Could problems with carbs cause significant smoke?

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audiocontr
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Could problems with carbs cause significant smoke?

Post by audiocontr » Sat Jul 04, 2009 11:20 pm

This smoking engine is bugging me. Its not like a smoke screen, but a good puff of dark smoke when i start it which eventually turns to a constant lighter gray smoke. I can really see it at night when the lights of the car behind me illuminate what my (and my passengers) nose already knows is there.

I have not found significant oil loss which i would expect with ths much smoke nor is it as blue as I would expect.

I've noticed my car idles rough and pulling on the choke either produces more smoke at its furthest extent, levels to nothing at a mid point (and idles much smoother, albeit a higher rpm) and finally starts smoking again when pressed all the way down. I usually drive with it just ever so slightly pulled up from its furthest down point.

I've also noticed a strong gas odor... who hasnt in their pins?... and the lower half of the front carb is wet with fuel.



I KNOW i have to get a compression check (have the gauge, just not the 14mm adapter yet) and check for valve seals. I'm really hoping that someone will say that leaky untuned carbs can cause above average smoking and stink-ness (technical term).

So, what do you say my friendly gurus?

Twin Pinzies
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Post by Twin Pinzies » Sun Jul 05, 2009 12:37 am

Mine (all three) smoke and smell like gas. I've also had the carbs rebuilt and it doesn't seem to help much. Pulling out your choke lever should kill a warm, well tuned engine. Try adjusting your choke cable on the carbs at a warm idle. It might be as simple as that, or not.

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Post by jacksonpinz » Sun Jul 05, 2009 12:41 pm

Mine were pretty bad before the rebuild. I also re-jetted. Not much smoke at all now. Runs 65 down the highway no problem.
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Post by M Wehrman » Sun Jul 05, 2009 1:47 pm

O/H of the carbs will help with the driveability,but I think you will be going deeper than valve seals for the smoke.....
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audiocontr
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Post by audiocontr » Sun Jul 05, 2009 3:29 pm

Ran a compression check today and adjusted the valves.

148. 142. 125 and 132 BEFORE adjusting the valves. Some variance there. I also checked and it does not have valve seals.

I'm going to have to re adjust the valves. After doing what i thought was correct, the engine is much louder now. half of the valves needed to be loosened with none in the other direction. I may need to re-do them.

With remorse, its probably cyl number 3 causing the smoke

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Post by Middlebury_Pinz » Sun Jul 05, 2009 6:24 pm

Were the cylinders with the tight valves also the ones with low compression? Tight valves won't allow the valves to seat properly and can cause the low compression. If this problem was allowed to persist for a while, carbon can build up on the seat and it may take a while for them to reseat properly.

Drive it a while and check the compression again. Also, you can do a cylinder leakage test which will tell you more specifically where the loss in compression, if any, is going. Unless you think you got the timing order screwed up and adjusted the valves incorrectly, IE: NOT at TDC when adjusted, just drive it a bit and then adjust and retest.

A wise old sage once told me it's usually the simple obvious stuff that bites you in the back side. Always check the basics first!!! Most people assume the worst and make things way to complicated. Patience grasshopper!!

Good luck

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audiocontr
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Post by audiocontr » Sun Jul 05, 2009 7:05 pm

#1 and #4 TDC are easy, line up the pointer on timing to the red line on the main pulley. Is there an easy way to set it for #2 and #3?

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Post by pinzinator » Sun Jul 05, 2009 8:37 pm

You can go by the firing order in the ditributor. For example the rotor is pointing to #3, that piston will be near TDC of the compression stroke. Slowly rotate the crank pulley and watch the rockers on #2 (that piston is also at TDC of the exhaust stroke). Find a point where the intake rocker starts to move on #2, then rotate the crank in the OPPOSITE direction until the exhaust rocker starts to move. The rotate BACK to a point halfway to where the intake starts to open. At that halfway point you set the valves on #3, because both pushrods are against the low point of the cam.
To set the valves on #2 do the same proceedure while watching #3
To set the valves on #1 do the same proceedure while watching #4
To set the valves on #4 do the same proceedure while watching #1
An old German mechanic taught me this method, it is the only way you can be sure the valves are fully closed on the cylinder you want to adjust.
#1 and #4 are at TDC at the same time, #2 and #3 are at TDC at the same time. One will be on compression, the other will be on exhaust. You have 4 firings for evey 720 degrees of crankshaft rotation, hence the formula.

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Post by milesdzyn » Sun Jul 05, 2009 8:39 pm

Here are some different ways.

1. Make a mark 180 deg. from the timing mark for #2 & #3
2. Assuming the plugs are out. Put your thumb over the spark plug hole and turn the motor by hand (in the propper rotation) till you stop feeling pressure against your thumb.
3. Buy or make a spark plug top dead center guage.

Here's a link to make a TDC tool in concept, may have to change dimensions for the Pinz. I may even make one of these myself.
http://www.scooterhelp.com/tips/timing/ ... ml#tdctool

Miles
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audiocontr
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Post by audiocontr » Sun Jul 05, 2009 10:09 pm

Just to make sure, I find TDC for #1. Adjust both the intake and exhaust valves with a .203 mm feeler gauge on BOTH 1 and 4.

Locate TDC for #2. Adjust both the intake and exhaust valves with a .203 mm feeler gauge on BOTH 2 and 3?


Basically its locating TDC twice in the whole process, correct?

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Post by milesdzyn » Sun Jul 05, 2009 10:32 pm

No you only do one at a time, in the order of fire at the distributor. Rotating clockwise at the distributor starting from the #1 mark.

#1-#2-#4-#3

Start with the rotor pointing to the mark at the #1 cylinder mark on the distributor and check that the pully TDC mark is lined up. Adjust the valves for the #1 cylinder.

Next turn the engine so the pully turns 180 deg. ( 1/2 turn opposite the TDC mark ) your rotor should be pointed to the #2 position at the distributor. Adjust the valves for the #2 cylinder.

Next turn the engine so the pully turns another 180 deg. back to the TDC mark, your rotor should be pointed to the #4 position at the distributor. Adjust the valves for the #4 cylinder.

Last turn the engine so the pully turns another 180 deg. ( 1/2 turn opposite the TDC mark ) your rotor should be pointed to the #3 position at the distributor. Adjust the valves for the #3 cylinder.

Your done.

Miles
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audiocontr
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Post by audiocontr » Mon Jul 06, 2009 8:22 am

and thats where i messed up. Thank you for clarifying! Time to re-do once i get the civilian ignition upgrade installed.

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audiocontr
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Post by audiocontr » Fri Jul 24, 2009 8:12 pm

Well found a bad needle valve in the front carb. Just replaced it and what do you know, SUBSTANTIAL decrease in smoke and smell. Its still running a bit rich and i see black smoke on revs, but its much better while at idle.

Now its time to figure out how to sync the carbs without a tool.

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Post by Jimm391730 » Sat Jul 25, 2009 1:17 pm

Now its time to figure out how to sync the carbs without a tool.
Syncing of the carbs is really only an idle issue; you want all four cylinders firing evenly for a smooth idle. At WOT a slight difference is not noticeable (one might be at 100%, the other at 98%, big deal).

Before I had the tool I would cup my hand over each carb top and create a 1/2" to 3/4" opening between my thumb and index finger; you can get an idea of how much air is running through each carb this way just by feel. Which ever carb seems to have weaker flow needs to be opened up more; if the idle gets too high, back off on both carbs evenly.

On my old twin cylinder motorcycle I would check for balance by using the "spit popping test" by swiping a licked finger over the exhaust manifolds; which ever was cooler was not working as hard, so that carb needed opening more.

Jim M.

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Post by pinzinator » Sat Jul 25, 2009 9:08 pm

Here's some simple common sense advice, something I should have done myself, and that is to have a set of new valve cover gaskets on hand BEFORE you set the valves. This way, when you mess up a gasket like I did today, you don't turn the Pinzgauer into a Corvair, the legendary air-cooled road oiler. My Pinz is now parked until new gaskets arrive, but it really sucks to have to park any vehicle due to the lack of a $3 part. Sure, I could improvise, but planning ahead is the lesson learned. Duh.

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