffing out a lot though it might be because the inlet valve isn't closing completely because the clearance is too small.

Tip a bit of fuel in and see if it fires, or, get some starting fluid in a spary can and see if it will fire and run for a few seconds on that .. That checks that the compression and valves and all that is ok, and that the problem is only lack of fuel.
Aaand the spark is gone.... it had spark then I took engine cover off, put it back on and next day theres no spark...
This 4wheeler is really a pain.
Ha.. well you know where to start looking.. You could test or disconnect the kill switch.

It might be a wire broken. Wires nearly always break near the ends, where they go into their metal terminal mostly. If you wriggle them carefully you might feel one flex too easily because it's only the insulation holding it. Check near the stator and the cdi connectors. Check the wiring looms for chafed insulation where it could be shorting to the frame.
If there's no obvious broken wire then use an ohm meter to check for resistance through the stator windings, and the wires going from the stator to the cdi. If there is some continuity through the stator windings then use a volt gauge to look for some small amount of power out of the stator when the engine is cranking over. If there is some voltage there, check for the voltage at the cdi wires.
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Last time I it had spark I was holding the spark boot and I zapped the kill switch, not sure if it did something. Plus theres hardly any oil in the engine cuz it drained when I took cover of, probly not it though. I dont have a ohm or anything like that, nothing to check the volts with.
Ok the ll switch has 3 settings and i got it to spark again. I put gas in the sparkplug hole and nothing happened.
Try another spark plug. One you know works. Or, use a butane cooking flame to heat the porcelain tip where the spark happens on the old plug till it stops smoking then try it while it's still hot.. A new plug would be best though.

You need compression, fuel and spark to make it fire. Even if the flywheel key has broken and the timing's out so it won't run, it should fire and/or make flames or popping out the inlet or exhaust.
If you are getting no reaction at all, then it's lacking either compression, fuel or spark. The spark though can be drowned by too much fuel. Try cleaning or replacing the plug and then try starting it as normal. If the plug gets wet, turn the fuel off and try again, if it's dry, check the fuel supply and carby.
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