Engine Trouble

[donman77]

I have a Honda 13hp motor that suputters when it runs on idle ( it’s not the idle screw that’s the problem) when I rev it up without a load sounds fine. But if it gets a load it will throttle up once I give it full gas for 2sec and then throttle down and repeat. So anyone who can help? It’s not the spark plug or the fly wheel& magnet. (Just polished it)

 

[Denny]

Take the carb off and take it apart and clean it! Make sure every orfice and passage is as clean as a whistle. Make sure there is no junk in the gas tank either.


Denny

 

[itsid]

Please post pics of what kind of load we are talking about.
How bad is your gear ratio? (cent clutch, 3:1 and 22" wheels or such?)

I have a funny feeling it's not about fuel or carb at all, but all about fixing a crappy setup
to give the engine a fighting chance to move

'sid

 

[donman77]

My setup is fine, it’s on a kart and should work very well. That’s not the problem. It’s possible that it would be the carb. Because there is another guy with the same setup and his works fine.

 

[itsid]

...and posts like this make me think I'm on the right track

Don't get me wrong, but we've seen some idiotic setups in the past, and most have been justified with exactly such "that other guy.." comments.
And in all known cases that was a Chicago Bulls shirt ... [as in red flag!]
As long as you're unwilling to tell us I suspect there's a reason for that

Anywho, I step back and watch.

good luck!

'sid

 

[JTSpeedDemon]

Take the carb off and take it apart and clean it! Make sure every orfice and passage is as clean as a whistle. Make sure there is no junk in the gas tank either.


Denny

Junk in the carb makes for about 70% of go kart problems.
When I got my kart, it wouldn't really start, and fuel would leak out of the carb.
Then I found out what the problems were.
Dented carb float, and a missing carburetor body gasket.
Try to get a carburetor rebuild kit, and replace all the parts you can, cleaning it in the process.

---------- Post added at 11:10 AM ---------- Previous post was at 11:09 AM ----------

Another thought:
I think it may be running a little rich, thus bogging the engine down at certain throttle levels.

 

[65ShelbyClone]

Please post pics of what kind of load we are talking about.

Or a short video of the problem.

You've said "it's fine" and "that's not the problem" a lot. If you don't know what is causing the problem, how do you know what isn't? All we know is that you have a big Honda with a running issue that isn't clearly described. What have you done up to this point?

 

[donman77]

I put in a new spark plug so it really isn’t the problem. Tried a different carb from another Honda but it didn’t make a difference. The engine runs tough and rough it needs to be choked to start and it could very well be a gasket or dirty carb. Btw itsid I am not on idiot on how to have my machine setup. I have done many trials. Clutch on motor down to a 45t sprocket on a jackshaft amd on the other end a 13t down to a 69t on the axle 22in tires.

 

[J.S.@SMS]

A couple questions. Where did you find those sprockets? I don’t recall any 45t jackshaft sprockets, or 69t axle sprockets. And at 23.88:1 reduction (I’m assuming a 10t clutch) do you even move? Also, I don’t think that both carbs are that dirty. Have you examined the intake gaskets? And, please, post some pics. They make it so much easier to help.

 

[itsid]

gx270 (the smallest 13hp Honda) is a 1" shaft
gx390 (the current 13hp Honda) is also a 1" shaft
So no 10T clutch... rather a 14 or 16T which brings that to a 15:1 ratio roughly
(and that should move upwards of 600lbs just fine)

Now.. engine runs rough even with a different carb..
You said you swapped the spark plug..
what did the plug look like (plug color reading)
dark, light, tan.. what color, greasy/oily dry and pitted?
that gives you a very good idea about the fuel/air ratio
and with that tell you about carb issues.

But there are plenty other things causing issues
Have you removed the governor?
If so, have you checked that the cam is still lined up properly?
A one tooth offset can cause such rough running engine.

Have you done anything else to the engine?
(intake, exhaust, valves etc?)
By accident set the valve lash at some other point than TDC for example.
Or did the cam fell out popping the crankcase open and the lefters dropped out
(swapped lifters and therefor incorrect valve lash)
have you swapped the spark plug wire/boot maybe it's leaking?

A 'sound sample' would be indeed very nice that'd make things more obvious
a bit of idle (to have a base line)
and some slow rev up to detect the flaw/hiccup

A video some pics also might help a long way narrowing in on the problem.

'sid

 

[Nosandwich]

Isn't it fun when people want a lot while supplying very little?

He's so smart, he must be rich.

 

[donman77]

here a couple pics. I'm rather slow at replying i might add

 

[mckutzy]

When you reinstalled the carb did you put back the gaskets and insulator plate in the correct sequence.... The insulator plate gasket has a corresponding pathway for one of the idle air holes to the motor side of the carb...

Equally speaking... How is the braking?...... It looks like you have the caliper hard mounted and the disc the same....
Setup up this way, wont allow it to fully optimize the braking capabilities of the caliper as it cant float....
A remedy for this in your current state... Float the rotor.... As in undo the setscrew for the disc. Make sure the disc can move laterally along the shaft freely. Take 2 pipe clamps(like what you have done for the one sprocket) and clamp them on the sides of the brake disc, with just about 1/8" spaced out from the sides.... this will keep the key inplace from letting go and have it float...

 

[donman77]

I took the motor to a professional mechanic and he saw the engine was running rich and he needs to fix the carb float. It was leaking when it was level. Btw the brakes are crap.

 

[landuse]

I took the motor to a professional mechanic and he saw the engine was running rich and he needs to fix the carb float. It was leaking when it was level. Btw the brakes are crap.

I am glad you got it sorted out.

A plug check would have told us if it was running rich or lean. I think Itsid asked about what the original one looked like. You said that you had tried another carb. Was that ones float also messed up?

 

[JTSpeedDemon]

Teehee, I was actually the first one that suggested that it was running rich...
Anywhoo, glad you got it sorted out!
I think the reason why MY kart wouldn't start at first was because the carb float had a big fat DENT in it, so it was leaking and I think running way rich since the gas was leaking into the other parts of the carb, in effect fouling the spark plug/flooding the cylinder.

 

[donman77]

Well idk about the older carb but I know that the motor will run after the guy is finished with it because I know how good he is with mechanics.

 

[donman77]

So the mechanic installed a needle and a float in the motor and it ran good. But upon using the motor it would die on me. I would later find out that if I took off the fuel lid off it would suck a bit air. Then i ran for a certain time and stopped. Then open the fuel tank and drive again but I found out that the carb still leaks could I see a pool of gas on my shop floor today? So I am wondering what I should do to fix it?

 

[JTSpeedDemon]

As far as the carb goes, it's most likely a bad bowl gasket.
And for the gas tank, that's a very simple one. Your gas tank does not have a vent, so it creates a vacuum, starving the carburetor of fuel until you remove the cap. Get a vented gas cap and/or make your own.

 

[itsid]

I doubt it's the gasket tbh (or say it's certainly NOT JUST the gasket)

first I'd check the needle valve and seat to be perfect, and if they are,
I'd check the actual floats to be in good shape.
if they are as well, you need to adjust their position
(some use screws some can be bent to properly close the valve)

Afterwards you must clear your tank ventilation.
if your tank doesn't have one you need to find yourself a ventilated cap
(maybe it was replaced by a non venitlated cap)

The bowl on a good working carb is NEVER filled to the brim, so it's gasket prevents splashing, not leaking in the garage..
if it's leaking standing around, it'll be the needle valve and/or floats
causing the issue (those cut of the fuel supply as soon as the bowl is filled)

'sid

PS hm.. so now WE also know how good your guy is with engines