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

[barnett468]

HELLO

I reread your posts and thought about it and I think there is an issue with your new carb like you think. This is almost impossible because Kehins are xlnt quality. Anyway once you answer the questions below we’ll know more.

Get ALL the jet info I requested from BOTH carbs.

1. Do you have venier calipers to measure the bore id of both carbs?

2. Do you know if the OLD carb is ORIGINAL, or are you just assuming it is?

3. What are any numbers on it?

4. Did it have the SAME starting problem once you cleaned the carb with the OLD electrical parts?

5. Was the plug always wet when it wouldn’t start with the CLEAN old carb and OLD electrical parts?


NEW KEHIN
1. Are you sure it is a real kehin and not a copy? Areal kehin will say kehin on it a copy should not.

2. Since it looks different it is NOT a new ORIG, is it replacement?

3. Is it the same size [cfm] as the original?

4. It could easily be jetted richer than orig.

5. Where did the new one come from?

6. What numbers are on the outside?

7. Any part numbers on the box?

[woodyatc]

Hi Barnett, as soon as i get chance i'll get back to you with all the info you requested

For now -
I do'nt have venir calipers to measure the carbs.
Im just assuming the old carb is original (as the bike is pretty much original and complete).
i di have starting problems with the old carb in place after i cleaned it (but im assuming that was down to the old worn out electrical parts ?) i never tried the old carb new electrical parts combo, i just went with new electrical / new carb setup.
plug was always wet with the old cleaned out carb when it would'nt start.
it has the Kehin marks on the new replacement carb so i assume its an original Kehin ?
I purchased the carb from ebay in the US, it did not come in a box, but the seller stated it was sutible for an Atc 70 .
yes its the same size as the original.
As for jet sizes etc i'll get back to you as soon as i can.
I just assumed (STUPIDLY) it would be a simple bolt on replacement and did not bother to check jet sizes etc againt the old one.

Many thanks once agin for your help and imput

Gav.

[barnett468]

hello woodyatc

thanks for the info, now you're not bored while you are at work because i gave you something to do, lol. I guess we'll attribute your previous problem to old electrical and the new one to the new carb for now. I'd like to do the test with the old since it did start and run fine at one point in time with it.

"Seller said it was "suitable" for an atc 70", lol. We'll see.

Did the bike ever NOT have the problem with the new carb or was the problem there from the start?

Condenser - I think since it is the ONLY chinese part we may try disconnecting it. If it still sparks without it we'll test it that way also.

Plug - A carbon black plug can sometimes spark whem laid on head but not whwn under compression from cylinder pressure so again we''ll use a new one.

thanks

[woodyatc]

Hi Barnett

Got the new and old carbs stripped down today, new carb is definatley a Ke hin (as carb is stamped up ke hin on main body and on jets etc)

SO NEW CARB
has model number stamped on body PB 88 B D 0B21
Needle is marked 89Q needle slide is marked 4UG
Main jet is a 72
smaller jet is a 38

OLD CARB
has model number PB 38 A G V I +
needle is marked J2302G, needle slide is marked 85C
Main jet is a 58
smaller jet is a 38

Im no expert (obviously) but to me its seems the new carb is jetted bigger and delivering to much fuel ?

so i cleaned and reinstalled the original carb and the bike starts easialy and runs ok (tickover is a bit lumpy)
rides realy good (good pick up / acceleration)
i installed a new plug, (which after an hour of running is a bit black and sooty)
so im guessing its still running a bit rich ? (it will run with the mixture screw turned all the way in, as well as turned out 1 to 2 full turns
The intake is leak free
So am i correct in thinking the original carb is worn badly, jets needle etc ?
Or could there be another reason its running rich ?

Regards

Gav.

[woodyatc]

Forgot to say the trike started fine on the new carb when it was 1st fitted, never ran the bike much when it was started after 1st fitting the new carb, but the next time i went to use the trike (around 3 days after fitting the new carb) thats when i started having the starting problems, sometimes would start easialy, sometimes was difficult to stsrt, other times would not start at all.

Gav.

[trike savior]

i would put the 58 jet in new carb and see what happens. black soot is good you want it running a bit rich. wet like it was before is what you do not want to see.

[woodyatc]

Thanks Trike saviour

The plug is a bit black and sooty (and it was a brand new plug fitted at the same time as i refitted the original carb) and the trike was only running for around an hour, its not getting overly wet when starting or running, i just assumed if it was fouling the plug by running rich it would cause problems ? im not sure if the 58 jet will fit in the new carb ?

Regards

Gav.

[barnett468]

Hello


Good jetting and performance info however you missed one number I mentioned which is the one on the long brass tube that holds the main jet but I may not need it now we'll see.


I don’t want to step on anyone’s toes so I can only offer you my suggestions based on my level of experience what ever that might be. Different suggestions are good to have so another one I have is to recommend you do what makes the most sense to you. Your bike starts and runs pretty good now right, ok. You have guessed most of your own problems with our help right, ok. Well my opinion is that you are very close to right again. Please reread my previous posts, I already told you how to read your plug color in one of those.

I don’t like to retype things but I will give you the short explanation again. BLACK soot is caused by EXCESS fuel. If your plug is DRY and sooty BLACK then your jetting is rich. If it is WET and sooty BLACK then it is rich AND you are burning OIL through the rings and you should see some lite blue/white smoke from the pipe HOWEVER if it is also RICH at the same time the excess fuel will cause the exhaust to look GRAY/BLACK and the GRAY/BLACK color will OBSCURE the the lite blue/gray oil smoke so you can’t see it. Your plug will NEVER be wet when you remove it from a RUNNING engine no matter how RICH it is. This is because the excess fuel will always BURN/EVAPORATE etc. It is combustible some of it isn’t going to just hanf around simply it was too lazy to burn.

It would most likely NOT start cold after you put the new carb on and ran it for a while because the continued soot build up started by the previous running condition finally built up to the point where it caused a weak spark. The reason it would start easier after it was hot is because your motor was hot enough to warm your fuel just enough that it would now ignite the gas a weak spark. Pretty cool again huh.

If you look at the plug in your new car it will be almost white and dry and so is the plug in a street bike, lawn mower and so on. A properly jetted engine of ANY kind will NEVER have a plug that looks SOOTY and BLACK. It’s simply impossible. You can verify this for yourself simply by going online and searching for “spark plug reading”. This is because they burn all the fuel and even though their plugs are white they are jetted fine. If they were too LEAN they would have a flat spot on acceleration. If we get your bike to be to lean I’ll fix it dont worry, but this probably won’t happen. We may need to burn off the excess built up carbon by riding it some more or clean it off by spraying carb cleaner in your motor when it is cold and while it is not running. Do not do this yet though. I want to keep your bike running and not take chances just yet, maybe later.

Even though your bike will probably run fine if you rejet your NEW carb I suggest you do NOT use it because I can’t find out EXACTLY what it is and It makes more sense to me to try and simply fix the one that is more original. Your old one did NOT wear out. Below is what I personally suggest you do.


Clean the new plug with a WIRE brush and carb cleaner.

Is the air clean and not soaked with air filter oil? If so clean it.

I still suggest doing my choke test I previously mentioned otherwise do the following but I can’t help you jet your carb perfectly this way but it will be close.

How much choke are you using to start when cold now, ¼ ½ etc?

How soon can you remove choke and have it idle?

What EXACTLY do you mean by LUMPY when starting, please explain the problem in DETAIL.

Did it ever do this before?

Since you do NOT have spare jets right now then do this instead. Lower the NEEDLE in the slide by RAISING the CLIP. Be EXTREMELY CAREFUL because it will want to FLY OFF and DISAPPEAR. Because of this tendency we call them JESUS clips because when they disappear we say “JESUS where did it go?” along with some other colorful phrases.

How does it start and run now, any flat spots?

Is the LUMPY thing gone?

DOES THE MIXTURE SCREW HAVE ANY EFFECT NOW, it should NOT yet because this regulates idle and just off idle.

How does the plug look, it should still look black etc?

When you can get a 56 and 54 main jet and a 35 pilot jet. Get a 60 main and 35 pilot for the new carb too if you want.

Clean the plug.

Install the 54, and any flat spot, lumpy gone etc?

Any flat spots on acceleration that you did not have before the jet change?

Does the mixture screw have any effect now?

How does the plug look now, it should look noticeably lighter.

We will probably install the pilot jet next and see how much choke it takes to start and see if the mixture screw has any effect now etc. but clean the plug and get a new one if it remains brown.

[trike savior]

you will have to excuse barnett he was an engineer for kawasaki and helped develop their race bikes. in those situations everything has to be perfect and that must be what hes used to. he is definately good and i would want him tuning my race bike but for what you are doing with a little atc 70 it is a little overkill. as long as it starts and runs consistently it should be good enough. if you start having problems with fouling plugs or it floods out again go ahead and start buying jets and getting it tuned.

sorry barnett i know you prolly spent alot of time writing that but it sounds like this is just a toy and they are not looking for a super performing race/trail bike.

[barnett468]

HELLO
Yes trike savior is right to at least some degree. I am anal. I did not want to mention the kawi engineer thing because I don’t want to sound like I know more than others. As you can see from my posts I value others opinions. However if you want a fire breathin 12 hp 70 cc bike I’m probably your guy, Just ride a klt 110 and you’ll see, that thing will do the ¼ mile in less than 1 minute flat, lol.

Look at it this way if I wasn’t thorough, we at the very least wouldn’t know your new carb is too rich which caused so much carbon build up in your motor it loaded the plug up and the carbon my still be in there.


Here’s a plug chart. The black oil fouled one has been in a motor a while a new oil fouled plug will just look wet.

http://forums.highperformancepontiac...ug-chart-pics/


TRIKESAVIOR

It still doesn't run right and still carbons up the plug shouldn't we try to fix that at least, sounds like he's willing to try it?

so i cleaned and reinstalled the original carb and the bike starts easialy and runs ok (tickover is a bit lumpy)
rides realy good (good pick up / acceleration)
i installed a new plug, (which after an hour of running is a bit black and sooty)
so im guessing its still running a bit rich ? (it will run with the mixture screw turned all the way in, as well as turned out 1 to 2 full turns

[woodyatc]

Hi Barnett

I looked for a number on the brass tube that holds the main jet on both carbs but could not find one ?

The plug is black sooty and dry (no evidence of oily deposits) it do'es smoke a little (white grey smoke)

The air cleaner is the proper one for the trike not an after market bolt on, i'll give it a clean to make sure its ok.

The trike starts up on next to no choke at all (sometimes on no choke) it started on no choke this morning after being stood in a cold garage for 18 hrs (with the gas tap turned off) and it stared quite easily and setteled down to idle in around 30 secs)

By lumpy i mean its idles fine for around a minute the tends to drop its idle and will stall, unless you give it a little rev then it idles fine again.

How far should i lower the needle ? (its currently set on the third notch from the top of the needle) should i try it a notch at a time ?

Once i try the needle lowering i'll get back to you with the info on running plug condition etc

Mant thanks

[woodyatc]

Hi again Trike savior, i am after getting the little trike running and starting concistently, its for my boy to learn to ride on (he's never ridden gears before) as soon as he's mastered this one he'll be moving onto something a bit bigger, id like it to run without causing problems in the future though, many thanks once again for the help imput and info it much appareciated !!!!!!!!!!!!!

[barnett468]

hello woodyatc

Very good info, it will certainly help anyone that checks in.

Where is your idle mixture screw set right now, in all the way, 1 turn out 2 turns out etc.

You forgot to tell me if it starts with 0 throttle and no choke or not so i'm going to have to guess for now and that doesn't really help you but i'll try.

The plug is finally DRY great sign, the smoke is a little oil but not enough to foul the plug.

My guess is that it is rich on the pilot, if it starts with no throttle and no choke this is a guarantee but your mixture screw must be turned out for this.

Lower the needle just like i said 2 not 1.

don't use choke to start since it starts without it or you will flood the motor again.

get the 35 pilot i mentioned and other jets.

drive it as is with the needle down.

check plug periodically

toss the new jets in when you get them and try it again, any flat spots, plug color etc.

I think we're pretty much there i hope.

[woodyatc]

Hi Barnett

The idle mixture is set at one full turn out from seated at present.

It starts with about a third throttle when starting from cold at present (but once warm it starts with just a pull of the pull starter)

I'll give it a try with the needle lowered and see how thats go'es ?

And try and source the new jets (but like i say parts here in the uk are pretty scarse)
in fact these little trike are very scarse.

Thanks once again for all your help / imput and PATIENCE

Best regards

Gav.

[trike savior]

alright i admit after reading more you may need some more tuning because it should not start without choke on a cold start. ill drag my 70 out of the back of the shed and yank the carb to see what jets are in it. ive been meaning to do it anyway so why not now. it was always pretty good running and reliable so it should be a good comparison.

you never answered one of my questions. did the carb have a brass or plastic float. because if it is plastic that can be the whole problem because they get weak and cause the float to allow more fuel into bowl causing a rich condition. if its brass we can start messing with float height and maybe solve your problem. i think this may be the way to go because we are now dealing with the stock carb which should have had it running right at some point.