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| Palmer BH 25 running rough |
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Message |
    
Rick Batt
New member
Username: belfry
Post Number: 3
Registered: 08-2014
| | Posted on Tuesday, June 30, 2015 - 05:05 pm: | 
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I have a lovely 20' launch built in 1912 that I recommissioned having been sunk and on the hard for four years.
The engine is a Palmer BH-25 which has low compression, 60-65 psi. It starts easily and with no load it runs fairly smooth at low idle, although it skips occasionally . But under a load it runs rough and does not run much above 1/4 throttle. The high speed jet is not taking adjustment. The fuel is clean. The carburetor has had a cleaning and new parts from the rebuilt kit. The electric pump delivers fuel well. The engine has new wires and spark plug to match the magneto. I haven't tried adjusting the magneto yet but I have doubts it will help much if at all.
My question is how much of the problem of no power and rough running can be attributed to low compression or am I missing something? Perhaps the carburetor needs to be cleaned again? Or do I have to change the engine color from gray to green? |
J.B. Castagnos
Senior Member
Username: jb_castagnos
Post Number: 1075
Registered: 07-2002
| | Posted on Thursday, July 02, 2015 - 05:53 am: |
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Rick, the compression does sound a little low, but the carburetor is definitely not right. I'm not familiar enough with that carb to offer advice without seeing it. Can you find another carb to fit, try it and see if it improves. Did you try adding oil to the cylinder and doing a wet compression check, see if it helps? A valve job wouldn't be too hard, cylinder work would require a complete tear down. |
David C. Dunbar
Advanced Member
Username: david_in_ma
Post Number: 34
Registered: 03-2010
| | Posted on Thursday, July 02, 2015 - 08:50 pm: |
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Rick, Don't confuse eng vibration w/ rough running. The BHs are smooth about 500-700RPM then vibrate more w/ increased speed. They can be balanced for a higher RPM range. If your engine has been sitting a long time the valve springs may be weak, will run as you describe and usually blow black smoke as if it's too rich. First verify ignition and proper fuel mix being delivered prior to eng work. The cyl can be removed for boring and piston replacement without fully dismantling the eng. Good time to service the valves & guides, too. David |
Ernie
Senior Member
Username: ernie
Post Number: 2109
Registered: 01-2002
| | Posted on Friday, July 03, 2015 - 11:20 am: |
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These carbs are very fussy. You need to get ALL the jets out of it then run small wire though all the passages in both halves of the carb body and jets. Since the high speed adjustment makes no difference at this point I wouldn't worry about compression, valve springs etc.
Here are a couple of cutaway pics showing the passages and jets. I can't stress enough to make sure to get a piece of fine wire through every passage. I use wire from a shipping tag.
Also here is a link to some info and pics on the net.
Hope this helps
Ernie
http://operatormanuals.tpub.com/TM-55-4920-384-13-P/TM-55-4920-384-13-P0217.htm
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Rick Batt
Member
Username: belfry
Post Number: 4
Registered: 08-2014
| | Posted on Saturday, July 04, 2015 - 11:57 am: |
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Success. I mentioned that I used new gas, new tank, new fuel lines, and clean carburetor. I failed to mention old fuel pump and no filter. And as you all said check the carburetor. Well you all were right. Now runs great. New filter and gravity feed, no problem. Next Sea trials under a load and final adjustment. Optimistic. Thanks again all. |
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