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Discussion Starter · #1 ·
Where do i even start?....

We did a quick service in the spring - Oil, Filter, Spark Plug and Air filter along with fresh Premium gas

Started rough
Exhaust out of only 1 muffler
After running fo about 10 minutes - lots of white smoke....
 

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Discussion Starter · #3 ·
Thanks for reply. I have bought an old used GT, own a socket set and multimeter - that鈥檚 my knowledge base / experience. Completely lost 馃
Should I start taking it all apart or can I do things whilst still together?
I鈥檓 going to empty the oil and gas and refill fresh again to discount them. I will check spark in the plugs today. I had to bypass both the safety switches ( clutch & mower) to get it to start in the first place.
 

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First off
2457853
no need to change the oil...and if fuel is burning in 1 cylinder...I don't see an immediate need to do that either...start by getting a spark tester and see what you have...sounds like POSSIBLY a bad coil
 

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Discussion Starter · #5 ·
UPDATE:

So I've taken alot of bits off, cleaned, checked and reinstalled - Exhausts, Carb and Manifold, Tappet covers and reed valve.
I checked the gap on the plugs and good connection to plug leads.
The Battery is good and fully charged.

I tested the Coil as per a B49G manual I found online:
Test limit: Primary 3.87-4.73 ohms Secondary 12,600-15,400 ohms
Actual: P 4.8 S 14,070

There is a good pressure coming out of the forward exhaust - But next to no pressure out of the rear exhaust.
Would being just half an ohm out on the primary coil make this not run properly and only on 1 side??
Also there seems to be a better, but weak, spark on the rear plug than the front - confused...
 

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Check and see if its got compression on the rear cylinder..a stuck valve or busted rod will cause no air movement out the plug hole
 

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Discussion Starter · #9 ·
Not stuck rods. All 4 move when I hand turn. Don鈥檛 have a compression tester...
 

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So just turn it over with spark plug out with my hand over the hole??
Yes...you should feel a large sharp burst of air. Ill stick my finger over the plug hole, it should suck hard then sharply pop it off.
 
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Discussion Starter · #11 ·
So it's gone into a shop - I gave up!

Will let you know the outcome and diagnosis
 

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Discussion Starter · #12 ·
so after new capacitor, coil, plugs, leads and fuel pump - No compression on one cylinder :(
Time for it to be someone else's project I think...
 

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Who put all these parts in:
"new capacitor, coil, plugs, leads and fuel pump"?

If it was the 'mechanic', you should demand a refund. If there was no compression, that should have been the first thing to check as it involves no parts, and just sacrifice of one thumb.
Actually, a no compression situation should be noticeable when the engine is cranked over by the starter motor. The sound will change when the weak cylinder is being compressed.
I do not know models by their number, so looked up an Onan B48G. You can get a new short block(if the search engine is not lying) for $449 on the web, free shipping.
You can learn a bit about engines at low cost if you want to check the valves for adjustment and sealing. You would have to remove the 'shrouds' that direct cooling air over the cylinders and head. Remove the head(about 6-9 bolts), and then the valves. The valves have a spring that holds them against their seat which must be removed.
I find it bothersome that somone would put in all those parts and finally conclude there is no compression.
A fuel pump is a ridiculous part to replace in that you can check for absence/presence of fuel in the carburetor without replacing the pump. The other parts can be checked without removing anything but a spark plug lead, and cranking the engine over, while looking for spark.


Oh, if you did have a 'mechanic' do this 'work', did you get a report of compression pressure developed by each cylinder? Or, the generic "It's worn out, and you don't have compression in one cylinder."?
From what I have heard of Onan engines, they are pretty much bullet proof, though their parts are priced as if they were platinum plated and delivered by a coach and four. Were it mine, I'd get a head gasket(2) and a spring chamber gasket, and take it apart to fiddle with. Can't make it worse.
I won't put down what I think happened next at the shop. I'd be surprised if an offer of a substitute was not made. And of course a trade-in was expected.
tom
 

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What was the purpose in getting this tractor? Were you intending to use it to learn about mechanical things?
If so, you will learn a lot. Old tractors need a lot of love.
And if you have to pay someone to do it for you, very expensive.

If you are not planning on working on it, pass it on and buy a new/er tractor.

"Thanks for reply. I have bought an old used GT, own a socket set and multimeter - that鈥檚 my knowledge base / experience. Completely lost" 馃
 
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