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Author Topic: White smoke, pump timing  (Read 922 times)

Powdermonkey

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White smoke, pump timing
« on: November 21, 2023, 01:02:10 PM »
Folks- I've been plagued by disproportionate white smoke coming out the exhaust of #2 cylinder of my 16hp twin.  Oily residue drips/sputters from that muffler.  No matter how I adjusted the proportioning rods to change the relative pump fuel delivery, it had NO benefit.  I thought it might have been a difference in compression between the two cylinders; rigged up a compression gauge and ran each cylinder under-power...and NO significant difference.  Thought it might have been poor valve fit.  Lapped all the valves at the 1,000 hour rebuild.  NO benefit.  Thought it might have been rings or the condition of the cylinder walls (not seating the rings).  Nope.  By re-lapping the cylinders, NO benefit.  New rings.  NO benefit. 

Then one day, I was searching the internet for other possible causes.  Pump timing.  NOW....I'd made a custom built camshaft, using the existing pined on cams.  I'd advanced both pump-timing cams by 3-degrees, getting me into the efficiency of ~ 26 degrees of pump advance BTDC.  And, the efficiency of the engine DID improve, as per the university study.  But....the white smoke....

Now, everybody knows about adjusting the length of the cam follower, so as to optimize the pump timing. Me, I'm of the opinion that THIS method ONLY STARTS or RETARDS the pump timing, but does NOT change the PEAK timing...at all.  THUS, I build a new cam. 

So, in furtherance of pump timing:  As an experiment, I placed some standard automotive body shims under the mating surface of the pump and cam cover.  1/32 of an inch.  Thus, RETARDING the START of the pump timing, but NOT affecting the location of PEAK timing.  And...sure enough.  The white smoke went away.  The oily drippage stopped.  AND, referencing the oil pressure gauge, it's no longer bouncing around all over the place.  Matter of fact, once the engine warms up, the needle barely moves off the 3-5 PSI indicator. 

This engine's got almost 2,000 hour on it.  Dare I say, I may be one of the few who use these engines as true day-in-day-out prime movers. 

BTW- for those following my exploits.....the toilet-paper oil filter works just fine. 

cobbadog

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Re: White smoke, pump timing
« Reply #1 on: November 22, 2023, 10:01:39 AM »
Glad you solved the issue but I am puzzled why only one cylinder not both were bloke white smoke. Yes I am still sceptical of dunny roll filters.
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keith71

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Re: White smoke, pump timing
« Reply #2 on: November 22, 2023, 05:47:10 PM »
So what you are saying is you only shimmed cyl #2 pump ?  That may explain why smoking in only one cylinder, if the shimming of the #2 fixed it.  Nice fix..

Could you share any details on how you modified the factory camshaft? Did you drill new holes to move the lobes?  Thanks.
« Last Edit: November 22, 2023, 06:17:53 PM by keith71 »
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keith71

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Re: White smoke, pump timing
« Reply #3 on: November 22, 2023, 06:13:15 PM »
"BTW- for those following my exploits.....the toilet-paper oil filter works just fine". 

I have read alot of positive things about the toilet paper filter.. Do not think I have found anyone who has used one say they have had a bad exeperience or experienced any engine wear or damage using one.  Do you have any pics of the install of the filter?  I have a 12/2 clone I may want to try one on.
You can pm the pics if you took any and willing to send..
« Last Edit: November 22, 2023, 06:19:21 PM by keith71 »
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Powdermonkey

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Re: White smoke, pump timing
« Reply #4 on: November 25, 2023, 02:46:06 AM »

Keith- Yes.  I got a length of the proper alloy (can't remember it at the moment, but it's purposed alloy for cam-shafts).  I DID drill the cam pin holes 3-degrees advanced from the standard factory setting for the PUMPS.  All else remained as-per factory location.  Thus, I was able to get 26 degrees of pump timing advance, WITHOUT bottoming out my pumps (too long a cam-follower will over-drive the pump...ask me how I know....)

I can take a video of the filter and associated plumbing and post a YouTube link.   Give me a day or so...





"BTW- for those following my exploits.....the toilet-paper oil filter works just fine". 

I have read alot of positive things about the toilet paper filter.. Do not think I have found anyone who has used one say they have had a bad exeperience or experienced any engine wear or damage using one.  Do you have any pics of the install of the filter?  I have a 12/2 clone I may want to try one on.
You can pm the pics if you took any and willing to send..