Low Compression vs. Carb issue

[ksanders]

I'm at one of those points where I'd rather have a second knowledgable opinion instead of doing 10 trial and error things over the course of a week. I'm messing with my 169 finally. Got sidetracked by repainting an Original for a gentleman and it got put on hold. Anyway, the 169 ran okay before repainting with the carb main idle screw set at about 4 turns out. Tried it after a carb rebuild and reassembly now and it wants to die unless the choke is almost all the way closed whether I have it at 2 turns or up to 5. Tried a different main jet and recleaning the carb ports. Carb is clean. So my question is:
Will low compression cause this sort of behavior or does it have to be carb? My compression tester showed about 25lbs. which I know can't be right because it wouldn't run and it only showed about 30 on another tractor that runs perfect (must be the guage). If I knew the answer to this I could rule out valves or anything else and focus on fuel.

[wdeturck]

You can't check compression on engines with Compression Releases(CR) unless you spin them fast enough or spin them backwards. I think you have a partially blocked passage in the high section or very bad air leaks from the throttle and choke shafts.

[ksanders]

I know the newer motor I checked for reference with the guage is ACR, but is the 16hp in the 169? I'll pull the carb again and check the ports more thouroughly. I think I have some extra #30 carbs I could try worst case scenario. Has a new bushing on the throttle shaft so that should be fine.

[SWilliams]

The only K series without ACR is the little K91
The easy way to do a compression test is to use a big drill and socket to spin the engine over at speed then measure the pressure.

[wdeturck]

The K-161 with the 2 piece cams use spark advance instead of ACR.

[aar]

Silly question but do you have a good flow of fuel to the carb? If it ran fine before it is unlikely you have a compression issue. Pulling the choke richens the mixture which is keeping it running. Either you have an air leak, blocked fuel passages, or a weak spark imo.

[ksanders]

I took the carb off today before I had to leave and cleaned it all good again. I'm fairly certain its clean. Also tried a main jet from a known good runner and no difference. It seems to be way worse at low idle so I'm starting to lean toward either an air leak or something in the spark.

aar, You're right on the compression. I even put a new head gasket on anyway since it was leaking a little before (still ran okay though). Fuel coming into the bowl is fine so you're probably right on the air leak. I once heard that air leaks are easier to determine if it runs better under a load than at idle, and it won't run at idle without heavy choking but you can almost mess with the fuel screw at high idle and have no choke. I need a few hours of free time to really tear into it.

[l palma]

Did you put gas in the tank?
Hehehe
The 149 and 169 carbs use 2 different main jet needles,depending on which carb spec # it has.Is the vent clogged on the tank?How about the gasket for the air cleaner housing,using the correct one? How is the bowl height set?Try a remote tank,you may have something blocking the fuel outlet on the one on the 169.Just throwing out some things to check.

[ksanders]

Lew,
I'd done all that except the remote tank but have good fuel flow. Didn't know about different jets though. Add that to the thousands of things I've picked up on from this site over the last several years.
It must be dirt or a sediment that got lodged somewhere in the carb during cleaning it. All the ports seem clean and air goes through them but I put an unrebuilt #30 on it and it was perfect I have 3 #30 bases around here so I'll just throw the kit in one and forget about it. Thanks guys.

[Dbaumanjr]

If you have a carb with "issues" a good way to clean the carb before rebuilding is by boiling it in lemon juice. You won't believe the mung you get out of an already cleaned carb! Note that it will remove anodizing & probably paint.

[aar]

Really? I've never heard of that before.

[ksanders]

Neither have I. I bet I grab some lemon juice next time I'm in town and just see what comes out of the problematic carb.

[EdWells]

kevin I know kindof a apple and orange situation my shreader with bs quantum got to acting up would loose lot of rpm then come back to wot cleaned carb several time did not find anything used another tank and now fine. Origional tank seemed to have good out flow but would still occur.I blew air carb cleaner thru outlet could not find restriction so just mounted aux tank.

[Dbaumanjr]

My brother-in-law boils carbs in Lemon juice for about 20 minutes to clean them. You'll be surprised by the sediment.