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Tool Talk Discussion Forum

Time an 18 hp briggs

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George Marsh

12-24-2013 13:33:42
50.121.6.110



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Got a new can for 18 hp single cylinder briggs. Cam gear has a dot on it. No Dot on smaller gear on crank. However there is a key way on crank to hold smaller gear in place. Going to guess that to time motor, the dot on the cam lines up with the key way on the crank. Am I right?

Also what is the valve clearance?

Model # is 31H7070????

Thanks,
George




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GUIDO

12-26-2013 11:12:13
71.168.200.122



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-24-2013 13:33:42  
Hello George Marsh,

I forgot to add that sometimes the timing mark is on the crankshaft counterweight. Either way should be clearly marked............

Guido.



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George Marsh

12-26-2013 15:15:50
50.121.6.110



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 Re: Time an 18 hp briggs in reply to GUIDO, 12-26-2013 11:12:13  
Guido,
I found the very small tiny timing mark. Got new cam today. Installed it. Engine fired off. It also backfired throught carb. The ehow video I watched said intake is from .003-.005 1/4 after TDC. I put it at .003. I may try .005 tomorrow. It just doesn't sound right. Also set it up my old way, TDC, not 1/4 inch below TDC. May do some research and see what others say.
George

George



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GUIDO

12-26-2013 16:10:02
71.168.200.122



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-26-2013 15:15:50  
Hello George Marsh, .003 is NOT enough. Set the intake at.006. They have a tendency to get tight. @.003 won't take long to go to zero,

Guido.



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George Marsh

12-26-2013 18:36:09
50.121.6.110



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 Re: Time an 18 hp briggs in reply to GUIDO, 12-26-2013 16:10:02  
Looked up clearance on a briggs sight, .003 to.005. Some recommend going a 1/4 inch past TDC. I've always used TDC, except for today. Going to set it at .005 TDC and see what happens. However on older models it shows .004 - .006. I've always found the clearance increases, then the decompression valve doesn't work. Come to think of it, because the cam in new, there may be more decompression than needed, so I may have to go past .006. Starter spins the motor over like there is no spark plug, very little compression. With the bad cam, motor would lock up it had too much compression.

I'll play around with until I get it to work.

Have a happy new year.

George

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GUIDO

12-27-2013 05:49:52
71.168.200.122



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-26-2013 18:36:09  
Hello George Marsh,

The 1/4 in past TDC insures that you have past the compression release,

Guido.



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George Marsh

12-27-2013 06:38:24
50.121.6.110



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 Re: Time an 18 hp briggs in reply to GUIDO, 12-27-2013 05:49:52  
Guido,
You can feel the compression release. Piston is about half way up the cylinder. I'm going for TDC. Let you know what happens tonight.
George



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GUIDO

12-26-2013 10:14:21
71.168.200.122



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-24-2013 13:33:42  

Hello George Marsh,

The cam gear has a timing mark between the teeth, while the crank gear has the timing mark on a single tooth, just match the two..........

Guido.



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Whizkidkyus

12-25-2013 15:24:27
64.130.151.65



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-24-2013 13:33:42  
George,

I know that you got it figured out ,but I have been told that there is a a dot just like on the one cylinders, but it is located under the crank gear instead of on top of it. I work on small engines, mostly on Briggs, but it"s mostly been on one cylinders instead of twins. Another small engine mechanic that i used to work with told me about the dot underneath the one cylinders.

Whizkid

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George Marsh

12-25-2013 21:20:44
50.121.6.110



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 Re: Time an 18 hp briggs in reply to Whizkidkyus, 12-25-2013 15:24:27  
Whizkid,
I'll look for the dot tomorrow. The video I watched showed a single cylinder, like mine, except it has an oil pump and filter. The video shows the small gear going on the crank first, then the cam is installed. When I put my old crank in engine to see how to put it back together, I had to install the cam first, then gear was flipped around so the smooth side was facing out, other wise I couldn't get the sump cover on all the way.

Hope the guy I'm doing this for free appriciates the work I'm doing.
George

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George Marsh

12-25-2013 06:07:18
50.121.6.110



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-24-2013 13:33:42  
Many thanks to all. I found an ehow to video. It showed where they hide the timing mark, torque pattern and a few other things I wasn't aware of like the push rod for the intake is aluminum, exhaust is metal.

Have a MERRY CHRISTMAS.

Thanks again.
George



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Hobo,NC

12-25-2013 04:46:15
173.189.219.174



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 Re: Time an 18 hp briggs in reply to sotxbill, 12-24-2013 13:33:42  
Quoting Removed, click Modern View to see

What he said then maybe you can find were the reference mark is just to satisfy ya...



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Steve@Advance

12-24-2013 20:33:12
107.203.134.67



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-24-2013 13:33:42  
Just put the piston at TDC, and the cam in valve overlap (between exhaust and intake) position.



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TomIN

12-24-2013 19:08:14
99.130.187.120



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-24-2013 13:33:42  
As I said, I'm an internet searcher rather than a mechanic.

The Briggs parts manual shows that the timing gear is part 697128. A search on that part number has quite a few hits. Some have pictures that show a timing mark.



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JD Seller

12-24-2013 18:34:48
208.126.196.144



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-24-2013 13:33:42  
George: Some B&S cam drive gears do not have a dot on them. They just have one or two teeth with the corners ground off at a 45 degree angle.

I have never seen one that was not marked in some way. Dots, different teeth, slash lines,etc.



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huntingreen2day

12-24-2013 17:23:57
75.131.120.19



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-24-2013 13:33:42  
Are you sure you did not slip the gear on backwards and the dot is on the inside?



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George Marsh

12-24-2013 19:42:24
50.121.6.110



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 Re: Time an 18 hp briggs in reply to huntingreen2day, 12-24-2013 17:23:57  
You can't put the gear on backwards. One side of the gear acts like a thrust bearing.



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TomIN

12-24-2013 14:57:28
99.130.187.120



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 Re: Time an 18 hp briggs in reply to George Marsh, 12-24-2013 13:33:42  
First let me say than I'm not a Briggs mechanic.

I did a search on the model number you listed and it didn't match anything. As close as I can come is a model 31H707 series 0212 E1

The factory manual for this engine suggests an intake valve clearance of .003 to .005 and an exhaust valve clearance of .005 to .007

Another site recommended intake .004 to .006 and exhaust .007 to .009

I found several generic posts about Briggs crankshaft timing marks. They suggest that there should be a line engraved on the crankshaft BEHIND the crank gear (which is keyed to the shaft)

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George Marsh

12-24-2013 16:56:53
64.12.116.207



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 Re: Time an 18 hp briggs in reply to TomIN, 12-24-2013 14:57:28  
Tom,
Model is 31H7070212E1.

I'll look closer to a timing mark on crank. The gear on crank just slips on over a key in crank. Didn't see a mark on that gear, but I'll look even closer.

Thanks,
George



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