85 250r problems

[threewheelin-feelin]

ok guys 85 atc250r fully rebuilt motor. new sleeve back to 66mm bore, wiseco piston,new honda seals and bearings, rebuild crankshaft and new full fmf fatty exhaust. got the bike back together and cannot for the life of me get it running right. no matter how i set the float height it would either run rich or lean and it keeps running fuel out of the over flow. so i replaced the float and needle valve and its still doing the same. i did a leak down test and found the intake boot leaking. i fixed that and it passed a leak down test 3 times. i still cant seem to get it right...and no matter how lean i set the float at the carb still over flows. this is the float jetsrus sent me..the float on the right is the one that came out...which one is correct? starting to think this carb is junk

[threewheelin-feelin]

on the leak down test i lost about half a psi after ten minutes...i read that this is completely acceptable... is that correct?

[yaegerb]

on the leak down test i lost about half a psi after ten minutes...i read that this is completely acceptable... is that correct?

Where is it leaking from?

[threewheelin-feelin]

Where is it leaking from?
was leaking at the intake boot and dropping as soon as i pumped it up. after i fixed that it dropped from 6 psi to about 5 and a half psi after ten minutes...i think my home made leak down tested may not have been 100 percent air tight

[yaegerb]

If you are able I would retest, find the leak and ensure that it is your pressure tester and not something else. Is the carb original?

[christph]

Sounds like it's a carb problem and not an air leak problem. If you have your float height right, I would check the float valve--it doesn't sound like it is sealing. You might try hooking it up to the tank without the float bowl on, hold it over a bowl to catch gas, and lift the float to see at what point--or if--it shuts off the float valve.

[threewheelin-feelin]

Sounds like it's a carb problem and not an air leak problem. If you have your float height right, I would check the float valve--it doesn't sound like it is sealing. You might try hooking it up to the tank without the float bowl on, hold it over a bowl to catch gas, and lift the float to see at what point--or if--it shuts off the float valve.

float valve is new...i will check it with no bowl and see what it does

[yaegerb]

I am not suggesting it’s an air leak problem. He has two issues, 1 he’s losing half pound of pressure over 10 minutes. You should be able to let that sit all day and not loose any pressure. 2, you have a carb problem. I asked if it was original to the atc....stock carb? If so, maybe it’s time for a new carb.

[3Z with Fangs!]

Just for poops did you try putting the original float and needle back in it or is it too damaged to be used?

[ironchop]

...i think my home made leak down tested may not have been 100 percent air tight
Nevermind

It was already covered by someone else



Sent from my Z958 using Tapatalk

[Outlaw #24]

Put the Floats in water submerge them under and see if they leak air by bubbling under water.

[threewheelin-feelin]

I am not suggesting it’s an air leak problem. He has two issues, 1 he’s losing half pound of pressure over 10 minutes. You should be able to let that sit all day and not loose any pressure. 2, you have a carb problem. I asked if it was original to the atc....stock carb? If so, maybe it’s time for a new carb.

i believe it is the original carb. they sent me a float that looks different then what came out of it. but someone was doing some shady stuff to this carb so i dont know which one is correct. heres a pic of what the carb looked like when i first took it apart. also i have read in several places and seen in several videos that a very small pressure drop is acceptable on a leak down test

[threewheelin-feelin]

ok so i checked the carb with out the bowl tonight.. with the float valve closed it still leaked gas. i tried my new float valve and my old one and it did the same thing. can the brass piece in the carb body be replaced or do i need to just get a new carb? new carb is probably the best bet anyway after the idiot that worked on this carb before me

[yaegerb]

why is a straw in where your main jet screws in? You took it apart and that’s what was in there? I don’t know how it’s running at all. 6psi for 6min is the rule of thumb because quite honestly we have better things to do than to sit for an hour and watch a pressure gauge. In relatity it should hold at the same pressure for as long as you have it pressurized. This excerpt is from Harry Klemm.

The Theory of Air-leaks

Unlike all 4 cycle engines, the two cycle engines in all two-stroke engines must have a completely air tight lower end.

The normal vacuum in the 2 cycle engine's lower end will draw a mixture of fuel and air from the carburetor though the intake manifold. Once this fuel air mixture has been sealed off by the reed valve or a piston skirt, the resulting crankcase pressure moves the mixture through the transfer ports upward into the cylinder. A small "air leak" at a crank seal or an intake gasket will cause the usually perfect fuel/air mixture in the crankcase to become slightly lean...sometimes very lean. This lean mixture can quickly result in a seized piston. Air leaks are, by far, the number one cause of vintage engine piston seizures.

The Pressure Test

The step by step is :

A) Seal off the intake manifold with a plug or rubber gasket

B) Seal off the exhaust port with an automotive expanding rubber “freeze plug”.

C) Attach an air fitting that lets you pressurize the motor (usually thru the inlet plug or the spark plug hole

D) Pressurize the motor to 6-9 psi via a hose that has an in-line gauge.

E) Watch your in-line gauge for 5-10 minutes to confirm you have “absolutely no loss” of air pressure. A loss of even 2-3 psi is not acceptable.

F) If your gauge shows a leak, spray the gasket seams and seals on the pressurized motor with WD-40. The WD40 will make visible bubbles, and a leaking sound, when you spray the leak point.

[threewheelin-feelin]

i have no clue why the straw was there haha. but it ran. the motor had a crack in the crankcase that i had repaired by a machinist. the only thing i can figure is they tried to make the carb as rich as they could to get it to run with a massive air leak. the carb has all new parts in it now... is still leaking fuel with the new float valve closed...like i said im trying to fix all the BS that someone did to this poor 250r

[yaegerb]

i have no clue why the straw was there haha. but it ran. the motor had a crack in the crankcase that i had repaired by a machinist. the only thing i can figure is they tried to make the carb as rich as they could to get it to run with a massive air leak. the carb has all new parts in it now... is still leaking fuel with the new float valve closed...like i said im trying to fix all the BS that someone did to this poor 250r

Slap a 38 on it. I will even clean it before shipping

http://www.3wheelerworld.com/showthread.php/187240-Aftermarket-First-and-Second-Gen-ATC-250R-Parts-for-Sale

[fieldy]

Can you stop the gas or any liquid from flowing out with just using your finger against the float valve, leaving the floats off the carb? Seems like not enough pressure against the valve to stop flow. Just curious.

[threewheelin-feelin]

Can you stop the gas or any liquid from flowing out with just using your finger against the float valve, leaving the floats off the carb? Seems like not enough pressure against the valve to stop flow. Just curious.

i just tried it with my finger on the float valve it stopped but i had to put more pressure than i should on it

[threewheelin-feelin]

Slap a 38 on it. I will even clean it before shipping

http://www.3wheelerworld.com/showthread.php/187240-Aftermarket-First-and-Second-Gen-ATC-250R-Parts-for-Sale

i really want to keep this bike stock. the only thing i wanted to put on it was the fmf exhaust and that was only because i hate the sound of a stock exhaust. and a 38mm on a stock 250r would open up a can of worms for jetting wouldnt it? im looking at a couple nice 85 oem carbs on ebay right now...i guess i could try my 38mm airstriker on it from my 310r

[fieldy]

Take a look at the seating tip on your new float valve. You may see some kind of impression on that sealing surface like a burr is keeping it from sealing. Maybe the new float valve is a few years past prime? Some how soften that up? Just to see if its the issue? Laquer thinner or heat? Maybe heat in linseed oil? I know not really the perfect plan.
My thought is buying a new carburetor, i would listen to the Honda guys. A 38mm should jet down to a stock motor fine. Now for me fitment would have to be easy for the change up.
If buying more jets is all, trying your 38mm seems cool. You would already have it jetted when the new carb arrives.
Plus if you plan on keeping both r's i would definitely have both of them on 38mm's for interchangeability, if thats a word.

[yaegerb]

i really want to keep this bike stock. the only thing i wanted to put on it was the fmf exhaust and that was only because i hate the sound of a stock exhaust. and a 38mm on a stock 250r would open up a can of worms for jetting wouldnt it? im looking at a couple nice 85 oem carbs on ebay right now...i guess i could try my 38mm airstriker on it from my 310r

Actually a 38 will work on stock or built engines. They are a great all around carb on the 3rd gen r’s