I have an old 2007 Jianshi js 400cc mountain lion, had this for about 3 years now, bit of an old dog! But I live in the middle of nowhere, and I use this thing to
Haul a small trailer, around out yard picking up wood and staking it ready for the winter, which can get down to -25 to -30c, not all the time but it can go down that far, with 1 to 1.5 meters of snow, I have the snowblade for it, and I clear the snow, to get at the wood and pick it up, alsoneed to keep out lane clear, if someone is ill or injured, as an ambulance has no chance when it’s that bad to get here unless I keep it sort of clear, SO it’s a must this old bird keeps going; As she only does about 20 miles year, max, small little runs around the yard 95% of the time!

When she is warmed up she will pull near 2 tone, and seems to run fine, BUT, I have a new heavy duty battery on her, but it seems when she is cold and I don’t even mean real cold, just not used for a few days, any time of year, I turn the key and she does not even fire, turns over fine, but if I try to use a little choke, the turn over speed slows right down, and it seems the more choke I use, the slower it turns over, full choke, and it just seems to die, like won’t turn over, starts to, and just stops/ like it jams. Hand throttle it does the same, more throttle, less it turn over. I often try flicking the hand throttle a couple of time, before trying to start her up, and then it sometimes does the trick. But in the winter, I dump a little gas down the air intake, and also use a spare car battery to make it fly over, and 99% of the time it will then start up ok.

I have cleaned the carburetor out , the spark plug does seem a little on the blackside, so I am guessing, it’s sort of running too rich, but don’t have a manual or hand book, so can’t find anything to adjust air/fuel mix, air filter, not sure if you clean them or bin them and that foam cover, some engines say use light oil on it after cleaning, again not sure. Anyway, am a bit stuck, can anyone give us a pointer on this one.

I have also checked the carburetor make, and it says JAPAN stamped on the side, as (they) said it supposed to be a copy of Yamaha big bear 400c, Umm not so sure on that but that’s what I was told.

Thanks!!

 

I would check the battery voltage as you crank the engine over.. Id guess the new battery isnt all that good.

 

Ok, it's an angle I have not thought of, will give it a go today, and post back the readings from my meter. I will re check voltage as is, check voltage when I turn the key, give half chock ( enough to normaly stop it turning over, ) and hit stat button, while checking volts again, and see what the meter says then!

Question; when I hit the start button what should the voltage drop to, roughly?

what about that air filter thing, are they clean out with cleaner, and oil on the foam before putting it back or is it one of those take out and bin jobs?

 

Ok had a check up, volts before turning key, 12.9V full chock,
Temperature about 17c had not been started over night. started OK within 2 or 3 seconds ( so thats good) meter Dropped voltage to around 11.7 volts while it was turningover, with full chock on.

One other thing, I noticed was the air pipe, which is attached to air box the second pipe, not the one which is attached to air filter in air box and goes to the carb, but the other one which is like the little snorkel goes up under the seat had come of the air box connection, and there was also a hole in the same pipe which was torn, it's lttle right angle bend bit near the top of that pipe is also just down from the seat underside. I am wondering if this will mess up the air fuel mixture, when running.

haha, also does any have an idea on Tappet clearance inlet outlet, measure, hot or cold, have not got a clue on what they should be!!


thanks again;





thanks again.

OK update;

repaired the hose stuff, cleaned air filter, used car
Battery with jump leads as well as the charged ATV battery to give it a little extra, and guess what?

STILL THE SAME; as soon as you try and start it with full or near full choke, it sort of half turns over and goes urrrrrrr, stops turning, same old, same old, no choke, and she turns over like a rocket and starts, but had been started a few min before, and it's summer, so that don't count!
SO, I am at this minute all out of idea's. unless, it's sort of somehow normal with these things, who knows!!

Ummmmm.

 

I'm thinking starter problem.

 

Ummm not so sure I can buy inot that one! but I love to brain storm.
I managed to get a service manual online, so now have all the info regards setting up, tappets, everything, well almost, so now I have tech info for anyone else with one ofthese who has the JS 400. Today, it seems fine, cleaned the filter out, I didwash it out with gas and let it dry, and it seemed to work, but not supposed todo that, use air line, and soap and water for the foam outer filter, opps but I now know next time!