# B&S twin cylinder question



## Jake T. (May 5, 2007)

Hello; 

I have a B&S question. I am working on a B&S twin cylinder. After having performed all things listed below it still runs rough. Sounds like it's missing at any speed and won't idle well. The carb. only has a low speed mixture screw. High speed is fixed. Engine dosen't smoke or leak oil.

B&S twin cylinder 14 h.p. (1985)
mod. 400707
type 0126-01
code 90081711

These are the things I'm sure about and have confirmed.

replaced both spark plugs
replaced fuel (flushed fuel tank)
replaced mag with new unit
performed compression test (#1 cylinder 53 psi) (#2 cylinder 63 psi)
note: changed head gasket on #1 cylinder...compression remaind at 53 psi.
performed ignition test. Inspected timing key
cleaned carb. and replaced carb. diaphragms
inspected valve / breather cover
confirmed air gap on flywheel
checked governor setting
replaced fuel filter
replaced air filter
installed new govenor bushing 
intake bolts are tight

Anything else I could try?
Thanks in advance.
Jake..


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## cajunh2s (Apr 19, 2007)

jake

i've read your post over and over, looking at all the work you have done so far...and all though i'm fairly new to small engine repair and am still in school taking a small engine course....the only thing that keeps coming to mind with your engine is maybe a fly wheel problem....like its warped....or the magnets are shot and messing up the ignition system at the magneto...it could be worth a look....my two cents may not be worth much...but figured i'd throw it in the hat.....lol

cajun


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## tommyj3 (Sep 16, 2006)

Check valve lash.


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## justin3 (Apr 10, 2007)

Wrong fuel filter causing to much restriction?
If you had the crankcase open, the cam gear may be off a tooth or two.


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## glenjudy (Aug 26, 2006)

Make sure the idle mixture screw is turned out 1 1/4 turns from finger tight. Also, make sure the crankcase impulse hose to carb fuel pump (I'm assuming it has one) is in good shape, replace it to make sure.


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## scrench (Dec 8, 2004)

i would have to say tommyj3 got it , do a wet dry compression test , i would bet its the valves , 10 psi lower is too much , disconnect the kill wire and eliminate any questions with the wiring , but sounds like one of the valves are not seating ,


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## Jake T. (May 5, 2007)

scrench said:


> i would have to say tommyj3 got it , do a wet dry compression test , i would bet its the valves , 10 psi lower is too much , disconnect the kill wire and eliminate any questions with the wiring , but sounds like one of the valves are not seating ,


I pulled the valves and will refurbish. Should have it running in a few dats. I'll report the findings. Thanks guys for the responses
Jake...


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## scrench (Dec 8, 2004)

might just be the lash , you can set them without taking the valves completely out , or without removing the springs , could be a seat , did you check the rps ? could be floating . could be running too fast , post some pictures if you can , pictures of the seats , and valve face ,


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## Jake T. (May 5, 2007)

scrench said:


> might just be the lash , you can set them without taking the valves completely out , or without removing the springs , could be a seat , did you check the rps ? could be floating . could be running too fast , post some pictures if you can , pictures of the seats , and valve face ,


Pulled the valves. Exhaust valves need refacing. I cut the eats already and need to reface the valves. I'll post in a few days. Lash was checked prior to valve removal and was o.k. 

Jake


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## glenjudy (Aug 26, 2006)

With the compression difference, particularly with one being so low, I bet the valve job will do the trick. Another possibility is the carb. This model will have the fuel pump attached with 3 screws. The first diaphragm next to carb body will have two teeny tiny springs on either side of a check valve flap. May be one or both of these springs was overlooked on the rebuild.


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## Jake T. (May 5, 2007)

glenjudy said:


> With the compression difference, particularly with one being so low, I bet the valve job will do the trick. Another possibility is the carb. This model will have the fuel pump attached with 3 screws. The first diaphragm next to carb body will have two teeny tiny springs on either side of a check valve flap. May be one or both of these springs was overlooked on the rebuild.


I will reface the valves in the next few days (working on other project) I replaced the diaphragms and springs last week. I'm thinking the valve job will do the trick. I was concerned about the 10 psi difference also. When I pulled the valves out, the exhaust valves looked a little iffy.

Jake...


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## Jake T. (May 5, 2007)

I completed the valve job today. Started the engine. Runs very good. Thanks for any advise posted to this question.

Jake...


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