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318 B43G surge repair / carb cleaning & whatever else you guys might suggest!

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32K views 7 replies 3 participants last post by  Chuckv  
G
#1 ·
Hi folks.. Sorry I'm doubling up on a thread I already started.. Now that I'm dealing with the carb vs spark plug wires, I wanted to start again with a new title to make sure that folks who might have some input would notice and possibly contribute.. I was moments away from loading up and heading to the dealer to have it corrected. However Chuck pointed me in the right direction to take another run at curing a surging issue that appears to be quite common with these machines. So I figured, what the heck. May as well try.. Anyway, here's the symptoms.. Under load or not, the engine surges up and down.. I can somewhat control it as well with the choke.. By messing around with the idle control arm and the screw on the side of the carb that backs it in and out I was able to get it to run fairly smooth at wot with no choke.. However this means turning in the screw that controls the idle arm travel in to far, so the idle is then way to high.. So that didn't work.. After some more research it appears that it may be the idle jet that's clogged and causing the surge or possibly something to do with the welch screw..
Wondering if you guys can answer a few questions now that I have taken off the top of the carb.. 1) Is there another jet I need to remove and clean besides the one at the front of the carb?.. 2) How tight is the welch screw supposed to be?.. 3) Am I ok to spray the heck out of every nook and cranny of the carb with carb cleaner?, and after doing so, do I need to pull a spark plug wire and crank to purge excess carb cleaning fluid out or does it just mix with the gas and burn off?.. 4) After I removed the float I looked at the fuel in the carb and it was crystal clear.. After about 10 mins though the fuel appeared to be kind of cloudy. So I soaked all of the fuel in the carb up with paper towel.. The bottom of the carb definitely had some sludge in it.. Does that mean I likely have crap in my gas tank?.. If I'm lucky enough to have the overall fix for the surge be nothing more than a dirty jet from junk in the tank. How difficult is it to remove the tank and clean it?..
I know I've probably well exceeded the limit for questions in a single post.. Just figured I may as well get it all out on the table.. Thanks again for any guidance..
 
#2 · (Edited)
Golf 12,

I am still betting that a serious surge like the one you describe is an air leak. There are lots of threads on the WFM site that show good photos of resealing an Onan intake manifold -- here is a representative one:
Weekend Freedom Machines: 318 surge fix question for newbe

You can do this type of repair with just hand tools and attention to detail so don't be afraid to try it.

As for the welch plug, it is supposed to be a closure for a manufacturing access hole in the casting -- if yours is intact there is nothing else you need to do (it does not move or adjust...) If it is missing, it looks like this:

The carburetor cleaning is also something you can do yourself if you have ever tinkered on other engines or cars, etc. You might want to have the CTM2 engine manual handy to refer to the illustrations and so forth.

Ask questions as they come up and you will have the Onan purring like new in no time...

Chuck
 
G
#3 ·
Ok, here's where I'm at.. I had hoped to get off easy by removing the top of the carb and cleaning the idle jet etc.. Did that, put it back on. No luck, still surging.. So plan B is under way.. Remove the intake and replace every gasket I see and cross my fingers.. Everything came off pretty easy which was a nice surprise and I have been very careful to catalogue nuts - bolts and screws so hopefully everything goes back on just as smoothly.. In the pics below, you can see there was little no to no gasket material at all left between the two halfs of the intake.. Really hoping that is my problem!.. With these parts off and the motor sort of opened up like this.. Is there anything else I should do?.. Do I do anything with what I assume are the valve springs in the pics below?.. Check any clearances - gaps - etc?..







 
#4 · (Edited)
You could check and make sure your valve adjustment is OK. Intake is .005". Exhaust is .013" I'm assuming the B43 is the same as the P218G in that respect.
As for the intake repair,you CANNOT use just any sealant. I found that out when I attempted to reseal mine. Long story short,I ended up with a new intake.
As ChuckV has mentioned WFM is a gold mine of information on any type of repair to these tractors.:good2: Anyway, the sealant that was recommended was Permatex Moto Seal 1
Ultimate Gasket Maker.
 
G
#5 ·
thanks Greg.. you just answered a key question I had.. the dealer ordered all of my new gaskets for me today and was stumped when it came to the intake gasket.. In that there isn't a specific gasket to be replaced.. You have to apply your own.. That said, they offered me a tube of the stuff they had on their shelves but I told the guy I needed to ask some folks I know (all of you!).. What is recommended.. I certainly do not want to do this again any time soon so I need to make sure I get the right gasket maker.. Where can you buy permatex?..

And thanks for the tip!
 
#6 · (Edited)
Golf12,

Permatex makes a very wide range of products -- be sure to get the specific one listed above as that is going to stand up to fuel mixtures...

Here is a link to the product page: Specialty Gasket Makers : Permatex® MotoSeal® 1 Ultimate Gasket Maker Grey

Notice that it stands up to gasoline AND high temperatures. You should be able to get this at most auto supply houses. From your pictures, restoring this manifold seal should take care of all your surging issues...

To adjust your valves, do this set of steps from the CTM2 engine manual...



You do not have to have the heads off to do this, just be sure that you are at the correct crank rotation when you do the adjustment...even looking down the spark plug hole (or using a small wooden dowel) can help you see when the piston is all the way up.

Chuck
 
G
#7 ·
well Chuck.. You're a beauty!.. Pulling the intake and resealing it was the solution.. Between that and dismantling and properly cleaning the carb. I cannot believe how smooth it runs from slow idle to wot.. There is not so much as a cough or a sputter now.. Even before the surge it did not run this smoothly and it would hesitate slightly as throttle was increased or decreased.. There is not even a puff of smoke now when I start it now.. The repair is fresh so that may change I suppose but for now what can I say.. I'm thrilled that the surge is gone. But I gotta tell ya'.. The way it runs now far exceeded my expectations.. I have only owned this machine for two months and I clearly remember how impressed I was with how quiet and smooth it was when I first tested it.. After this more or less "simple" repair, it is like a new machine.. I am literally stunned at how much better it runs now than before I even knew there was a problem.. That surge made my heart sink when it happened, thinking I had just bought a basket case.. Thanks to this forum.. I kept about $400 out of the dealers hands and I learned a ton about this machine by tearing into it.. Props to Chuck again for convincing me to take this on myself!..
 
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