gy6 white smoke from exhust

[Bigrustysr]

my twister z150r smokes very heavy when first started-decreases as engine warms-never stops completely-valve guides or rings?-runs ok with plenty of power

[Miamieddie]

Check ur compression, if its ok then check ur clutch.

[351mustanger]

A leak down test will tell you if your rings or valves are not sealing good.

[Bigrustysr]

Miamieddie--what would clutch have to do with exhaust smoke at idle?

[Miamieddie]

If its coming out of exhause disregard if white smoke is coming out of the rear somewhere other than ezhause its probably ur clutch burning inside ur cvt.

[Bigrustysr]

351mustanger--how to do leak down test? PS: love the 351 bet it screams in a mustang

[351mustanger]

You can youtube it. They make an actual leakdown test kit that measures the percentage of the leak(nice but not necessary). I use the hose from my compression tester. One end threads into the spark plug hole and the other end has a male air hose fitting. Put the piston at top dead center of the compression stroke (both valves closed) and pressurize the cylinder. You may have to hold the rotor to keep the crank from spinning as the air pressure will try to push the piston down. While the cylinder is pressurized, listen for air leaking from various areas of the engine; exhaust, valve cover breather, intake manifold or carb, bubbles in the radiator if it has one, etc.

The 351 is in a 5 speed fox body mustang, and it does scream. Fun car to drive.

[Bigrustysr]

thanks -will give it a try:

[Bigrustysr]

ran leak down test- didnt hear any leaks-did leak down very slowly-(8 mins) compression is 125 (think my gauge reads a little high 10 maybe)
squirted oil in cylinder - no change, dont know where to go from here

[Miamieddie]

If ur guage reads 10high ur probably at 115 compression.. that's low may want to put new rings. Replace all gaskets and torque head bolts to specs.

[Miamieddie]

While in there check ur sleeve and ur piston.

[Bigrustysr]

we have a oval track out back for the kids- straight aways about 100yrds long one side is slighly up hill (about 10 degrees) when on up hill side smokes bad -no smoke on level side with same throttle pressure whats up with that?

[bear]

Just a silly question, but are yur fluid levels correct?!

[Bigrustysr]

yes but it seems when oil level goes down (half way below full mark)it smokes less

[Masteryota]

If I read this correctly, you have smoke on cold engine start, and it decreases as the engine warms up, that is a sign of worn valve stem seals. The reason the smoke tapers off when the oil level drops is that there isn't enough oil to seep past the seals. Most times it it the intake seal, but replace both. If you are seeing good compression, and no change when oil is squirted into the cylinder, then the rings are ok. You may get a somewhat low reading if it has been run like this for some time, as oil carbon is stickier than fuel carbon, and is harder to remove or burn off the valves and piston. Start with a seal set, run some throttle body cleaner through the intake, and retest once everything clears out. Be careful though, replacing the seals require taking the retainers and springs off, and if not properly supported, the valves will drop into the cylinder, requiring head removal. I hate to outsource, but youtube should have something along those lines to help you out.

[Bigrustysr]

thanks -that was my thinking that it was valvue guides-once had a 390ci ford that did the same and guides fixed it-can the seals be replaced with engine on the cart? (hard to keep grandson off it long enough lol}you think valvues need to be replaced also? lost my 10mm compression adapter- duh- got one coming to recheck compression-last time i check it was 125 may need ring also still has a lot torge thu -if you think valvues need to be replaced might as well do rings at the same time

[Masteryota]

Originally Posted by Bigrustysr

thanks -that was my thinking that it was valvue guides-once had a 390ci ford that did the same and guides fixed it-can the seals be replaced with engine on the cart? (hard to keep grandson off it long enough lol}you think valvues need to be replaced also? lost my 10mm compression adapter- duh- got one coming to recheck compression-last time i check it was 125 may need ring also still has a lot torge thu -if you think valvues need to be replaced might as well do rings at the same time

If you have an air compressor, and the correct compression fitting, you can fill the cylinder with air to hold the valves up. You will need an overhead valve spring tool and needle nose or valve stem seal pliers to get the old seal out. It may be easier to do if you pulled the whole swingarm out and stood the engine up vertically, but I'm sure it is possible with it still installed. It would be easier if the head was off, but I doubt the guides need replaced. It really is up to you how far you want to go into the engine, put a fresh piston and gaskets are never a bad idea, plus cleaning all that old burnt oil out.

[351mustanger]

Were you using a thread in compression gauge or one that you press in? The press in gauge can lose some of the reading. That number is low. I find it hard to believe a leak down test revealed no leaks with your engine putting out 125psi of compression.

[Bigrustysr]

was using press in tester, lost my 10mm adapter could'nt find one locally- ordered one- should be here today-going to do all over again using my screw in gauge hopefully will have more accurate info-going to try to use a quick connect T with regular pressure gauge in one side to watch pressure on leak down test (cant depend on my old ears lol) and dont trust my press in gauge PS my oil level is about 1/8 inch below full mark and doesnt smoke near as bad-going to order valvue seals today cant hurt anything and will eliminate 1 possibility

[351mustanger]

The leak down test is done with an air compressor. You run constant air pressure to the cylinder and listen for air leaks. It cannot be done with just a compression tester. Also, I am guessing that when you did the compression test, you were not holding the throttle wide open. Both of those tests (if done correctly) can give valuable information and keep you from buying unnecessary parts.

[Bigrustysr]

being new to buggys every tip helps -thanks-was planning on compressor hooked to T and a guage and watch to see how fast it loses pressure (turning compressor off)then listen for leaks with compressor on -my compressor is so noisey hard to hear-going to move compressor 100 feet away(length of my hose)maybe that will help- got to wait on new 10mm adapter to get here (lost my old one proably still in a engine some where-duh -)

[351mustanger]

You will need a regulator. It would be best to start with a low pressure and turn it up after it is connected. Like I said before, you will need to stop the crank from spinning (the air pressure will try to push the piston down) and the piston needs to be at tdc with both valves closed.

[Johnny 5]

My red dune 150 smokes on start up.The valve seals are bad but it runs good and I don't want to mess with it till the spring. Some smoke is okay but if you are pumping smoke it will probably get worse.

[Johnny 5]

125 psi is what both my Baja dune 150s had until I put srp 155cc pop top piston kits in to get 140 psi.

[toomanytoys2]

When you get the fitting for your compression checker, you should also do the oil test. Warm up the engine and then take a compression reading. Next squirt some oil in the spark plug hole and redo the compression check. If the pressure goes up, you have a ring issue, but if it doesn't, you have a valve issue. Remember, that the throttle should be wide open when doing a compression check. In my short time dealing with these engines, I have found that the rings (especially the oil ring), are pretty minimal at sealing. Also, how fast are you losing oil? If the oil ring is not sealing well, you will tend to lose your oil faster then if it is the valve seals.

[Bigrustysr]

think its fixed--adjusted valvues-put new valvue seals in=starts great and NO SMOKE compression did go up 5psi with oil test not going to worry about it right now has plenty of power with me on it Great gran son (5yrs old) loves it -thinks he's Dale Earnhart-- thanks to every one for your help

[Masteryota]

Great! Glad to hear it wasn't the rings. Bear in mind you might have a top end rebuild coming soon with that pressure difference. Don't worry, they are easy and cheap, as long as you don't need a cylinder.