Question for Walker-What do the recirc valves do?

[Stumedic]

My 175 crossflow fouls plugs like mad. Engine hates to run slow. When the plugs load up I get a high speed miss. Change the plugs and it runs great again. Rebuilt power head, carbs, power packs. The recirc valves have been suggested. What do they do? Thanks. Stu

 

[Walker]

Re: Question for Walker-What do the recirc valves do?

Raw, liquid fuel/oil mixture accumulates behind the carbs in intake manifold. When this happens you get a rich fuel/air mixture in the crankcase and thus in the combustion chambers. At idle this mixture can become too rich to burn, beyond the upper flammability range of gasoline. The recirculation valves suck the liquid fuel out of the crankcase.

 

[Stumedic]

Re: Question for Walker-What do the recirc valves do?

Thanks Walker. I'm convinced that they're my problem, probably by the process of elimination. My service manual says they're there, but doesn't say where, how many, hose routing, etc. Can they be cleaned, or are they a replacement item? Stu

 

[Walker]

Re: Question for Walker-What do the recirc valves do?

Check your floats/valves/seats too. One thing you might do while checking the floats is to drop them in a can of gas and makes sure they DO float. Thats' not much of a problem usually with the plastic floats but I have seen it once or twice.

 

[Stumedic]

Re: Question for Walker-What do the recirc valves do?

Checked that when I did the carbs. Engine runs great. Even idles fine. Smokes like mad if you rev it in neutral. No smoke under load. Fouls plugs after trolling. Sometimes they clear themselves. Sometimes the engine will start bucking at speed and loses rpm's. Change the plugs and all is well again. Stu

 

[Walker]

Re: Question for Walker-What do the recirc valves do?

What plugs and what gap are you running?

 

[cobra 3.0]

Re: Question for Walker-What do the recirc valves do?

How's the compression on this rebuilt engine?

You may also wish to try running a synthetic oil instead (at a slightly lighter mix if you mix your own or is there a separate oil tank?) and do a decarb with seafoam.


..also, have you ever replaced the thermostat? The engine might be running cool and contibute to the fouling.

 

[Stumedic]

Re: Question for Walker-What do the recirc valves do?

I replaced the tstats even though they're only a year old. I use pennzoil 2 cycle oil. I changed from the surface gap plugs to regular plugs, overgapped to .040 Stu

 

[Cricket Too]

Re: Question for Walker-What do the recirc valves do?

You can clean the re-circs out as preventative maintenance, but if they are causing a problem (clogged), you might as well change them out.

I always thought they lubricated the crank bearings as well, to some degree?