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I recently acquired an early 1983 318 with the B43G engine which has about 1800 hours on it, and I have been doing a bunch of work to it. I recently did the standard tune-up items, new plugs, wires, coil, points, condenser, all new fuel lines, cleaned out the fuel tank, cleaned a lot of the gunk and debris from the tractor, fixed leaking steering hoses, and replaced the oil in the engine and the transmission (with new filters).

I believe the 318 runs well now, before it didn't run at all. My question is in regards to when I change the throttle from Idle to Max. When its running at Idle and I increase the throttle, the rpms of the engine first goes down, and then it recovers and runs at full throttle. When the RPMs go down, its almost like its going to stall, but recovers and runs.

My question is, is this normal, or should I be looking at possibly doing something with the carb or intake? I have heard that the intakes on these leak, could it be when I increase the the throttle its getting to much air or not enough fuel to have it run smoothly?

I appreciate the time and help!

Jesse C.

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1983 318 with 1804 hours B43G
 

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My question is: Is the engine warmed up/at operating temp or near?

I've heard of many people turning the key, the engine fires, they back off on the choke and increase the throttle! THIS is NOT good for the engine!! Start engine at whatever throttle & choke combination works best for the temperature. Back off choke to maintain smooth operation. Increase throttle to ~about 1/2 and let sit for 2 or 3 minutes...more if it's colder.

If the engine also does this after warming up, could be a manifold or carb problem though. Try warming engine up and report back, Bob
 

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I will say that I didn't let the engine warm up too much. It was about 12 degrees out when I did this last night. I will try it again tonight, let it run for 10 minutes or so and will see how it responds.


I appreciate the response!

Jesse C.
 

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Generally speaking...it's best to let everything come up to temperature before you get on the throttle. Aside from that a carbed engine won't give a smooth, immediate throttle response right after starting...not like a fuel-injected engine. As you get older, the effects of temperature command new respect...and various emoliants/rubs, etc.
 

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Jesse,

The operator's manual for this tractor has specific instructions on warming the engine on page 12 -- below is a snapshot of that part of the page. You should get this document if you don't already have it...

Onan engine warming from operator's manual.jpg

Chuck
 

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I recently acquired an early 1983 318 with the B43G engine which has about 1800 hours on it, and I have been doing a bunch of work to it. I recently did the standard tune-up items, new plugs, wires, coil, points, condenser, all new fuel lines, cleaned out the fuel tank, cleaned a lot of the gunk and debris from the tractor, fixed leaking steering hoses, and replaced the oil in the engine and the transmission (with new filters).

I believe the 318 runs well now, before it didn't run at all. My question is in regards to when I change the throttle from Idle to Max. When its running at Idle and I increase the throttle, the rpms of the engine first goes down, and then it recovers and runs at full throttle. When the RPMs go down, its almost like its going to stall, but recovers and runs.

My question is, is this normal, or should I be looking at possibly doing something with the carb or intake? I have heard that the intakes on these leak, could it be when I increase the the throttle its getting to much air or not enough fuel to have it run smoothly?

I appreciate the time and help!

Jesse C.

---------
1983 318 with 1804 hours B43G
If you think about how many more complex carburetors work, when you try to increase the rpm from idle to max quickly, there's usually a squirt of gasoline from the accelerator pump to enrich the mixture to avoid this lag - for a moment, the engine is running very lean and that's what causes it to loose rpm. There's an alternate way to avoid this rpm lag, and that's to increase the throttle slowly or have a mechanism that will do that for you. On the B43 engine, you don't have an accelerator pump but you do have a dash pot and a bunch of linkage to slow the application of the throttle. I would check the operation of the dash pot (it's like a shock absorber - in fact it's used in many shocks, it's designed to resist motion) and associated linkage. It takes a lot to screw up the dash pot, but at 1800 hours, it's likely that the linkage joints have developed enough slop that the dash pot essentially does nothing.
 

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Also, your carb may be set up to operate on the lean side or you may have some level of a manifold air leak - all these things would exacerbate the lagging situation when you try to throttle up. Hope some of this insight works for you.
 

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Discussion Starter #8
Thanks for all the responses. Since I posted this question a few weeks ago, I've only run the tractor only a few more times, and it does seem to get better after it warms up, but still has a lag in it. My Work is taking up too much of my time, so I haven't had a chance to really dig into this more (not enough time for fun stuff!) I did buy new gaskets for the intake manifold and carb, so at some point in the near future I plan on doing those anyways.

A lot of this tractor has not been maintained well, so I am working on redoing a bunch of things. I just got new AG tires on it, the old tires were all dry-rotted. The brakes also didnt work so I am in the process of redoing those. I hope I can post a few pictures of it in the near future.

Thanks for all the help and info!

Jesse.
 
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