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Briggs 20hp twin opposed carb issue
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Posted by hankll (7) Tennessee (My Page) on Sat, Jan 30, 10 at 13:34
OK, I've about had it with this beast. I have a carb without a idle air adjuster screw. IN its place is a screw in fixed jet. This has 26 stamped on the face of it. It also has a hole in it, that doesn't seem to go through to the inside. ON the inside tip of the jet, is a hole that goes up to a cross bore hole just before the threads of the screw start. That is clear. I can blow air with my mouth that way, to the cross bore, but cannot get air from the outside to the inside ports. Is this normal or is there a jet hole that is clogged. My question is because it is not running without a intermittent miss, and will not idle down without dieing. In fact if I cut the throttle from WOT to nudge down a bit, it tries to stall and I have to choke it to keep it running. Any suggestions?
The engine is mod 460777 typ 2277E1 code 9804215A |
Follow-Up Postings:
RE: Briggs 20hp twin opposed carb issue
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| Carb jets never take in air from the outside. What you are seeing is the way that jet is made and your description is correct. Sounds like your carb has a blockage somewhere in the low speed circuit and/or the bowl isn't getting enough gas. Remove the carb and clean each and every passage with a small wire. Follow the path that gas travels in the low speed circuit and look for a blocked passage. Be sure you have no vacuum leaks either. Check manifold gaskets and vacuum ports (if any) and make sure everything related is tight. Check fuel flow from the tank. New filter?? Good luck. |
RE: Briggs 20hp twin opposed carb issue
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- Posted by hankll (7) Tennessee (My Page) on
Sat, Jan 30, 10 at 21:24
| Tried to start it today, temps in our area 27*. It was flooding it and never got it to even fire once. Cold weather start wasn't helping. It has to be something I missed in cleaning it. I will go back through it. But I'd feel more confident about it if it had the idle air mixture screw. I'm thinking with it being flooding as a symptom now, that I better focus on the float valve or float. |
RE: Briggs 20hp twin opposed carb issue
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| These floats are set level with the top inverted btw. Also, some needles have a wire that can bind if it is flipped to the pin side. Verify the proper body gasket was used and clean as rdaystrom posted above. |
RE: Briggs 20hp twin opposed carb issue
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- Posted by hankll (7) Tennessee (My Page) on
Mon, Feb 1, 10 at 0:14
I decided to try to get the twin to start today with starting fluid. It finally fired. Just choking seemed to only flood it. Because of that, I noticed that gas was seeping out of the spacer gasket which indicated my possible problem. I took off the manifold and removed the carb. The gaskets were just old and cold. So against my better judgment, I put some gasket adhesive cement on both of the gaskets and re-installed the carb. One of the problems with the running issues was that it wouldn't stay running unless I was running it WOT, and that seemed to manage to mostly keep running, but had to choke it occasionally to keep it from choking down. A couple of things I noticed while running it without the air filter installed, was that it was seeming to have a lot of gas dribbling into the bottom of the manifold floor. This to me indicated the flooding problem. The other thing about it was that it seems to have a slight intermittent miss but just enough to notice it, and not a dead miss.
The crankcase breather tube is putting a noticeable amount of oil smoke. But the muffler doesn't show smoke, only for a few minutes after starting it. So my guess is that it really getting on verge of worn rings and my other guess, is it probably needs a valve job. I think I noticed a back flow of gas coming out of the carb throat, mostly when I had the choke closed, so one of the intakes is weak, or consistently leaking and causing interference with the air/fuel mix going into the chamber. While it was running today, pushing snow, it was doing a slight miss but would push the snow without faltering. And the last thing is that I solved the idle problem with the gasket repair seal job. So it is a tired engine. I'll need to try and get a set of rings installed in it. I think that would solve the miss.
Any thoughts would be appreciated! |
RE: Briggs 20hp twin opposed carb issue
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| Even if the engine has some wear, I doubt if this is causing the problems you are describing. Your description indicates the problem is fuel related. Your equipment is over 10 years old and everything from the fuel tank to the engine needs to be evaluated. Here are some ideas.
1. Pull the fuel tank and dump all the old fuel and dirt. Old fuel will not burn very well. Clean the tank interior using a spray carburetor cleaner. Drain and allow the tank to dry. Evaluate the fuel cap to ensure it is venting.
2. Inspect the entire fuel line for cracks. Frequently the old lines deteriorate and air is sucked in cracks and around fuel clamp connections. If the line is hard, it would be a good idea to replace it. Sometimes small stones become lodged in the line - blocking adequate fuel flow.
3. If the fuel filter has been there for a while, it should be replaced. Additionally, if the fuel hose has been pulled off, small particle of rubber hose may have entered your fuel system.
4. The fuel pump is vacuum operated. frequently the rubber hose to the crankcase port leakes vacuum because the hose has deteriorated or was installed without clamps. This results in a weak fuel pump.
5. Fuel pumps are built as part of the carburetor and fuel flow is difficult to test. Sometimes, I install a vacuum gauge on the fuel line to the carburetor fuel pump to see how much vacuum the pump is drawing.
6. If the carburetor has never been opened, it may be time to refresh it by disassembling, cleaning and installing a new carburetor kit. The kits on these do not include all the fuel pump parts, so additional parts may be needed.
7. Gasket surfaces between the carburetor and cylinder should be evaluated for vacuum leaks.
8. Check the valve clearance. Sometimes valve clearance decreases on a high time engine. This results in lower - or perhaps inadequate compression. When looking over the fuel system, pull the baffles around the cylinders to clean grass and debris from the cooling fins.
good luck |
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