85 ATC70 new carb, cdi converted, no power and will not rev high!!

[mcelroy4life]

my atc70 was running gr8 with the original points then it quit and could not get spark back, so i converted to cdi with the 99.00 ebay kit from malaysia. it ran good for a day or two. now it will not hit high rpms and no power, i have adjusted valves to specs. new parts added: spark plug, coil, carby, and cdi ignition conversion. the trike will start with a lot of choke on and off and so on. but it seems and smell like it is getting hot. the top end seems to be oiling good and i pulled exhaust to make sure it was clear and it was. someone please help, before my 4 year old son goes insane or drives me that way!! Hard start, no high rpms, dies when put in gear, and overall poor engine performance!! i dont have a compression tester.

[hoosierlogger]

Sounds like some of the symptoms of a broken/stuck timing advance weight.

[Thorpe]

Pull that carb apart and look for debris. Alot of those chinese carbs come pre-dirty...

[mcelroy4life]

hoosier I have thought this was a timing issue myself. but everything seems to be good. i just got done pulling the head to inspect the piston, cylinder, and combustion chamber for wear, cracks, or carbon build up. I was kinda surprised to see it all looked great! however the two rubber o-rings were distorted. the head gasket looked good with no sign of being faulty. I am starting to think that maybe my new coil is a p.o.s and might be breaking down under a load. Also i checked carb again and the jets and inside were crystal clean. hmmmmmmm. scratching my head!!

[hoosierlogger]

There may be something to the coil theory. They do funny things when they start to head south.

[KASEY]

sounds like some of the symptoms of a broken/stuck timing advance weight.

atc70's do not have these parts,,,,,,,,,,,,,,,,,,,,,,,,,,

[hoosierlogger]

Roger that I didnt know I never been into a atc 70. Good to know.

[mcelroy4life]

i am aware that those parts are not on an atc 70. however the backfiring thru the carb leads me to think its a timing issue! i know there is the valve timing, and ignition timing if it had points that is. any ideas on what parts that could be causing these issues kasey?

[KASEY]

i have never heard of a problem with the kits from malaysia at all.... what is this new carb you list? what is the jetting compared to the original carb? sounds lean to me is the kit installed properly?

[mcelroy4life]

k so in attempt to check compression i pulled spark plug and put some oil on to of piston then held my thumb over the spark plug hole and pulled the rope and there was not enough pressure to lift my thumb off the plug hole, so i did the same on my sl70 same engine and it lifted my thumb enough to show me that i definitely have a compression issue on the atc.

[ctbale]

I got the $99 kit on my 83, yea kasey is right on, the advance is handled thru the box. Still have not figured out how the thing knows crank position, but it works well!! I have about 15 or 20 hours on mine, no problems. Thorp is also right about the china carbs, I have a few, but you have to open up/take them apart, and clean out all the manufacturing residue, and check the security on EVERYTHING! I have had main jets half way screwed in, and all others stuff, like the choke plate loose, once gone thru they work great! My money is on the carb

[mcelroy4life]

PROBLEM SOLVED!!! The exhaust valve was not seating good so all my compression was blowing right out the exhaust pipe. so i tore the cylinder head down and lapped the valves. now just waiting on new gaskets and I will have it purring like a kitten. Thanx for everyones input and assistance. i will post back on this when i get it put back together just in case anyone wants to know. too many people never post the follow up to tell others what the solution was.

[mcelroy4life]

Got my gasket set in today!! I put my atc70 back together and wouldn't you know it fired right up on the second pull. no choke at all and just idled great gave it a test run and now its pulling a wheelie with me on it and i weigh 180lbs.

[Frankencelery]

Excellent. Thanks for posting the solution. A wheelie with 180lbs on it? Wow...mine has never done that well. I've always wondered if I didn't get something exactly right, because it's always been pretty weak at the bottom end. Maybe I should check the valves too....