Atc 70 hellllllp pllllllllease !! Im going insane !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

[woodyatc]

So i have a 1985 atc 70, it did run fine engine / compression transmission all fine, started 1st pull ticked over ok, pulled strongly, then it developed an intermitant starting fault, its had a carb clean out, then brand new carb, then brand new points / condensor and coil (has good spark and fuel delivery) all wiring ok, timing ok, when it do'es start it usually start within a few pulls and runs great no problems, yet other times it wo'nt start at all - like today it fired 1st time this morning yet would not even bump start 2 hours later ???? Despite timing / spark being ok and carb brand new, i just do'nt understand how it can run great one minute and not run the next ? Could the plug possibly be the problem ? (the plug is a d6hs as opposed to th cr7hs usualy fitted to the atc 70, i can only assume the plug threads got stripprd at some point and a different plug was needed ? It do'es run ok with this plug when it starts though ) im thinking maybe plug ? Or a slipping flywheel due to flywheel key / woodruff key ?? (what size woodruff key for an atc 70 ?) any help would be greatly appreciated as this little trike it cracking me up !!!!!!!!!!!!!!!

[Flossyb20]

Is the handlebar switch turned to on?? Maybe there's a short in it....

[Handy Andy]

When it won't start, take out the plug and hold it against the engine with wire attached and see if it sparks. If not, you know it is an electrical problem. Have you checked the valve adjustment? I have a honda MC, and when I checked the valves, the top one was too loose, and the bottom one was too tight. It also had difficulty starting. Think the bottom valve was leaking compression.

[barnett468]

Hello

OK Sometimes it will not start even though there is spark. Are you checking the plug itself for spark or just grounding the plug cap?

Could it be flooding. A gas soaked plug will aften sparkwhen removed and laid on the head and checked but will fail to start the motor.

A dirty ground like coil to frame or dirty wire connection will some times cause an incosistent problem. It will sometimes allow the plug to spark when laid on the head but it will not have a good enough spark to fire the fuelnunder compression. Try cleaning the connections.

You can by pass the kill switch also

Is the spark bright and strong looking or is it a pale yellow orange etc. If it's weak your coil is likely weak.

Your d6 heat range plug should not cause the problem.

Did it run fine with the old points and condensor? If so then it is the points or condensor or their installation especially if they were made in China not Japan or the US.

It is not your flywheel key. Once out of time enough not to start it will never come back.

[woodyatc]

Handlebar switch seems to be working fine, plug sparks when its switched to on and doe'snt when its switched to off, so i think its ok ?

[woodyatc]

Hi, it sparks ok with the plug out no problem, so i do,nt see it being electrical ? i just assumed as when it do'es run its sweet as a nut that the valve clearances were fine ?

[woodyatc]

Hi there, im checking the spark at the plug which is strong bright blue / white, the carb is a brand new replacement with the fuel air mixture set as per the manual (one full turn out from seated) it will run fine on the carb once it starts, the coil is brand new as are the points and condensor, the ground on the coil is good as are all the wiring conectors, it had the same problem with intermitant starting on the old set up (carb points coil condensor, although the spark was much weaker and sometimes none exsistant on the old set up) it used to run and start fine then just developed this intermitant problem ? i just do'nt see why it wo'nt start if its got a good strong spark, good fuel / air delivery, and is in timing ? like i said its got me beat !!!!!!!!!!

[barnett468]

Does it have a BATTERY? If so do a voltage test when it will start to see if it is charging just to see.

Even thought the problem existed with all the old parts are the electrical parts you replaced CHINESE?

Is the plug WET or DRY when it won't start?

If you don't check everything everyone is suggesting it will be hard to determine your problem.

Here is a new potential problem. You now say that it "runs on the carb once it starts". This suggests that you have to spray starting fluid in it when you are trying to start it. Is this the case and do you have to do this all yhe time and with the old carb too?. This is important info. It suggests a couple things, two of them are you may have an intake air leak but since it still won't start if you try to push start it this is unlikely so if the plug is dry after a push start attempt then it sounds like it is not getting fuel consistently.

When it refuses to start, check to see if the plug is wet. If it is not then try to start it by pushing it with the choke half on and the throttle wide open. If it still refuses to start then remove the the plug and if it is DRY it is not getting fuel. Since it did this with the last carb also the problem is in your fuel petcock. It is getting intermittently plugged most likely from rust in the tank.

Let us know what you find after doing this.

[fabiodriven]

My favorite answer lately- Next time it won't run, remove the gas cap. If the bike starts up, your gas cap is the problem.

[barnett468]

My favorite answer lately- Next time it won't run, remove the gas cap. If the bike starts up, your gas cap is the problem.

Gas cap sounds like another good suggestion to me however if it sits for two hours and then wont restart like the guy said and he left the petcock open when he stopped it two hours prior it would loose any potential vacuum it might have had providing it could suck air past the needle and seat. If it was running fine and he turned it off and shut the petcock off then the tank would not have much if any vacuum at that time or two hours later but your idea is fast and easy could still be problem, i'd try it too.

[woodyatc]

Hi thanks very much for the reply
Has no battery
Good and consistent spark (when plug is out)
Replacement parts are chine sets but it did start and run fine when they were fitted
Plug is getting wet when pull starting and bump starting so I do'nt think fuel delivery is a problem ?
Never had to use starting spray
Air intake is fine new gaskets and sealant
Maybe valves clearance or stuck ?
But if it was valves I did'nt think it would run even internmitantly ? When it do'es start it starts and run fine good compression pulls strong.

[woodyatc]

Thanks I'll try that, but it gets fuel through the carb and into the cylinder no problem, do you still think the cap maybe the problem ?

[woodyatc]

I'll try the gas cap and see if it makes a difference ? Fuel delivery is ok though tank has been cleaned and flushed has new fuel and fuel is getting through the carb and into the cylinder all the time, plug is wet when pull starting or push starting, and when it do'es start it runs fine and will then start ok if you switch it off and back on no problem at all, I really just cannot understand it at all ? Unless some how it's losing its spark when the plugs in the cylinder ?

[woodyatc]

ok so i removed the gas cap and it started after three pulls after being stood 24 hrs and ran fine (it has done this in the past though with the gas cap in place like i said its an intermitant starting problem) i know its getting fuel with the gas cap in place as i've checked and rechecked the plug when trying to start it in the pas and its always wet, so maybe it starting with the gas cap off was a coincidence and it was just one of those times it was gonna start anyway ? guess i'll know in time when i try to start it again (with gas cap off)the gas cap is the original Honda one with the on / off position barin place, what difference will starting it with the cap off or on make ? im showing my lack of knowledge now, but have'nt worked on these machines much at all, most of what i do is tackled with the aid of the haynes manual, and that says nothing about the fuel cap.

[trike savior]

even though it has on off switch on cap, it can quit working sealing the tank and not allowing gravity to do its job properly.

hard to tell from posts but is the engine always cold when this happens or is engine hot or both. somethimes electrical components can start acting funny when hot. mainly generator inside engine. also heard ignition coils can act funny like you are saying. it sounds like you know when it wont start the plug is wet, so its either flooding or loosing spark. i would say next time it wont start, push start it as you say you do. if it still wont start immediately pull plug and check for spark, if no spark then check for wet plug. if it is wet quickly dry it or use another plug and check for spark again. if it sparks, flooding is only your problem, if no spark look at generator or coil.

also check your harness for bare wires or bad connections. could be intermittently grounding or loosing connection