ATC70 only runs choked

[Frankencelery]

My son's ATC70, which admittedly desperately needs an engine overhaul, only runs when the choke is on. I moved this carb to another ATC70, and it did the same thing. To me that would indicate an air leak somewhere in the carb, but if the gaskets are good between carb and engine, what could it be? I replaced the o-ring, and I've tried spraying carb cleaner around while the engine is running, but I haven't been able to find the leak.

Any ideas?

[tecat-z]

Clean the pilot jet and thouroughly blow carb cleaner through all internal circuits, and finish off with blowing air through all circuits again. Should fix you up.

[ATCwithdrawals]

Clean the pilot jet and thouroughly blow carb cleaner through all internal circuits, and finish off with blowing air through all circuits again. Should fix you up.

Tecate-z is right, your problem is internal.

[james9r9r]

Well I rebuilt my whole carb on my 1983 atc 70 and the damm thing takes forever to start. I have to push it in gear to start and when it does run it still has no power and boggs, almost dies when I put it in 1st gear and fouls plugs if I can get it started?

NOTE:I am missing the little cap that goes on the choke lever I am thinking I am sucking air threw it. Also it won't idle at all unless I push in where the cap used to be with my thumb???

[Frankencelery]

It seems like we gave it a good cleaning when we first got the machine, but I suppose I should take it apart again and give it a shot. Otherwise I'll have to buy a carb.

Speaking of buying carbs, Beatrice Cycle is selling a substitute carb for less than $50. The only thing wrong with it is the fuel barbs are on the wrong side. I'm thinking if I can't work this out, I may try one of those. Anyone have any experience with these carbs?

[Frankencelery]

In my long standing tradition of answering my own posts, I had to add a comment. Once I decided to rebuild the engine on the 70, I bought one of those carbs from Beatrice Cycle. It was several months until I got around to opening it and last night, I did. Turns out it doesn't fit! It looks like it will fit my CT70 intake, but not the ATC70. I didn't realize they were different! So now I'm back to trying to fix that old carb that only runs with the choke on. Arrrrgh!

[bigreddaddy]

Go through the carb man. Its probably a clogged pilot jet.

[J.D.]

I've had the same issue as you there fella. I've already pulled mine apart 3 times and cleaned it all out and blew through all passages. Now, I'm going a step further. I've taken the carb off, dissassembled, remove all rubber/plastic parts, and putting it in this stuff called "CHEMPDIP, carb/parts cleaner" by Berryman. This stuff works wonders, leave it in there for about a week, take it out douse it all down the carb cleaner and blow all the crap out. You can buy it at a parts store, Oreillys etc etc, it's about 20 bucks for the gallon, but it'll last you for several several carbs....it looks about like a 1 gallon can of paint. I'm positive after letting mine sit in there for a week and cleaning it out good, it's going to be fine.

My Big Red was EXTREMELY hard to start, took carb apart let it sit in this stuff for a week, put it back on....starts first kick now :)

[Frankencelery]

Ok, here's what happened: I rebuilt the carb completely. I took the unit apart and soaked it in solvent. Then I used some very good carb cleaner and made sure to spray out all the passages, making sure that the spray comes out where it's supposed to. Replaced main and pilot jet, needle, gaskets, etc. Adjusted according to specs. Today I put it all back together and with the top end completely rebuilt, the damn thing still won't run. Oddly, it ran for about 2-3 minutes, very badly, and only with the choke on, and now it won't start at all. Just sputters. Double-checked timing and all that, and it's right on.

There's not much to these carbs, I just can't figure out where the problem is! Anyone have any ideas what I might be missing? Otherwise I'm headed to Ebay for another carb.

[bigreddaddy]

Have you checked your compression? I don't know if the problem is just the carb. If the carb was the only problem then it should have improved a little after you soaked/cleaned it.

[Frankencelery]

Yeah, I was thinking along the same lines. I ran a compression test, and with my automotive compression tester, I got about 120lbs. I figure I'm losing at least 5cc with the tester, so that should be great. I'm thinking about pulling the cam cover and checking the valve timing and making sure I didn't do something wrong there. There's just not that much to go wrong with these carbs!

[hrc200x]

Sure sounds like carb, but you could also clean and adjust the points, make sure gas cap vent isn't plugged, air filter clean?

What is the difference between the new carb you bought and the stock one? I have a couple trail 70s both with carb issues if your willing to sell.

[Frankencelery]

The points are new and properly adjusted. I made sure to remove the gas cap to make sure I had fuel flow (besides, I'm using clear fuel filters, so I can see it) and there's no element in the air filter yet.

The replacement carb I bought from Beatrice Cycle has a different bolt pattern to the intake. I thought about trying to use a CT70 intake, but I don't think it would fit in the space between engine and tank. I have a CT70 that I will be rebuilding sometime, so I guess I'll keep it.

[300rman]

only runnning with the choke on would indicate a carb issue.
did you check the entire electrical system to make sure you are getting a good spark?

whats so special about these carbs? to they slip into a rubber boot, or are they like a lawn mower carb where the mounting flange is built onto the carb?

[Frankencelery]

Yeah, spark is a good strong blue spark. And I replaced the spark plug. Just now I went out to make sure I got the cam chain on correctly, and there's no problem there either, it's right on. So the carb is where I started, and the carb is where I'm ending up, I think. 300rman, you asked about the carb- the engine side of the carb has a mounting flange that has two bolts. The air filter side has the rubber boot.

[KASEY]

NOTE:I am missing the little cap that goes on the choke lever I am thinking I am sucking air threw it. Also it won't idle at all unless I push in where the cap used to be with my thumb???


think about it,,,, the choke shaft it after the slide so if it was leaking air it would NOT effect idle,,, you have other problems,,, like a plugged pilot jet or imporperly adjusted idle screw,,,,

[KASEY]

and there's no element in the air filter yet.


there is one of your problems right there!!! you need an air cleaner or it will really run lean,,,

[Frankencelery]

Maybe you're right Kasey. I'll get the element, but I'm still pretty convinced I'm going to need a carb. Does the air filter require oiling on those?

[3Razors]

This is the rebuild kit I would buy: http://www.dratv.com/atsakitrest1.html

I also found that unless you really like tinkering run the oem air filter setup on the 70, or you will be doing lots of jetting changes to make it run right.

[iamschme]

yeah, i agree with 3razors, i had similar issues with my 83 and 85 and once i put the oem style air filter on, it ran much better. i got everything i needed from dratv. check your air fuel screw. make sure you have the screw, spring, washer and oring. if you are missing anything it will cause problems. i think the factory setting is 1 1/2 or 1 3/8 turns out, but i'm not 100% sure. it should give you a good starting point. make sure there is not a broken piece of oring in the air fuel hole. i had that problem as well. easy to over- look...lots of trouble.

[Frankencelery]

Yeah, I don't know what I was thinking. Last fall I put a cheap aftermarket filter on my ATC90, eliminating the stock one, and I needed tons of readjusting before it would run right, AND it still won't run worth a crap in winter weather. I only replaced the filter because the rubber pipe between air filter and carb rotted out, and I'm trying to figure out how to put it back to stock.

Anyway, I imagine that the 70 is at least that sensitive, maybe more.
I picked up the filter element today, (can you believe my local Honda dealer actually had it in stock?) and I'll try it tonight when I get home from work.

[Frankencelery]

This is the rebuild kit I would buy: http://www.dratv.com/atsakitrest1.html

I've breezed by that several times and never looked at it! You're right, I do need one of those! I bought the regular carb kit, but that one includes the bowl, the slide and other stuff.

Thanks!

[3Razors]

Your welcome. It should run a smooth as a little clock when you get it straightened out.

[Frankencelery]

Well, the air filter didn't make a bit of difference. Won't start at all. Choke on, choke off, makes no difference. Looks like I need to try that carb repair kit from DrATV.

[Frankencelery]

I took the carb off last night, and I noticed something interesting- I can see the float bowl o-ring! The bowl (or the top portion, I haven't decided which) is warped to the point where there's a gap in the middle. I'm sure that's must be the problem. In a fit of frustration I ordered a whole new carb from DrATV. Don't even ask me how much. It was twice what I paid for the 3-wheeler.

[Frankencelery]

Oh, how to start this post....

I got my new carb...put it on....pulled the cord....no start! What the...?

Suddenly I was hit by the proverbial 2x4.

Did I mention that I had replaced the head with a brand new one? Well, I took the valve caps off, and the locknut on the bottum fell out. The top one was still there, but just barely. I had visually inspected them when I got the head, but I hadn't actually checked to see if they were tight. So I adjusted the valves and TIGHTENED the locknuts, and as you might have guessed, it started on the first pull and runs great.

This is good news, but this also has to be my boneheaded move of the year. It sucks to have to admit all this, but maybe it will help someone else to avoid the same mistakes.

Thanks to everyone for all your help. My son's having a blast on his new ATC70, and it pulls me around pretty good too!

[rugabugadouglas]

so i wonder if this will fix my 70 i just put a carb kit on it and it ran good for a few min then crapy i dont have a stock filter yet but had a k&n would it be my intake valves?