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What's the best way to check reeds? 1988 XR-4 150HP

Cut2Short

Member
Howdy everyone, was hoping to get some advice on checking reed condition on a 1988 Mercury XR-4 150 hp.

I've tried everything else that could contribute to the motor dying when getting out of the hole and this seems to be the last thing to look at.

I've build the carbs, fuel pressure is above 8 psi, timing is set, plugs are new, compression is within 5 psi across cylinders and running about 120 psi, tried a variety of jets.

About give up. Please Help. I don't have a borescope but what are my alternatives.

Thanks for any help.
 
Re: What's the best way to check reeds?

You can remove the intake manifold with the carburetors attached.---------------Inspect reeds and re-install with a new gasket.--------------Easier to do than to explain it.------You have verified that you have spark at each plug that will jump a gap of 7/16" or more.
 
Re: What's the best way to check reeds?

Thanks for the input "racerone", I've checked the spark with one of those cheap units, spark gap I had set was about a 2/0 or 1/2 inch, all cylinders jumped the gap with a consistent looking spark. When I pull the intake, what should I be looking for when I'm inspecting the reeds? Of course the obvious, chips cracks ets, but are there some specifications associated with gaps or anything like that? I have a feeling I'm asking a dumb question but I really haven't dealt with reeds at all when I've worked on motors before. If the reeds need replacing, what other parts should I be looking at to replace while I have it tore down? Thanks agian for the help.
 
If they are original factory metal reeds they rarely fail.----------------Debris ( screws , mouse nest material , tree leaves ) can get in there and do hold them open. ----Then should be closed or nearly so.------------------When the motor is running and you shine a strong flashlight into carburetor bores do you see any " spitback "---that would indicate a broken / bad reed.
 
Interesting racerone, I've spent quite a bit of time looking at the motor run but never shined a flaslight into the cafburetor bores to see if there is and "spitback" I'll give that a try. Thanks!
 
If the carbs open before enough spark advance occurs the motor will bog every time. Try making the carbs come in later. I've had bad reeds before and the motor idles like crap! Since yours doesn't.....

Jeff
 
Actually it won't hold an idle when put in gear, it slowly dies. I've raise the motor thinking it maybe setting too low but that didn't seem to help at all. Any other symptoms associated with bad reeds I could be looking for before I pull them?

Thanks for all of the input.
Steve
 
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