150cc bogs after 1/2 throttle By backyardmech (Read 10,210 times)

[backyardmech]

OK, 130, so good compression. Valve lash is good. Will have to wait to pull the variator as I don't have impact and the nut was too stubbern for my old skool rope in the cylinder trick as I didn't have room for much leverage (worked good on stator side).

I did pull the carb to find the leak which was getting a little worse and found that the bowl gasket had been pinched upon assy. Gasket from my old bowl was to wore to use it. Will have to see if I can come up with just a bowl gasket without having to buy the whole kit.
I live out in the boonies and use ebay usually. Ideas?

I don't think it was leaking bad enough to starve for gas at top end, pretty small leak, but who knows? didn't seem to be a problem when up on the stands...

Did go ahead and pull and check the main while I had the bowl off just to be sure it was clear. It was.

I hope I find the weights are messed up to be honest because after that I have no ideas...but to me the weights still don't explain it running so good for the first hour or on the stands? Trying to wrap my head around it. I'll be near a harbor freight on tues. I think.

BTW, the plug looks beautiful, just that nice light brown speckle of a good burning spark.

[beachbum]

I wonder if that little gap would cause air to be pulled in the bowl as you accelerate under load? Alleyoop would know about this.

[Alleyoop]

When you tested the COMPRESSIOn did you hold the THROTTLE WIDE open when cranking.

Also you can verify if the 130 compression are your rings pour a teaspoon of oil down the plug whole and test the compression again if it goes up higher your about due for a ring job which is most likely the readings on the low side.
Alleyoop

[backyardmech]

"When you tested the COMPRESSIOn did you hold the THROTTLE WIDE open when cranking."

ooops! no I just turned it over...guess I better do it again...

will throttle wide open make it higher or lower?

"Also you can verify if the 130 compression are your rings pour a teaspoon of oil down the plug whole and test the compression again if it goes up higher your about due for a ring job which is most likely the readings on the low side."

I thought you said anything over 120 was good?

[Alleyoop]

Thorttle wide open you want as much air as possible and the compression should be higher.

Yes 120 is mininium so 130 the motor will still run pretty good but your power will be down some. But since you did not hold the throttle wide open I expect the PSI to go up.
Alleyoop

[backyardmech]

...so I ran back down to mini storage and checked compression while the carb is still off...not gonna suck anymore air than that!

180 (I think that rates AWESOME in Alleyoops... lol)

[Alleyoop]

YEP that is AWSEOME mine pulls 200PSI, you got a hotrod there bud, just have to find the problem child holding it up so you can tear up the asphalt.
Alleyoop

[Alleyoop]

Now the other thing I was thinking since it is a buggy, they may have it set up for Really Low Torque and changed the gearing on it with low gearing. You know if they were using it on the beach in the sand and or mud fields climbing hills etcc..

But check the Weights in the Variator they maybe shot.
Alleyoop

[backyardmech]

best I can tell they didn't do anything but buy it, ride it into the ground and when it wouldn't run anymore they threw it out behind the shed and let it go totally to hell....lol

yeah...I'll round up an impact wrench and confirm or eliminate that as the problem. I was watching the kidnme video on cvt's in the tech section and they mentioned flatspots in the weights would cause hesitation on the low end?

You know, another thing I've been thinking...since the carb, some of the hoses, etc, were all severely stopped up, the one thing that is not new in the fuel delivery is the vacuum petcock.
Can a vacuum petcock be partially bad on the vacuum side or is it all or nothing. Just thinking since it fires right up, accelerates nice to 1/2 throttle or so, then just stays the same speed/rpm the rest of the way to full throttle (other than at that point it feels a little stuttery) maybe I'm hitting a starvation point for fuel.

Also, considering that, would you agree or disagree that the slight leak at the bowl gasket is a non issue? Even tho there was a leak there, when I pulled the carb the bowl had a lot of gas in it...

[Alleyoop]

Well you can check the Fuel Delivery here is something I wrote up to save on typeing it over and over.

CHECK FUEL DELIVERY:

Take the Carb Fuel hose off the Carb put it in a container and crank the motor over.

A. IF FUEL STREAMS OUT, fuel to the carb is good, Filter is not clogged and Petcock is working

Re-connect the Fuel hose back onto the carb—GO TO CHECK CARB.

B. NO FUEL COMES OUT OR DRIBBLES OUT, take the Fuel Filter off and crank it again

a. If fuel STREAMS out the Fuel Filter is Clogged.

b. If fuel does not come out or DRIBBLES out –GO TO CHECK PETCOCK.



CHECK PETCOCK:

Take the Vacuum Line OFF going to the Petcock from near the carb and suck on the VACUUM LINE.

A. If fuel STREAMS out you have a VACUUM PROBLEM.

B. If fuel does not come out OR DRIBBLES out you either have a bad petcock or a clog from the tank to the petcock.

Disconnect the fuel line going to the Petcock from the tank.

a. If fuel STREAMS out the petcock is bad

b. If fuel does not STREAM out either the hose from the tank is clogged or the tank outlet is clogged.

CHECK CARB:

Here you are looking for any air leaks or carb leaks.
If the Carb Bowl Gasket is leaking take it off and dab a little bit of ATV gasket maker red or black does not matter. Also check the disphgram seal that is on the TOP of the carb usually BLACK or GOLD or Silver with two screws holding it. If that is leaking it will not raise the needle out and you will loose top end.

Also check the AIR INLET to the diapghram that is on the AIR FILTER SIDE of the carb. If the AIR INLET to the DIAPHGRAM is clogged it will not raise your needle for top end.
Alleyoop

[Alleyoop]

Find anything that is not working or maybe mañana.
Alleyoop

[backyardmech]

PROBLEM SOLVED

Anytime I post for help on a forum I like to make my last post a detailed acct. of what I found as I so much appreciate the time that members like Alleyoop, Beachbum, etc. are willing to devote to total strangers. I recommend anyone recieving help do this so that other members will benefit from the search function for solutions. Thanks guys!!!

So anyway, as you know, the only visual problem I had found so far was a leaking/defective bowl gasket on the carb. So this morning I replaced the gasket with the used one from my old carb, carefully using a light coating of black gasket maker as that is what I had laying around. (I do not normally recommend sealers on a carb as you have to be able to take it apart and back together easily plus sealers can stop up passages etc., but the old gasket was flattened out and prolly would not seal, I did not have another one and was ready to get this show on the road...lol)

I then reinstalled the carb, fired up the buggy and took it for a spin not bothering to put the airbox back on and it ran like a bat outta hell all the way through the throttle.

So I'm thinking how the heck can a minor leak from a bowl gasket have cause this?

So I go ahead and button up the stock airbox on it and take it for another spin.

Right back to where I started..no additional speed/rpms, whatever past about 1/2 throttle!

So I take the side cover and filter off the airbox and try again...no improvement...

Alright then. I remove the complete airbox and tube to carb. She runs like a bat outta helll again!!!

She just simply wasn't getting enough air at the top end even with nothing but the stock airbox opened up and the airbox tube.

So I got to looking in the tube and noticed that where the tube curves then curves back again, even though there were no foreign restrictions, just the way it curved and the fact that it was old and a bit soft and ovaled out seemed to cause a weird flow and restriction.

That being said, I will be rigging up a straight pipe with pod so as not to trash out my carb. In the meantime, think I'll just throw a piece of pantyhose over the throat so my kid can play today....lol

Some may think I just solved a jetting issue at the main from the opposite direction by increasing air flow...but I don't think so because...

1) I am running a new stock replacement carb, and altho I don't know what the jet sizes are they are stock for the original airbox.

2) I've pulled the plug after every test run throughout this ordeal and its the best I've ever seen a plug look, right on the money.

3) Has always, since I did other initial repairs, started right up and idled smooth, and been responsive up to that 1/2 or so throttle mark.

So it was just starving for air at higher rpm.

So just another simple thing ou can try if you have this problem!

Thanks so much, I learned alot about these gy6's here....totally different from the old skool chops I build. AWESOME forum! I will enjoy popping back in.

[Alleyoop]

FANTASTIC A MOONDOE!!!! And your correct a weak tubing will cause air flow turblence and since it is suction that is being applied the tubing can collapse and cause air restriction.
I have a 5 inch metal stack on mine with a K&N filter, I also have it bolted down so it does not bounce up and down or move and crack the INTAKE MANIFOLD. The Intake Manifold is the Orginial almost 4 years old now, I do have a couple of spares if I need a new one.
Alleyoop

[backyardmech]

yeah, I have extra pods laying around from my chopper builds, just need to gather up the rest. I like your stabalizer bracket. I can see where it would help alot on the intake manifold side as well...a big deal with this buggy since it bounces all over the place.

I live out in the boonies in the Ozarks, so threw the pantyhose on it and went for about a 1-2 mile run through fields and dirt roads, and this thing is a blast...makes ya feel like a kid again...

probably will play with the weights now that it runs right as I need a bit more torque for climbing the hills around here...

[Alleyoop]

Very cool riding around hills and stuff, to handle them you need more low end torque so lighter weights and or stronger Contra spring will require higher rpms to move the belt up and keep the belt in the lower part of the variator.
Alleyoop